Directly use 4x4 matrices with surface textures instead of converting to and from the 3x3 variants.

shell/platform/android/android_shell_holder_unittests.cc

@@ -48,9 +48,9 @@ class MockPlatformViewAndroidJNI : public PlatformViewAndroidJNI {
               SurfaceTextureUpdateTexImage,
               (JavaLocalRef surface_texture),
               (override));
-  MOCK_METHOD(void,
+  MOCK_METHOD(SkM44,
               SurfaceTextureGetTransformMatrix,
-              (JavaLocalRef surface_texture, SkMatrix& transform),
+              (JavaLocalRef surface_texture),
               (override));
   MOCK_METHOD(void,
               SurfaceTextureDetachFromGLContext,

shell/platform/android/jni/jni_mock.h

@@ -59,9 +59,9 @@ class JNIMock final : public PlatformViewAndroidJNI {
               (JavaLocalRef surface_texture),
               (override));
 
-  MOCK_METHOD(void,
+  MOCK_METHOD(SkM44,
               SurfaceTextureGetTransformMatrix,
-              (JavaLocalRef surface_texture, SkMatrix& transform),
+              (JavaLocalRef surface_texture),
               (override));
 
   MOCK_METHOD(JavaLocalRef,

shell/platform/android/jni/platform_view_android_jni.h

@@ -107,8 +107,8 @@ class PlatformViewAndroidJNI {
   ///             Then, it updates the `transform` matrix, so it fill the canvas
   ///             and preserve the aspect ratio.
   ///
-  virtual void SurfaceTextureGetTransformMatrix(JavaLocalRef surface_texture,
-                                                SkMatrix& transform) = 0;
+  virtual SkM44 SurfaceTextureGetTransformMatrix(
+      JavaLocalRef surface_texture) = 0;
 
   //----------------------------------------------------------------------------
   /// @brief      Detaches a SurfaceTexture from the OpenGL ES context.

shell/platform/android/platform_view_android_jni_impl.cc

@@ -1502,20 +1502,19 @@ void PlatformViewAndroidJNIImpl::SurfaceTextureUpdateTexImage(
   FML_CHECK(fml::jni::CheckException(env));
 }
 
-void PlatformViewAndroidJNIImpl::SurfaceTextureGetTransformMatrix(
-    JavaLocalRef surface_texture,
-    SkMatrix& transform) {
+SkM44 PlatformViewAndroidJNIImpl::SurfaceTextureGetTransformMatrix(
+    JavaLocalRef surface_texture) {
   JNIEnv* env = fml::jni::AttachCurrentThread();
 
   if (surface_texture.is_null()) {
-    return;
+    return {};
   }
 
   fml::jni::ScopedJavaLocalRef<jobject> surface_texture_local_ref(
       env, env->CallObjectMethod(surface_texture.obj(),
                                  g_java_weak_reference_get_method));
   if (surface_texture_local_ref.is_null()) {
-    return;
+    return {};
   }
 
   fml::jni::ScopedJavaLocalRef<jfloatArray> transformMatrix(
@@ -1527,36 +1526,12 @@ void PlatformViewAndroidJNIImpl::SurfaceTextureGetTransformMatrix(
 
   float* m = env->GetFloatArrayElements(transformMatrix.obj(), nullptr);
 
-  // SurfaceTexture 4x4 Column Major -> Skia 3x3 Row Major
-
-  // SurfaceTexture 4x4 (Column Major):
-  // | m[0] m[4] m[ 8] m[12] |
-  // | m[1] m[5] m[ 9] m[13] |
-  // | m[2] m[6] m[10] m[14] |
-  // | m[3] m[7] m[11] m[15] |
-
-  // According to Android documentation, the 4x4 matrix returned should be used
-  // with texture coordinates in the form (s, t, 0, 1). Since the z component is
-  // always 0.0, we are free to ignore any element that multiplies with the z
-  // component. Converting this to a 3x3 matrix is easy:
-
-  // SurfaceTexture 3x3 (Column Major):
-  // | m[0] m[4] m[12] |
-  // | m[1] m[5] m[13] |
-  // | m[3] m[7] m[15] |
-
-  // Skia (Row Major):
-  // | m[0] m[1] m[2] |
-  // | m[3] m[4] m[5] |
-  // | m[6] m[7] m[8] |
-
-  SkScalar matrix3[] = {
-      m[0], m[4], m[12],  //
-      m[1], m[5], m[13],  //
-      m[3], m[7], m[15],  //
-  };
+  static_assert(sizeof(SkScalar) == sizeof(float));
+  const auto transform = SkM44::ColMajor(m);
+
   env->ReleaseFloatArrayElements(transformMatrix.obj(), m, JNI_ABORT);
-  transform.set9(matrix3);
+
+  return transform;
 }
 
