vk: New method to describe external image in Vulkan Android (#8551)

To match the GL platform add a new function to describe
an external image.

Also make `ExternalImageVulkanAndroid` and
`getExternalImageMetadata` protected, so only the
backend has access to it.

filament/backend/include/backend/platforms/VulkanPlatformAndroid.h

@@ -26,6 +26,20 @@ namespace filament::backend {
 
 class VulkanPlatformAndroid : public VulkanPlatform {
 public:
+    Platform::ExternalImageHandle UTILS_PUBLIC createExternalImage(AHardwareBuffer const* buffer,
+            bool sRGB) noexcept;
+
+    struct UTILS_PUBLIC ExternalImageDescAndroid {
+        uint32_t width;      // Texture width
+        uint32_t height;     // Texture height
+        TextureFormat format;// Texture format
+        TextureUsage usage;  // Texture usage flags
+    };
+
+    ExternalImageDescAndroid UTILS_PUBLIC getExternalImageDesc(
+            ExternalImageHandleRef externalImage) const noexcept;
+
+protected:
     struct ExternalImageVulkanAndroid : public Platform::ExternalImage {
         AHardwareBuffer* aHardwareBuffer = nullptr;
         bool sRGB = false;
@@ -38,9 +52,6 @@ public:
         ~ExternalImageVulkanAndroid() override;
     };
 
-    Platform::ExternalImageHandle createExternalImage(AHardwareBuffer const* buffer,
-            bool sRGB) noexcept;
-
     virtual ExternalImageMetadata getExternalImageMetadata(ExternalImageHandleRef externalImage);
 
     using ImageData = VulkanPlatform::ImageData;
@@ -48,7 +59,6 @@ public:
             const ExternalImageMetadata& metadata, uint32_t memoryTypeIndex,
             VkImageUsageFlags usage);
 
-protected:
     virtual ExtensionSet getSwapchainInstanceExtensions() const;
 
     using SurfaceBundle = VulkanPlatform::SurfaceBundle;

filament/backend/src/vulkan/platform/VulkanPlatformAndroid.cpp

@@ -223,6 +223,19 @@ Platform::ExternalImageHandle VulkanPlatformAndroid::createExternalImage(
     return Platform::ExternalImageHandle{};
 }
 
+VulkanPlatformAndroid::ExternalImageDescAndroid VulkanPlatformAndroid::getExternalImageDesc(
+        ExternalImageHandleRef externalImage) const noexcept {
+    auto const* fvkExternalImage =
+            static_cast<ExternalImageVulkanAndroid const*>(externalImage.get());
+
+    return {
+        .width = fvkExternalImage->width,
+        .height = fvkExternalImage->height,
+        .format = fvkExternalImage->format,
+        .usage = fvkExternalImage->usage,
+    };
+}
+
 VulkanPlatform::ExternalImageMetadata VulkanPlatformAndroid::getExternalImageMetadata(
         ExternalImageHandleRef externalImage) {
     auto const* fvkExternalImage =