Create CheckShaderMax.js

Author: photonstorm

src/renderer/webgl/CheckShaderMax.js

@@ -0,0 +1,58 @@
+//  From Pixi v5
+
+function GenerateSrc (maxIfs)
+{
+    var src = '';
+
+    for (var i = 0; i < maxIfs; ++i)
+    {
+        if (i > 0)
+        {
+            src += '\nelse ';
+        }
+
+        if (i < maxIfs - 1)
+        {
+            src += 'if(test == ' + i + '.0){}';
+        }
+    }
+
+    return src;
+}
+
+var CheckShaderMax = function (gl, maxIfs)
+{
+    var shader = gl.createShader(gl.FRAGMENT_SHADER);
+
+    var fragTemplate = [
+        'precision mediump float;',
+        'void main(void){',
+        'float test = 0.1;',
+        '%forloop%',
+        'gl_FragColor = vec4(0.0);',
+        '}'
+    ].join('\n');
+
+    // eslint-disable-next-line no-constant-condition
+    while (true)
+    {
+        var fragmentSrc = fragTemplate.replace(/%forloop%/gi, GenerateSrc(maxIfs));
+
+        gl.shaderSource(shader, fragmentSrc);
+        gl.compileShader(shader);
+
+        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
+        {
+            maxIfs = (maxIfs / 2) | 0;
+        }
+        else
+        {
+            // valid!
+            break;
+        }
+    }
+
+    return maxIfs;
+};
+
+module.exports = CheckShaderMax;