From 2f7c97f25acca00a5f744e332fd6a96efd98a5f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89ric=20Lemoine?= <eric.lemoine@gmail.com>
Date: Thu, 20 Nov 2014 13:40:23 +0100
Subject: [PATCH] Use OES_element_index_uint when available

---
 src/ol/has.js                      | 22 +++++++++++++++++-----
 src/ol/render/webgl/webglreplay.js | 22 +++++++++++++++++-----
 src/ol/webgl/context.js            | 14 ++++++++++++++
 3 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/src/ol/has.js b/src/ol/has.js
index 63745b48ac..ed05a84f85 100644
--- a/src/ol/has.js
+++ b/src/ol/has.js
@@ -113,6 +113,15 @@ ol.has.POINTER = 'PointerEvent' in goog.global;
 ol.has.MSPOINTER = !!(goog.global.navigator.msPointerEnabled);
 
 
+/**
+ * True if browser supports WebGL.
+ * @const
+ * @type {boolean}
+ * @api stable
+ */
+ol.has.WEBGL;
+
+
 /**
  * The maximum supported WebGL texture size in pixels. If WebGL is not
  * supported, the value is set to `-1`.
@@ -123,17 +132,18 @@ ol.has.WEBGL_MAX_TEXTURE_SIZE;
 
 
 /**
- * True if browser supports WebGL.
+ * List of supported WebGL extensions.
  * @const
- * @type {boolean}
- * @api stable
+ * @type {Array.<string>}
  */
-ol.has.WEBGL;
+ol.has.WEBGL_EXTENSIONS;
 
 
 (function() {
   if (ol.ENABLE_WEBGL) {
-    var hasWebGL = false, textureSize = -1;
+    var hasWebGL = false;
+    var textureSize = -1;
+    var /** @type {Array.<string>} */ extensions = [];
     if ('WebGLRenderingContext' in goog.global) {
       try {
         var canvas = /** @type {HTMLCanvasElement} */
@@ -145,10 +155,12 @@ ol.has.WEBGL;
           hasWebGL = true;
           textureSize = /** @type {number} */
               (gl.getParameter(gl.MAX_TEXTURE_SIZE));
+          extensions = gl.getSupportedExtensions();
         }
       } catch (e) {}
     }
     ol.has.WEBGL = hasWebGL;
     ol.has.WEBGL_MAX_TEXTURE_SIZE = textureSize;
+    ol.has.WEBGL_EXTENSIONS = extensions;
   }
 })();
diff --git a/src/ol/render/webgl/webglreplay.js b/src/ol/render/webgl/webglreplay.js
index da5c234f4f..1c1335b5c9 100644
--- a/src/ol/render/webgl/webglreplay.js
+++ b/src/ol/render/webgl/webglreplay.js
@@ -434,8 +434,19 @@ ol.render.webgl.ImageReplay.prototype.finish = function(context) {
 
   this.indicesBuffer_ = gl.createBuffer();
   gl.bindBuffer(goog.webgl.ELEMENT_ARRAY_BUFFER, this.indicesBuffer_);
-  gl.bufferData(goog.webgl.ELEMENT_ARRAY_BUFFER,
-      new Uint16Array(this.indices_), goog.webgl.STATIC_DRAW);
+  var /** @type {ArrayBufferView} */ arrayBuffer, bits;
+  if (context.hasOESElementIndexUint) {
+    bits = 32;
+    arrayBuffer = new Uint32Array(this.indices_);
+  } else {
+    bits = 16;
+    arrayBuffer = new Uint16Array(this.indices_);
+  }
+  goog.asserts.assert(this.indices_[this.indices_.length - 1] < (1 << bits),
+      'Too large element index detected, and OES_element_index_uint ' +
+      'extension not available.');
+  gl.bufferData(goog.webgl.ELEMENT_ARRAY_BUFFER, arrayBuffer,
+      goog.webgl.STATIC_DRAW);
 
   goog.asserts.assert(this.textures_.length === 0);
 
@@ -611,9 +622,10 @@ ol.render.webgl.ImageReplay.prototype.replay = function(context,
     gl.bindTexture(goog.webgl.TEXTURE_2D, this.textures_[i]);
     var end = this.groupIndices_[i];
     var numItems = end - start;
-    var offsetInBytes = start * 2;  // 2 Bytes for UNSIGNED_SHORT
-    gl.drawElements(goog.webgl.TRIANGLES, numItems,
-        goog.webgl.UNSIGNED_SHORT, offsetInBytes);
+    var offsetInBytes = start * (context.hasOESElementIndexUint ? 4 : 2);
+    var elementType = context.hasOESElementIndexUint ?
+        goog.webgl.UNSIGNED_INT : goog.webgl.UNSIGNED_SHORT;
+    gl.drawElements(goog.webgl.TRIANGLES, numItems, elementType, offsetInBytes);
     start = end;
   }
 };
diff --git a/src/ol/webgl/context.js b/src/ol/webgl/context.js
index 307837dc66..674526eac4 100644
--- a/src/ol/webgl/context.js
+++ b/src/ol/webgl/context.js
@@ -1,9 +1,11 @@
 goog.provide('ol.webgl.Context');
 
+goog.require('goog.array');
 goog.require('goog.asserts');
 goog.require('goog.events');
 goog.require('goog.log');
 goog.require('goog.object');
+goog.require('ol.has');
 goog.require('ol.structs.Buffer');
 goog.require('ol.structs.IntegerSet');
 goog.require('ol.webgl.WebGLContextEventType');
@@ -66,6 +68,18 @@ ol.webgl.Context = function(canvas, gl) {
    */
   this.currentProgram_ = null;
 
+  /**
+   * @type {boolean}
+   */
+  this.hasOESElementIndexUint = goog.array.contains(
+      ol.has.WEBGL_EXTENSIONS, 'OES_element_index_uint');
+
+  // use the OES_element_index_uint extension if available
+  if (this.hasOESElementIndexUint) {
+    var ext = gl.getExtension('OES_element_index_uint');
+    goog.asserts.assert(!goog.isNull(ext));
+  }
+
   goog.events.listen(this.canvas_, ol.webgl.WebGLContextEventType.LOST,
       this.handleWebGLContextLost, false, this);
   goog.events.listen(this.canvas_, ol.webgl.WebGLContextEventType.RESTORED,