Implement Vulkan surface snapshot (#4314)

platform/android/MapLibreAndroid/src/cpp/android_renderer_backend.hpp

@@ -31,6 +31,7 @@ public:
     virtual void destroySurface() {}
 
     virtual void resizeFramebuffer(int width, int height);
+    virtual void enableFramebufferRead(bool value) {}
     virtual PremultipliedImage readFramebuffer();
 
     gfx::Renderable::SwapBehaviour getSwapBehavior() const { return swapBehaviour; }

platform/android/MapLibreAndroid/src/cpp/android_vulkan_renderer_backend.cpp

@@ -83,9 +83,12 @@ void AndroidVulkanRendererBackend::resizeFramebuffer(int, int) {
     }
 }
 
+void AndroidVulkanRendererBackend::enableFramebufferRead(bool value) {
+    getResource<AndroidVulkanRenderableResource>().enableSurfaceRead();
+}
+
 PremultipliedImage AndroidVulkanRendererBackend::readFramebuffer() {
-    // TODO not implemented
-    return PremultipliedImage(Size(2, 2));
+    return std::move(*getResource<AndroidVulkanRenderableResource>().readImage());
 }
 
 } // namespace android

platform/android/MapLibreAndroid/src/cpp/android_vulkan_renderer_backend.hpp

@@ -24,6 +24,7 @@ public:
     std::vector<const char*> getInstanceExtensions() override;
 
     void resizeFramebuffer(int width, int height) override;
+    void enableFramebufferRead(bool value) override;
     PremultipliedImage readFramebuffer() override;
 
     // mbgl::gfx::RendererBackend implementation

platform/android/MapLibreAndroid/src/cpp/map_renderer.cpp

@@ -207,6 +207,12 @@ void MapRenderer::resetRenderer() {
 
 void MapRenderer::scheduleSnapshot(std::unique_ptr<SnapshotCallback> callback) {
     snapshotCallback = std::move(callback);
+
+    if (backend) {
+        gfx::BackendScope backendGuard{backend->getImpl()};
+        backend->enableFramebufferRead(true);
+    }
+
     requestRender();
 }