VrShell: Allow native control of UI element opacity.

chrome/browser/android/vr_shell/vr_shell_renderer.cc

 // Copyright 2016 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 "chrome/browser/android/vr_shell/vr_shell_renderer.h"
 
 #include "chrome/browser/android/vr_shell/vr_gl_util.h"
 
 namespace {
 
@@ skipping 72 matching lines @@
                     void main() {
                       v_TexCoordinate = a_TexCoordinate;
                       gl_Position = u_CombinedMatrix * a_Position;
                     });
     case vr_shell::ShaderID::TEXTURE_QUAD_FRAGMENT_SHADER:
       return OEIE_SHADER(
           precision highp float;
           uniform samplerExternalOES u_Texture;
           uniform vec4 u_CopyRect;  // rectangle
           varying vec2 v_TexCoordinate;
+          uniform lowp vec4 color;
+          uniform mediump float opacity;
+
           void main() {
             vec2 scaledTex =
                 vec2(u_CopyRect[0] + v_TexCoordinate.x * u_CopyRect[2],
                      u_CopyRect[1] + v_TexCoordinate.y * u_CopyRect[3]);
-            gl_FragColor = texture2D(u_Texture, scaledTex);
+            lowp vec4 color = texture2D(u_Texture, scaledTex);
+            gl_FragColor = vec4(color.xyz, color.w * opacity);
           });
     case vr_shell::ShaderID::WEBVR_VERTEX_SHADER:
       return SHADER(
           attribute vec4 a_Position;
           varying vec2 v_TexCoordinate;
 
           void main() {
             // Pack the texcoord into the position to avoid state changes.
             v_TexCoordinate = a_Position.zw;
             gl_Position = vec4(a_Position.xy, 0.0, 1.0);
@@ skipping 115 matching lines @@
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 }
 
 TexturedQuadRenderer::TexturedQuadRenderer()
     : BaseRenderer(TEXTURE_QUAD_VERTEX_SHADER, TEXTURE_QUAD_FRAGMENT_SHADER) {
   combined_matrix_handle_ =
       glGetUniformLocation(program_handle_, "u_CombinedMatrix");
   tex_uniform_handle_ = glGetUniformLocation(program_handle_, "u_Texture");
   copy_rect_uniform_handle_ =
       glGetUniformLocation(program_handle_, "u_CopyRect");
+  opacity_handle_ = glGetUniformLocation(program_handle_, "opacity");
 }
 
 void TexturedQuadRenderer::Draw(int texture_data_handle,
                                 const gvr::Mat4f& combined_matrix,
-                                const Rectf& copy_rect) {
+                                const Rectf& copy_rect,
+                                float opacity) {
   PrepareToDraw(combined_matrix_handle_, combined_matrix);
 
   // Link texture data with texture unit.
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_EXTERNAL_OES, texture_data_handle);
   glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 
   glUniform1i(tex_uniform_handle_, 0);
   glUniform4fv(copy_rect_uniform_handle_, 1, (float*)(&copy_rect));
+  glUniform1f(opacity_handle_, opacity);
 
   glDrawArrays(GL_TRIANGLES, 0, kVerticesNumber);
 
   glDisableVertexAttribArray(position_handle_);
   glDisableVertexAttribArray(tex_coord_handle_);
 }
 
 TexturedQuadRenderer::~TexturedQuadRenderer() = default;
 
 WebVrRenderer::WebVrRenderer() :
@@ skipping 137 matching lines @@
 
 VrShellRenderer::VrShellRenderer()
     : textured_quad_renderer_(new TexturedQuadRenderer),
       webvr_renderer_(new WebVrRenderer),
       reticle_renderer_(new ReticleRenderer),
       laser_renderer_(new LaserRenderer) {}
 
 VrShellRenderer::~VrShellRenderer() = default;
 
 }  // namespace vr_shell