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/input_manager.c

@@ -7,33 +7,6 @@
 #include "util/lock.h"
 #include "util/log.h"
 
-// Convert window coordinates (as provided by SDL_GetMouseState() to renderer
-// coordinates (as provided in SDL mouse events)
-//
-// See my question:
-// <https://stackoverflow.com/questions/49111054/how-to-get-mouse-position-on-mouse-wheel-event>
-static void
-convert_to_renderer_coordinates(SDL_Renderer *renderer, int *x, int *y) {
-    SDL_Rect viewport;
-    float scale_x, scale_y;
-    SDL_RenderGetViewport(renderer, &viewport);
-    SDL_RenderGetScale(renderer, &scale_x, &scale_y);
-    *x = (int) (*x / scale_x) - viewport.x;
-    *y = (int) (*y / scale_y) - viewport.y;
-}
-
-static struct point
-get_mouse_point(struct screen *screen) {
-    int x;
-    int y;
-    SDL_GetMouseState(&x, &y);
-    convert_to_renderer_coordinates(screen->renderer, &x, &y);
-    return (struct point) {
-        .x = x,
-        .y = y,
-    };
-}
-
 static const int ACTION_DOWN = 1;
 static const int ACTION_UP = 1 << 1;
 
@@ -487,11 +460,17 @@ convert_touch(const SDL_TouchFingerEvent *from, struct screen *screen,
 
     to->inject_touch_event.pointer_id = from->fingerId;
     to->inject_touch_event.position.screen_size = screen->frame_size;
+
+    int ww;
+    int wh;
+    SDL_GL_GetDrawableSize(screen->window, &ww, &wh);
+
     // SDL touch event coordinates are normalized in the range [0; 1]
-    float x = from->x * screen->content_size.width;
-    float y = from->y * screen->content_size.height;
+    int32_t x = from->x * ww;
+    int32_t y = from->y * wh;
     to->inject_touch_event.position.point =
         screen_convert_to_frame_coords(screen, x, y);
+
     to->inject_touch_event.pressure = from->pressure;
     to->inject_touch_event.buttons = 0;
     return true;
@@ -508,13 +487,6 @@ input_manager_process_touch(struct input_manager *im,
     }
 }
 
-static bool
-is_outside_device_screen(struct input_manager *im, int x, int y)
-{
-    return x < 0 || x >= im->screen->content_size.width ||
-           y < 0 || y >= im->screen->content_size.height;
-}
-
 static bool
 convert_mouse_button(const SDL_MouseButtonEvent *from, struct screen *screen,
                      struct control_msg *to) {
@@ -552,10 +524,15 @@ input_manager_process_mouse_button(struct input_manager *im,
             action_home(im->controller, ACTION_DOWN | ACTION_UP);
             return;
         }
+
         // double-click on black borders resize to fit the device screen
         if (event->button == SDL_BUTTON_LEFT && event->clicks == 2) {
-            bool outside =
-                is_outside_device_screen(im, event->x, event->y);
+            int32_t x = event->x;
+            int32_t y = event->y;
+            screen_hidpi_scale_coords(im->screen, &x, &y);
+            SDL_Rect *r = &im->screen->rect;
+            bool outside = x < r->x || x >= r->x + r->w
+                        || y < r->y || y >= r->y + r->h;
             if (outside) {
                 screen_resize_to_fit(im->screen);
                 return;
@@ -579,9 +556,15 @@ input_manager_process_mouse_button(struct input_manager *im,
 static bool
 convert_mouse_wheel(const SDL_MouseWheelEvent *from, struct screen *screen,
                     struct control_msg *to) {
+
+    // mouse_x and mouse_y are expressed in pixels relative to the window
+    int mouse_x;
+    int mouse_y;
+    SDL_GetMouseState(&mouse_x, &mouse_y);
+
     struct position position = {
         .screen_size = screen->frame_size,
-        .point = get_mouse_point(screen),
+        .point = screen_convert_to_frame_coords(screen, mouse_x, mouse_y),
     };
 
     to->type = CONTROL_MSG_TYPE_INJECT_SCROLL_EVENT;

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

@@ -30,10 +30,10 @@ get_rotated_size(struct size size, int rotation) {
 
 // get the window size in a struct size
 static struct size
-get_window_size(SDL_Window *window) {
+get_window_size(const struct screen *screen) {
     int width;
     int height;
-    SDL_GetWindowSize(window, &width, &height);
+    SDL_GetWindowSize(screen->window, &width, &height);
 
     struct size size;
     size.width = width;
@@ -41,31 +41,12 @@ get_window_size(SDL_Window *window) {
     return size;
 }
 
