feat(learn): Markdown files beside the PDFs, read formatted

A studyset's files take Markdown (.md, .markdown) as well as PDFs, in
the same synced rows with a kind (payload schema 3, written only for
Markdown, so older apps skip those rows). Upload a PDF becomes Upload a
file; a Markdown file must be UTF-8 text.

The reader opens one formatted and read-only through the editor's
Markdown reader, keeping fenced code, which that reader drops; the file
itself never changes, and its source text is a tap away, selectable too.
It has neither search, zoom nor screenshots. It reads in 100 parts by
its top-level blocks, so reading progress, deadlines and the cards and
notes tied to a place work as a PDF's pages do, shown as a share; its
outermost headings are its chapters.

Whats-New: Upload Markdown files beside your PDFs: they open formatted, with reading progress, deadlines and flashcards from what you select.
Whats-New-De: Lade Markdown-Dateien neben deine PDFs hoch: Sie öffnen sich formatiert, mit Lesefortschritt, Fristen und Karteikarten aus deiner Auswahl.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/lib/l10n/app_de.arb

@@ -281,7 +281,7 @@
   "studysetNotesInTopics": "Die Notizen sind in seinen Themen",
   "studysetNotesInTopicsHint": "Oder schreib hier eine: „Material hinzufügen → Notiz erstellen“.",
   "studysetFilesInTopics": "Die Dateien sind in seinen Themen",
-  "studysetFilesInTopicsHint": "Oder füg hier eine hinzu: „Material hinzufügen → PDF hochladen“.",
+  "studysetFilesInTopicsHint": "Oder füg hier eine hinzu: „Material hinzufügen → Datei hochladen“.",
   "studysetBrowseAllFlashcards": "{count, plural, =1{Ansehen} other{Alle {count} ansehen}}",
   "studysetCreateFlashcards": "Karteikarten erstellen",
   "studysetStudy": "Lernen",
@@ -1153,8 +1153,8 @@
   "studyButtonGone": "Dieses Lernset gibt es nicht mehr.",
   "pdfPageField": "PDF-Seite",
   "studysetTabFiles": "Dateien",
-  "pdfUploadMenu": "PDF hochladen",
+  "pdfUploadMenu": "Datei hochladen",
-  "pdfFileType": "PDFs",
+  "pdfFileType": "PDFs und Markdown",
   "pdfAdded": "„{title}“ hinzugefügt.",
   "pdfNotPdf": "Diese Datei ist kein PDF.",
   "pdfTooLarge": "Dieses PDF ist größer als {megabytes} MB.",
@@ -1163,7 +1163,7 @@
   "pdfDuplicateKeep": "Vorhandenes behalten",
   "pdfDuplicateAdd": "Kopie hinzufügen",
   "filesEmpty": "Noch keine Dateien",
-  "filesEmptyHint": "Nutze „Material hinzufügen → PDF hochladen“, um eines hinzuzufügen.",
+  "filesEmptyHint": "Nutze „Material hinzufügen → Datei hochladen“, um eines hinzuzufügen.",
   "filesSort": "Sortieren",
   "filesSortCustom": "Eigene Reihenfolge",
   "filesSortName": "Name (A–Z)",
@@ -2182,5 +2182,25 @@
   "pathViewSteps": "Schritte",
   "pathViewScroll": "Scrollen",
   "runnerOutline": "Gliederung",
-  "runnerScrollLocked": "Beantworte die Frage oben, um weiterzumachen."
+  "runnerScrollLocked": "Beantworte die Frage oben, um weiterzumachen.",
+  "markdownNotText": "Diese Datei ist kein Markdown-Text in UTF-8.",
+  "markdownTooLarge": "Diese Markdown-Datei ist größer als {megabytes} MB.",
+  "markdownShare": "{percent} %",
+  "markdownAt": "Bei {percent} %",
+  "readerByPlace": "Stelle",
+  "proposalsFromPart": "Aus diesem Abschnitt",
+  "readerReferencedShare": "Referenzierte Stelle: {percent} %",
+  "readerUseCurrentShare": "Aktuelle verwenden ({percent} %)",
+  "progressMarkdownShare": "{percent} % gelesen",
+  "markdownDeadlineUpcoming": "Beginnt in {days, plural, =1{1 Tag} other{{days} Tagen}} – {percent} %/Tag geplant",
+  "markdownDeadlinePassed": "Frist abgelaufen – noch {percent} %",
+  "markdownDeadlineToday": "Heute fällig – noch {percent} %",
+  "markdownDeadlinePace": "{percent} %/Tag, um in {days, plural, =1{1 Tag} other{{days} Tagen}} {target} % zu erreichen",
+  "markdownDeadlineHelp": "Lies bis zu einem Tag einen Teil der Datei. Der Fortschritt folgt der weitesten Stelle, bis zu der du beim Lesen scrollst.",
+  "markdownDeadlineReach": "Erreichen (%)",
+  "markdownDeadlineChapterEntry": "{title}  ·  bis {percent} %",
+  "markdownToShareToday": "heute bis {percent} %",
+  "markdownDeadlinesProgress": "{furthest} %/{target} % · {when}",
+  "readerShowSource": "Quelltext zeigen",
+  "readerShowFormatted": "Formatiert zeigen"
 }

apps/learn/halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -330,7 +330,7 @@
   "studysetNotesInTopics": "The notes are in its topics",
   "studysetNotesInTopicsHint": "Or write one here: \"Add material → Create a note\".",
   "studysetFilesInTopics": "The files are in its topics",
-  "studysetFilesInTopicsHint": "Or add one here: \"Add material → Upload a PDF\".",
+  "studysetFilesInTopicsHint": "Or add one here: \"Add material → Upload a file\".",
   "studysetBrowseAllFlashcards": "{count, plural, =1{Browse it} other{Browse all {count}}}",
   "@studysetBrowseAllFlashcards": {"description": "Opens the card browser on every flashcard of a studyset's topics.", "placeholders": {"count": {"type": "int"}}},
   "studysetCreateFlashcards": "Create flashcards",
@@ -1326,8 +1326,8 @@
   "studyButtonGone": "That studyset no longer exists.",
   "pdfPageField": "PDF page",
   "studysetTabFiles": "Files",
-  "pdfUploadMenu": "Upload a PDF",
+  "pdfUploadMenu": "Upload a file",
-  "pdfFileType": "PDFs",
+  "pdfFileType": "PDFs and Markdown",
   "pdfAdded": "Added \"{title}\".",
   "@pdfAdded": {"placeholders": {"title": {"type": "String"}}},
   "pdfNotPdf": "This file isn't a PDF.",
@@ -1339,7 +1339,7 @@
   "pdfDuplicateKeep": "Keep the one there",
   "pdfDuplicateAdd": "Add a copy",
   "filesEmpty": "No files yet",
-  "filesEmptyHint": "Use \"Add material → Upload a PDF\" to add one.",
+  "filesEmptyHint": "Use \"Add material → Upload a file\" to add one.",
   "filesSort": "Sort",
   "filesSortCustom": "Custom order",
   "filesSortName": "Name (A–Z)",
@@ -2690,5 +2690,45 @@
   "runnerOutline": "Outline",
   "@runnerOutline": {"description": "The list of a learning path's steps beside or over its page in the Scroll view."},
   "runnerScrollLocked": "Answer the question above to go on.",
-  "@runnerScrollLocked": {"description": "Below the question a learning path's page stops at, in the Scroll view."}
+  "@runnerScrollLocked": {"description": "Below the question a learning path's page stops at, in the Scroll view."},
+  "markdownNotText": "This file isn't Markdown text in UTF-8.",
+  "@markdownNotText": {"description": "A file named .md or .markdown that couldn't be read as text."},
+  "markdownTooLarge": "This Markdown file is larger than {megabytes} MB.",
+  "@markdownTooLarge": {"description": "A Markdown file over the server's limit for files.", "placeholders": {"megabytes": {"type": "int"}}},
+  "markdownShare": "{percent}%",
+  "@markdownShare": {"description": "How much of a Markdown file is read, or where in it something is, in percent", "placeholders": {"percent": {"type": "int"}}},
+  "markdownAt": "At {percent}%",
+  "@markdownAt": {"description": "Where in a Markdown file the cards or the note below are: a heading in the reader's panels", "placeholders": {"percent": {"type": "int"}}},
+  "readerByPlace": "Place",
+  "@readerByPlace": {"description": "Segment in a Markdown file's cards panel: the cards grouped by where in the file they are (as Page does for PDFs)"},
+  "proposalsFromPart": "From this part",
+  "@proposalsFromPart": {"description": "Button in a Markdown file's cards panel: an assistant proposes flashcards from the part of the file in view"},
+  "readerReferencedShare": "Referenced place: {percent}%",
+  "@readerReferencedShare": {"description": "Below a card being written beside a Markdown file: where in the file it is tied to", "placeholders": {"percent": {"type": "int"}}},
+  "readerUseCurrentShare": "Use current ({percent}%)",
+  "@readerUseCurrentShare": {"description": "Button: ties the card to the place in the Markdown file in view", "placeholders": {"percent": {"type": "int"}}},
+  "progressMarkdownShare": "{percent}% read",
+  "@progressMarkdownShare": {"description": "A studyset's Progress: how much of a Markdown file is read", "placeholders": {"percent": {"type": "int"}}},
+  "markdownDeadlineUpcoming": "Starts in {days, plural, =1{1 day} other{{days} days}} — {percent}%/day planned",
+  "@markdownDeadlineUpcoming": {"description": "A Markdown file's reading deadline not started yet", "placeholders": {"days": {"type": "int"}, "percent": {"type": "int"}}},
+  "markdownDeadlinePassed": "Deadline passed — {percent}% left",
+  "@markdownDeadlinePassed": {"description": "A Markdown file's reading deadline that passed", "placeholders": {"percent": {"type": "int"}}},
+  "markdownDeadlineToday": "Due today — {percent}% left",
+  "@markdownDeadlineToday": {"description": "A Markdown file's reading deadline due today", "placeholders": {"percent": {"type": "int"}}},
+  "markdownDeadlinePace": "{percent}%/day to reach {target}% in {days, plural, =1{1 day} other{{days} days}}",
+  "@markdownDeadlinePace": {"description": "A Markdown file's reading deadline on its way: how much to read a day", "placeholders": {"percent": {"type": "int"}, "target": {"type": "int"}, "days": {"type": "int"}}},
+  "markdownDeadlineHelp": "Read a share of the file by a day. Progress follows the furthest you scroll as you read.",
+  "@markdownDeadlineHelp": {"description": "Help in the deadline sheet of a Markdown file"},
+  "markdownDeadlineReach": "Reach (%)",
+  "@markdownDeadlineReach": {"description": "Field in the deadline sheet of a Markdown file: the share to reach, in percent"},
+  "markdownDeadlineChapterEntry": "{title}  ·  to {percent}%",
+  "@markdownDeadlineChapterEntry": {"description": "A heading of a Markdown file offered as a deadline's target, with the share it ends at", "placeholders": {"title": {"type": "String"}, "percent": {"type": "int"}}},
+  "markdownToShareToday": "to {percent}% today",
+  "@markdownToShareToday": {"description": "Chip on a Markdown file's deadline: how far to read today", "placeholders": {"percent": {"type": "int"}}},
+  "markdownDeadlinesProgress": "{furthest}%/{target}% · {when}",
+  "@markdownDeadlinesProgress": {"description": "A Markdown file's deadline: how far it is read of the share to reach, and when", "placeholders": {"furthest": {"type": "int"}, "target": {"type": "int"}, "when": {"type": "String"}}},
+  "readerShowSource": "Show the source text",
+  "@readerShowSource": {"description": "Tooltip: shows a Markdown file as written, rather than formatted"},
+  "readerShowFormatted": "Show it formatted",
+  "@readerShowFormatted": {"description": "Tooltip: shows a Markdown file formatted again, after its source text"}
 }

