Auto merge of #121 - MortimerGoro:swap_buffers_panic, r=fabricedesre

bors-servo · web-flow · commit 6f9ef98494dd · 2017-03-31T05:44:25.000-05:00
Fix Android swap_buffers panic when the app goes to background Fixes a panic on swap_buffers call because NativeActivity's `TermWindow (on_surface_destroyed)` event can be processed with some delay due to multithreading communication and a swap_buffers call from Servo may arrive in that period of time.  --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/glutin/121)
diff --git a/src/api/egl/mod.rs b/src/api/egl/mod.rs
@@ -310,13 +310,22 @@ impl GlContext for Context {
 
     #[inline]
     fn swap_buffers(&self) -> Result<(), ContextError> {
+        if self.surface.get() == ffi::egl::NO_SURFACE {
+            return Err(ContextError::ContextLost);
+        }
         let ret = unsafe {
             self.egl.SwapBuffers(self.display, self.surface.get())
         };
 
         if ret == 0 {
             match unsafe { self.egl.GetError() } as u32 {
                 ffi::egl::CONTEXT_LOST => return Err(ContextError::ContextLost),
+                // 'on_surface_destroyed' Android event can arrive with some delay because multithreading communication.
+                // Because of that, swap_buffers can be called before processing 'on_surface_destroyed' event, with the
+                // native window surface already destroyed. EGL generates a BAD_SURFACE error in this situation.
+                // We treat it as CONTEXT_LOST error to avoid a panic in servo.
+                // The surface will be restored when the app comes to foreground.
+                #[cfg(target_os = "android")] ffi::egl::BAD_SURFACE => return Err(ContextError::ContextLost),
                 err => panic!("eglSwapBuffers failed (eglGetError returned 0x{:x})", err)
             }
 
