Detect if browser actually supports readPixels with float type, if it does not, use fallback readPixels mode

fuzzie360 · fuzzie360 · commit ba9a51386d6f · 2016-12-25T16:44:58.000+08:00
diff --git a/src/backend/mode_gpu.js b/src/backend/mode_gpu.js
@@ -142,8 +142,11 @@
 		function ret() {
 			if (opt.floatTextures === true && !GPUUtils.OES_texture_float) {
 				throw "Float textures are not supported on this browser";
+			} else if (opt.floatOutput === true && opt.floatOutputForce !== true && !GPUUtils.test_floatReadPixels(gpu)) {
+				throw "Float texture outputs are not supported on this browser";
 			} else if (opt.floatTextures === undefined && GPUUtils.OES_texture_float) {
 				opt.floatTextures = true;
+				opt.floatOutput = GPUUtils.test_floatReadPixels(gpu);
 			}
 			
 			if (!opt.dimensions || opt.dimensions.length === 0) {
diff --git a/src/utils.js b/src/utils.js
@@ -416,5 +416,36 @@ var GPUUtils = (function() {
 	}
 	GPUUtils.init_webgl = init_webgl;
 	
+	// test_readPixels closure based memoizer
+	var test_floatReadPixels_memoizer = null;
+	///
+	/// Function: test_floatReadPixels_memoizer
+	///
+	/// Checks if the browser supports readPixels with float type
+	///
+	/// Parameters:
+	/// 	gpu - {gpu.js object} the gpu object
+	///
+	/// Returns:
+	/// 	{Boolean} true if browser supports
+	///
+	function test_floatReadPixels(gpu) {
+		if (test_floatReadPixels_memoizer !== null) {
+			return test_floatReadPixels_memoizer
+		}
+		
+		var x = gpu.createKernel(function() {
+			return 1;
+		}, {
+			'dimensions': [2],
+			'floatTextures': true,
+			'floatOutput': true,
+			'floatOutputForce': true
+		}).dimensions([2])();
+		
+		return x[0] == 1;
+	}
+	GPUUtils.test_floatReadPixels = test_floatReadPixels;
+	
 	return GPUUtils;
 })();