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations.dart

@@ -1729,7 +1729,7 @@ abstract class AppLocalizations {
   /// No description provided for @studysetFilesInTopicsHint.
   ///
   /// In en, this message translates to:
-  /// **'Or add one here: \"Add material → Upload a PDF\".'**
+  /// **'Or add one here: \"Add material → Upload a file\".'**
   String get studysetFilesInTopicsHint;
 
   /// Opens the card browser on every flashcard of a studyset's topics.
@@ -6793,13 +6793,13 @@ abstract class AppLocalizations {
   /// No description provided for @pdfUploadMenu.
   ///
   /// In en, this message translates to:
-  /// **'Upload a PDF'**
+  /// **'Upload a file'**
   String get pdfUploadMenu;
 
   /// No description provided for @pdfFileType.
   ///
   /// In en, this message translates to:
-  /// **'PDFs'**
+  /// **'PDFs and Markdown'**
   String get pdfFileType;
 
   /// No description provided for @pdfAdded.
@@ -6853,7 +6853,7 @@ abstract class AppLocalizations {
   /// No description provided for @filesEmptyHint.
   ///
   /// In en, this message translates to:
-  /// **'Use \"Add material → Upload a PDF\" to add one.'**
+  /// **'Use \"Add material → Upload a file\" to add one.'**
   String get filesEmptyHint;
 
   /// No description provided for @filesSort.
@@ -12877,6 +12877,126 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'Answer the question above to go on.'**
   String get runnerScrollLocked;
+
+  /// A file named .md or .markdown that couldn't be read as text.
+  ///
+  /// In en, this message translates to:
+  /// **'This file isn\'t Markdown text in UTF-8.'**
+  String get markdownNotText;
+
+  /// A Markdown file over the server's limit for files.
+  ///
+  /// In en, this message translates to:
+  /// **'This Markdown file is larger than {megabytes} MB.'**
+  String markdownTooLarge(int megabytes);
+
+  /// How much of a Markdown file is read, or where in it something is, in percent
+  ///
+  /// In en, this message translates to:
+  /// **'{percent}%'**
+  String markdownShare(int percent);
+
+  /// Where in a Markdown file the cards or the note below are: a heading in the reader's panels
+  ///
+  /// In en, this message translates to:
+  /// **'At {percent}%'**
+  String markdownAt(int percent);
+
+  /// Segment in a Markdown file's cards panel: the cards grouped by where in the file they are (as Page does for PDFs)
+  ///
+  /// In en, this message translates to:
+  /// **'Place'**
+  String get readerByPlace;
+
+  /// Button in a Markdown file's cards panel: an assistant proposes flashcards from the part of the file in view
+  ///
+  /// In en, this message translates to:
+  /// **'From this part'**
+  String get proposalsFromPart;
+
+  /// Below a card being written beside a Markdown file: where in the file it is tied to
+  ///
+  /// In en, this message translates to:
+  /// **'Referenced place: {percent}%'**
+  String readerReferencedShare(int percent);
+
+  /// Button: ties the card to the place in the Markdown file in view
+  ///
+  /// In en, this message translates to:
+  /// **'Use current ({percent}%)'**
+  String readerUseCurrentShare(int percent);
+
+  /// A studyset's Progress: how much of a Markdown file is read
+  ///
+  /// In en, this message translates to:
+  /// **'{percent}% read'**
+  String progressMarkdownShare(int percent);
+
+  /// A Markdown file's reading deadline not started yet
+  ///
+  /// In en, this message translates to:
+  /// **'Starts in {days, plural, =1{1 day} other{{days} days}} — {percent}%/day planned'**
+  String markdownDeadlineUpcoming(int days, int percent);
+
+  /// A Markdown file's reading deadline that passed
+  ///
+  /// In en, this message translates to:
+  /// **'Deadline passed — {percent}% left'**
+  String markdownDeadlinePassed(int percent);
+
+  /// A Markdown file's reading deadline due today
+  ///
+  /// In en, this message translates to:
+  /// **'Due today — {percent}% left'**
+  String markdownDeadlineToday(int percent);
+
+  /// A Markdown file's reading deadline on its way: how much to read a day
+  ///
+  /// In en, this message translates to:
+  /// **'{percent}%/day to reach {target}% in {days, plural, =1{1 day} other{{days} days}}'**
+  String markdownDeadlinePace(int percent, int target, int days);
+
+  /// Help in the deadline sheet of a Markdown file
+  ///
+  /// In en, this message translates to:
+  /// **'Read a share of the file by a day. Progress follows the furthest you scroll as you read.'**
+  String get markdownDeadlineHelp;
+
+  /// Field in the deadline sheet of a Markdown file: the share to reach, in percent
+  ///
+  /// In en, this message translates to:
+  /// **'Reach (%)'**
+  String get markdownDeadlineReach;
+
+  /// A heading of a Markdown file offered as a deadline's target, with the share it ends at
+  ///
+  /// In en, this message translates to:
+  /// **'{title}  ·  to {percent}%'**
+  String markdownDeadlineChapterEntry(String title, int percent);
+
+  /// Chip on a Markdown file's deadline: how far to read today
+  ///
+  /// In en, this message translates to:
+  /// **'to {percent}% today'**
+  String markdownToShareToday(int percent);
+
+  /// A Markdown file's deadline: how far it is read of the share to reach, and when
+  ///
+  /// In en, this message translates to:
+  /// **'{furthest}%/{target}% · {when}'**
+  String markdownDeadlinesProgress(int furthest, int target, String when);
+
+  /// Tooltip: shows a Markdown file as written, rather than formatted
+  ///
+  /// In en, this message translates to:
+  /// **'Show the source text'**
+  String get readerShowSource;
+
+  /// Tooltip: shows a Markdown file formatted again, after its source text
+  ///
+  /// In en, this message translates to:
+  /// **'Show it formatted'**
+  String get readerShowFormatted;
 }
 
 class _AppLocalizationsDelegate

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_de.dart

@@ -1039,7 +1039,7 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get studysetFilesInTopicsHint =>
-      'Oder füg hier eine hinzu: „Material hinzufügen → PDF hochladen“.';
+      'Oder füg hier eine hinzu: „Material hinzufügen → Datei hochladen“.';
 
   @override
   String studysetBrowseAllFlashcards(int count) {
@@ -4216,10 +4216,10 @@ class AppLocalizationsDe extends AppLocalizations {
   String get studysetTabFiles => 'Dateien';
 
   @override
-  String get pdfUploadMenu => 'PDF hochladen';
+  String get pdfUploadMenu => 'Datei hochladen';
 
   @override
-  String get pdfFileType => 'PDFs';
+  String get pdfFileType => 'PDFs und Markdown';
 
   @override
   String pdfAdded(String title) {
@@ -4253,7 +4253,7 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get filesEmptyHint =>
-      'Nutze „Material hinzufügen → PDF hochladen“, um eines hinzuzufügen.';
+      'Nutze „Material hinzufügen → Datei hochladen“, um eines hinzuzufügen.';
 
