Always apply UniformMatrix4fvStreamTextureMatrixCHROMIUM matrix argument.

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 7599 matching lines @@
                                    &type,
                                    &count)) {
     return;
   }
   glUniformMatrix4fv(real_location, count, transpose, value);
 }
 
 void GLES2DecoderImpl::DoUniformMatrix4fvStreamTextureMatrixCHROMIUM(
     GLint fake_location,
     GLboolean transpose,
-    const GLfloat* default_value) {
+    const GLfloat* transform) {
   float gl_matrix[16];
 
-  // If we can't get a matrix from the texture, then use a default.
-  // TODO(liberato): remove |default_value| and replace with an identity matrix.
-  // It is only present as a transitionary step until StreamTexture supplies
-  // the matrix via GLImage.  Once that happens, GLRenderer can quit sending
-  // in a default.
-  memcpy(gl_matrix, default_value, sizeof(gl_matrix));
-
   // This refers to the bound external texture on the active unit.
   TextureUnit& unit = state_.texture_units[state_.active_texture_unit];
   if (TextureRef* texture_ref = unit.bound_texture_external_oes.get()) {
     if (GLStreamTextureImage* image =
             texture_ref->texture()->GetLevelStreamTextureImage(
                 GL_TEXTURE_EXTERNAL_OES, 0)) {
       image->GetTextureMatrix(gl_matrix);

[liberato (no reviews please), 2016/03/31 15:03:16]

maybe not for this CL, but GetFlippedTextureMatrix might not be the best name in
retrospect.  GetChromiumTextureMatrix or similar, since nobody will care what
changes are made to the original, only that it's now in chromium coordinates.

or, just GetTextureMatrix.  i think that was your original proposal, and i agree
that you were right.  :)

[liberato (no reviews please), 2016/03/31 15:03:16]

don't we want this to be GetFlippedTextureMatrix?  that lets the shader be more
intuitive.

[Tobias Sargeant, 2016/04/01 11:59:10]

Done. On reflection I decided against GetChromiumTextureMatrix in favour of
requiring GetTextureMatrix to return a matrix that converts chromium orientation
texel coordinates into whatever coordinates are appropriate for whatever
GLStreamTextureImage wraps. For ADVA and StreamTextureAndroid this involves a
y-flip, so I made both use a convenience function for that explicitly.

[liberato (no reviews please), 2016/04/01 14:07:13]

makes sense.

+      GLfloat tmp[16];

[liberato (no reviews please), 2016/03/31 15:03:16]

without this premultiply, does the y-flip without UMP come back?  if so, then it
raises the question why !UMP is sending down a y-flip.

i don't see what else in this CL could change the behavior, but i also don't see
why it would affect !UMP only.

+      for (int c = 0; c < 16; c += 4) {
+        for (int r = 0; r < 4; ++r) {
+          tmp[c + r] = 0.0f;
+          for (int i = 0; i < 4; ++i) {
+            tmp[c + r] += gl_matrix[r + 4 * i] * transform[c + i];
+          }
+        }
+      }
+      std::copy(tmp, tmp + 16, gl_matrix);
+    } else {
+      // Missing stream texture. Treat matrix as identity.
+      memcpy(gl_matrix, transform, sizeof(gl_matrix));
     }
   } else {
     LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION,
                        "DoUniformMatrix4vStreamTextureMatrix",
                        "no texture bound");
     return;
   }
 
   GLenum type = 0;
   GLint real_location = -1;
@@ skipping 8730 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu