Always call vertexAttribDivisor

Previously, if the divisor property was absent, the
gl.vertexAttribDivisor call would be omitted, which
caused the divisor value to be inherited from the
previous program.

With this change, an absent divisor causes an explicit
call to gl.vertexAttribDivisor with parameter zero.

Note this is a breaking change if people have been
deliberately or accidentally carrying divisor values
forward from one program to the next.

src/attributes.js

@@ -198,7 +198,7 @@ function makeTypedArray(array, name) {
  * @property {boolean} [normalize] whether or not to normalize the data. Default = false
  * @property {number} [offset] offset into buffer in bytes. Default = 0
  * @property {number} [stride] the stride in bytes per element. Default = 0
- * @property {number} [divisor] the divisor in instances. Default = undefined. Note: undefined = don't call gl.vertexAttribDivisor
+ * @property {number} [divisor] the divisor in instances. Default = 0
  *    where as anything else = do call it with this value
  * @property {WebGLBuffer} buffer the buffer that contains the data for this attribute
  * @property {number} [drawType] the draw type passed to gl.bufferData. Default = gl.STATIC_DRAW
@@ -221,7 +221,7 @@ function makeTypedArray(array, name) {
  * @property {boolean} [normalize] normalize for `vertexAttribPointer`. Default is true if type is `Int8Array` or `Uint8Array` otherwise false.
  * @property {number} [stride] stride for `vertexAttribPointer`. Default = 0
  * @property {number} [offset] offset for `vertexAttribPointer`. Default = 0
- * @property {number} [divisor] divisor for `vertexAttribDivisor`. Default = undefined. Note: undefined = don't call gl.vertexAttribDivisor
+ * @property {number} [divisor] divisor for `vertexAttribDivisor`. Default = 0
  *    where as anything else = do call it with this value
  * @property {string} [attrib] name of attribute this array maps to. Defaults to same name as array prefixed by the default attribPrefix.
  * @property {string} [name] synonym for `attrib`.

src/programs.js

@@ -395,9 +395,7 @@ function floatAttribSetter(gl, index) {
       gl.enableVertexAttribArray(index);
       gl.vertexAttribPointer(
           index, b.numComponents || b.size, b.type || FLOAT, b.normalize || false, b.stride || 0, b.offset || 0);
-      if (b.divisor !== undefined) {
-        gl.vertexAttribDivisor(index, b.divisor);
-      }
+      gl.vertexAttribDivisor(index, b.divisor || 0);
     }
   };
 }
@@ -416,9 +414,7 @@ function intAttribSetter(gl, index) {
       gl.enableVertexAttribArray(index);
       gl.vertexAttribIPointer(
           index, b.numComponents || b.size, b.type || INT, b.stride || 0, b.offset || 0);
-      if (b.divisor !== undefined) {
-        gl.vertexAttribDivisor(index, b.divisor);
-      }
+      gl.vertexAttribDivisor(index, b.divisor || 0);
     }
   };
 }
@@ -437,9 +433,7 @@ function uintAttribSetter(gl, index) {
       gl.enableVertexAttribArray(index);
       gl.vertexAttribIPointer(
           index, b.numComponents || b.size, b.type || UNSIGNED_INT, b.stride || 0, b.offset || 0);
-      if (b.divisor !== undefined) {
-        gl.vertexAttribDivisor(index, b.divisor);
-      }
+      gl.vertexAttribDivisor(index, b.divisor || 0);
     }
   };
 }
@@ -462,9 +456,7 @@ function matAttribSetter(gl, index, typeInfo) {
       gl.enableVertexAttribArray(index + i);
       gl.vertexAttribPointer(
           index + i, size, type, normalize, stride, offset + rowOffset * i);
-      if (b.divisor !== undefined) {
-        gl.vertexAttribDivisor(index + i, b.divisor);
-      }
+      gl.vertexAttribDivisor(index + i, b.divisor || 0);
     }
   };
 }