-// get the windowed window size
-static struct size
-get_windowed_window_size(const struct screen *screen) {
-    if (screen->fullscreen || screen->maximized) {
-        return screen->windowed_window_size;
-    }
-    return get_window_size(screen->window);
-}
-
-// apply the windowed window size if fullscreen and maximized are disabled
-static void
-apply_windowed_size(struct screen *screen) {
-    if (!screen->fullscreen && !screen->maximized) {
-        SDL_SetWindowSize(screen->window, screen->windowed_window_size.width,
-                                          screen->windowed_window_size.height);
-    }
-}
-
 // set the window size to be applied when fullscreen is disabled
 static void
 set_window_size(struct screen *screen, struct size new_size) {
-    // setting the window size during fullscreen is implementation defined,
-    // so apply the resize only after fullscreen is disabled
-    screen->windowed_window_size = new_size;
-    apply_windowed_size(screen);
+    assert(!screen->fullscreen);
+    assert(!screen->maximized);
+    SDL_SetWindowSize(screen->window, new_size.width, new_size.height);
 }
 
 // get the preferred display bounds (i.e. the screen bounds with some margins)
@@ -87,6 +68,16 @@ get_preferred_display_bounds(struct size *bounds) {
     return true;
 }
 
+static bool
+is_optimal_size(struct size current_size, struct size content_size) {
+    // The size is optimal if we can recompute one dimension of the current
+    // size from the other
+    return current_size.height == current_size.width * content_size.height
+                                                     / content_size.width
+        || current_size.width == current_size.height * content_size.width
+                                                     / content_size.height;
+}
+
 // return the optimal size of the window, with the following constraints:
 //  - it attempts to keep at least one dimension of the current_size (i.e. it
 //    crops the black borders)
@@ -99,47 +90,43 @@ get_optimal_size(struct size current_size, struct size content_size) {
         return current_size;
     }
 
-    struct size display_size;
-    // 32 bits because we need to multiply two 16 bits values
-    uint32_t w;
-    uint32_t h;
+    struct size window_size;
 
+    struct size display_size;
     if (!get_preferred_display_bounds(&display_size)) {
         // could not get display bounds, do not constraint the size
-        w = current_size.width;
-        h = current_size.height;
+        window_size.width = current_size.width;
+        window_size.height = current_size.height;
     } else {
-        w = MIN(current_size.width, display_size.width);
-        h = MIN(current_size.height, display_size.height);
+        window_size.width = MIN(current_size.width, display_size.width);
+        window_size.height = MIN(current_size.height, display_size.height);
     }
 
-    if (h == w * content_size.height / content_size.width
-     || w == h * content_size.width / content_size.height) {
-        // The size is already optimal, if we ignore rounding errors due to
-        // integer window dimensions
-        return (struct size) {w, h};
+    if (is_optimal_size(window_size, content_size)) {
+        return window_size;
     }
 
-    bool keep_width = content_size.width * h > content_size.height * w;
+    bool keep_width = content_size.width * window_size.height
+                    > content_size.height * window_size.width;
     if (keep_width) {
         // remove black borders on top and bottom
-        h = content_size.height * w / content_size.width;
+        window_size.height = content_size.height * window_size.width
+                           / content_size.width;
     } else {
         // remove black borders on left and right (or none at all if it already
         // fits)
-        w = content_size.width * h / content_size.height;
+        window_size.width = content_size.width * window_size.height
+                          / content_size.height;
     }
 
-    // w and h must fit into 16 bits
-    assert(w < 0x10000 && h < 0x10000);
-    return (struct size) {w, h};
+    return window_size;
 }
 
 // same as get_optimal_size(), but read the current size from the window
 static inline struct size
 get_optimal_window_size(const struct screen *screen, struct size content_size) {
-    struct size windowed_size = get_windowed_window_size(screen);
-    return get_optimal_size(windowed_size, content_size);
+    struct size window_size = get_window_size(screen);
+    return get_optimal_size(window_size, content_size);
 }
 
 // initially, there is no current size, so use the frame size as current size
@@ -169,6 +156,43 @@ get_initial_optimal_size(struct size content_size, uint16_t req_width,
     return window_size;
 }
 
