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Merge pull request #1065 from arturadib/lazy-textlayer

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Lazy textLayer rendering - pauses after scroll event
This commit is contained in:
notmasteryet 2012-01-19 16:21:04 -08:00
commit 6969a2b40d
1 changed files with 43 additions and 10 deletions
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53
web/viewer.js
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@ -960,22 +960,55 @@ var TextLayerBuilder = function textLayerBuilder(textLayerDiv) {
var self = this;
var textDivs = this.textDivs;
var textLayerDiv = this.textLayerDiv;
this.textLayerTimer = setInterval(function renderTextLayer() {
var renderTimer = null;
var renderingDone = false;
var renderInterval = 0;
var resumeInterval = 500; // in ms
// Render the text layer, one div at a time
function renderTextLayer() {
if (textDivs.length === 0) {
clearInterval(self.textLayerTimer);
clearInterval(renderTimer);
renderingDone = true;
return;
}
var textDiv = textDivs.shift();
if (textDiv.dataset.textLength >= 1) { // avoid div by zero
if (textDiv.dataset.textLength > 0) {
textLayerDiv.appendChild(textDiv);
// Adjust div width (via letterSpacing) to match canvas text
// Due to the .offsetWidth calls, this is slow
textDiv.style.letterSpacing =
((textDiv.dataset.canvasWidth - textDiv.offsetWidth) /
(textDiv.dataset.textLength - 1)) + 'px';
if (textDiv.dataset.textLength > 1) { // avoid div by zero
// Adjust div width (via letterSpacing) to match canvas text
// Due to the .offsetWidth calls, this is slow
// This needs to come after appending to the DOM
textDiv.style.letterSpacing =
((textDiv.dataset.canvasWidth - textDiv.offsetWidth) /
(textDiv.dataset.textLength - 1)) + 'px';
}
} // textLength > 0
}
renderTimer = setInterval(renderTextLayer, renderInterval);
// Stop rendering when user scrolls. Resume after XXX milliseconds
// of no scroll events
var scrollTimer = null;
function textLayerOnScroll() {
if (renderingDone) {
window.removeEventListener('scroll', textLayerOnScroll, false);
return;
}
}, 0);
};
// Immediately pause rendering
clearInterval(renderTimer);
clearTimeout(scrollTimer);
scrollTimer = setTimeout(function textLayerScrollTimer() {
// Resume rendering
renderTimer = setInterval(renderTextLayer, renderInterval);
}, resumeInterval);
}; // textLayerOnScroll
window.addEventListener('scroll', textLayerOnScroll, false);
}; // endLayout
this.appendText = function textLayerBuilderAppendText(text,
fontName, fontSize) {