4444
4545static_assert (FLUTTER_ENGINE_VERSION == 1 , " "
4646
47+ static constexpr double kDpPerInch = 160.0 ;
48+
4749// Struct for storing state within an instance of the GLFW Window.
4850struct FlutterEmbedderState {
4951 FlutterEngine engine;
@@ -57,6 +59,12 @@ struct FlutterEmbedderState {
5759 // Handles raw key interactions from GLFW.
5860 // TODO: Revisit ownership model once Issue #102 is resolved.
5961 std::unique_ptr<flutter_desktop_embedding::KeyEventHandler> key_event_handler;
62+
63+ // The screen coordinates per inch on the primary monitor. Defaults to a sane
64+ // value based on pixel_ratio 1.0.
65+ double monitor_screen_coordinates_per_inch = kDpPerInch ;
66+ // The ratio of pixels per screen coordinate for the window.
67+ double window_pixels_per_screen_coordinate = 1.0 ;
6068};
6169
6270static constexpr char kDefaultWindowTitle [] = " Flutter"
@@ -67,41 +75,78 @@ static FlutterEmbedderState *GetSavedEmbedderState(GLFWwindow *window) {
6775 glfwGetWindowUserPointer (window));
6876}
6977
78+ // Returns the number of screen coordinates per inch for the main monitor.
79+ // If the information is unavailable, returns a default value that assumes
80+ // that a screen coordinate is one dp.
81+ static double GetScreenCoordinatesPerInch () {
82+ auto *primary_monitor = glfwGetPrimaryMonitor ();
83+ auto *primary_monitor_mode = glfwGetVideoMode (primary_monitor);
84+ int primary_monitor_width_mm;
85+ glfwGetMonitorPhysicalSize (primary_monitor, &primary_monitor_width_mm,
86+ nullptr );
87+ if (primary_monitor_width_mm == 0 ) {
88+ return kDpPerInch ;
89+ }
90+ return primary_monitor_mode->width / (primary_monitor_width_mm / 25.4 );
91+ }
92+
93+ // When GLFW calls back to the window with a framebuffer size change, notify
94+ // FlutterEngine about the new window metrics.
95+ // The Flutter pixel_ratio is defined as DPI/dp.
96+ static void GLFWFramebufferSizeCallback (GLFWwindow *window, int width_px,
97+ int height_px) {
98+ int width;
99+ glfwGetWindowSize (window, &width, nullptr );
100+
101+ auto state = GetSavedEmbedderState (window);
102+ state->window_pixels_per_screen_coordinate = width_px / width;
103+
104+ double dpi = state->window_pixels_per_screen_coordinate *
105+ state->monitor_screen_coordinates_per_inch ;
106+
107+ FlutterWindowMetricsEvent event = {};
108+ event.struct_size = sizeof (event);
109+ event.width = width_px;
110+ event.height = height_px;
111+ event.pixel_ratio = dpi / kDpPerInch ;
112+ FlutterEngineSendWindowMetricsEvent (state->engine , &event);
113+ }
114+
70115// When GLFW calls back to the window with a cursor position move, forwards to
71116// FlutterEngine as a pointer event with appropriate phase.
72- static void GLFWcursorPositionCallbackAtPhase (GLFWwindow *window,
117+ static void GLFWCursorPositionCallbackAtPhase (GLFWwindow *window,
73118 FlutterPointerPhase phase,
74119 double x, double y) {
120+ auto state = GetSavedEmbedderState (window);
75121 FlutterPointerEvent event = {};
76122 event.struct_size = sizeof (event);
77123 event.phase = phase;
78- event.x = x;
79- event.y = y;
124+ event.x = x * state-> window_pixels_per_screen_coordinate ;
125+ event.y = y * state-> window_pixels_per_screen_coordinate ;
80126 event.timestamp =
81127 std::chrono::duration_cast<std::chrono::microseconds>(
82128 std::chrono::high_resolution_clock::now ().time_since_epoch ())
83129 .count ();
84- FlutterEngineSendPointerEvent (GetSavedEmbedderState (window)->engine , &event,
85- 1 );
130+ FlutterEngineSendPointerEvent (state->engine , &event, 1 );
86131}
87132
88133// Reports cursor move to the Flutter engine.
