flutter/engine#27141 will provide a Pbuffer surface when on screen surface is not available. It applies to Android and it is for background specific.

However, there is another scenario that needs to be considered here. When method PlatformViewAndroid::NotifyCreated is called, there will be a situation where AndroidSurfaceGL::on_screen_surface_ is set, but Rasterizer::surface_ has not been set.

void PlatformViewAndroid::NotifyCreated(
    fml::RefPtr<AndroidNativeWindow> native_window) {
  if (android_surface_) {
    InstallFirstFrameCallback();

    fml::AutoResetWaitableEvent latch;
    fml::TaskRunner::RunNowOrPostTask(
        task_runners_.GetRasterTaskRunner(),
        [&latch, surface = android_surface_.get(),
         native_window = std::move(native_window)]() {
          surface->SetNativeWindow(native_window);  // 1. Setup AndroidSurfaceGL::on_screen_surface_
          latch.Signal();
        });
    latch.Wait();
  }

  PlatformView::NotifyCreated();  // 2. Setup Rasterizer::surface_
}

If Rasterizer::DoMakeRasterSnapshot is called at this time, because Rasterizer::surface_ has not been set yet, it will call AndroidSurfaceGL::CreatePbufferSurface to generate Pbuffer. At this time, the AndroidSurfaceGL::on_screen_surface_ will be replaced by the new one which size is 1x1.

In fact, my application encountered this issue. I was using Flutter 2.5.3. When I opened the first flutter screen, the entire screen did not display any content, it was blank screen. Eventually I found out that the reason caused this problem is above. Unfortunately, it is difficult for me to give a reproducible sample. But I suspect that this problem still exists on the 'main' branch.

/cc @dnfield