   @override
   String get filesSort => 'Sortieren';
@@ -8224,4 +8224,103 @@ class AppLocalizationsDe extends AppLocalizations {
   @override
   String get runnerScrollLocked =>
       'Beantworte die Frage oben, um weiterzumachen.';
+
+  @override
+  String get markdownNotText => 'Diese Datei ist kein Markdown-Text in UTF-8.';
+
+  @override
+  String markdownTooLarge(int megabytes) {
+    return 'Diese Markdown-Datei ist größer als $megabytes MB.';
+  }
+
+  @override
+  String markdownShare(int percent) {
+    return '$percent %';
+  }
+
+  @override
+  String markdownAt(int percent) {
+    return 'Bei $percent %';
+  }
+
+  @override
+  String get readerByPlace => 'Stelle';
+
+  @override
+  String get proposalsFromPart => 'Aus diesem Abschnitt';
+
+  @override
+  String readerReferencedShare(int percent) {
+    return 'Referenzierte Stelle: $percent %';
+  }
+
+  @override
+  String readerUseCurrentShare(int percent) {
+    return 'Aktuelle verwenden ($percent %)';
+  }
+
+  @override
+  String progressMarkdownShare(int percent) {
+    return '$percent % gelesen';
+  }
+
+  @override
+  String markdownDeadlineUpcoming(int days, int percent) {
+    String _temp0 = intl.Intl.pluralLogic(
+      days,
+      locale: localeName,
+      other: '$days Tagen',
+      one: '1 Tag',
+    );
+    return 'Beginnt in $_temp0 – $percent %/Tag geplant';
+  }
+
+  @override
+  String markdownDeadlinePassed(int percent) {
+    return 'Frist abgelaufen – noch $percent %';
+  }
+
+  @override
+  String markdownDeadlineToday(int percent) {
+    return 'Heute fällig – noch $percent %';
+  }
+
+  @override
+  String markdownDeadlinePace(int percent, int target, int days) {
+    String _temp0 = intl.Intl.pluralLogic(
+      days,
+      locale: localeName,
+      other: '$days Tagen',
+      one: '1 Tag',
+    );
+    return '$percent %/Tag, um in $_temp0 $target % zu erreichen';
+  }
+
+  @override
+  String get markdownDeadlineHelp =>
+      'Lies bis zu einem Tag einen Teil der Datei. Der Fortschritt folgt der weitesten Stelle, bis zu der du beim Lesen scrollst.';
+
+  @override
+  String get markdownDeadlineReach => 'Erreichen (%)';
+
+  @override
+  String markdownDeadlineChapterEntry(String title, int percent) {
+    return '$title  ·  bis $percent %';
+  }
+
+  @override
+  String markdownToShareToday(int percent) {
+    return 'heute bis $percent %';
+  }
+
+  @override
+  String markdownDeadlinesProgress(int furthest, int target, String when) {
+    return '$furthest %/$target % · $when';
+  }
+
+  @override
+  String get readerShowSource => 'Quelltext zeigen';
+
+  @override
+  String get readerShowFormatted => 'Formatiert zeigen';
 }

apps/learn/halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -1030,7 +1030,7 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get studysetFilesInTopicsHint =>
-      'Or add one here: \"Add material → Upload a PDF\".';
+      'Or add one here: \"Add material → Upload a file\".';
 
   @override
   String studysetBrowseAllFlashcards(int count) {
@@ -4178,10 +4178,10 @@ class AppLocalizationsEn extends AppLocalizations {
   String get studysetTabFiles => 'Files';
 
   @override
-  String get pdfUploadMenu => 'Upload a PDF';
+  String get pdfUploadMenu => 'Upload a file';
 
   @override
-  String get pdfFileType => 'PDFs';
+  String get pdfFileType => 'PDFs and Markdown';
 
   @override
   String pdfAdded(String title) {
@@ -4215,7 +4215,7 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get filesEmptyHint =>
-      'Use \"Add material → Upload a PDF\" to add one.';
+      'Use \"Add material → Upload a file\" to add one.';
 
   @override
   String get filesSort => 'Sort';
@@ -8150,6 +8150,105 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get runnerScrollLocked => 'Answer the question above to go on.';
+
+  @override
+  String get markdownNotText => 'This file isn\'t Markdown text in UTF-8.';
+
+  @override
+  String markdownTooLarge(int megabytes) {
+    return 'This Markdown file is larger than $megabytes MB.';
+  }
+
+  @override
+  String markdownShare(int percent) {
+    return '$percent%';
+  }
+
+  @override
+  String markdownAt(int percent) {
+    return 'At $percent%';
+  }
+
+  @override
+  String get readerByPlace => 'Place';
+
+  @override
+  String get proposalsFromPart => 'From this part';
+
+  @override
+  String readerReferencedShare(int percent) {
+    return 'Referenced place: $percent%';
+  }
+
+  @override
+  String readerUseCurrentShare(int percent) {
+    return 'Use current ($percent%)';
+  }
+
+  @override
+  String progressMarkdownShare(int percent) {
+    return '$percent% read';
+  }
+
+  @override
+  String markdownDeadlineUpcoming(int days, int percent) {
+    String _temp0 = intl.Intl.pluralLogic(
+      days,
+      locale: localeName,
+      other: '$days days',
+      one: '1 day',
+    );
+    return 'Starts in $_temp0 — $percent%/day planned';
+  }
+
+  @override
+  String markdownDeadlinePassed(int percent) {
+    return 'Deadline passed — $percent% left';
+  }
+
+  @override
+  String markdownDeadlineToday(int percent) {
+    return 'Due today — $percent% left';
+  }
+
+  @override
+  String markdownDeadlinePace(int percent, int target, int days) {
+    String _temp0 = intl.Intl.pluralLogic(
+      days,
+      locale: localeName,
+      other: '$days days',
+      one: '1 day',
+    );
+    return '$percent%/day to reach $target% in $_temp0';
+  }
+
+  @override
+  String get markdownDeadlineHelp =>
+      'Read a share of the file by a day. Progress follows the furthest you scroll as you read.';
+
+  @override
+  String get markdownDeadlineReach => 'Reach (%)';
+
+  @override
+  String markdownDeadlineChapterEntry(String title, int percent) {
+    return '$title  ·  to $percent%';
+  }
+
+  @override
+  String markdownToShareToday(int percent) {
+    return 'to $percent% today';
+  }
+
+  @override
+  String markdownDeadlinesProgress(int furthest, int target, String when) {
+    return '$furthest%/$target% · $when';
+  }
+
+  @override
+  String get readerShowSource => 'Show the source text';
+
+  @override
+  String get readerShowFormatted => 'Show it formatted';
 }
 
 /// The translations for English, as used in the United Kingdom (`en_GB`).

apps/learn/halkyon_learn_flutter/lib/src/core/editor/rich_content_markdown.dart

@@ -1,5 +1,6 @@
 import 'package:appflowy_editor/appflowy_editor.dart';
 import 'package:halkyon_editor/halkyon_editor.dart';
+import 'package:markdown/markdown.dart' as md;
 
 /// What Markdown has no words of its own for, in the person's language: a
 /// sound's link, a video's link without a caption, a spoiler's summary, a
@@ -243,3 +244,30 @@ class const _SpoilerParser(final String _summary) extends NodeParser {
     return '<details><summary>$_summary</summary>\n\n$text\n\n</details>\n';
   }
 }
+
+/// [markdown] read into the editor's document, as the editor's own reader
+/// reads it, but keeping fenced and indented code, which that reader drops:
+/// each block of it a paragraph of its lines as written, in code's style.
+Document markdownToRichDocument(String markdown) =>
+    markdownToDocument(markdown, markdownParsers: const [_CodeReader()]);
+
+class const _CodeReader() extends CustomMarkdownParser {
+  @override
+  List<Node> transform(
+    md.Node element,
+    List<CustomMarkdownParser> parsers, {
+    MarkdownListType listType = MarkdownListType.unknown,
+    int? startNumber,
+  }) {
+    if (element is! md.Element || element.tag != 'pre') {
+      return const [];
+    }
+    final code = element.textContent.replaceFirst(RegExp(r'\n$'), '');
+    return [
+      paragraphNode(
+        delta: Delta()
+          ..insert(code, attributes: {AppFlowyRichTextKeys.code: true}),
+      ),
+    ];
+  }
+}

apps/learn/halkyon_learn_flutter/lib/src/feature/explore/data/copy_updater.dart

@@ -696,6 +696,7 @@ class CopyUpdater(
     pageCount: content.pageCount,
     deadline: content.deadline,
     published: origin,
+    kind: content.kind,
   );
 }
 

apps/learn/halkyon_learn_flutter/lib/src/feature/explore/data/release_copier.dart

@@ -566,6 +566,7 @@ class ReleaseCopier(
     assetId: content.assetId,
     pageCount: content.pageCount,
     published: origin,
+    kind: content.kind,
   );
 }
 

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/bloc/pdf_reader_bloc.dart

@@ -1,16 +1,18 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:developer';
 
 import 'package:equatable/equatable.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:halkyon_learn_flutter/src/core/asset/data/asset_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/markdown_document.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_engine.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_source_repository.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_chapter.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
 
