fix issue 15?

The window dimensions are integers, so resizing to fit the content may
not be exact.

When computing the optimal size, it could cause to reduce alternatively
the width and height by few pixels, making the "optimal size" unstable.

To avoid this problem, check if the optimal size is already correct
either by keeping the width or the height.

app/src/input_manager.c

@@ -442,36 +442,6 @@ input_manager_process_key(struct input_manager *im,
     }
 }
 
-static struct point
-rotate_position(struct screen *screen, int32_t x, int32_t y) {
-    unsigned rotation = screen->rotation;
-    assert(rotation < 4);
-
-    int32_t w = screen->content_size.width;
-    int32_t h = screen->content_size.height;
-    struct point result;
-    switch (rotation) {
-        case 0:
-            result.x = x;
-            result.y = y;
-            break;
-        case 1:
-            result.x = h - y;
-            result.y = x;
-            break;
-        case 2:
-            result.x = w - x;
-            result.y = h - y;
-            break;
-        default:
-            assert(rotation == 3);
-            result.x = y;
-            result.y = w - x;
-            break;
-    }
-    return result;
-}
-
 static bool
 convert_mouse_motion(const SDL_MouseMotionEvent *from, struct screen *screen,
                      struct control_msg *to) {
@@ -480,7 +450,7 @@ convert_mouse_motion(const SDL_MouseMotionEvent *from, struct screen *screen,
     to->inject_touch_event.pointer_id = POINTER_ID_MOUSE;
     to->inject_touch_event.position.screen_size = screen->frame_size;
     to->inject_touch_event.position.point =
-        rotate_position(screen, from->x, from->y);
+        screen_convert_to_frame_coords(screen, from->x, from->y);
     to->inject_touch_event.pressure = 1.f;
     to->inject_touch_event.buttons = convert_mouse_buttons(from->state);
 
@@ -515,14 +485,13 @@ convert_touch(const SDL_TouchFingerEvent *from, struct screen *screen,
         return false;
     }
 
-    struct size frame_size = screen->frame_size;
-
     to->inject_touch_event.pointer_id = from->fingerId;
-    to->inject_touch_event.position.screen_size = frame_size;
+    to->inject_touch_event.position.screen_size = screen->frame_size;
     // SDL touch event coordinates are normalized in the range [0; 1]
-    float x = from->x * frame_size.width;
-    float y = from->y * frame_size.height;
-    to->inject_touch_event.position.point = rotate_position(screen, x, y);
+    float x = from->x * screen->content_size.width;
+    float y = from->y * screen->content_size.height;
+    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;
@@ -558,7 +527,7 @@ convert_mouse_button(const SDL_MouseButtonEvent *from, struct screen *screen,
     to->inject_touch_event.pointer_id = POINTER_ID_MOUSE;
     to->inject_touch_event.position.screen_size = screen->frame_size;
     to->inject_touch_event.position.point =
-        rotate_position(screen, from->x, from->y);
+        screen_convert_to_frame_coords(screen, from->x, from->y);
     to->inject_touch_event.pressure = 1.f;
     to->inject_touch_event.buttons =
         convert_mouse_buttons(SDL_BUTTON(from->button));

app/src/scrcpy.c

@@ -109,9 +109,10 @@ static int
 event_watcher(void *data, SDL_Event *event) {
     (void) data;
     if (event->type == SDL_WINDOWEVENT
-            && event->window.event == SDL_WINDOWEVENT_RESIZED) {
-        // called from another thread, not very safe, but it's a workaround!
-        screen_render(&screen);
+            && event->window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
+        // In practice, it seems to always be called from the same thread in
+        // that specific case. Anyway, it's just a workaround.
+        screen_handle_window_event(&screen, &event->window);
     }
     return 0;
 }

app/src/screen.c

@@ -113,6 +113,13 @@ get_optimal_size(struct size current_size, struct size content_size) {
         h = 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};
+    }
+
     bool keep_width = content_size.width * h > content_size.height * w;
     if (keep_width) {
         // remove black borders on top and bottom
@@ -491,7 +498,8 @@ screen_resize_to_fit(struct screen *screen) {
     struct size optimal_size =
         get_optimal_window_size(screen, screen->content_size);
     SDL_SetWindowSize(screen->window, optimal_size.width, optimal_size.height);
-    LOGD("Resized to optimal size");
+    LOGD("Resized to optimal size: %ux%u", optimal_size.width,
+                                           optimal_size.height);
 }
 
 void
@@ -507,7 +515,17 @@ screen_resize_to_pixel_perfect(struct screen *screen) {
 
     struct size content_size = screen->content_size;
     SDL_SetWindowSize(screen->window, content_size.width, content_size.height);
-    LOGD("Resized to pixel-perfect");
+    LOGD("Resized to pixel-perfect: %ux%u", content_size.width,
+                                            content_size.height);
+}
+
+static void
+screen_reset_logical_size(struct screen *screen) {
+    // Re-apply the current logical size.
+    if (SDL_RenderSetLogicalSize(screen->renderer, screen->content_size.width,
+                                 screen->content_size.height)) {
+        LOGE("Could not reset renderer logical size: %s", SDL_GetError());
+    }
 }
 
