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CanvasBlocker/lib/webgl.js

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JavaScript
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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
(function(){
"use strict";
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const logging = require("./logging");
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let scope;
if ((typeof exports) !== "undefined"){
scope = exports;
}
else {
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scope = require.register("./webgl", {});
}
scope.copyCanvasToWebgl = function copyCanvasToWebgl(window, canvas, webGLVersion = "webgl"){
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const webGlCanvas = canvas.cloneNode(true);
const context =
window.HTMLCanvasElement.prototype.getContext.call(webGlCanvas, webGLVersion) ||
window.HTMLCanvasElement.prototype.getContext.call(webGlCanvas, "experimental-" + webGLVersion);
if (!context){
// unable to get a context...
logging.warning("unable to create webgl context.");
return {canvas: false, context: false};
}
context.viewport(0, 0, webGlCanvas.width, webGlCanvas.height);
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const program = context.createProgram();
const vertexShader = context.createShader(context.VERTEX_SHADER);
const vertex = "attribute vec4 a_position;\nattribute vec2 a_texCoord;\nvarying vec2 v_texCoord;\n" +
"void main(){\n\tgl_Position = a_position;\n\tv_texCoord = a_texCoord;\n}";
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context.shaderSource(vertexShader, vertex);
context.compileShader(vertexShader);
if (!context.getShaderParameter(vertexShader, context.COMPILE_STATUS)){
context.deleteShader(vertexShader);
logging.warning("webgl: failed to compile vertex shader.");
return {canvas: false, context: false};
}
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context.attachShader(program, vertexShader);
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const fragmentShader = context.createShader(context.FRAGMENT_SHADER);
const fragmenter = "precision mediump float;\nuniform sampler2D u_image;\nvarying vec2 v_texCoord;\n" +
"void main(){\n\tgl_FragColor = texture2D(u_image, v_texCoord);\n}";
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context.shaderSource(fragmentShader, fragmenter);
context.compileShader(fragmentShader);
if (!context.getShaderParameter(fragmentShader, context.COMPILE_STATUS)){
context.deleteShader(fragmentShader);
logging.warning("webgl: failed to compile fragmenter shader.");
return {canvas: false, context: false};
}
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context.attachShader(program, fragmentShader);
context.linkProgram(program);
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if (!context.getProgramParameter(program, context.LINK_STATUS)){
context.deleteProgram(program);
logging.warning("webgl: failed to link program.");
return {canvas: false, context: false};
}
context.useProgram(program);
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const positionBuffer = context.createBuffer();
context.bindBuffer(context.ARRAY_BUFFER, positionBuffer);
context.bufferData(context.ARRAY_BUFFER, new Float32Array([
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-1, -1,
-1, 1,
1, -1,
1, 1,
-1, 1,
1, -1
]), context.STATIC_DRAW);
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const positionAttributeLocation = context.getAttribLocation(program, "a_position");
context.enableVertexAttribArray(positionAttributeLocation);
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const size = 2; // 2 components per iteration
const type = context.FLOAT; // the data is 32bit floats
const normalize = false; // don't normalize the data
const stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
const offset = 0; // start at the beginning of the buffer
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context.vertexAttribPointer(positionAttributeLocation, size, type, normalize, stride, offset);
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const texCoordLocation = context.getAttribLocation(program, "a_texCoord");
// provide texture coordinates for the rectangle.
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const texCoordBuffer = context.createBuffer();
context.bindBuffer(context.ARRAY_BUFFER, texCoordBuffer);
context.bufferData(context.ARRAY_BUFFER, new Float32Array([
0, 1,
0, 0,
1, 1,
1, 0,
0, 0,
1, 1
]), context.STATIC_DRAW);
context.enableVertexAttribArray(texCoordLocation);
context.vertexAttribPointer(texCoordLocation, 2, context.FLOAT, false, 0, 0);
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context.bindTexture(context.TEXTURE_2D, context.createTexture());
context.texParameteri(context.TEXTURE_2D, context.TEXTURE_WRAP_S, context.CLAMP_TO_EDGE);
context.texParameteri(context.TEXTURE_2D, context.TEXTURE_WRAP_T, context.CLAMP_TO_EDGE);
context.texParameteri(context.TEXTURE_2D, context.TEXTURE_MIN_FILTER, context.NEAREST);
context.texParameteri(context.TEXTURE_2D, context.TEXTURE_MAG_FILTER, context.NEAREST);
context.texImage2D(context.TEXTURE_2D, 0, context.RGBA, context.RGBA, context.UNSIGNED_BYTE, canvas);
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context.drawArrays(context.TRIANGLES /*primitiveType*/, 0 /*triangleOffset*/, 6 /*count*/);
return {webGlCanvas, context};
};
}());