Add resize functions to GLFW shell (flutter/engine#8864)

Adds methods to get and set the window size, as well as to query the
window's scale factor. This is useful both for custom clients, and for
building a window resize plugin to prototype what will eventually likely
be a system channel.

engine/src/flutter/shell/platform/glfw/client_wrapper/include/flutter/flutter_window.h

@@ -14,6 +14,14 @@
 
 namespace flutter {
 
+// A data type for window position and size.
+struct WindowFrame {
+  int left;
+  int top;
+  int width;
+  int height;
+};
+
 // A window displaying Flutter content.
 class FlutterWindow {
  public:
@@ -48,6 +56,30 @@ class FlutterWindow {
     FlutterDesktopWindowSetIcon(window_, pixel_data, width, height);
   }
 
+  // Returns the frame of the window, including any decoration (e.g., title
+  // bar), in screen coordinates.
+  WindowFrame GetFrame() {
+    WindowFrame frame = {};
+    FlutterDesktopWindowGetFrame(window_, &frame.left, &frame.top, &frame.width,
+                                 &frame.height);
+    return frame;
+  }
+
+  // Set the frame of the window, including any decoration (e.g., title
+  // bar), in screen coordinates.
+  void SetFrame(const WindowFrame& frame) {
+    FlutterDesktopWindowSetFrame(window_, frame.left, frame.top, frame.width,
+                                 frame.height);
+  }
+
+  // Returns the number of pixels per screen coordinate for the window.
+  //
+  // Flutter uses pixel coordinates, so this is the ratio of positions and sizes
+  // seen by Flutter as compared to the screen.
+  double GetScaleFactor() {
+    return FlutterDesktopWindowGetScaleFactor(window_);
+  }
+
  private:
   // Handle for interacting with the C API's window.
   //

engine/src/flutter/shell/platform/glfw/client_wrapper/testing/stub_flutter_glfw_api.cc

@@ -93,6 +93,34 @@ void FlutterDesktopWindowSetIcon(FlutterDesktopWindowRef flutter_window,
   }
 }
 
+void FlutterDesktopWindowGetFrame(FlutterDesktopWindowRef flutter_window,
+                                  int* x,
+                                  int* y,
+                                  int* width,
+                                  int* height) {
+  if (s_stub_implementation) {
+    s_stub_implementation->GetWindowFrame(x, y, width, height);
+  }
+}
+
+void FlutterDesktopWindowSetFrame(FlutterDesktopWindowRef flutter_window,
+                                  int x,
+                                  int y,
+                                  int width,
+                                  int height) {
+  if (s_stub_implementation) {
+    s_stub_implementation->SetWindowFrame(x, y, width, height);
+  }
+}
+
+double FlutterDesktopWindowGetScaleFactor(
+    FlutterDesktopWindowRef flutter_window) {
+  if (s_stub_implementation) {
+    return s_stub_implementation->GetWindowScaleFactor();
+  }
+  return 1.0;
+}
+
 void FlutterDesktopRunWindowLoop(FlutterDesktopWindowControllerRef controller) {
   if (s_stub_implementation) {
     s_stub_implementation->RunWindowLoop();

engine/src/flutter/shell/platform/glfw/client_wrapper/testing/stub_flutter_glfw_api.h

@@ -59,6 +59,17 @@ class StubFlutterGlfwApi {
   //  Called for FlutterDesktopWindowSetIcon.
   virtual void SetWindowIcon(uint8_t* pixel_data, int width, int height) {}
 
+  // Called for FlutterDesktopWindowGetFrame.
+  virtual void GetWindowFrame(int* x, int* y, int* width, int* height) {
+    x = y = width = height = 0;
+  }
+
+  // Called for FlutterDesktopWindowGetFrame.
+  virtual void SetWindowFrame(int x, int y, int width, int height) {}
+
+  // Called for FlutterDesktopWindowGetScaleFactor.
+  virtual double GetWindowScaleFactor() { return 1.0; }
+
   // Called for FlutterDesktopRunWindowLoop.
   virtual void RunWindowLoop() {}
 

engine/src/flutter/shell/platform/glfw/flutter_glfw.cc

@@ -69,8 +69,6 @@ struct FlutterDesktopWindowControllerState {
   // The screen coordinates per inch on the primary monitor. Defaults to a sane
   // value based on pixel_ratio 1.0.
   double monitor_screen_coordinates_per_inch = kDpPerInch;
-  // The ratio of pixels per screen coordinate for the window.
-  double window_pixels_per_screen_coordinate = 1.0;
 };
 
 // Opaque reference for the GLFW window itself. This is separate from the
@@ -82,6 +80,9 @@ struct FlutterDesktopWindow {
 
   // Whether or not to track mouse movements to send kHover events.
   bool hover_tracking_enabled = false;
+
+  // The ratio of pixels per screen coordinate for the window.
+  double pixels_per_screen_coordinate = 1.0;
 };
 