-/// A PDF being read: its file found (downloaded if this device lacks it)
+/// A PDF being read, or a Markdown file read as one ([MarkdownDocument]):
-/// and opened, its page count noted, where reading starts, and each page
+/// its file found (downloaded if this device lacks it) and opened, its page count noted, where reading starts, and each page
 /// shown recorded, the furthest kept (decided 2026-10-03).
 ///
 /// Reading starts at [page] when asked for, else at the furthest page read
@@ -45,7 +47,10 @@ class PdfReaderBloc(
     }
     final PdfDocumentView document;
     try {
-      document = await _engine.open(file.bytes);
+      document = switch (source.content.kind) {
+        FileKind.pdf => await _engine.open(file.bytes),
+        FileKind.markdown => MarkdownDocument(utf8.decode(file.bytes)),
+      };
     } on FormatException catch (error) {
       log('Opening a PDF failed', name: 'PDFs', error: error);
       emit(const PdfReaderStateUnreadable());

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/data/markdown_document.dart

@@ -0,0 +1,232 @@
+import 'dart:async';
+import 'dart:typed_data';
+
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:halkyon_editor/halkyon_editor.dart';
+import 'package:halkyon_learn_flutter/src/core/editor/core_blocks.dart';
+import 'package:halkyon_learn_flutter/src/core/editor/rich_content_markdown.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_engine.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_chapter.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
+import 'package:halkyon_ui/halkyon_ui.dart';
+import 'package:material_ui/material_ui.dart';
+
+/// A Markdown file read as the PDFs are (decided 10 Nov 2026): rendered by
+/// the editor's Markdown reader, read-only, the file itself never changed.
+///
+/// It has no pages, so it reads in [markdownParts] parts, each top-level
+/// block of the rendered file in the part of where it stands among them
+/// ([partOf]): reading progress, deadlines and the cards tied to a page take
+/// a part as a PDF's page, shown as a share.
+class MarkdownDocument(final String source) implements PdfDocumentView {
+  late final Document _document = markdownToRichDocument(source);
+
+  List<Node> get _blocks => _document.root.children;
+
+  /// How many top-level blocks it has.
+  int get blockCount => _blocks.length;
+
+  @override
+  int get pageCount => markdownParts;
+
+  /// The part the block at [index] (from 0) is in, from 1.
+  int partOf(int index) => blockCount == 0
+      ? 1
+      : 1 + (index * markdownParts ~/ blockCount).clamp(0, markdownParts - 1);
+
+  /// The first block in [part] or after it, the last block for a part
+  /// beyond them.
+  int firstBlockOf(int part) {
+    for (var index = 0; index < blockCount; index++) {
+      if (partOf(index) >= part) {
+        return index;
+      }
+    }
+    return blockCount == 0 ? 0 : blockCount - 1;
+  }
+
+  @override
+  Future<List<PdfChapter>> chapters() async {
+    final headings = [
+      for (final (index, block) in _blocks.indexed)
+        if (block.type == HeadingBlockKeys.type)
+          (
+            index: index,
+            level: block.attributes[HeadingBlockKeys.level] as int? ?? 1,
+            title: _textOf(block).trim(),
+          ),
+    ];
+    if (headings.isEmpty) {
+      return const [];
+    }
+    final outermost = headings
+        .map((heading) => heading.level)
+        .reduce((a, b) => a < b ? a : b);
+    return [
+      for (final heading in headings)
+        if (heading.level == outermost && heading.title.isNotEmpty)
+          (title: heading.title, page: partOf(heading.index)),
+    ];
+  }
+
+  @override
+  Future<Uint8List?> renderRegion(int page, Rect region) async => null;
+
+  @override
+  Future<String> pageText(int page) async => [
+    for (final (index, block) in _blocks.indexed)
+      if (partOf(index) == page) _textOf(block),
+  ].where((text) => text.isNotEmpty).join('\n');
+
+  @override
+  Widget viewer(PdfReaderController controller) =>
+      _MarkdownViewer(document: this, controller: controller);
+
+  @override
+  Future<void> dispose() async {}
+}
+
+/// The text of [node] and of the blocks inside it, a line each.
+String _textOf(Node node) => [
+  if (node.delta?.toPlainText() case final text? when text.isNotEmpty) text,
+  for (final child in node.children) _textOf(child),
+].where((text) => text.isNotEmpty).join('\n');
+
+class const _MarkdownViewer({
+  required final MarkdownDocument document,
+  required final PdfReaderController controller,
+}) extends StatefulWidget {
+  @override
+  State<_MarkdownViewer> createState() => _MarkdownViewerState();
+}
+
+/// The rendered file, its text selectable but not editable; the part in
+/// view is that of the first block on screen, or the last part once the
+/// last block is.
+class _MarkdownViewerState()
+    extends State<_MarkdownViewer>
+    implements PdfViewerHandle {
+  // A document of its own: the editor's state disposes it with itself.
+  late final _editorState = EditorState(
+    document: markdownToRichDocument(widget.document.source),
+  )..editable = false;
+  late final _scroll = EditorScrollController(editorState: _editorState);
+
+  @override
+  void initState() {
+    super.initState();
+    _scroll.visibleRangeNotifier.addListener(_onScroll);
+    _editorState.selectionNotifier.addListener(_onSelection);
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (mounted) {
+        widget.controller
+          ..attach(this)
+          ..report(zoom: 1);
+      }
+    });
+  }
+
+  @override
+  void dispose() {
+    widget.controller.attach(null);
+    _scroll.visibleRangeNotifier.removeListener(_onScroll);
+    _editorState.selectionNotifier.removeListener(_onSelection);
+    _scroll.dispose();
+    _editorState.dispose();
+    super.dispose();
+  }
+
+  void _onScroll() {
+    final (first, last) = _scroll.visibleRangeNotifier.value;
+    if (first < 0) {
+      return;
+    }
+    final document = widget.document;
+    widget.controller.report(
+      page: last >= document.blockCount - 1
+          ? markdownParts
+          : document.partOf(first),
+    );
+  }
+
+  void _onSelection() {
+    final selection = _editorState.selection;
+    widget.controller.report(
+      selectedText: selection == null || selection.isCollapsed
+          ? ''
+          : _editorState.getTextInSelection(selection).join('\n'),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final blocks = blocksOf(context);
+    return ColoredBox(
+      color: Theme.of(context).colorScheme.surface,
+      child: Center(
+        child: ConstrainedBox(
+          constraints: const BoxConstraints(maxWidth: readableContentMaxWidth),
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 24),
+            child: AppFlowyEditor(
+              editorState: _editorState,
+              editorScrollController: _scroll,
+              editorStyle: editorStyleOf(
+                context,
+                editing: false,
+                blocks: blocks,
+              ).copyWith(padding: const EdgeInsets.symmetric(vertical: 24)),
+              blockComponentBuilders: buildersWithUnknown(
+                blocks,
+                HalkyonEditorLocalizations.of(context),
+              ),
+              editable: false,
+              disableKeyboardService: true,
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  @override
+  Future<void> goToPage(int page) async {
+    if (widget.document.blockCount > 0) {
+      _scroll.itemScrollController.jumpTo(
+        index: widget.document.firstBlockOf(page),
+      );
+    }
+  }
+
+  // A rendered text has no zoom nor search of its own; the reader offers
+  // neither for it.
+  @override
+  Future<void> zoomIn() async {}
+
+  @override
+  Future<void> zoomOut() async {}
+
+  @override
+  Future<void> fitWidth() async {}
+
+  @override
+  Future<void> fitHeight() async {}
+
+  @override
+  Future<void> setZoom(double zoom) async {}
+
+  @override
+  void search(String text) {}
+
+  @override
+  Future<void> nextMatch() async {}
+
+  @override
+  Future<void> previousMatch() async {}
+
+  @override
+  void clearSearch() {}
+
+  @override
+  Rect? pageRect(int page) => null;
+}

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/data/pdf_source_payload.dart

@@ -9,27 +9,36 @@ import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.da
 // count once known, and a reading deadline ({"targetPage", "due", "start"},
 // days as YYYY-MM-DD; left out when none). Schema 2 added where a copy's PDF
 // came from (`published`, see published_ref.dart), left out for a PDF of its
-// own.
+// own. Schema 3 added the file's kind (`kind`: `markdown`; decided 10 Nov
+// 2026), written only for a file other than a PDF, so that apps from before
+// skip it rather than open it as one; a PDF is still written in schema 2.
 