89- static void GLFWcursorPositionCallback (GLFWwindow *window, double x, double y) {
90- GLFWcursorPositionCallbackAtPhase (window, FlutterPointerPhase::kMove , x, y);
134+ static void GLFWCursorPositionCallback (GLFWwindow *window, double x, double y) {
135+ GLFWCursorPositionCallbackAtPhase (window, FlutterPointerPhase::kMove , x, y);
91136}
92137
93138// Reports mouse button press to the Flutter engine.
94- static void GLFWmouseButtonCallback (GLFWwindow *window, int key, int action,
139+ static void GLFWMouseButtonCallback (GLFWwindow *window, int key, int action,
95140 int mods) {
96141 double x, y;
97142 if (key == GLFW_MOUSE_BUTTON_1 && action == GLFW_PRESS) {
98143 glfwGetCursorPos (window, &x, &y);
99- GLFWcursorPositionCallbackAtPhase (window, FlutterPointerPhase::kDown , x, y);
100- glfwSetCursorPosCallback (window, GLFWcursorPositionCallback );
144+ GLFWCursorPositionCallbackAtPhase (window, FlutterPointerPhase::kDown , x, y);
145+ glfwSetCursorPosCallback (window, GLFWCursorPositionCallback );
101146 }
102147 if (key == GLFW_MOUSE_BUTTON_1 && action == GLFW_RELEASE) {
103148 glfwGetCursorPos (window, &x, &y);
104- GLFWcursorPositionCallbackAtPhase (window, FlutterPointerPhase::kUp , x, y);
149+ GLFWCursorPositionCallbackAtPhase (window, FlutterPointerPhase::kUp , x, y);
105150 glfwSetCursorPosCallback (window, nullptr );
106151 }
107152}
@@ -123,24 +168,12 @@ static void GLFWKeyCallback(GLFWwindow *window, int key, int scancode,
123168 }
124169}
125170
126- // Reports window size changes to the Flutter engine.
127- static void GLFWwindowSizeCallback (GLFWwindow *window, int width, int height) {
128- FlutterWindowMetricsEvent event = {};
129- event.struct_size = sizeof (event);
130- event.width = width;
131- event.height = height;
132- // TODO: Handle pixel ratio for different DPI monitors.
133- event.pixel_ratio = 1.0 ;
134- FlutterEngineSendWindowMetricsEvent (GetSavedEmbedderState (window)->engine ,
135- &event);
136- }
137-
138171// Flushes event queue and then assigns default window callbacks.
139172static void GLFWAssignEventCallbacks (GLFWwindow *window) {
140173 glfwPollEvents ();
141174 glfwSetKeyCallback (window, GLFWKeyCallback);
142175 glfwSetCharCallback (window, GLFWCharCallback);
143- glfwSetMouseButtonCallback (window, GLFWmouseButtonCallback );
176+ glfwSetMouseButtonCallback (window, GLFWMouseButtonCallback );
144177}
145178
146179// Clears default window events.
@@ -311,10 +344,12 @@ GLFWwindow *CreateFlutterWindow(size_t initial_width, size_t initial_height,
311344
312345 AddPlugin (window, std::move (input_plugin));
313346
314- int width, height;
315- glfwGetWindowSize (window, &width, &height);
316- GLFWwindowSizeCallback (window, width, height);
317- glfwSetWindowSizeCallback (window, GLFWwindowSizeCallback);
347+ state->monitor_screen_coordinates_per_inch = GetScreenCoordinatesPerInch ();
348+ int width_px, height_px;
349+ glfwGetFramebufferSize (window, &width_px, &height_px);
350+ glfwSetFramebufferSizeCallback (window, GLFWFramebufferSizeCallback);
351+ GLFWFramebufferSizeCallback (window, width_px, height_px);
352+
318353 GLFWAssignEventCallbacks (window);
319354 return window;
320355}
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