<!--
--------------------------------------
HTML QPA Image Viewer
--------------------------------------

Copyright (c) 2020 The Khronos Group Inc.
Copyright (c) 2020 Valve Corporation.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<html>
    <head>
        <meta charset="utf-8"/>
        <title>Load PNGs from QPA output</title>
        <style>
            body {
                background: white;
                text-align: left;
                font-family: sans-serif;
            }
            h1 {
                margin-top: 2ex;
            }
            h2 {
                font-size: large;
            }
            figure {
                display: flex;
                flex-direction: column;
            }
            img {
                margin-right: 1ex;
                margin-bottom: 1ex;
                /* Attempt to zoom images using the nearest-neighbor scaling
                algorithm. Unfortunately, not supported under Firefox at the
                time this text is being written. */
                image-rendering: pixelated;
                /* Use a black background color for images in case some pixels
                are transparent to some degree. In the worst case, the image
                could appear to be missing. */
                background: black;
            }
            button {
                margin: 1ex;
                border: none;
                border-radius: .5ex;
                padding: 1ex;
                background-color: steelblue;
                color: white;
                font-size: large;
            }
            button:hover {
                opacity: .8;
            }
            #clearimagesbutton {
                background-color: seagreen;
            }
            select {
                font-size: large;
                padding: 1ex;
                border-radius: .5ex;
                border: 1px solid darkgrey;
            }
            select:hover {
                opacity: .8;
            }
            .loadoption {
                text-align: center;
                margin: 1ex;
                padding: 2ex;
                border: 1px solid darkgrey;
                border-radius: 1ex;
            }
            #options {
                display: flex;
                flex-wrap: wrap;
            }
            #qpatext {
                display: block;
                min-width: 80ex;
                max-width: 132ex;
                min-height: 25ex;
                max-height: 25ex;
                margin: 1ex auto;
            }
            #fileselector {
                display: none;
            }
            #zoomandclear {
                margin: 2ex;
            }
            #images {
                margin: 2ex;
                display: flex;
                flex-direction: column;
            }
            .imagesblock {
                display: flex;
                flex-wrap: wrap;
            }
        </style>
    </head>
    <body>
        <h1>Load PNGs from QPA output</h1>

        <div id="options">
            <div class="loadoption">
                <h2>Option 1: Load local QPA files</h2>
                <!-- The file selector text cannot be changed, so we use a hidden selector trick. -->
                <button id="fileselectorbutton">&#x1F4C2; Load files</button>
                <input id="fileselector" type="file" multiple>
            </div>

            <div class="loadoption">
                <h2>Option 2: Paste QPA text or text extract containing &lt;Image&gt; elements below and click "Load images"</h2>
                <textarea id="qpatext"></textarea>
                <button id="loadimagesbutton">&#x1F4C3; Load images</button>
            </div>
        </div>

        <div id="zoomandclear">
            &#x1F50E; Image zoom
            <select id="zoomselect">
                <option value="1" selected>1x</option>
                <option value="2">2x</option>
                <option value="4">4x</option>
                <option value="8">8x</option>
                <option value="16">16x</option>
                <option value="32">32x</option>
            </select>
            <button id="clearimagesbutton">&#x267B; Clear images</button>
        </div>

        <div id="images"></div>

        <script>
            // Returns zoom factor as a number.
            var getSelectedZoom = function () {
                return new Number(document.getElementById("zoomselect").value);
            }

            // Scales a given image with the selected zoom factor.
            var scaleSingleImage = function (img) {
                var factor = getSelectedZoom();
                img.style.width = (img.naturalWidth * factor) + "px";
                img.style.height = (img.naturalHeight * factor) + "px";
            }

            // Rescales all <img> elements in the page. Used after changing the selected zoom.
            var rescaleImages = function () {
                var imageList = document.getElementsByTagName("img");
                for (var i = 0; i < imageList.length; i++) {
                    scaleSingleImage(imageList[i])
                }
            }

            // Removes everything contained in the images <div>.
            var clearImages = function () {
                var imagesNode = document.getElementById("images");
                while (imagesNode.hasChildNodes()) {
                    imagesNode.removeChild(imagesNode.lastChild);
                }
            }

