Call Looper.prepareMainLooper() to avoid exception

Some devices internally create a Handler when creating an input Surface,
causing an exception:

> Surface: java.lang.RuntimeException: Can't create handler inside
> thread that has not called Looper.prepare()

As a workaround, call Looper.prepareMainLooper() beforehand.

Fixes:
 - <https://github.com/Genymobile/scrcpy/issues/240>
 - <https://github.com/Genymobile/scrcpy/issues/921>

Signed-off-by: Romain Vimont <rom@rom1v.com>

app/src/scrcpy.c

@@ -144,7 +144,12 @@ handle_event(SDL_Event *event, bool control) {
             }
             break;
         case SDL_WINDOWEVENT:
-            screen_handle_window_event(&screen, &event->window);
+            switch (event->window.event) {
+                case SDL_WINDOWEVENT_EXPOSED:
+                case SDL_WINDOWEVENT_SIZE_CHANGED:
+                    screen_render(&screen);
+                    break;
+            }
             break;
         case SDL_TEXTINPUT:
             if (!control) {
@@ -213,7 +218,6 @@ event_loop(bool display, bool control) {
             case EVENT_RESULT_STOPPED_BY_USER:
                 return true;
             case EVENT_RESULT_STOPPED_BY_EOS:
-                LOGW("Device disconnected");
                 return false;
             case EVENT_RESULT_CONTINUE:
                 break;

app/src/screen.c

@@ -30,28 +30,23 @@ get_window_size(SDL_Window *window) {
 // get the windowed window size
 static struct size
 get_windowed_window_size(const struct screen *screen) {
-    if (screen->fullscreen || screen->maximized) {
+    if (screen->fullscreen) {
         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;
+    if (screen->fullscreen) {
-    apply_windowed_size(screen);
+        // SDL_SetWindowSize will be called when fullscreen will be disabled
+        screen->windowed_window_size = new_size;
+    } else {
+        SDL_SetWindowSize(screen->window, new_size.width, new_size.height);
+    }
 }
 
 // get the preferred display bounds (i.e. the screen bounds with some margins)
@@ -199,8 +194,6 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         return false;
     }
 
-    screen->windowed_window_size = window_size;
-
     return true;
 }
 
@@ -294,6 +287,10 @@ screen_render(struct screen *screen) {
 
 void
 screen_switch_fullscreen(struct screen *screen) {
+    if (!screen->fullscreen) {
+        // going to fullscreen, store the current windowed window size
+        screen->windowed_window_size = get_window_size(screen->window);
+    }
     uint32_t new_mode = screen->fullscreen ? 0 : SDL_WINDOW_FULLSCREEN_DESKTOP;
     if (SDL_SetWindowFullscreen(screen->window, new_mode)) {
         LOGW("Could not switch fullscreen mode: %s", SDL_GetError());
@@ -301,7 +298,11 @@ screen_switch_fullscreen(struct screen *screen) {
     }
 
     screen->fullscreen = !screen->fullscreen;
-    apply_windowed_size(screen);
+    if (!screen->fullscreen) {
+        // fullscreen disabled, restore expected windowed window size
+        SDL_SetWindowSize(screen->window, screen->windowed_window_size.width,
+                          screen->windowed_window_size.height);
+    }
 
     LOGD("Switched to %s mode", screen->fullscreen ? "fullscreen" : "windowed");
     screen_render(screen);
@@ -309,75 +310,20 @@ screen_switch_fullscreen(struct screen *screen) {
 
 void
 screen_resize_to_fit(struct screen *screen) {
-    if (screen->fullscreen) {
+    if (!screen->fullscreen) {
-        return;
+        struct size optimal_size = get_optimal_window_size(screen,
+                                                           screen->frame_size);
+        SDL_SetWindowSize(screen->window, optimal_size.width,
+                          optimal_size.height);
+        LOGD("Resized to optimal size");
     }
-
-    if (screen->maximized) {
-        SDL_RestoreWindow(screen->window);
-        screen->maximized = false;
-    }
-
-    struct size optimal_size =
-        get_optimal_window_size(screen, screen->frame_size);
-    SDL_SetWindowSize(screen->window, optimal_size.width, optimal_size.height);
-    LOGD("Resized to optimal size");
 }
 
