Bug 1913568 - Add texture transform support to GLReadTexImageHelper. r=gfx-reviewers,nical

Add the capability to transform the texture coordinates when reading
from a texture, similar to existing support in GLBlitHelper and
CompositorOGL.

This patch doesn't change any behaviour, but this capability will be
made use of by a later patch in this series.

Differential Revision: https://phabricator.services.mozilla.com/D220580

gfx/gl/GLReadTexImageHelper.cpp

@@ -41,8 +41,12 @@ GLReadTexImageHelper::~GLReadTexImageHelper() {
 static const GLchar readTextureImageVS[] =
     "attribute vec2 aVertex;\n"
     "attribute vec2 aTexCoord;\n"
+    "uniform mat4 uTexMatrix;\n"
     "varying vec2 vTexCoord;\n"
-    "void main() { gl_Position = vec4(aVertex, 0, 1); vTexCoord = aTexCoord; }";
+    "void main() {\n"
+    "  gl_Position = vec4(aVertex, 0, 1);\n"
+    "  vTexCoord = (uTexMatrix * vec4(aTexCoord, 0.0, 1.0)).xy;\n"
+    "}";
 
 static const GLchar readTextureImageFS_TEXTURE_2D[] =
     "#ifdef GL_ES\n"
@@ -482,6 +486,7 @@ already_AddRefed<DataSourceSurface> ReadBackSurface(GLContext* gl,
 
 already_AddRefed<DataSourceSurface> GLReadTexImageHelper::ReadTexImage(
     GLuint aTextureId, GLenum aTextureTarget, const gfx::IntSize& aSize,
+    const gfx::Matrix4x4& aTexMatrix,
     /* ShaderConfigOGL.mFeature */ int aConfig, bool aYInvert) {
   /* Allocate resulting image surface */
   int32_t stride = aSize.width * BytesPerPixel(SurfaceFormat::R8G8B8A8);
@@ -491,8 +496,8 @@ already_AddRefed<DataSourceSurface> GLReadTexImageHelper::ReadTexImage(
     return nullptr;
   }
 
-  if (!ReadTexImage(isurf, aTextureId, aTextureTarget, aSize, aConfig,
-                    aYInvert)) {
+  if (!ReadTexImage(isurf, aTextureId, aTextureTarget, aSize, aTexMatrix,
+                    aConfig, aYInvert)) {
     return nullptr;
   }
 
@@ -501,7 +506,7 @@ already_AddRefed<DataSourceSurface> GLReadTexImageHelper::ReadTexImage(
 
 bool GLReadTexImageHelper::ReadTexImage(
     DataSourceSurface* aDest, GLuint aTextureId, GLenum aTextureTarget,
-    const gfx::IntSize& aSize,
+    const gfx::IntSize& aSize, const gfx::Matrix4x4& aTexMatrix,
     /* ShaderConfigOGL.mFeature */ int aConfig, bool aYInvert) {
   MOZ_ASSERT(aTextureTarget == LOCAL_GL_TEXTURE_2D ||
              aTextureTarget == LOCAL_GL_TEXTURE_EXTERNAL ||
@@ -567,7 +572,10 @@ bool GLReadTexImageHelper::ReadTexImage(
     mGL->fUseProgram(program);
     CLEANUP_IF_GLERROR_OCCURRED("when using program");
     mGL->fUniform1i(mGL->fGetUniformLocation(program, "uTexture"), 0);
-    CLEANUP_IF_GLERROR_OCCURRED("when setting uniform location");
+    CLEANUP_IF_GLERROR_OCCURRED("when setting uniform uTexture");
+    mGL->fUniformMatrix4fv(mGL->fGetUniformLocation(program, "uTexMatrix"), 1,
+                           false, aTexMatrix.components);
+    CLEANUP_IF_GLERROR_OCCURRED("when setting uniform uTexMatrix");
 
     /* Setup quad geometry */
     mGL->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, 0);

gfx/gl/GLReadTexImageHelper.h

@@ -11,6 +11,7 @@
 #include "mozilla/Attributes.h"
 #include "nsSize.h"
 #include "mozilla/RefPtr.h"
+#include "mozilla/gfx/MatrixFwd.h"
 #include "mozilla/gfx/Types.h"
 
 namespace mozilla {
@@ -72,11 +73,13 @@ class GLReadTexImageHelper final {
    */
   already_AddRefed<gfx::DataSourceSurface> ReadTexImage(
       GLuint aTextureId, GLenum aTextureTarget, const gfx::IntSize& aSize,
+      const gfx::Matrix4x4& aTexMatrix,
       /* ShaderProgramType */ int aShaderProgram, bool aYInvert = false);
 
   bool ReadTexImage(gfx::DataSourceSurface* aDest, GLuint aTextureId,
                     GLenum aTextureTarget, const gfx::IntSize& aSize,
-                    int aShaderProgram, bool aYInvert = false);
+                    const gfx::Matrix4x4& aTexMatrix, int aShaderProgram,
+                    bool aYInvert = false);
 };
 
 }  // namespace gl

gfx/webrender_bindings/RenderAndroidHardwareBufferTextureHost.cpp

@@ -209,8 +209,8 @@ RenderAndroidHardwareBufferTextureHost::ReadTexImage() {
   int shaderConfig = config.mFeatures;
 
   bool ret = mGL->ReadTexImageHelper()->ReadTexImage(
-      surf, mTextureHandle, LOCAL_GL_TEXTURE_EXTERNAL, GetSize(), shaderConfig,
-      /* aYInvert */ false);
+      surf, mTextureHandle, LOCAL_GL_TEXTURE_EXTERNAL, GetSize(),
+      gfx::Matrix4x4(), shaderConfig, /* aYInvert */ false);
   if (!ret) {
     return nullptr;
   }

gfx/webrender_bindings/RenderAndroidSurfaceTextureHost.cpp

@@ -251,7 +251,7 @@ RenderAndroidSurfaceTextureHost::ReadTexImage() {
 
   bool ret = mGL->ReadTexImageHelper()->ReadTexImage(
       surf, mSurfTex->GetTexName(), LOCAL_GL_TEXTURE_EXTERNAL, mSize,
-      shaderConfig, /* aYInvert */ false);
+      gfx::Matrix4x4(), shaderConfig, /* aYInvert */ false);
   if (!ret) {
     return nullptr;
   }

gfx/webrender_bindings/RenderEGLImageTextureHost.cpp

@@ -209,8 +209,8 @@ RenderEGLImageTextureHost::ReadTexImage() {
   int shaderConfig = config.mFeatures;
 
   bool ret = mGL->ReadTexImageHelper()->ReadTexImage(
-      surf, mTextureHandle, mTextureTarget, mSize, shaderConfig,
-      /* aYInvert */ false);
+      surf, mTextureHandle, mTextureTarget, mSize, gfx::Matrix4x4(),
+      shaderConfig, /* aYInvert */ false);
   if (!ret) {
     return nullptr;
   }