-/// The schema this app writes.
+/// The newest schema this app writes.
-const pdfSourceSchemaVersion = 2;
+const pdfSourceSchemaVersion = 3;
 
-/// Encodes a PDF's content into its payload.
+/// The schema a PDF is written in, which apps from before Markdown files
-ByteData encodePdfSourcePayload(PdfSourceContent content) =>
+/// read.
-    encodePayload(pdfSourceSchemaVersion, {
+const _pdfSchema = 2;
-      'title': content.title,
+
-      'fileName': content.fileName,
+/// Encodes a file's content into its payload.
-      'asset': content.assetId,
+ByteData encodePdfSourcePayload(PdfSourceContent content) => encodePayload(
-      'pageCount': ?content.pageCount,
+  content.kind == FileKind.pdf ? _pdfSchema : pdfSourceSchemaVersion,
-      if (content.deadline case final deadline?)
+  {
-        'deadline': {
+    if (content.kind != FileKind.pdf) 'kind': content.kind.name,
-          'targetPage': deadline.targetPage,
+    'title': content.title,
-          'due': _day(deadline.due),
+    'fileName': content.fileName,
-          if (deadline.start case final start?) 'start': _day(start),
+    'asset': content.assetId,
-        },
+    'pageCount': ?content.pageCount,
-      if (content.published case final published?)
+    if (content.deadline case final deadline?)
-        'published': publishedRefToJson(published),
+      'deadline': {
-    });
+        'targetPage': deadline.targetPage,
+        'due': _day(deadline.due),
+        if (deadline.start case final start?) 'start': _day(start),
+      },
+    if (content.published case final published?)
+      'published': publishedRefToJson(published),
+  },
+);
 
 /// Decodes a PDF's payload.
 ///
@@ -66,6 +75,13 @@ PdfSourceContent decodePdfSourcePayload(ByteData payload) {
         _ => throw const FormatException('A malformed deadline.'),
       },
       published: publishedRefFromJson(json['published']),
+      kind: switch (json['kind']) {
+        null => FileKind.pdf,
+        final String name =>
+          FileKind.values.where((kind) => kind.name == name).firstOrNull ??
+              (throw FormatException('A kind of file unknown here.', name)),
+        _ => throw const FormatException('A malformed kind.'),
+      },
     );
   }
   throw const FormatException('Not a PDF payload.');

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/data/pdf_source_repository.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:developer';
 import 'dart:typed_data';
 
@@ -34,8 +35,15 @@ enum PdfRefusal() {
   /// It isn't a PDF.
   notPdf,
 
-  /// It is larger than [PdfSourceRepository.maxBytes].
+  /// It is a PDF larger than [PdfSourceRepository.maxBytes].
   tooLarge,
+
+  /// It is named a Markdown file but isn't text in UTF-8.
+  notText,
+
+  /// It is a Markdown file larger than the server takes of a file
+  /// ([AssetRepository.maxBytes]).
+  textTooLarge,
 }
 
 /// The file wasn't taken, for [reason].
@@ -120,25 +128,39 @@ class PdfSourceRepository(
     return counts;
   }
 
-  /// Adds the PDF [bytes], a file named [fileName], to [studysetId], titled
+  /// Adds the file [bytes], named [fileName], to [studysetId], titled by
-  /// by its name. A file the studyset holds already is added again only
+  /// its name: a Markdown file where the name ends in `.md` or `.markdown`
-  /// [evenIfThere]; a file that isn't a PDF, or is too large, not at all.
+  /// (decided 10 Nov 2026), read by share ([markdownParts]), else a PDF. A
+  /// file the studyset holds already is added again only [evenIfThere]; a
+  /// file that isn't what its name says, or is too large, not at all.
   Future<PdfImport> import(
     String studysetId, {
     required Uint8List bytes,
     required String fileName,
     bool evenIfThere = false,
   }) async {
-    if (!_isPdf(bytes)) {
+    final kind = fileKindOf(fileName);
-      return const PdfRefused(PdfRefusal.notPdf);
+    final mimeType = switch (kind) {
+      FileKind.pdf => AssetRepository.pdfMediaType,
+      FileKind.markdown => markdownMediaType,
+    };
+    if (bytes.length > AssetRepository.maxBytesOf(mimeType)) {
+      return PdfRefused(switch (kind) {
+        FileKind.pdf => PdfRefusal.tooLarge,
+        FileKind.markdown => PdfRefusal.textTooLarge,
+      });
     }
-    if (bytes.length > maxBytes) {
+    switch (kind) {
-      return const PdfRefused(PdfRefusal.tooLarge);
+      case FileKind.pdf when !_isPdf(bytes):
+        return const PdfRefused(PdfRefusal.notPdf);
+      case FileKind.markdown when !_isText(bytes):
+        return const PdfRefused(PdfRefusal.notText);
+      case _:
     }
     final assetId = await _assets.add(
       bytes,
       fileName: fileName,
-      mimeType: AssetRepository.pdfMediaType,
+      mimeType: mimeType,
       studysetId: studysetId,
     );
     if (!evenIfThere) {
@@ -155,6 +177,8 @@ class PdfSourceRepository(
           title: titleFromFileName(fileName),
           fileName: fileName,
           assetId: assetId,
+          kind: kind,
+          pageCount: kind == FileKind.markdown ? markdownParts : null,
         ),
       ),
     );
@@ -400,5 +424,15 @@ Map<String, int> furthestOf(List<PdfReadingRow> rows) {
 }
 
 /// Whether [bytes] are a PDF's: they start as every PDF does.
+/// Whether [bytes] are text in UTF-8.
+bool _isText(Uint8List bytes) {
+  try {
+    utf8.decode(bytes);
+    return true;
+  } on FormatException {
+    return false;
+  }
+}
+
 bool _isPdf(Uint8List bytes) =>
     bytes.length >= 5 && String.fromCharCodes(bytes.sublist(0, 5)) == '%PDF-';

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/model/pdf_source.dart

@@ -32,8 +32,42 @@ final class const ReadingDeadline({
   List<Object?> get props => [targetPage, due, start];
 }
 
-/// What a PDF says about itself: its title, the name its file came with, the
+/// What kind of file a studyset's file is (decided 10 Nov 2026): a PDF, or
-/// file, its page count once a device has read it, and a reading deadline.
+/// Markdown, kept as it came and shown rendered.
+enum FileKind() {
+  pdf,
+  markdown,
+}
+
+/// How many parts a Markdown file is read in, as a PDF in pages: its
+/// share read, in hundredths.
+const markdownParts = 100;
+
+/// How much of a Markdown file is read, in percent, once [part] (from 1)
+/// is reached: none at its first part, all at its last.
+int markdownShareOf(int part) =>
+    part >= markdownParts ? 100 : (part - 1).clamp(0, 100);
+
+/// The part (from 1) reached once [share] percent of a Markdown file is
+/// read; [markdownShareOf]'s inverse.
+int markdownPartOf(int share) =>
+    share >= 100 ? markdownParts : (share + 1).clamp(1, markdownParts);
+
+/// A Markdown file's media type.
+const markdownMediaType = 'text/markdown';
+
+/// The kind of the file named [fileName]: Markdown where it ends in `.md`
+/// or `.markdown`, else a PDF.
+FileKind fileKindOf(String fileName) {
+  final name = fileName.trim().toLowerCase();
+  return name.endsWith('.md') || name.endsWith('.markdown')
+      ? FileKind.markdown
+      : FileKind.pdf;
+}
+
+/// What a file says about itself: its title, the name its file came with,
+/// the file, its kind, its page count once a device has read it (a
+/// Markdown file's 100, read by share), and a reading deadline.
 final class const PdfSourceContent({
   /// The title; the file's name without `.pdf` until renamed.
   required final String title,
@@ -53,6 +87,9 @@ final class const PdfSourceContent({
   /// Where it came from, in a copy of a published studyset; null for a PDF
   /// of the person's own.
   final PublishedRef? published,
+
+  /// What kind of file it is.
+  final FileKind kind = FileKind.pdf,
 }) with Equatable {
   /// This content titled [title].
   PdfSourceContent withTitle(String title) => PdfSourceContent(
@@ -62,6 +99,7 @@ final class const PdfSourceContent({
     pageCount: pageCount,
     deadline: deadline,
     published: published,
+    kind: kind,
   );
 
   /// This content with [pageCount] pages.
@@ -72,6 +110,7 @@ final class const PdfSourceContent({
     pageCount: pageCount,
     deadline: deadline,
     published: published,
+    kind: kind,
   );
 
   /// This content with [deadline], or none.
@@ -82,6 +121,7 @@ final class const PdfSourceContent({
     pageCount: pageCount,
     deadline: deadline,
     published: published,
+    kind: kind,
   );
 
   @override
@@ -92,6 +132,7 @@ final class const PdfSourceContent({
     pageCount,
     deadline,
     published,
+    kind,
   ];
 }
 
@@ -115,10 +156,15 @@ final class const PdfSource({
   List<Object?> get props => [id, studysetId, content, position];
 }
 
-/// The title a PDF named [fileName] gets: the name without `.pdf`.
+/// The title a file named [fileName] gets: the name without `.pdf`, `.md`
+/// or `.markdown`.
 String titleFromFileName(String fileName) {
   final name = fileName.trim();
-  return name.toLowerCase().endsWith('.pdf')
+  final lower = name.toLowerCase();
-      ? name.substring(0, name.length - 4)
+  for (final extension in const ['.pdf', '.markdown', '.md']) {
-      : name;
+    if (lower.endsWith(extension)) {
+      return name.substring(0, name.length - extension.length);
+    }
+  }
+  return name;
 }

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/deadline_sheet.dart

@@ -46,7 +46,15 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
   late final _today = clock.now();
   late final ReadingDeadline? _current = widget.source.content.deadline;
   late int _page = _current?.targetPage ?? widget.source.content.pageCount ?? 1;
-  late final _pageField = TextEditingController(text: '$_page');
+
+  /// Whether the target is a share of a Markdown file rather than a page:
+  /// shown and typed in percent, kept as the part it reaches.
+  late final _shares = widget.source.content.kind == FileKind.markdown;
+
+  /// [page] as shown: its share of a Markdown file, else itself.
+  int _shown(int page) => _shares ? markdownShareOf(page) : page;
+
+  late final _pageField = TextEditingController(text: '${_shown(_page)}');
   late DateTime _due = switch (_current?.due) {
     final due? => DateTime(due.year, due.month, due.day),
     null => DateTime(_today.year, _today.month, _today.day + 14),
@@ -66,12 +74,26 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
 
   void _setPage(int page) {
     setState(() => _page = page.clamp(1, _maxPage));
+    final text = '${_shown(_page)}';
     _pageField.value = TextEditingValue(
-      text: '$_page',
+      text: text,
-      selection: TextSelection.collapsed(offset: '$_page'.length),
+      selection: TextSelection.collapsed(offset: text.length),
     );
   }
 
