halkyon/apps/learn/halkyon_learn_flutter/windows/runner/flutter_window.cpp

#include "flutter_window.h"

#include <flutter/standard_method_codec.h>

#include <optional>

#include "flutter/generated_plugin_registrant.h"

// Kept out of captures altogether (Windows 10 2004 and later); older SDKs
// don't name it.
#ifndef WDA_EXCLUDEFROMCAPTURE
#define WDA_EXCLUDEFROMCAPTURE 0x00000011
#endif

namespace {

// Whether this Windows keeps a window out of captures with
// WDA_EXCLUDEFROMCAPTURE: Windows 10 2004 (build 19041) and later. Before,
// it takes the value without failing and acts as WDA_MONITOR, so the
// version decides, not a failure. RtlGetVersion tells the real version;
// GetVersionEx tells what the app's manifest claims.
bool ExcludesFromCapture() {
  using RtlGetVersionFunction = LONG(WINAPI*)(PRTL_OSVERSIONINFOW);
  const HMODULE ntdll = GetModuleHandleW(L"ntdll.dll");
  if (!ntdll) {
    return false;
  }
  const auto rtl_get_version = reinterpret_cast<RtlGetVersionFunction>(
      GetProcAddress(ntdll, "RtlGetVersion"));
  if (!rtl_get_version) {
    return false;
  }
  RTL_OSVERSIONINFOW version = {};
  version.dwOSVersionInfoSize = sizeof(version);
  if (rtl_get_version(&version) != 0) {
    return false;
  }
  return version.dwMajorVersion > 10 ||
         (version.dwMajorVersion == 10 && version.dwBuildNumber >= 19041);
}

}  // namespace

FlutterWindow::FlutterWindow(const flutter::DartProject& project)
    : project_(project) {}

FlutterWindow::~FlutterWindow() {}

bool FlutterWindow::OnCreate() {
  if (!Win32Window::OnCreate()) {
    return false;
  }

  RECT frame = GetClientArea();

  // The size here must match the window dimensions to avoid unnecessary surface
  // creation / destruction in the startup path.
  flutter_controller_ = std::make_unique<flutter::FlutterViewController>(
      frame.right - frame.left, frame.bottom - frame.top, project_);
  // Ensure that basic setup of the controller was successful.
  if (!flutter_controller_->engine() || !flutter_controller_->view()) {
    return false;
  }
  RegisterPlugins(flutter_controller_->engine());
  GuardScreen();
  SetChildContent(flutter_controller_->view()->GetNativeWindow());

  flutter_controller_->engine()->SetNextFrameCallback([&]() {
    this->Show();
  });

  // Flutter can complete the first frame before the "show window" callback is
  // registered. The following call ensures a frame is pending to ensure the
  // window is shown. It is a no-op if the first frame hasn't completed yet.
  flutter_controller_->ForceRedraw();

  return true;
}

void FlutterWindow::GuardScreen() {
  screen_guard_ =
      std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
          flutter_controller_->engine()->messenger(),
          "app.halkyon/screen_guard",
          &flutter::StandardMethodCodec::GetInstance());
  screen_guard_->SetMethodCallHandler(
      [this](const flutter::MethodCall<flutter::EncodableValue>& call,
             std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>>
                 result) {
        if (call.method_name() == "hold") {
          secrets_shown_++;
          // Before Windows 10 2004 the window shows black in captures
          // instead.
          static const bool excludes = ExcludesFromCapture();
          SetWindowDisplayAffinity(
              GetHandle(), excludes ? WDA_EXCLUDEFROMCAPTURE : WDA_MONITOR);
          result->Success();
        } else if (call.method_name() == "release") {
          secrets_shown_ = secrets_shown_ > 0 ? secrets_shown_ - 1 : 0;
          if (secrets_shown_ == 0) {
            SetWindowDisplayAffinity(GetHandle(), WDA_NONE);
          }
          result->Success();
        } else {
          result->NotImplemented();
        }
      });
}

void FlutterWindow::OnDestroy() {
  screen_guard_ = nullptr;
  if (flutter_controller_) {
    flutter_controller_ = nullptr;
  }

  Win32Window::OnDestroy();
}

LRESULT
FlutterWindow::MessageHandler(HWND hwnd, UINT const message,
                              WPARAM const wparam,
                              LPARAM const lparam) noexcept {
  // Give Flutter, including plugins, an opportunity to handle window messages.
  if (flutter_controller_) {
    std::optional<LRESULT> result =
        flutter_controller_->HandleTopLevelWindowProc(hwnd, message, wparam,
                                                      lparam);
    if (result) {
      return *result;
    }
  }

  switch (message) {
    case WM_FONTCHANGE:
      flutter_controller_->engine()->ReloadSystemFonts();
      break;
  }

  return Win32Window::MessageHandler(hwnd, message, wparam, lparam);
}