commit 98b439949ba9412db7bebc8cc229754ed910def9 · kitten.sh/frag-canvas-element

.changeset/angry-dogs-win.md

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       ---

     

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       'frag-canvas': patch

     

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       ---

     

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       Add preprocessing matching Shadertoy input API vaguely

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src/frag-canvas-element.ts

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       const VERSION_300 = '#version 300 es';

     

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       const VS_SOURCE_100 =

     

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         'attribute vec2 vPos;\n' +

     

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         'void main() {\n' +

     

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         '  gl_Position = vec4(vPos, 0.0, 1.0);\n' +

     

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         '}';

     

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       const VS_SOURCE_300 =

     

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         '#version 300 es\n' +

     

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         `${VERSION_300}\n` +

     

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         'in vec4 vPos;\n' +

     

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         'void main() {\n' +

     

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         '  gl_Position = vPos;\n' +

     
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           DATE.getSeconds() +

     

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           DATE.getMilliseconds() * 0.001;

     

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         return [year, month, day, time] as const;

     

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       };

     

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       const preprocessShader = (source: string, isES300: boolean) => {

     

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         let header = '';

     

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         let output = source;

     

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         if (output.startsWith(VERSION_300)) {

     

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           output = output.slice(VERSION_300.length + 1);

     

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           header += `${VERSION_300}\n`;

     

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         }

     

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         if (!/^\s*precision /.test(output)) header += 'precision highp float;\n';

     

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         if (output.includes('iChannel0')) header += 'uniform sampler2D iChannel0;\n';

     

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         if (output.includes('iResolution')) header += 'uniform vec2 iResolution;\n';

     

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         if (output.includes('iChannelResolution'))

     

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           header += 'uniform vec3 iChannelResolution[1];\n';

     

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         if (output.includes('iTime')) header += 'uniform float iTime;\n';

     

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         if (output.includes('iTimeDelta')) header += 'uniform float iTimeDelta;\n';

     

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         if (output.includes('iFrame')) header += 'uniform float iFrame;\n';

     

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         if (output.includes('iChannel')) header += 'uniform float iChannel;\n';

     

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         if (output.includes('iDate')) header += 'uniform vec4 iDate;\n';

     

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         if (isES300 && output.includes('gl_FragColor'))

     

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           header += 'out vec4 gl_FragColor;\n';

     

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         if (isES300 && output.includes('gl_FragCoord'))

     

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           header += 'in vec2 gl_FragCoord;\n';

     

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         if (!/main\s*\(/.test(output)) {

     

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           const ioRe = /\(\s*out\s+vec4\s+(\S+)\s*,\s*in\s+vec2\s+(\S+)\s*\)/g;

     

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           const io = ioRe.exec(source);

     

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           output = output.replace(/mainImage\s*\(/, 'main(').replace(ioRe, '()');

     

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           if (io && io[1] !== 'gl_FragColor')

     

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             header += `#define ${io[1]} gl_FragColor\n`;

     

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           if (io && io[2] !== 'gl_FragCoord')

     

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             header += `#define ${io[2]} gl_FragCoord.xy\n`;

     

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         }

     

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         if (!isES300) output = output.replace(/texture\s+\(/g, 'texture2D(');

     

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         return `${header}\n${output}`;

     

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       };

     

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       interface InitState {

     
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           updateFragShader(fragSource: string) {

     

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             fragSource = fragSource.trim();

     

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             gl.shaderSource(fragShader, fragSource);

     

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             const isES300 = /\s+#version 300/i.test(fragSource);

     

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             gl.shaderSource(fragShader, preprocessShader(fragSource, isES300));

     

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             gl.compileShader(fragShader);

     

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             const vertShader = /\s+#version 300/i.test(fragSource)

     

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               ? vertShader300

     

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               : vertShader100;

     

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             const vertShader = isES300 ? vertShader300 : vertShader100;

     

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             gl.attachShader(program, vertShader);

     

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             gl.attachShader(program, fragShader);

     

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