            // Returns a properly sized image with the given base64-encoded PNG data.
            var createImage = function (pngData, imageName) {
                var imageContainer = document.createElement("figure");
                if (imageName.length > 0) {
                    var newFileNameHeader = document.createElement("figcaption");
                    newFileNameHeader.textContent = escape(imageName);
                    imageContainer.appendChild(newFileNameHeader);
                }
                var newImage = document.createElement("img");
                newImage.src = "data:image/png;base64," + pngData;
                newImage.onload = (function () {
                    // Grab the image for the callback. We need to wait until
                    // the image has been properly loaded to access its
                    // naturalWidth and naturalHeight properties, needed for
                    // scaling.
                    var cbImage = newImage;
                    return function () {
                        scaleSingleImage(cbImage);
                    };
                })();
                imageContainer.appendChild(newImage);
                return imageContainer;
            }

            // Returns a new h3 header with the given file name.
            var createFileNameHeader = function (fileName) {
                var newHeader = document.createElement("h3");
                newHeader.textContent = fileName;
                return newHeader;
            }

            // Returns a new image block to contain images from a file.
            var createImagesBlock = function () {
                var imagesBlock = document.createElement("div");
                imagesBlock.className = "imagesblock";
                return imagesBlock;
            }

            // Processes a chunk of QPA text from the given file name. Creates
            // the file name header and a list of images in the images <div>, as
            // found in the text.
            var processText = function(textString, fileName) {
                var imagesNode = document.getElementById("images");
                var newHeader = createFileNameHeader(fileName);
                imagesNode.appendChild(newHeader);
                var imagesBlock = createImagesBlock();
                // [\s\S] is a match-anything regexp like the dot, except it
                // also matches newlines. Ideally, browsers would need to widely
                // support the "dotall" regexp modifier, but that's not the case
                // yet and this does the trick.
                // Group 1 are the image element properties, if any.
                // Group 2 is the base64 PNG data.
                var imageRegexp = /<Image\b(.*?)>([\s\S]*?)<\/Image>/g;
                var imageNameRegexp = /\bName="(.*?)"/;
                var result;
                var innerResult;
                var imageName;
                while ((result = imageRegexp.exec(textString)) !== null) {
                    innerResult = result[1].match(imageNameRegexp);
                    imageName = ((innerResult !== null) ? innerResult[1] : "");
                    // Blanks need to be removed from the base64 string.
                    var pngData = result[2].replace(/\s+/g, "");
                    imagesBlock.appendChild(createImage(pngData, imageName));
                }
                imagesNode.appendChild(imagesBlock);
            }

            // Loads images from the text in the text area.
            var loadImages = function () {
                processText(document.getElementById("qpatext").value, "<Pasted Text>");
            }

            // Loads images from the files in the file selector.
            var handleFileSelect = function (evt) {
                var files = evt.target.files;
                for (var i = 0; i < files.length; i++) {
                    // Creates a reader per file.
                    var reader = new FileReader();
                    // Grab the needed objects to use them after the file has
                    // been read, in order to process its contents and add
                    // images, if found, in the images <div>.
                    reader.onload = (function () {
                        var cbFileName = files[i].name;
                        var cbReader = reader;
                        return function () {
                            processText(cbReader.result, cbFileName);
                        };
                    })();
                    // Reads file contents. This will trigger the event above.
                    reader.readAsText(files[i]);
                }
            }

            // File selector trick: click on the selector when clicking on the
            // custom button.
            var clickFileSelector = function () {
                document.getElementById("fileselector").click();
            }

            // Clears selected files to be able to select them again if needed.
            var clearSelectedFiles = function() {
                document.getElementById("fileselector").value = "";
            }

            // Set event handlers for interactive elements in the page.
            document.getElementById("fileselector").onclick = clearSelectedFiles;
            document.getElementById("fileselector").addEventListener("change", handleFileSelect, false);
            document.getElementById("fileselectorbutton").onclick = clickFileSelector;
            document.getElementById("loadimagesbutton").onclick = loadImages;
            document.getElementById("zoomselect").onchange = rescaleImages;
            document.getElementById("clearimagesbutton").onclick = clearImages;
        </script>
    </body>
</html>