+  /// The page or part [typed] stands for.
+  int _typed(String typed) {
+    final value = int.tryParse(typed) ?? 1;
+    return (_shares ? markdownPartOf(value.clamp(1, 100)) : value).clamp(
+      1,
+      _maxPage,
+    );
+  }
+
+  /// The page or part a step before or after.
+  int _step(int by) =>
+      _shares ? markdownPartOf(markdownShareOf(_page) + by) : _page + by;
+
   /// The last page of the chapter at [index] of [chapters]: the page before
   /// the next one starts, the PDF's last for the last chapter.
   int _lastPageOf(List<PdfChapter> chapters, int index) =>
@@ -125,7 +147,7 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: [
           Text(
-            l10n.deadlineSheetHelp,
+            _shares ? l10n.markdownDeadlineHelp : l10n.deadlineSheetHelp,
             style: theme.textTheme.bodyMedium?.copyWith(
               color: theme.colorScheme.onSurfaceVariant,
             ),
@@ -136,7 +158,7 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
               IconButton.outlined(
                 icon: const Icon(LucideIcons.minus),
                 tooltip: l10n.deadlineDecrease,
-                onPressed: _page > 1 ? () => _setPage(_page - 1) : null,
+                onPressed: _page > 1 ? () => _setPage(_step(-1)) : null,
               ),
               const SizedBox(width: 8),
               Expanded(
@@ -146,20 +168,20 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
                   inputFormatters: [FilteringTextInputFormatter.digitsOnly],
                   textAlign: TextAlign.center,
                   decoration: InputDecoration(
-                    labelText: pageCount == null
+                    labelText: _shares
+                        ? l10n.markdownDeadlineReach
+                        : pageCount == null
                         ? l10n.deadlineReachPage
                         : l10n.deadlineReachPageOf(pageCount),
                   ),
-                  onChanged: (text) => setState(
+                  onChanged: (text) => setState(() => _page = _typed(text)),
-                    () => _page = (int.tryParse(text) ?? 1).clamp(1, _maxPage),
-                  ),
                 ),
               ),
               const SizedBox(width: 8),
               IconButton.outlined(
                 icon: const Icon(LucideIcons.plus),
                 tooltip: l10n.deadlineIncrease,
-                onPressed: _page < _maxPage ? () => _setPage(_page + 1) : null,
+                onPressed: _page < _maxPage ? () => _setPage(_step(1)) : null,
               ),
             ],
           ),
@@ -193,7 +215,15 @@ class _DeadlineSheetState() extends State<_DeadlineSheet> {
                           DropdownMenuItem(
                             value: last,
                             child: Text(
-                              l10n.deadlineChapterEntry(chapter.title, last),
+                              _shares
+                                  ? l10n.markdownDeadlineChapterEntry(
+                                      chapter.title,
+                                      markdownShareOf(last),
+                                    )
+                                  : l10n.deadlineChapterEntry(
+                                      chapter.title,
+                                      last,
+                                    ),
                               overflow: TextOverflow.ellipsis,
                             ),
                           ),

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/file_kind_icon.dart

@@ -0,0 +1,9 @@
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
+import 'package:lucide_icons_flutter/lucide_icons.dart';
+import 'package:material_ui/material_ui.dart';
+
+/// The icon of a file of [kind] wherever files are listed.
+IconData fileKindIcon(FileKind kind) => switch (kind) {
+  FileKind.pdf => LucideIcons.fileText,
+  FileKind.markdown => LucideIcons.fileCode,
+};

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/pdf_list.dart

@@ -16,6 +16,7 @@ import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/deadline_stat
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_chapter.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/widget/deadline_sheet.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/widget/file_kind_icon.dart';
 import 'package:halkyon_ui/halkyon_ui.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import 'package:material_ui/material_ui.dart';
@@ -80,7 +81,7 @@ class const SliverPdfList({
             itemBuilder: (context, index) => ListTile(
               key: ValueKey(rows[index].source.id),
               leading: Icon(
-                LucideIcons.fileText,
+                fileKindIcon(rows[index].source.content.kind),
                 color: theme.colorScheme.primary,
               ),
               title: Text(
@@ -248,7 +249,7 @@ class const _PdfTile({
             children: [
               Padding(
                 padding: const EdgeInsets.only(top: 2),
-                child: Icon(LucideIcons.fileText, color: colors.primary),
+                child: Icon(fileKindIcon(content.kind), color: colors.primary),
               ),
               const SizedBox(width: 16),
               Expanded(
@@ -263,7 +264,9 @@ class const _PdfTile({
                     ),
                     ContentCountsLine(
                       counts: [
-                        (count: pageCount, label: l10n.pdfPages),
+                        // A Markdown file's parts are no pages to count.
+                        if (content.kind == FileKind.pdf)
+                          (count: pageCount, label: l10n.pdfPages),
                         (count: row.cards, label: l10n.studysetCountFlashcards),
                         (count: row.notes, label: l10n.studysetCountNotes),
                         (
@@ -281,7 +284,9 @@ class const _PdfTile({
                     if (status != null) ...[
                       const SizedBox(height: 4),
                       Text(
-                        _deadlineLine(l10n, status, deadline!),
+                        content.kind == FileKind.markdown
+                            ? _markdownDeadlineLine(l10n, status, deadline!)
+                            : _deadlineLine(l10n, status, deadline!),
                         style: theme.textTheme.bodySmall?.copyWith(
                           color: switch (status.state) {
                             DeadlineState.overdue ||
@@ -327,6 +332,26 @@ class const _PdfTile({
     ),
   };
 
+  /// [_deadlineLine] for a Markdown file, in shares rather than pages.
+  String _markdownDeadlineLine(
+    AppLocalizations l10n,
+    DeadlineStatus status,
+    ReadingDeadline deadline,
+  ) => switch (status.state) {
+    DeadlineState.met => l10n.pdfDeadlineMet,
+    DeadlineState.upcoming => l10n.markdownDeadlineUpcoming(
+      status.daysUntilStart,
+      status.pagesPerDay,
+    ),
+    DeadlineState.overdue => l10n.markdownDeadlinePassed(status.pagesLeft),
+    DeadlineState.dueToday => l10n.markdownDeadlineToday(status.pagesLeft),
+    DeadlineState.onTrack => l10n.markdownDeadlinePace(
+      status.pagesPerDay,
+      markdownShareOf(deadline.targetPage),
+      status.daysLeft,
+    ),
+  };
+
   List<Widget> _actions(BuildContext context) {
     final l10n = AppLocalizations.of(context);
     final error = Theme.of(context).colorScheme.error;
@@ -450,11 +475,13 @@ class const _PdfTile({
             },
             copyable: false,
           ),
-          (
+          if (source.content.kind == FileKind.pdf)
-            label: l10n.pdfInfoPages,
+            (
-            value: source.content.pageCount?.toString() ?? l10n.pdfInfoUnknown,
+              label: l10n.pdfInfoPages,
-            copyable: false,
+              value:
-          ),
+                  source.content.pageCount?.toString() ?? l10n.pdfInfoUnknown,
+              copyable: false,
+            ),
         ],
       ),
     ]);

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/pdf_page_chip.dart

@@ -3,7 +3,7 @@ import 'package:halkyon_learn_flutter/src/core/content/pdf_page_ref.dart';
 import 'package:halkyon_learn_flutter/src/core/dependencies/person_dependencies.dart';
 import 'package:halkyon_learn_flutter/src/core/router/route_paths.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
-import 'package:lucide_icons_flutter/lucide_icons.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/widget/file_kind_icon.dart';
 import 'package:material_ui/material_ui.dart';
 
 /// The PDF [source] something was made from, small: a document and the
@@ -47,7 +47,7 @@ class _PdfPageChipState() extends State<PdfPageChip> {
               child: Row(
                 mainAxisSize: MainAxisSize.min,
                 children: [
-                  Icon(LucideIcons.fileText, size: 14, color: muted),
+                  Icon(fileKindIcon(pdf.content.kind), size: 14, color: muted),
                   const SizedBox(width: 4),
                   ConstrainedBox(
                     constraints: const BoxConstraints(maxWidth: 140),

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/pdf_reader_panels.dart

@@ -154,6 +154,9 @@ class const _CardsPanel({
 class _CardsPanelState()
     extends State<_CardsPanel>
     with AutomaticKeepAliveClientMixin {
+  /// Whether places are shares of a Markdown file rather than pages.
+  bool get _shares => widget.source.content.kind == FileKind.markdown;
+
   late final CardComposerBloc _bloc;
 
