<!--
Copyright (c) 2019 The Khronos Group Inc.
Use of this source code is governed by an MIT-style license that can be
found in the LICENSE.txt file.
-->

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL Rendering and Sampling Feedback Loop Tests</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../js/js-test-pre.js"></script>
<script src="../../js/webgl-test-utils.js"></script>
</head>
<body>
<canvas id="example" width="8" height="8"></canvas>
<div id="description"></div>
<div id="console"></div>

<script id="vs100" type="x-shader/x-vertex">
attribute vec4 aPosition;
attribute vec2 aTexCoord;
varying vec2 texCoord;
void main() {
    gl_Position = aPosition;
    texCoord = aTexCoord;
}
</script>

<script id="fs100" type="x-shader/x-fragment">
#extension GL_EXT_draw_buffers : require
precision mediump float;
uniform sampler2D tex;
varying vec2 texCoord;
void main() {
    gl_FragData[0] = texture2D(tex, texCoord);
    gl_FragData[1] = texture2D(tex, texCoord);
}
</script>

<script id="fs100-no-ext-draw-buffers" type="x-shader/x-fragment">
precision mediump float;
uniform sampler2D tex;
varying vec2 texCoord;
void main() {
    gl_FragData[0] = texture2D(tex, texCoord);
}
</script>

<script id="vs300" type="x-shader/x-vertex">#version 300 es
in highp vec4 aPosition;
in vec2 aTexCoord;
out vec2 texCoord;
void main() {
    gl_Position = aPosition;
    texCoord = aTexCoord;
}
</script>

<script id="fs300" type="x-shader/x-fragment">#version 300 es
precision mediump float;
uniform sampler2D tex;
in vec2 texCoord;
out vec4 oColor;
void main() {
    oColor = texture(tex, texCoord);
}
</script>

<script>
"use strict";

const wtu = WebGLTestUtils;
description("This test verifies the functionality of rendering to the same texture where it samples from.");

const gl = wtu.create3DContext("example");

const width = 8;
const height = 8;
let tex;
let fbo;
let drawBuffers = null;

if (!gl) {
    testFailed("WebGL context does not exist");
} else {
    testPassed("WebGL context exists");

    if (gl.drawBuffers) {
        debug("Using webgl2.drawBuffers.");
        drawBuffers = (x) => gl.drawBuffers(x);
    } else {
        const ext = gl.getExtension("WEBGL_draw_buffers");
        if (ext) {
            debug("Using WEBGL_draw_buffers.drawBuffersWEBGL.");
            drawBuffers = (x) => ext.drawBuffersWEBGL(x);
        }
    }

    init();

    // The sampling texture is bound to COLOR_ATTACHMENT1 during resource allocation
    allocate_resource();

    rendering_sampling_feedback_loop(null);
    if (drawBuffers) {
        rendering_sampling_feedback_loop([gl.NONE]);
        rendering_sampling_feedback_loop([gl.COLOR_ATTACHMENT0,
                                          gl.COLOR_ATTACHMENT0+1]);
        rendering_sampling_feedback_loop([gl.NONE,
                                          gl.COLOR_ATTACHMENT0+1]);
    }
}

function init() {
    let shaders = ["vs100", "fs100"];
    if (gl.texStorage2D) {
        shaders = ["vs300", "fs300"];
    } else if (!drawBuffers) {
        shaders = ["vs100", "fs100-no-ext-draw-buffers"];
    }
    const program = wtu.setupProgram(gl, shaders, ["aPosition", "aTexCoord"], [0, 1]);
    const positionLoc = gl.getAttribLocation(program, "aPosition");
    const texCoordLoc = gl.getAttribLocation(program, "aTexCoord");
    if (!program || positionLoc < 0 || texCoordLoc < 0) {
        testFailed("Set up program failed");
        return;
    }
    const texLoc = gl.getUniformLocation(program, "tex");
    gl.uniform1i(texLoc, 0);
    testPassed("Set up program succeeded");

    wtu.setupUnitQuad(gl, 0, 1);
    gl.viewport(0, 0, width, height);
}

function allocate_resource() {
    tex = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, tex);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 2, 2, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

    fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0);
}

function rendering_sampling_feedback_loop(draw_buffers) {
    debug("draw_buffers: " + JSON.stringify(draw_buffers));

    if (draw_buffers) {
        drawBuffers(draw_buffers);
    }

    // Make sure framebuffer is complete before feedback loop detection
    if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE) {
        testFailed("Framebuffer incomplete.");
        return;
    }

    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    wtu.clearAndDrawUnitQuad(gl);
    wtu.glErrorShouldBe(gl, gl.INVALID_OPERATION, "Feedback loop detection should ignore drawBuffers settings.");

    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST_MIPMAP_NEAREST);
    // The texture will be mipmap incomplete, so feedback cannot occur nor be consistently evaluated.
    wtu.clearAndDrawUnitQuad(gl);
    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "Feedback loop detection should ignore sampled incomplete textures.");

    if (draw_buffers) {
        drawBuffers([gl.COLOR_ATTACHMENT0]);
    }
}

gl.deleteTexture(tex);
gl.deleteFramebuffer(fbo);

var successfullyParsed = true;
</script>
<script src="../../js/js-test-post.js"></script>

</body>
</html>