 void
 screen_resize_to_pixel_perfect(struct screen *screen) {
-    if (screen->fullscreen) {
+    if (!screen->fullscreen) {
-        return;
+        SDL_SetWindowSize(screen->window, screen->frame_size.width,
-    }
+                          screen->frame_size.height);
-
+        LOGD("Resized to pixel-perfect");
-    if (screen->maximized) {
-        SDL_RestoreWindow(screen->window);
-        screen->maximized = false;
-    }
-
-    SDL_SetWindowSize(screen->window, screen->frame_size.width,
-                      screen->frame_size.height);
-    LOGD("Resized to pixel-perfect");
-}
-
-void
-screen_handle_window_event(struct screen *screen,
-                           const SDL_WindowEvent *event) {
-    switch (event->event) {
-        case SDL_WINDOWEVENT_EXPOSED:
-            screen_render(screen);
-            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);
-            break;
-        case SDL_WINDOWEVENT_MAXIMIZED:
-            // The backup size must be non-nul.
-            SDL_assert(screen->windowed_window_size_backup.width);
-            SDL_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:
-            screen->maximized = false;
-            apply_windowed_size(screen);
-            break;
     }
 }

app/src/screen.h

@@ -15,37 +15,28 @@ struct screen {
     SDL_Renderer *renderer;
     SDL_Texture *texture;
     struct size frame_size;
-    // The window size the last time it was not maximized or fullscreen.
+    //used only in fullscreen mode to know the windowed window size
     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 has_frame;
     bool fullscreen;
-    bool maximized;
     bool no_window;
 };
 
-#define SCREEN_INITIALIZER { \
+#define SCREEN_INITIALIZER {  \
-    .window = NULL, \
+    .window = NULL,           \
-    .renderer = NULL, \
+    .renderer = NULL,         \
-    .texture = NULL, \
+    .texture = NULL,          \
-    .frame_size = { \
+    .frame_size = {           \
-        .width = 0,  \
+        .width = 0,           \
-        .height = 0, \
+        .height = 0,          \
-    }, \
+    },                        \
     .windowed_window_size = { \
-        .width = 0, \
+        .width = 0,           \
-        .height = 0, \
+        .height = 0,          \
-    }, \
+    },                        \
-    .windowed_window_size_backup = { \
+    .has_frame = false,   \
-        .width = 0, \
+    .fullscreen = false,  \
-        .height = 0, \
+    .no_window = false,   \
-    }, \
-    .has_frame = false, \
-    .fullscreen = false, \
-    .maximized = false, \
-    .no_window = false, \
 }
 
 // initialize default values
@@ -85,8 +76,4 @@ screen_resize_to_fit(struct screen *screen);
 void
 screen_resize_to_pixel_perfect(struct screen *screen);
 
-// react to window events
-void
-screen_handle_window_event(struct screen *screen, const SDL_WindowEvent *event);
-
 #endif

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

@@ -56,13 +56,8 @@ public class ScreenEncoder implements Device.RotationListener {
 
     public void streamScreen(Device device, FileDescriptor fd) throws IOException {
         // Some devices internally create a Handler when creating an input Surface, causing an exception:
-        //   "Can't create handler inside thread that has not called Looper.prepare()"
+        // "Can't create handler inside thread that has not called Looper.prepare()"
         // <https://github.com/Genymobile/scrcpy/issues/240>
-        //
-        // Use Looper.prepareMainLooper() instead of Looper.prepare() to avoid a NullPointerException:
-        //   "Attempt to read from field 'android.os.MessageQueue android.os.Looper.mQueue'
-        //    on a null object reference"
-        // <https://github.com/Genymobile/scrcpy/issues/921>
         Looper.prepareMainLooper();
 
         MediaFormat format = createFormat(bitRate, frameRate, iFrameInterval);