   /// The card being written, by its draft's id; null while the list shows.
@@ -337,6 +340,8 @@ class _CardsPanelState()
       final page = draft.saved.source!.page;
       final heading = _byChapter
           ? chapterOf(widget.chapters, page)?.title ?? l10n.readerFrontMatter
+          : _shares
+          ? l10n.markdownAt(markdownShareOf(page))
           : l10n.readerPage(page);
       (sections[heading] ??= []).add(draft);
     }
@@ -348,7 +353,10 @@ class _CardsPanelState()
             padding: const EdgeInsets.fromLTRB(12, 8, 12, 0),
             child: SegmentedButton<bool>(
               segments: [
-                ButtonSegment(value: false, label: Text(l10n.readerByPage)),
+                ButtonSegment(
+                  value: false,
+                  label: Text(_shares ? l10n.readerByPlace : l10n.readerByPage),
+                ),
                 ButtonSegment(value: true, label: Text(l10n.readerByChapter)),
               ],
               selected: {_byChapter},
@@ -426,7 +434,9 @@ class _CardsPanelState()
                     icon: const Icon(LucideIcons.sparkles),
                     label: Text(
                       widget.controller.selectedText.trim().isEmpty
-                          ? l10n.proposalsFromPage
+                          ? _shares
+                                ? l10n.proposalsFromPart
+                                : l10n.proposalsFromPage
                           : l10n.proposalsFromSelection,
                     ),
                     onPressed: () => unawaited(_propose()),
@@ -498,7 +508,9 @@ class _CardsPanelState()
                 children: [
                   Expanded(
                     child: Text(
-                      l10n.readerReferencedPage(page),
+                      _shares
+                          ? l10n.readerReferencedShare(markdownShareOf(page))
+                          : l10n.readerReferencedPage(page),
                       style: theme.textTheme.bodySmall,
                     ),
                   ),
@@ -516,7 +528,11 @@ class _CardsPanelState()
                         ),
                       ),
                       child: Text(
-                        l10n.readerUseCurrentPage(widget.controller.page),
+                        _shares
+                            ? l10n.readerUseCurrentShare(
+                                markdownShareOf(widget.controller.page),
+                              )
+                            : l10n.readerUseCurrentPage(widget.controller.page),
                       ),
                     ),
                 ],
@@ -821,7 +837,12 @@ class _NotePanelState()
           padding: const EdgeInsets.fromLTRB(16, 12, 16, 8),
           child: Row(
             children: [
-              Text(l10n.readerPage(_page), style: theme.textTheme.titleSmall),
+              Text(
+                widget.source.content.kind == FileKind.markdown
+                    ? l10n.markdownAt(markdownShareOf(_page))
+                    : l10n.readerPage(_page),
+                style: theme.textTheme.titleSmall,
+              ),
               const Spacer(),
               Text(
                 switch (_status) {

apps/learn/halkyon_learn_flutter/lib/src/feature/pdf_source/widget/pdf_reader_screen.dart

@@ -14,8 +14,10 @@ import 'package:halkyon_learn_flutter/src/core/device_settings/bloc/device_setti
 import 'package:halkyon_learn_flutter/src/core/editor/core_blocks.dart';
 import 'package:halkyon_learn_flutter/src/core/router/route_paths.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/bloc/pdf_reader_bloc.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/markdown_document.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/data/pdf_engine.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_chapter.dart';
+import 'package:halkyon_learn_flutter/src/feature/pdf_source/model/pdf_source.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/widget/pdf_capture.dart';
 import 'package:halkyon_learn_flutter/src/feature/pdf_source/widget/pdf_reader_panels.dart';
 import 'package:halkyon_learn_flutter/src/feature/study/model/study_focus.dart';
@@ -158,6 +160,16 @@ class _ReaderState() extends State<_Reader> {
   var _searching = false;
   var _fullscreen = false;
 
+  /// A Markdown file shown as written rather than formatted.
+  var _showSource = false;
+
+  /// The Markdown file read, null for a PDF: it has no pages to zoom,
+  /// search or take screenshots of, and reads in shares.
+  MarkdownDocument? get _markdown => switch (widget.state.document) {
+    final MarkdownDocument markdown => markdown,
+    _ => null,
+  };
+
   /// The editor's width as dragged here; null until dragged, when it is
   /// the share of the room last dragged on this device, else the default.
   double? _sidebarWidth;
@@ -257,12 +269,30 @@ class _ReaderState() extends State<_Reader> {
     }
   }
 