+static void
+screen_update_content_rect(struct screen *screen) {
+    int dw;
+    int dh;
+    SDL_GL_GetDrawableSize(screen->window, &dw, &dh);
+
+    struct size content_size = screen->content_size;
+    // The drawable size is the window size * the HiDPI scale
+    struct size drawable_size = {dw, dh};
+
+    SDL_Rect *rect = &screen->rect;
+
+    if (is_optimal_size(drawable_size, content_size)) {
+        rect->x = 0;
+        rect->y = 0;
+        rect->w = drawable_size.width;
+        rect->h = drawable_size.height;
+        return;
+    }
+
+    bool keep_width = content_size.width * drawable_size.height
+                    > content_size.height * drawable_size.width;
+    if (keep_width) {
+        rect->x = 0;
+        rect->w = drawable_size.width;
+        rect->h = drawable_size.width * content_size.height
+                                      / content_size.width;
+        rect->y = (drawable_size.height - rect->h) / 2;
+    } else {
+        rect->y = 0;
+        rect->h = drawable_size.height;
+        rect->w = drawable_size.height * content_size.width
+                                       / content_size.height;
+        rect->x = (drawable_size.width - rect->w) / 2;
+    }
+}
+
 void
 screen_init(struct screen *screen) {
     *screen = (struct screen) SCREEN_INITIALIZER;
@@ -258,13 +282,6 @@ screen_init_rendering(struct screen *screen, const char *window_title,
     const char *renderer_name = r ? NULL : renderer_info.name;
     LOGI("Renderer: %s", renderer_name ? renderer_name : "(unknown)");
 
-    if (SDL_RenderSetLogicalSize(screen->renderer, content_size.width,
-                                 content_size.height)) {
-        LOGE("Could not set renderer logical size: %s", SDL_GetError());
-        screen_destroy(screen);
-        return false;
-    }
-
     // starts with "opengl"
     screen->use_opengl = renderer_name && !strncmp(renderer_name, "opengl", 6);
     if (screen->use_opengl) {
@@ -308,7 +325,12 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         return false;
     }
 
-    screen->windowed_window_size = window_size;
+    // 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;
 }
@@ -331,6 +353,45 @@ screen_destroy(struct screen *screen) {
     }
 }
 
+static void
+resize_for_content(struct screen *screen, struct size old_content_size,
+                                                 struct size new_content_size) {
+    struct size window_size = get_window_size(screen);
+    struct size target_size = {
+        .width = (uint32_t) window_size.width * new_content_size.width
+                / old_content_size.width,
+        .height = (uint32_t) window_size.height * new_content_size.height
+                / old_content_size.height,
+    };
+    target_size = get_optimal_size(target_size, new_content_size);
+    set_window_size(screen, target_size);
+}
+
+static void
+set_content_size(struct screen *screen, struct size new_content_size) {
+    if (!screen->fullscreen && !screen->maximized) {
+        resize_for_content(screen, screen->content_size, new_content_size);
+    } else if (!screen->resize_pending) {
+        // Store the windowed size to be able to compute the optimal size once
+        // fullscreen and maximized are disabled
+        screen->windowed_content_size = screen->content_size;
+        screen->resize_pending = true;
+    }
+
+    screen->content_size = new_content_size;
+}
+
+static void
+apply_pending_resize(struct screen *screen) {
+    assert(!screen->fullscreen);
+    assert(!screen->maximized);
+    if (screen->resize_pending) {
+        resize_for_content(screen, screen->windowed_content_size,
+                                   screen->content_size);
+        screen->resize_pending = false;
+    }
+}
+
 void
 screen_set_rotation(struct screen *screen, unsigned rotation) {
     assert(rotation < 4);
@@ -338,32 +399,15 @@ screen_set_rotation(struct screen *screen, unsigned rotation) {
         return;
     }
 
-    struct size old_content_size = screen->content_size;
     struct size new_content_size =
         get_rotated_size(screen->frame_size, rotation);
 
-    if (SDL_RenderSetLogicalSize(screen->renderer,
-                                 new_content_size.width,
-                                 new_content_size.height)) {
-        LOGE("Could not set renderer logical size: %s", SDL_GetError());
-        return;
-    }
+    set_content_size(screen, new_content_size);
 
-    struct size windowed_size = get_windowed_window_size(screen);
-    struct size target_size = {
-        .width = (uint32_t) windowed_size.width * new_content_size.width
-                / old_content_size.width,
-        .height = (uint32_t) windowed_size.height * new_content_size.height
-                / old_content_size.height,
-    };
-    target_size = get_optimal_size(target_size, new_content_size);
-    set_window_size(screen, target_size);
-
-    screen->content_size = new_content_size;
     screen->rotation = rotation;
     LOGI("Display rotation set to %u", rotation);
 
