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POHTML canvas double buffering frame-rate issues
 

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  1. POHTML canvas double buffering frame-rate issues
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    <p>I have a full-screen canvas with 3 images drawn on it. When I resize the window, these images change position; however, it appears to be very glitchy, more so in Firefox. </p> <p>I've been reading that double-buffering should resolve this issue, but I'm wondering how I would double buffer when the next position is unknown. That is to say, I cannot determine what should be buffered in the future, so how would this be possible?</p> <p>Here is one source that seems doable, but I do not fully understand the concept Fedor is trying to explain. </p> <p><a href="https://stackoverflow.com/questions/2795269/does-html5-canvas-support-double-buffering">Does HTML5/Canvas Support Double Buffering?</a></p> <p>So far I have,</p> <pre><code> $canvas = $('#myclouds')[0]; $canvas_buffer = $('canvas')[0].insertAfter($canvas).css('visibility', 'hidden'); context = $canvas.getContext('2d'); context_buffer = $canvas_buffer.getContext('2d'); clouds_arr = [$canvas, $canvas_buffer]; $(window).resize(function () { drawCanvas(); }; function initCanvas() { // Sources for cloud images var cloud1 = '/js/application/home/images/cloud1.png', cloud2 = '/js/application/home/images/cloud2.png', cloud3 = '/js/application/home/images/cloud3.png'; // add clouds to be drawn // parameters are as follows: // image source, x, y, ratio, adjustment) addCloud(cloud1, null, 125, .03); addCloud(cloud2, null, 75, .15); addCloud(cloud3, null, 50, .55); addCloud(cloud1, null, 125, .97, 300); addCloud(cloud2, null, 70, .85, 300); addCloud(cloud3, null, 45, .5, 300); // Draw the canvas drawCanvas(); } function drawCanvas() { // Reset $canvas.attr('height', $window.height()).attr('width', $window.width()); // draw the clouds var l = clouds.length; for (var i = 0; i &lt; l; i++) { clouds[i].x = ($window.width() * clouds[i].ratio) - clouds[i].offset; drawimage(context, clouds[i]); } } function Cloud() { this.x = 0; this.y = 0; } function addCloud(path, x, y, ratio, offset) { var c = new Cloud; c.x = x; c.y = y; c.path = path; c.ratio = ratio || 0; c.offset = offset || 0; clouds.push(c); } function drawimage(ctx, image) { var clouds_obj = new Image(); clouds_obj.src = image.path; clouds_obj.onload = function() { ctx.drawImage(clouds_obj, image.x, image.y); }; } </code></pre>
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