Fix possible division by zero

On sway (a window manager), SDL_WINDOWEVENT_EXPOSED and
SDL_WINDOWEVENT_SIZE_CHANGED might not be called before a mouse event is
triggered. As a consequence, the "content rectangle" might not be
initialized when the mouse event is processed, causing a division by
zero.

To avoid the problem, initialize the content rect immediately when the
window is shown.

Fixes #4115 <https://github.com/Genymobile/scrcpy/issues/4115>

app/src/screen.c

@@ -488,6 +488,7 @@ sc_screen_show_initial_window(struct sc_screen *screen) {
     }
 
     SDL_ShowWindow(screen->window);
+    sc_screen_update_content_rect(screen);
 }
 
 void
@@ -848,6 +849,8 @@ sc_screen_convert_drawable_to_frame_coords(struct sc_screen *screen,
     int32_t w = screen->content_size.width;
     int32_t h = screen->content_size.height;
 
+    // screen->rect must be initialized to avoid a division by zero
+    assert(screen->rect.w && screen->rect.h);
 
     x = (int64_t) (x - screen->rect.x) * w / screen->rect.w;
     y = (int64_t) (y - screen->rect.y) * h / screen->rect.h;

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

@@ -147,7 +147,6 @@ public class ScreenEncoder implements Device.RotationListener, Device.FoldListen
         // Downsizing on error is only enabled if an encoding failure occurs before the first frame (downsizing later could be surprising)
 
         int newMaxSize = chooseMaxSizeFallback(screenInfo.getVideoSize());
-        Ln.i("newMaxSize = " + newMaxSize);
         if (newMaxSize == 0) {
             // Must definitively fail
             return false;