-    screen_render(screen);
+    screen_render(screen, true);
 }
 
 // recreate the texture and resize the window if the frame size has changed
@@ -371,31 +415,16 @@ static bool
 prepare_for_frame(struct screen *screen, struct size new_frame_size) {
     if (screen->frame_size.width != new_frame_size.width
             || screen->frame_size.height != new_frame_size.height) {
-        struct size new_content_size =
-            get_rotated_size(new_frame_size, screen->rotation);
-        if (SDL_RenderSetLogicalSize(screen->renderer,
-                                     new_content_size.width,
-                                     new_content_size.height)) {
-            LOGE("Could not set renderer logical size: %s", SDL_GetError());
-            return false;
-        }
-
         // frame dimension changed, destroy texture
         SDL_DestroyTexture(screen->texture);
 
-        struct size content_size = screen->content_size;
-        struct size windowed_size = get_windowed_window_size(screen);
-        struct size target_size = {
-            (uint32_t) windowed_size.width * new_content_size.width
-                    / content_size.width,
-            (uint32_t) windowed_size.height * new_content_size.height
-                    / content_size.height,
-        };
-        target_size = get_optimal_size(target_size, new_content_size);
-        set_window_size(screen, target_size);
-
         screen->frame_size = new_frame_size;
-        screen->content_size = new_content_size;
+
+        struct size new_content_size =
+            get_rotated_size(new_frame_size, screen->rotation);
+        set_content_size(screen, new_content_size);
+
+        screen_update_content_rect(screen);
 
         LOGI("New texture: %" PRIu16 "x%" PRIu16,
                      screen->frame_size.width, screen->frame_size.height);
@@ -437,15 +466,19 @@ 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, NULL);
+        SDL_RenderCopy(screen->renderer, screen->texture, NULL, &screen->rect);
     } else {
         // rotation in RenderCopyEx() is clockwise, while screen->rotation is
         // counterclockwise (to be consistent with --lock-video-orientation)
@@ -455,12 +488,14 @@ screen_render(struct screen *screen) {
         SDL_Rect *dstrect = NULL;
         SDL_Rect rect;
         if (screen->rotation & 1) {
-            struct size size = screen->content_size;
-            rect.x = (size.width - size.height) / 2;
-            rect.y = (size.height - size.width) / 2;
-            rect.w = size.height;
-            rect.h = size.width;
+            rect.x = screen->rect.x + (screen->rect.w - screen->rect.h) / 2;
+            rect.y = screen->rect.y + (screen->rect.h - screen->rect.w) / 2;
+            rect.w = screen->rect.h;
+            rect.h = screen->rect.w;
             dstrect = &rect;
+        } else {
+            assert(screen->rotation == 2);
+            dstrect = &screen->rect;
         }
 
         SDL_RenderCopyEx(screen->renderer, screen->texture, NULL, dstrect,
@@ -478,23 +513,20 @@ screen_switch_fullscreen(struct screen *screen) {
     }
 
     screen->fullscreen = !screen->fullscreen;
-    apply_windowed_size(screen);
+    if (!screen->fullscreen && !screen->maximized) {
+        apply_pending_resize(screen);
+    }
 
     LOGD("Switched to %s mode", screen->fullscreen ? "fullscreen" : "windowed");
-    screen_render(screen);
+    screen_render(screen, true);
 }
 
 void
 screen_resize_to_fit(struct screen *screen) {
-    if (screen->fullscreen) {
+    if (screen->fullscreen || screen->maximized) {
         return;
     }
 
