From 26fa8d9d5331b889e95ab7d790d1bde18e2c6456 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Thu, 31 Oct 2013 16:48:37 +0100
Subject: [PATCH] Track current program in context, rather than renderers

---
 src/ol/renderer/webgl/webglmaprenderer.js     | 37 ++++++++-----------
 .../renderer/webgl/webgltilelayerrenderer.js  |  2 +-
 src/ol/webgl/context.js                       | 23 ++++++++++++
 3 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/src/ol/renderer/webgl/webglmaprenderer.js b/src/ol/renderer/webgl/webglmaprenderer.js
index c1c5561f07..87dd4f886f 100644
--- a/src/ol/renderer/webgl/webglmaprenderer.js
+++ b/src/ol/renderer/webgl/webglmaprenderer.js
@@ -425,7 +425,6 @@ ol.renderer.webgl.Map.prototype.renderFrame = function(frameState) {
 
   context.bindBuffer(goog.webgl.ARRAY_BUFFER, this.arrayBuffer_);
 
-  var currentProgram = null;
   var locations;
   for (i = 0, ii = layersArray.length; i < ii; ++i) {
     layer = layersArray[i];
@@ -453,29 +452,26 @@ ol.renderer.webgl.Map.prototype.renderFrame = function(frameState) {
     }
 
     var program = context.getProgram(fragmentShader, vertexShader);
-    if (program != currentProgram) {
 
-      gl.useProgram(program);
-      currentProgram = program;
-
-      if (useColor) {
-        if (goog.isNull(this.colorLocations_)) {
-          locations =
-              new ol.renderer.webgl.map.shader.Color.Locations(gl, program);
-          this.colorLocations_ = locations;
-        } else {
-          locations = this.colorLocations_;
-        }
+    if (useColor) {
+      if (goog.isNull(this.colorLocations_)) {
+        locations =
+            new ol.renderer.webgl.map.shader.Color.Locations(gl, program);
+        this.colorLocations_ = locations;
       } else {
-        if (goog.isNull(this.defaultLocations_)) {
-          locations =
-              new ol.renderer.webgl.map.shader.Default.Locations(gl, program);
-          this.defaultLocations_ = locations;
-        } else {
-          locations = this.defaultLocations_;
-        }
+        locations = this.colorLocations_;
       }
+    } else {
+      if (goog.isNull(this.defaultLocations_)) {
+        locations =
+            new ol.renderer.webgl.map.shader.Default.Locations(gl, program);
+        this.defaultLocations_ = locations;
+      } else {
+        locations = this.defaultLocations_;
+      }
+    }
 
+    if (context.useProgram(program)) {
       gl.enableVertexAttribArray(locations.a_position);
       gl.vertexAttribPointer(
           locations.a_position, 2, goog.webgl.FLOAT, false, 16, 0);
@@ -483,7 +479,6 @@ ol.renderer.webgl.Map.prototype.renderFrame = function(frameState) {
       gl.vertexAttribPointer(
           locations.a_texCoord, 2, goog.webgl.FLOAT, false, 16, 8);
       gl.uniform1i(locations.u_texture, 0);
-
     }
 
     layerRenderer = this.getLayerRenderer(layer);
diff --git a/src/ol/renderer/webgl/webgltilelayerrenderer.js b/src/ol/renderer/webgl/webgltilelayerrenderer.js
index 00e40b9bc7..cf73e018b8 100644
--- a/src/ol/renderer/webgl/webgltilelayerrenderer.js
+++ b/src/ol/renderer/webgl/webgltilelayerrenderer.js
@@ -175,7 +175,7 @@ ol.renderer.webgl.TileLayer.prototype.renderFrame =
     gl.disable(goog.webgl.BLEND);
 
     var program = context.getProgram(this.fragmentShader_, this.vertexShader_);
-    gl.useProgram(program);
+    context.useProgram(program);
     if (goog.isNull(this.locations_)) {
       this.locations_ =
           new ol.renderer.webgl.tilelayer.shader.Locations(gl, program);
diff --git a/src/ol/webgl/context.js b/src/ol/webgl/context.js
index 404fe4361e..bca86a5dc2 100644
--- a/src/ol/webgl/context.js
+++ b/src/ol/webgl/context.js
@@ -56,6 +56,12 @@ ol.webgl.Context = function(canvas, gl) {
    */
   this.programCache_ = {};
 
+  /**
+   * @private
+   * @type {WebGLProgram}
+   */
+  this.currentProgram_ = null;
+
   goog.events.listen(this.canvas_, ol.webgl.WebGLContextEventType.LOST,
       this.handleWebGLContextLost, false, this);
   goog.events.listen(this.canvas_, ol.webgl.WebGLContextEventType.RESTORED,
@@ -226,6 +232,7 @@ ol.webgl.Context.prototype.handleWebGLContextLost = function() {
   goog.object.clear(this.bufferCache_);
   goog.object.clear(this.shaderCache_);
   goog.object.clear(this.programCache_);
+  this.currentProgram_ = null;
 };
 
 
@@ -236,6 +243,22 @@ ol.webgl.Context.prototype.handleWebGLContextRestored = function() {
 };
 
 
+/**
+ * @param {WebGLProgram} program Program.
+ * @return {boolean} Changed.
+ */
+ol.webgl.Context.prototype.useProgram = function(program) {
+  if (program == this.currentProgram_) {
+    return false;
+  } else {
+    var gl = this.getGL();
+    gl.useProgram(program);
+    this.currentProgram_ = program;
+    return true;
+  }
+};
+
+
 /**
  * @private
  * @type {goog.log.Logger}