Implement Vulkan surface snapshot (#4314)

src/mbgl/vulkan/texture2d.cpp

@@ -580,6 +580,33 @@ void Texture2D::copyImage(vk::Image image, Size imageSize, uint16_t xOffset, uin
     });
 }
 
+void Texture2D::blitImage(vk::Image image, Size imageSize, uint16_t xOffset, uint16_t yOffset) {
+    if (!image) return;
+
+    create();
+
+    context.submitOneTimeCommand([&](const vk::UniqueCommandBuffer& commandBuffer) {
+        const std::array<vk::Offset3D, 2> offsets = {
+            vk::Offset3D{xOffset, yOffset, 0},
+            {static_cast<int32_t>(imageSize.width), static_cast<int32_t>(imageSize.height), 1}};
+        const auto blitInfo = vk::ImageBlit()
+                                  .setSrcOffsets(offsets)
+                                  .setDstOffsets(offsets)
+                                  .setSrcSubresource({vk::ImageAspectFlagBits::eColor, 0, 0, 1})
+                                  .setDstSubresource({vk::ImageAspectFlagBits::eColor, 0, 0, 1});
+
+        transitionToTransferWriteLayout(commandBuffer);
+        commandBuffer->blitImage(image,
+                                 vk::ImageLayout::eTransferSrcOptimal,
+                                 imageAllocation->image,
+                                 imageLayout,
+                                 blitInfo,
+                                 vk::Filter::eNearest,
+                                 context.getBackend().getDispatcher());
+        transitionToGeneralLayout(commandBuffer);
+    });
+}
+
 std::shared_ptr<PremultipliedImage> Texture2D::readImage() {
     if (!imageData) {
         imageData = std::make_shared<PremultipliedImage>();