Reset window size on initialization

On macOS with renderer "metal", HiDPI scaling may be incorrect on
initialization when several displays are connected.

Resetting the window size fixes the problem.

Refs #15 <https://github.com/Genymobile/scrcpy/issues/15>

app/src/scrcpy.c

@@ -136,7 +136,7 @@ event_watcher(void *data, SDL_Event *event) {
             && event->window.event == SDL_WINDOWEVENT_RESIZED) {
         // In practice, it seems to always be called from the same thread in
         // that specific case. Anyway, it's just a workaround.
-        screen_render(&screen);
+        screen_render(&screen, true);
     }
     return 0;
 }

app/src/screen.c

@@ -157,7 +157,7 @@ get_initial_optimal_size(struct size content_size, uint16_t req_width,
 }
 
 static void
-update_content_rect(struct screen *screen) {
+screen_update_content_rect(struct screen *screen) {
     int dw;
     int dh;
     SDL_GL_GetDrawableSize(screen->window, &dw, &dh);
@@ -325,7 +325,12 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         return false;
     }
 
-    update_content_rect(screen);
+    // Reset the window size to trigger a SIZE_CHANGED event, to workaround
+    // HiDPI issues with some SDL renderers when several displays having
+    // different HiDPI scaling are connected
+    SDL_SetWindowSize(screen->window, window_size.width, window_size.height);
+
+    screen_update_content_rect(screen);
 
     return true;
 }
@@ -402,8 +407,7 @@ screen_set_rotation(struct screen *screen, unsigned rotation) {
     screen->rotation = rotation;
     LOGI("Display rotation set to %u", rotation);
 
-    update_content_rect(screen);
-    screen_render(screen);
+    screen_render(screen, true);
 }
 
 // recreate the texture and resize the window if the frame size has changed
@@ -420,7 +424,7 @@ prepare_for_frame(struct screen *screen, struct size new_frame_size) {
             get_rotated_size(new_frame_size, screen->rotation);
         set_content_size(screen, new_content_size);
 
-        update_content_rect(screen);
+        screen_update_content_rect(screen);
 
         LOGI("New texture: %" PRIu16 "x%" PRIu16,
                      screen->frame_size.width, screen->frame_size.height);
@@ -462,12 +466,16 @@ screen_update_frame(struct screen *screen, struct video_buffer *vb) {
     update_texture(screen, frame);
     mutex_unlock(vb->mutex);
 
-    screen_render(screen);
+    screen_render(screen, false);
     return true;
 }
 
 void
-screen_render(struct screen *screen) {
+screen_render(struct screen *screen, bool update_content_rect) {
+    if (update_content_rect) {
+        screen_update_content_rect(screen);
+    }
+
     SDL_RenderClear(screen->renderer);
     if (screen->rotation == 0) {
         SDL_RenderCopy(screen->renderer, screen->texture, NULL, &screen->rect);
@@ -510,8 +518,7 @@ screen_switch_fullscreen(struct screen *screen) {
     }
 
     LOGD("Switched to %s mode", screen->fullscreen ? "fullscreen" : "windowed");
-    update_content_rect(screen);
-    screen_render(screen);
+    screen_render(screen, true);
 }
 
 void
@@ -549,12 +556,10 @@ screen_handle_window_event(struct screen *screen,
                            const SDL_WindowEvent *event) {
     switch (event->event) {
         case SDL_WINDOWEVENT_EXPOSED:
-            update_content_rect(screen);
-            screen_render(screen);
+            screen_render(screen, true);
             break;
         case SDL_WINDOWEVENT_SIZE_CHANGED:
-            update_content_rect(screen);
-            screen_render(screen);
+            screen_render(screen, true);
             break;
         case SDL_WINDOWEVENT_MAXIMIZED:
             screen->maximized = true;

app/src/screen.h

@@ -97,8 +97,11 @@ bool
 screen_update_frame(struct screen *screen, struct video_buffer *vb);
 
 // render the texture to the renderer
+//
+// Set the update_content_rect flag if the window or content size may have
+// changed, so that the content rectangle is recomputed
 void
-screen_render(struct screen *screen);
+screen_render(struct screen *screen, bool update_content_rect);
 
 // switch the fullscreen mode
 void