 void PlatformViewAndroidJNIImpl::SurfaceTextureDetachFromGLContext(

shell/platform/android/platform_view_android_jni_impl.h

@@ -49,8 +49,7 @@ class PlatformViewAndroidJNIImpl final : public PlatformViewAndroidJNI {
 
   void SurfaceTextureUpdateTexImage(JavaLocalRef surface_texture) override;
 
-  void SurfaceTextureGetTransformMatrix(JavaLocalRef surface_texture,
-                                        SkMatrix& transform) override;
+  SkM44 SurfaceTextureGetTransformMatrix(JavaLocalRef surface_texture) override;
 
   void SurfaceTextureDetachFromGLContext(JavaLocalRef surface_texture) override;
 

shell/platform/android/surface_texture_external_texture.cc

@@ -67,7 +67,7 @@ void SurfaceTextureExternalTexture::DrawFrame(
     PaintContext& context,
     const SkRect& bounds,
     const DlImageSampling sampling) const {
-  auto transform = GetCurrentUVTransformation();
+  auto transform = GetCurrentUVTransformation().asM33();
 
   // Android's SurfaceTexture transform matrix works on texture coordinate
   // lookups in the range 0.0-1.0, while Skia's Shader transform matrix works on
@@ -136,12 +136,11 @@ bool SurfaceTextureExternalTexture::ShouldUpdate() {
 void SurfaceTextureExternalTexture::Update() {
   jni_facade_->SurfaceTextureUpdateTexImage(
       fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
-  jni_facade_->SurfaceTextureGetTransformMatrix(
-      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_), transform_);
+  transform_ = jni_facade_->SurfaceTextureGetTransformMatrix(
+      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
 }
 
-const SkMatrix& SurfaceTextureExternalTexture::GetCurrentUVTransformation()
-    const {
+const SkM44& SurfaceTextureExternalTexture::GetCurrentUVTransformation() const {
   return transform_;
 }
 

shell/platform/android/surface_texture_external_texture.h

@@ -9,6 +9,7 @@
 
 #include "flutter/common/graphics/texture.h"
 #include "flutter/shell/platform/android/platform_view_android_jni_impl.h"
+#include "flutter/third_party/skia/include/core/SkM44.h"
 
 namespace flutter {
 
@@ -64,7 +65,7 @@ class SurfaceTextureExternalTexture : public flutter::Texture {
   ///
   /// @return     The current uv transformation.
   ///
-  const SkMatrix& GetCurrentUVTransformation() const;
+  const SkM44& GetCurrentUVTransformation() const;
 
   //----------------------------------------------------------------------------
   /// @brief      Provides an opportunity for the subclasses to sever the
@@ -111,7 +112,7 @@ class SurfaceTextureExternalTexture : public flutter::Texture {
   sk_sp<flutter::DlImage> dl_image_;
 
  private:
-  SkMatrix transform_;
+  SkM44 transform_;
 
   // |Texture|
   void Paint(PaintContext& context,

shell/platform/android/surface_texture_external_texture_vk_impeller.cc

@@ -148,9 +148,9 @@ void SurfaceTextureExternalTextureVKImpeller::ProcessFrame(
                    vk::ImageLayout::eColorAttachmentOptimal,
                    LayoutUpdateMode::kSync);
 
-  SkM44 transformation(GetCurrentUVTransformation());
   impeller::Matrix uv_transformation;
-  transformation.getColMajor(reinterpret_cast<SkScalar*>(&uv_transformation));
+  GetCurrentUVTransformation().getColMajor(
+      reinterpret_cast<SkScalar*>(&uv_transformation));
 
   glvk::Trampoline::GLTextureInfo src_texture;
   src_texture.texture = src_gl_texture;