+  void _toggleSource() => setState(() {
+    _showSource = !_showSource;
+    _controller.report(selectedText: '');
+  });
+
   @override
   Widget build(BuildContext context) {
     final wide = context.windowSize.isAtLeastMedium;
     final viewer = Stack(
       children: [
-        Positioned.fill(child: widget.state.document.viewer(_controller)),
+        // Kept while the source text shows, so the place read stays.
+        Positioned.fill(
+          child: Offstage(
+            offstage: _showSource,
+            child: widget.state.document.viewer(_controller),
+          ),
+        ),
+        if (_markdown case final markdown? when _showSource)
+          Positioned.fill(
+            child: _SourceText(
+              source: markdown.source,
+              controller: _controller,
+            ),
+          ),
         if (!_capture.active)
           Positioned(
             top: _searching ? 76 : 12,
@@ -299,6 +329,7 @@ class _ReaderState() extends State<_Reader> {
                 controller: _controller,
                 pageCount: widget.state.document.pageCount,
                 chapters: widget.state.chapters,
+                shares: _markdown != null,
               ),
             ),
           ),
@@ -310,6 +341,7 @@ class _ReaderState() extends State<_Reader> {
             child: _PageScrubber(
               controller: _controller,
               pageCount: widget.state.document.pageCount,
+              shares: _markdown != null,
             ),
           ),
         if (_searching)
@@ -367,12 +399,14 @@ class _ReaderState() extends State<_Reader> {
             child: SafeArea(
               child: Row(
                 children: [
-                  IconButton.filledTonal(
+                  if (_markdown == null) ...[
-                    icon: const Icon(LucideIcons.search),
+                    IconButton.filledTonal(
-                    tooltip: AppLocalizations.of(context).readerSearch,
+                      icon: const Icon(LucideIcons.search),
-                    onPressed: _toggleSearch,
+                      tooltip: AppLocalizations.of(context).readerSearch,
-                  ),
+                      onPressed: _toggleSearch,
-                  const SizedBox(width: 8),
+                    ),
+                    const SizedBox(width: 8),
+                  ],
                   IconButton.filledTonal(
                     icon: const Icon(LucideIcons.minimize2),
                     tooltip: AppLocalizations.of(context).readerExitFullscreen,
@@ -388,9 +422,9 @@ class _ReaderState() extends State<_Reader> {
     final appBlocks = blocksOf(context);
     if (!identical(appBlocks, _appBlocks)) {
       _appBlocks = appBlocks;
-      _panelBlocks = appBlocks.plus(
+      _panelBlocks = _markdown != null
-        screenshotBlocks(_capture, widget.state.source.id),
+          ? appBlocks
-      );
+          : appBlocks.plus(screenshotBlocks(_capture, widget.state.source.id));
     }
     final panels = EditorBlocksScope(
       blocks: _panelBlocks!,
@@ -435,8 +469,10 @@ class _ReaderState() extends State<_Reader> {
                     _Rail(
                       title: widget.state.source.content.title,
                       controller: _controller,
-                      onSearch: _toggleSearch,
+                      onSearch: _markdown == null ? _toggleSearch : null,
                       onFullscreen: () => setState(() => _fullscreen = true),
+                      showingSource: _markdown == null ? null : _showSource,
+                      onSource: _toggleSource,
                     ),
                     const VerticalDivider(width: 1),
                     Expanded(child: viewer),
@@ -478,8 +514,10 @@ class _ReaderState() extends State<_Reader> {
           children: [
             _TopBar(
               title: widget.state.source.content.title,
-              onSearch: _toggleSearch,
+              onSearch: _markdown == null ? _toggleSearch : null,
               onFullscreen: () => setState(() => _fullscreen = true),
+              showingSource: _markdown == null ? null : _showSource,
+              onSource: _toggleSource,
             ),
             Expanded(
               child: LayoutBuilder(
@@ -518,8 +556,15 @@ class _ReaderState() extends State<_Reader> {
 class const _Rail({
   required final String title,
   required final PdfReaderController controller,
-  required final VoidCallback onSearch,
   required final VoidCallback onFullscreen,
+  required final VoidCallback onSource,
+
+  /// Searching the text; none for a Markdown file, which has no zoom
+  /// either.
+  final VoidCallback? onSearch,
+
+  /// Whether a Markdown file shows its source text; null for a PDF.
+  final bool? showingSource,
 }) extends StatelessWidget {
   /// The room between the rail's groups of buttons.
   static const _groupGap = 16.0;
@@ -547,46 +592,50 @@ class const _Rail({
               ),
             ),
             const Divider(indent: 12, endIndent: 12),
-            IconButton(
+            if (showingSource case final showing?)
-              icon: const Icon(LucideIcons.search),
+              _SourceToggle(showing: showing, onPressed: onSource),
-              tooltip: l10n.readerSearch,
+            if (onSearch case final onSearch?) ...[
-              onPressed: onSearch,
+              IconButton(
-            ),
+                icon: const Icon(LucideIcons.search),
-            // Searching, fitting and zooming in groups of their own, set
+                tooltip: l10n.readerSearch,
-            // apart by space.
+                onPressed: onSearch,
-            const SizedBox(height: _groupGap),
-            IconButton(
-              icon: const Icon(LucideIcons.moveHorizontal),
-              tooltip: l10n.readerFitWidth,
-              onPressed: controller.fitWidth,
-            ),
-            IconButton(
-              icon: const Icon(LucideIcons.moveVertical),
-              tooltip: l10n.readerFitHeight,
-              onPressed: controller.fitHeight,
-            ),
-            const SizedBox(height: _groupGap),
-            IconButton(
-              icon: const Icon(LucideIcons.zoomIn),
-              tooltip: l10n.readerZoomIn,
-              onPressed: controller.zoomIn,
-            ),
-            Tooltip(
-              message: l10n.readerSetZoom,
-              child: TextButton(
-                style: TextButton.styleFrom(
-                  padding: EdgeInsets.zero,
-                  minimumSize: const Size(48, 36),
-                ),
-                onPressed: () => unawaited(_askZoom(context)),
-                child: Text('${(controller.zoom * 100).round()}%'),
               ),
-            ),
+              // Searching, fitting and zooming in groups of their own, set
-            IconButton(
+              // apart by space.
-              icon: const Icon(LucideIcons.zoomOut),
+              const SizedBox(height: _groupGap),
-              tooltip: l10n.readerZoomOut,
+              IconButton(
-              onPressed: controller.zoomOut,
+                icon: const Icon(LucideIcons.moveHorizontal),
-            ),
+                tooltip: l10n.readerFitWidth,
+                onPressed: controller.fitWidth,
+              ),
+              IconButton(
+                icon: const Icon(LucideIcons.moveVertical),
+                tooltip: l10n.readerFitHeight,
+                onPressed: controller.fitHeight,
+              ),
+              const SizedBox(height: _groupGap),
+              IconButton(
+                icon: const Icon(LucideIcons.zoomIn),
+                tooltip: l10n.readerZoomIn,
+                onPressed: controller.zoomIn,
+              ),
+              Tooltip(
+                message: l10n.readerSetZoom,
+                child: TextButton(
+                  style: TextButton.styleFrom(
+                    padding: EdgeInsets.zero,
+                    minimumSize: const Size(48, 36),
+                  ),
+                  onPressed: () => unawaited(_askZoom(context)),
+                  child: Text('${(controller.zoom * 100).round()}%'),
+                ),
+              ),
+              IconButton(
+                icon: const Icon(LucideIcons.zoomOut),
+                tooltip: l10n.readerZoomOut,
+                onPressed: controller.zoomOut,
+              ),
+            ],
             const Spacer(),
             IconButton(
               icon: const Icon(LucideIcons.maximize2),
@@ -660,8 +709,14 @@ class _ZoomDialogState() extends State<_ZoomDialog> {
 /// Below 600 dp, the bar above the pages.
 class const _TopBar({
   required final String title,
-  required final VoidCallback onSearch,
   required final VoidCallback onFullscreen,
+  required final VoidCallback onSource,
+
+  /// Searching the text; none for a Markdown file.
+  final VoidCallback? onSearch,
+
+  /// Whether a Markdown file shows its source text; null for a PDF.
+  final bool? showingSource,
 }) extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
@@ -683,11 +738,14 @@ class const _TopBar({
               style: Theme.of(context).textTheme.titleMedium,
             ),
           ),
-          IconButton(
+          if (showingSource case final showing?)
-            icon: const Icon(LucideIcons.search),
+            _SourceToggle(showing: showing, onPressed: onSource),
-            tooltip: l10n.readerSearch,
+          if (onSearch case final onSearch?)
-            onPressed: onSearch,
+            IconButton(
-          ),
+              icon: const Icon(LucideIcons.search),
+              tooltip: l10n.readerSearch,
+              onPressed: onSearch,
+            ),
           IconButton(
             icon: const Icon(LucideIcons.maximize2),
             tooltip: l10n.readerFullscreen,
@@ -705,6 +763,10 @@ class const _PageCounter({
   required final PdfReaderController controller,
   required final int pageCount,
   required final List<PdfChapter> chapters,
+
+  /// Whether it shows how much is read, in percent, rather than a page:
+  /// a Markdown file's parts.
+  final bool shares = false,
 }) extends StatefulWidget {
   @override
   State<_PageCounter> createState() => _PageCounterState();
@@ -766,49 +828,60 @@ class _PageCounterState() extends State<_PageCounter> {
               visualDensity: VisualDensity.compact,
             ),
           ),
-        Material(
+        if (widget.shares)
-          elevation: 2,
+          Material(
-          color: theme.colorScheme.surfaceContainerHigh,
+            elevation: 2,
-          borderRadius: BorderRadius.circular(24),
+            color: theme.colorScheme.surfaceContainerHigh,
-          child: Padding(
+            borderRadius: BorderRadius.circular(24),
-            padding: const EdgeInsets.symmetric(horizontal: 4),
+            child: Padding(
-            child: Row(
+              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
-              mainAxisSize: MainAxisSize.min,
+              child: Text(l10n.markdownShare(markdownShareOf(page))),
-              children: [
+            ),
-                IconButton(
+          )
-                  icon: const Icon(LucideIcons.chevronLeft),
+        else
-                  tooltip: l10n.readerPreviousPage,
+          Material(
-                  onPressed: page > 1
+            elevation: 2,
-                      ? () => widget.controller.goToPage(page - 1)
+            color: theme.colorScheme.surfaceContainerHigh,
-                      : null,
+            borderRadius: BorderRadius.circular(24),
-                ),
+            child: Padding(
-                SizedBox(
+              padding: const EdgeInsets.symmetric(horizontal: 4),
-                  width: 48,
+              child: Row(
-                  child: TextField(
+                mainAxisSize: MainAxisSize.min,
-                    controller: _field,
+                children: [
-                    focusNode: _focus,
+                  IconButton(
-                    textAlign: TextAlign.center,
+                    icon: const Icon(LucideIcons.chevronLeft),
-                    keyboardType: TextInputType.number,
+                    tooltip: l10n.readerPreviousPage,
-                    inputFormatters: [FilteringTextInputFormatter.digitsOnly],
+                    onPressed: page > 1
-                    decoration: const InputDecoration(
+                        ? () => widget.controller.goToPage(page - 1)
-                      isDense: true,
+                        : null,
-                      border: InputBorder.none,
-                    ),
-                    onSubmitted: (_) => _commit(),
                   ),
-                ),
+                  SizedBox(
-                Text(l10n.readerPageOf(widget.pageCount)),
+                    width: 48,
-                IconButton(
+                    child: TextField(
-                  icon: const Icon(LucideIcons.chevronRight),
+                      controller: _field,
-                  tooltip: l10n.readerNextPage,
+                      focusNode: _focus,
-                  onPressed: page < widget.pageCount
+                      textAlign: TextAlign.center,
-                      ? () => widget.controller.goToPage(page + 1)
+                      keyboardType: TextInputType.number,
-                      : null,
+                      inputFormatters: [FilteringTextInputFormatter.digitsOnly],
-                ),
+                      decoration: const InputDecoration(
-              ],
+                        isDense: true,
+                        border: InputBorder.none,
+                      ),
+                      onSubmitted: (_) => _commit(),
+                    ),
+                  ),
+                  Text(l10n.readerPageOf(widget.pageCount)),
+                  IconButton(
+                    icon: const Icon(LucideIcons.chevronRight),
+                    tooltip: l10n.readerNextPage,
+                    onPressed: page < widget.pageCount
+                        ? () => widget.controller.goToPage(page + 1)
+                        : null,
+                  ),
+                ],
+              ),
             ),
           ),
-        ),
       ],
     );
   }
@@ -819,6 +892,9 @@ class _PageCounterState() extends State<_PageCounter> {
 class const _PageScrubber({
   required final PdfReaderController controller,
   required final int pageCount,
+
+  /// Whether it shows how much is read, in percent, rather than a page.
+  final bool shares = false,
 }) extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
@@ -861,7 +937,13 @@ class const _PageScrubber({
                             vertical: 6,
                           ),
                           child: Text(
-                            '${controller.page}',
+                            shares
+                                ? AppLocalizations.of(
+                                    context,
+                                  ).markdownShare(
+                                    markdownShareOf(controller.page),
+                                  )
+                                : '${controller.page}',
                             style: theme.textTheme.labelLarge?.copyWith(
                               color: theme.colorScheme.onPrimaryContainer,
                             ),
@@ -1231,3 +1313,58 @@ class _SidebarHandleState() extends State<_SidebarHandle> {
     );
   }
 }
+
+/// Switches a Markdown file between formatted and its source text.
+class const _SourceToggle({
+  required final bool showing,
+  required final VoidCallback onPressed,
+}) extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
+    return IconButton(
+      isSelected: showing,
+      icon: const Icon(LucideIcons.code),
+      tooltip: showing ? l10n.readerShowFormatted : l10n.readerShowSource,
+      onPressed: onPressed,
+    );
+  }
+}
+
+/// A Markdown file as written, its text selectable for cards and notes as
+/// the formatted one's.
+class const _SourceText({
+  required final String source,
+  required final PdfReaderController controller,
+}) extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return ColoredBox(
+      color: theme.colorScheme.surface,
+      child: Scrollbar(
+        child: SingleChildScrollView(
+          padding: const EdgeInsets.all(24),
+          child: Center(
+            child: ConstrainedBox(
+              constraints: const BoxConstraints(
+                maxWidth: readableContentMaxWidth,
+              ),
+              child: SelectableText(
+                source,
+                style: theme.textTheme.bodyMedium?.copyWith(
+                  fontFamily: 'monospace',
+                ),
+                onSelectionChanged: (selection, _) => controller.report(
+                  selectedText: selection.isCollapsed
+                      ? ''
+                      : selection.textInside(source),
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}