-    if (screen->maximized) {
-        SDL_RestoreWindow(screen->window);
-        screen->maximized = false;
-    }
-
     struct size optimal_size =
         get_optimal_window_size(screen, screen->content_size);
     SDL_SetWindowSize(screen->window, optimal_size.width, optimal_size.height);
@@ -524,39 +556,24 @@ screen_handle_window_event(struct screen *screen,
                            const SDL_WindowEvent *event) {
     switch (event->event) {
         case SDL_WINDOWEVENT_EXPOSED:
-            screen_render(screen);
+            screen_render(screen, true);
             break;
         case SDL_WINDOWEVENT_SIZE_CHANGED:
-            if (!screen->fullscreen && !screen->maximized) {
-                // Backup the previous size: if we receive the MAXIMIZED event,
-                // then the new size must be ignored (it's the maximized size).
-                // We could not rely on the window flags due to race conditions
-                // (they could be updated asynchronously, at least on X11).
-                screen->windowed_window_size_backup =
-                    screen->windowed_window_size;
-
-                // Save the windowed size, so that it is available once the
-                // window is maximized or fullscreen is enabled.
-                screen->windowed_window_size = get_window_size(screen->window);
-            }
-            screen_render(screen);
+            screen_render(screen, true);
             break;
         case SDL_WINDOWEVENT_MAXIMIZED:
-            // The backup size must be non-nul.
-            assert(screen->windowed_window_size_backup.width);
-            assert(screen->windowed_window_size_backup.height);
-            // Revert the last size, it was updated while screen was maximized.
-            screen->windowed_window_size = screen->windowed_window_size_backup;
-#ifdef DEBUG
-            // Reset the backup to invalid values to detect unexpected usage
-            screen->windowed_window_size_backup.width = 0;
-            screen->windowed_window_size_backup.height = 0;
-#endif
             screen->maximized = true;
             break;
         case SDL_WINDOWEVENT_RESTORED:
+            if (screen->fullscreen) {
+                // On Windows, in maximized+fullscreen, disabling fullscreen
+                // mode unexpectedly triggers the "restored" then "maximized"
+                // events, leaving the window in a weird state (maximized
+                // according to the events, but not maximized visually).
+                break;
+            }
             screen->maximized = false;
-            apply_windowed_size(screen);
+            apply_pending_resize(screen);
             break;
     }
 }
@@ -568,6 +585,13 @@ screen_convert_to_frame_coords(struct screen *screen, int32_t x, int32_t y) {
 
     int32_t w = screen->content_size.width;
     int32_t h = screen->content_size.height;
+
+    screen_hidpi_scale_coords(screen, &x, &y);
+
+    x = (int64_t) (x - screen->rect.x) * w / screen->rect.w;
+    y = (int64_t) (y - screen->rect.y) * h / screen->rect.h;
+
+    // rotate
     struct point result;
     switch (rotation) {
         case 0:
@@ -590,3 +614,15 @@ screen_convert_to_frame_coords(struct screen *screen, int32_t x, int32_t y) {
     }
     return result;
 }
+
+void
+screen_hidpi_scale_coords(struct screen *screen, int32_t *x, int32_t *y) {
+    // take the HiDPI scaling (dw/ww and dh/wh) into account
+    int ww, wh, dw, dh;
+    SDL_GetWindowSize(screen->window, &ww, &wh);
+    SDL_GL_GetDrawableSize(screen->window, &dw, &dh);
+
+    // scale for HiDPI (64 bits for intermediate multiplications)
+    *x = (int64_t) *x * dw / ww;
+    *y = (int64_t) *y * dh / wh;
+}

app/src/screen.h

@@ -21,13 +21,16 @@ struct screen {
     struct sc_opengl gl;
     struct size frame_size;
     struct size content_size; // rotated frame_size
-    // The window size the last time it was not maximized or fullscreen.
-    struct size windowed_window_size;
-    // Since we receive the event SIZE_CHANGED before MAXIMIZED, we must be
-    // able to revert the size to its non-maximized value.
-    struct size windowed_window_size_backup;
+
+    bool resize_pending; // resize requested while fullscreen or maximized
+    // The content size the last time the window was not maximized or
+    // fullscreen (meaningful only when resize_pending is true)
+    struct size windowed_content_size;
+
     // client rotation: 0, 1, 2 or 3 (x90 degrees counterclockwise)
     unsigned rotation;
+    // rectangle of the content (excluding black borders)
+    struct SDL_Rect rect;
     bool has_frame;
     bool fullscreen;
     bool maximized;
@@ -49,15 +52,18 @@ struct screen {
         .width = 0, \
         .height = 0, \
     }, \
-    .windowed_window_size = { \
-        .width = 0, \
-        .height = 0, \
-    }, \
-    .windowed_window_size_backup = { \
+    .resize_pending = false, \
+    .windowed_content_size = { \
         .width = 0, \
         .height = 0, \
     }, \
     .rotation = 0, \
+    .rect = { \
+        .x = 0, \
+        .y = 0, \
+        .w = 0, \
+        .h = 0, \
+    }, \
     .has_frame = false, \
     .fullscreen = false, \
     .maximized = false, \
@@ -91,8 +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
@@ -119,4 +128,11 @@ screen_handle_window_event(struct screen *screen, const SDL_WindowEvent *event);
 struct point
 screen_convert_to_frame_coords(struct screen *screen, int32_t x, int32_t y);
 
+// Convert coordinates from window to drawable.
+// Events are expressed in window coordinates, but content is expressed in
+// drawable coordinates. They are the same if HiDPI scaling is 1, but differ
+// otherwise.
+void
+screen_hidpi_scale_coords(struct screen *screen, int32_t *x, int32_t *y);
+
 #endif