added windows system fonts listener

Author: Chun-Heng Tai

example/windows/main.cpp

@@ -77,7 +77,7 @@ int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE prev, wchar_t *command_line,
 
   // Create a top-level win32 window to host the Flutter view.
   Win32Window window;
-  if (!window.CreateAndShow(kFlutterWindowTitle, origin, size)) {
+  if (!window.CreateAndShow(kFlutterWindowTitle, origin, size, &flutter_controller)) {
     return EXIT_FAILURE;
   }
 

example/windows/win32_window.cc

@@ -28,7 +28,7 @@ Win32Window::Win32Window() {}
 Win32Window::~Win32Window() { Destroy(); }
 
 bool Win32Window::CreateAndShow(const std::wstring &title, const Point &origin,
-                                const Size &size) {
+                                const Size &size, flutter::FlutterViewController *controller) {
   Destroy();
 
   WNDCLASS window_class = RegisterWindowClass();
@@ -40,6 +40,8 @@ bool Win32Window::CreateAndShow(const std::wstring &title, const Point &origin,
 
   double scale_factor = static_cast<double>(dpi_x) / kBaseDpi;
 
+  controller_ = controller;
+
   HWND window = CreateWindow(
       window_class.lpszClassName, title.c_str(),
       WS_OVERLAPPEDWINDOW | WS_VISIBLE, Scale(origin.x, scale_factor),
@@ -114,6 +116,9 @@ Win32Window::MessageHandler(HWND hwnd, UINT const message, WPARAM const wparam,
         SetFocus(child_content_);
       }
       return 0;
+    case WM_FONTCHANGE:
+      controller_->OnFontChange();
+      return 0;
   }
 
   return DefWindowProc(window_handle_, message, wparam, lparam);

example/windows/win32_window.h

@@ -12,6 +12,8 @@
 #include <memory>
 #include <string>
 
+#include <flutter/flutter_view_controller.h>
+
 // A class abstraction for a high DPI-aware Win32 Window. Intended to be
 // inherited from by classes that wish to specialize with custom
 // rendering and input handling
@@ -40,7 +42,7 @@ class Win32Window {
   // as logical pixels and scale to appropriate for the default monitor. Returns
   // true if the window was created successfully.
   bool CreateAndShow(const std::wstring &title, const Point &origin,
-                     const Size &size);
+                     const Size &size, flutter::FlutterViewController *controller);
 
   // Release OS resources asociated with window.
   void Destroy();
@@ -81,6 +83,8 @@ class Win32Window {
   // should message loop keep running
   bool messageloop_running_ = true;
 
+  flutter::FlutterViewController *controller_;
+
   // Retrieves a class instance pointer for |window|
   static Win32Window *GetThisFromHandle(HWND const window) noexcept;