Apply transform to textures on android (#4486)

* Apply transform to textures on android

* Use RAII canvas save

shell/platform/android/android_external_texture_gl.cc

@@ -4,7 +4,6 @@
 
 #include "flutter/shell/platform/android/android_external_texture_gl.h"
 
-// #include <GLES/gl.h>
 #include <GLES/glext.h>
 #include "flutter/common/threads.h"
 #include "flutter/shell/platform/android/platform_view_android_jni.h"
@@ -15,7 +14,7 @@ namespace shell {
 AndroidExternalTextureGL::AndroidExternalTextureGL(
     int64_t id,
     const fml::jni::JavaObjectWeakGlobalRef& surfaceTexture)
-    : Texture(id), surface_texture_(surfaceTexture) {}
+    : Texture(id), surface_texture_(surfaceTexture), transform(SkMatrix::I()) {}
 
 AndroidExternalTextureGL::~AndroidExternalTextureGL() = default;
 
@@ -44,16 +43,42 @@ void AndroidExternalTextureGL::Paint(SkCanvas& canvas, const SkRect& bounds) {
     new_frame_ready_ = false;
   }
   GrGLTextureInfo textureInfo = {GL_TEXTURE_EXTERNAL_OES, texture_name_};
-  GrBackendTexture backendTexture(bounds.width(), bounds.height(),
-                                  kRGBA_8888_GrPixelConfig, textureInfo);
+  GrBackendTexture backendTexture(1, 1, kRGBA_8888_GrPixelConfig, textureInfo);
   sk_sp<SkImage> image = SkImage::MakeFromTexture(
       canvas.getGrContext(), backendTexture, kTopLeft_GrSurfaceOrigin,
       SkAlphaType::kPremul_SkAlphaType, nullptr);
   if (image) {
-    canvas.drawImage(image, bounds.x(), bounds.y());
+    SkAutoCanvasRestore autoRestore(&canvas, true);
+    canvas.translate(bounds.x(), bounds.y());
+    canvas.scale(bounds.width(), bounds.height());
+    if (!transform.isIdentity()) {
+      SkMatrix transformAroundCenter(transform);
+
+      transformAroundCenter.preTranslate(-0.5, -0.5);
+      transformAroundCenter.postScale(1, -1);
+      transformAroundCenter.postTranslate(0.5, 0.5);
+      canvas.concat(transformAroundCenter);
+    }
+    canvas.drawImage(image, 0, 0);
   }
 }
 
+void AndroidExternalTextureGL::UpdateTransform() {
+  JNIEnv* env = fml::jni::AttachCurrentThread();
+  fml::jni::ScopedJavaLocalRef<jobject> surfaceTexture =
+      surface_texture_.get(env);
+  jfloatArray transformMatrix = env->NewFloatArray(16);
+  SurfaceTextureGetTransformMatrix(env, surfaceTexture.obj(), transformMatrix);
+  float* m = env->GetFloatArrayElements(transformMatrix, nullptr);
+  SkScalar matrix3[] = {
+      m[0], m[1], m[2],   //
+      m[4], m[5], m[6],   //
+      m[8], m[9], m[10],  //
+  };
+  env->ReleaseFloatArrayElements(transformMatrix, m, JNI_ABORT);
+  transform.set9(matrix3);
+}
+
 void AndroidExternalTextureGL::OnGrContextDestroyed() {
   ASSERT_IS_GPU_THREAD;
   if (state_ == AttachmentState::attached) {
@@ -77,6 +102,7 @@ void AndroidExternalTextureGL::Update() {
       surface_texture_.get(env);
   if (!surfaceTexture.is_null()) {
     SurfaceTextureUpdateTexImage(env, surfaceTexture.obj());
+    UpdateTransform();
   }
 }
 

shell/platform/android/android_external_texture_gl.h

@@ -35,6 +35,8 @@ class AndroidExternalTextureGL : public flow::Texture {
 
   void Detach();
 
+  void UpdateTransform();
+
   enum class AttachmentState { uninitialized, attached, detached };
 
   fml::jni::JavaObjectWeakGlobalRef surface_texture_;
@@ -45,6 +47,8 @@ class AndroidExternalTextureGL : public flow::Texture {
 
   GLuint texture_name_ = 0;
 
+  SkMatrix transform;
+
   FXL_DISALLOW_COPY_AND_ASSIGN(AndroidExternalTextureGL);
 };
 

shell/platform/android/platform_view_android_jni.cc

@@ -90,6 +90,15 @@ void SurfaceTextureUpdateTexImage(JNIEnv* env, jobject obj) {
   FXL_CHECK(CheckException(env));
 }
 
+static jmethodID g_get_transform_matrix_method = nullptr;
+void SurfaceTextureGetTransformMatrix(JNIEnv* env,
+                                      jobject obj,
+                                      jfloatArray result) {
+  ASSERT_IS_GPU_THREAD;
+  env->CallVoidMethod(obj, g_get_transform_matrix_method, result);
+  FXL_CHECK(CheckException(env));
+}
+
 static jmethodID g_detach_from_gl_context_method = nullptr;
 void SurfaceTextureDetachFromGLContext(JNIEnv* env, jobject obj) {
   ASSERT_IS_GPU_THREAD;
@@ -502,6 +511,13 @@ bool PlatformViewAndroid::Register(JNIEnv* env) {
     return false;
   }
 
+  g_get_transform_matrix_method = env->GetMethodID(
+      g_surface_texture_class->obj(), "getTransformMatrix", "([F)V");
+
+  if (g_get_transform_matrix_method == nullptr) {
+    return false;
+  }
+
   g_detach_from_gl_context_method = env->GetMethodID(
       g_surface_texture_class->obj(), "detachFromGLContext", "()V");
 

shell/platform/android/platform_view_android_jni.h

@@ -33,6 +33,10 @@ void SurfaceTextureAttachToGLContext(JNIEnv* env, jobject obj, jint textureId);
 
 void SurfaceTextureUpdateTexImage(JNIEnv* env, jobject obj);
 
+void SurfaceTextureGetTransformMatrix(JNIEnv* env,
+                                      jobject obj,
+                                      jfloatArray result);
+
 void SurfaceTextureDetachFromGLContext(JNIEnv* env, jobject obj);
 
 }  // namespace shell