 void
@@ -515,6 +533,10 @@ screen_handle_window_event(struct screen *screen,
                            const SDL_WindowEvent *event) {
     switch (event->event) {
         case SDL_WINDOWEVENT_EXPOSED:
+            // Re-apply the current logical size, in case the window has been
+            // moved to a screen with a different HiDPI scaling
+            // <https://github.com/Genymobile/scrcpy/issues/15>
+            screen_reset_logical_size(screen);
             screen_render(screen);
             break;
         case SDL_WINDOWEVENT_SIZE_CHANGED:
@@ -551,3 +573,33 @@ screen_handle_window_event(struct screen *screen,
             break;
     }
 }
+
+struct point
+screen_convert_to_frame_coords(struct screen *screen, int32_t x, int32_t y) {
+    unsigned rotation = screen->rotation;
+    assert(rotation < 4);
+
+    int32_t w = screen->content_size.width;
+    int32_t h = screen->content_size.height;
+    struct point result;
+    switch (rotation) {
+        case 0:
+            result.x = x;
+            result.y = y;
+            break;
+        case 1:
+            result.x = h - y;
+            result.y = x;
+            break;
+        case 2:
+            result.x = w - x;
+            result.y = h - y;
+            break;
+        default:
+            assert(rotation == 3);
+            result.x = y;
+            result.y = w - x;
+            break;
+    }
+    return result;
+}

app/src/screen.h

@@ -114,4 +114,9 @@ screen_set_rotation(struct screen *screen, unsigned rotation);
 void
 screen_handle_window_event(struct screen *screen, const SDL_WindowEvent *event);
 
+// convert point from window coordinates to frame coordinates
+// x and y are expressed in pixels
+struct point
+screen_convert_to_frame_coords(struct screen *screen, int32_t x, int32_t y);
+
 #endif

server/src/main/java/com/genymobile/scrcpy/Device.java

@@ -36,10 +36,7 @@ public final class Device {
      */
     private final int layerStack;
 
-    /**
-     * The FLAG_PRESENTATION from the DisplayInfo
-     */
-    private final boolean isPresentationDisplay;
+    private final boolean supportsInputEvents;
 
     public Device(Options options) {
         displayId = options.getDisplayId();
@@ -53,7 +50,6 @@ public final class Device {
 
         screenInfo = ScreenInfo.computeScreenInfo(displayInfo, options.getCrop(), options.getMaxSize(), options.getLockedVideoOrientation());
         layerStack = displayInfo.getLayerStack();
-        isPresentationDisplay = (displayInfoFlags & DisplayInfo.FLAG_PRESENTATION) != 0;
 
         registerRotationWatcher(new IRotationWatcher.Stub() {
             @Override
@@ -73,8 +69,10 @@ public final class Device {
             Ln.w("Display doesn't have FLAG_SUPPORTS_PROTECTED_BUFFERS flag, mirroring can be restricted");
         }
 
-        if (!supportsInputEvents()) {
-            Ln.w("Input events are not supported for displays with FLAG_PRESENTATION enabled for devices with API lower than 29");
+        // main display or any display on Android >= Q
+        supportsInputEvents = displayId == 0 || Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q;
+        if (!supportsInputEvents) {
+            Ln.w("Input events are not supported for secondary displays before Android 10");
         }
     }
 
@@ -116,10 +114,7 @@ public final class Device {
     }
 
     public boolean supportsInputEvents() {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-            return true;
-        }
-        return !isPresentationDisplay;
+        return supportsInputEvents;
     }
 
     public boolean injectInputEvent(InputEvent inputEvent, int mode) {

server/src/main/java/com/genymobile/scrcpy/DisplayInfo.java

@@ -8,7 +8,6 @@ public final class DisplayInfo {
     private final int flags;
 
     public static final int FLAG_SUPPORTS_PROTECTED_BUFFERS = 0x00000001;
-    public static final int FLAG_PRESENTATION = 0x00000008;
 
     public DisplayInfo(int displayId, Size size, int rotation, int layerStack, int flags) {
         this.displayId = displayId;

server/src/main/java/com/genymobile/scrcpy/ScreenEncoder.java

@@ -136,12 +136,12 @@ public class ScreenEncoder implements Device.RotationListener {
     }
 
     private static MediaCodec createCodec() throws IOException {
-        return MediaCodec.createEncoderByType("video/avc");
+        return MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_VIDEO_AVC);
     }
 
     private static MediaFormat createFormat(int bitRate, int maxFps, int iFrameInterval) {
         MediaFormat format = new MediaFormat();
-        format.setString(MediaFormat.KEY_MIME, "video/avc");
+        format.setString(MediaFormat.KEY_MIME, MediaFormat.MIMETYPE_VIDEO_AVC);
         format.setInteger(MediaFormat.KEY_BIT_RATE, bitRate);
         // must be present to configure the encoder, but does not impact the actual frame rate, which is variable
         format.setInteger(MediaFormat.KEY_FRAME_RATE, 60);

server/src/main/java/com/genymobile/scrcpy/wrappers/InputManager.java

@@ -53,8 +53,7 @@ public final class InputManager {
             method.invoke(inputEvent, displayId);
             return true;
         } catch (InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
-            // just a warning, it might happen on old devices
-            Ln.w("Cannot associate a display id to the input event");
+            Ln.e("Cannot associate a display id to the input event", e);
             return false;
         }
     }