 // Struct for storing state of a Flutter engine instance.
@@ -152,9 +153,9 @@ static void GLFWFramebufferSizeCallback(GLFWwindow* window,
   glfwGetWindowSize(window, &width, nullptr);
 
   auto state = GetSavedWindowState(window);
-  state->window_pixels_per_screen_coordinate = width_px / width;
+  state->window_wrapper->pixels_per_screen_coordinate = width_px / width;
 
-  double dpi = state->window_pixels_per_screen_coordinate *
+  double dpi = state->window_wrapper->pixels_per_screen_coordinate *
                state->monitor_screen_coordinates_per_inch;
   // Limit the ratio to 1 to avoid rendering a smaller UI in standard resolution
   // monitors.
@@ -200,10 +201,12 @@ static void SendPointerEventWithData(GLFWwindow* window,
           std::chrono::high_resolution_clock::now().time_since_epoch())
           .count();
   // Convert all screen coordinates to pixel coordinates.
-  event.x *= state->window_pixels_per_screen_coordinate;
-  event.y *= state->window_pixels_per_screen_coordinate;
-  event.scroll_delta_x *= state->window_pixels_per_screen_coordinate;
-  event.scroll_delta_y *= state->window_pixels_per_screen_coordinate;
+  double pixels_per_coordinate =
+      state->window_wrapper->pixels_per_screen_coordinate;
+  event.x *= pixels_per_coordinate;
+  event.y *= pixels_per_coordinate;
+  event.scroll_delta_x *= pixels_per_coordinate;
+  event.scroll_delta_y *= pixels_per_coordinate;
 
   FlutterEngineSendPointerEvent(state->engine, &event, 1);
 
@@ -579,9 +582,54 @@ void FlutterDesktopWindowSetIcon(FlutterDesktopWindowRef flutter_window,
                                  uint8_t* pixel_data,
                                  int width,
                                  int height) {
-  GLFWwindow* window = flutter_window->window;
   GLFWimage image = {width, height, static_cast<unsigned char*>(pixel_data)};
-  glfwSetWindowIcon(window, pixel_data ? 1 : 0, &image);
+  glfwSetWindowIcon(flutter_window->window, pixel_data ? 1 : 0, &image);
+}
+
+void FlutterDesktopWindowGetFrame(FlutterDesktopWindowRef flutter_window,
+                                  int* x,
+                                  int* y,
+                                  int* width,
+                                  int* height) {
+  glfwGetWindowPos(flutter_window->window, x, y);
+  glfwGetWindowSize(flutter_window->window, width, height);
+  // The above gives content area size and position; adjust for the window
+  // decoration to give actual window frame.
+  int frame_left, frame_top, frame_right, frame_bottom;
+  glfwGetWindowFrameSize(flutter_window->window, &frame_left, &frame_top,
+                         &frame_right, &frame_bottom);
+  if (x) {
+    *x -= frame_left;
+  }
+  if (y) {
+    *y -= frame_top;
+  }
+  if (width) {
+    *width += frame_left + frame_right;
+  }
+  if (height) {
+    *height += frame_top + frame_bottom;
+  }
+}
+
+void FlutterDesktopWindowSetFrame(FlutterDesktopWindowRef flutter_window,
+                                  int x,
+                                  int y,
+                                  int width,
+                                  int height) {
+  // Get the window decoration sizes to adjust, since the GLFW setters take
+  // content position and size.
+  int frame_left, frame_top, frame_right, frame_bottom;
+  glfwGetWindowFrameSize(flutter_window->window, &frame_left, &frame_top,
+                         &frame_right, &frame_bottom);
+  glfwSetWindowPos(flutter_window->window, x + frame_left, y + frame_top);
+  glfwSetWindowSize(flutter_window->window, width - frame_left - frame_right,
+                    height - frame_top - frame_bottom);
+}
+
+double FlutterDesktopWindowGetScaleFactor(
+    FlutterDesktopWindowRef flutter_window) {
+  return flutter_window->pixels_per_screen_coordinate;
 }
 
 void FlutterDesktopRunWindowLoop(FlutterDesktopWindowControllerRef controller) {

engine/src/flutter/shell/platform/glfw/public/flutter_glfw.h

@@ -119,6 +119,27 @@ FLUTTER_EXPORT void FlutterDesktopWindowSetIcon(
     int width,
     int height);
 
+// Gets the position and size of |flutter_window| in screen coordinates.
+FLUTTER_EXPORT void FlutterDesktopWindowGetFrame(
+    FlutterDesktopWindowRef flutter_window,
+    int* x,
+    int* y,
+    int* width,
+    int* height);
+
+// Sets the position and size of |flutter_window| in screen coordinates.
+FLUTTER_EXPORT void FlutterDesktopWindowSetFrame(
+    FlutterDesktopWindowRef flutter_window,
+    int x,
+    int y,
+    int width,
+    int height);
+
+// Returns the scale factor--the number of pixels per screen coordinate--for
+// |flutter_window|.
+FLUTTER_EXPORT double FlutterDesktopWindowGetScaleFactor(
+    FlutterDesktopWindowRef flutter_window);
+
 // Runs an instance of a headless Flutter engine.
 //
 // The |assets_path| is the path to the flutter_assets folder for the Flutter