Sakurai/pdf.js
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Build Text Layer one div at a a time as an Interval instead of a all in a TimeOut to keep the browser responsive

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This commit is contained in:
Adil Allawi 2011-12-14 22:28:34 +00:00
parent 8231ed1b11
commit ce57bac447
1 changed files with 18 additions and 10 deletions
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28
src/canvas.js
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@ -259,7 +259,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
this.textLayerQueue = []; this.textLayerQueue = [];
// Prevent textLayerQueue from being rendered while rendering a new page // Prevent textLayerQueue from being rendered while rendering a new page
if (this.textLayerTimer) if (this.textLayerTimer)
clearTimeout(this.textLayerTimer); clearInterval(this.textLayerTimer);
}, },
executeIRQueue: function canvasGraphicsExecuteIRQueue(codeIR, executeIRQueue: function canvasGraphicsExecuteIRQueue(codeIR,
@ -329,17 +329,21 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
var self = this; var self = this;
var renderTextLayer = function canvasRenderTextLayer() { var renderTextLayer = function canvasRenderTextLayer() {
var finished = true;
var textDivs = self.textDivs; var textDivs = self.textDivs;
for (var i = 0, length = textDivs.length; i < length; ++i) { if (textDivs.length > 0) {
if (textDivs[i].dataset.textLength > 1) { // avoid div by zero var textDiv = textDivs.shift();
textLayer.appendChild(textDivs[i]); if (textDiv.dataset.textLength > 1) { // avoid div by zero
textLayer.appendChild(textDiv);
// Adjust div width (via letterSpacing) to match canvas text // Adjust div width (via letterSpacing) to match canvas text
// Due to the .offsetWidth calls, this is slow // Due to the .offsetWidth calls, this is slow
textDivs[i].style.letterSpacing = textDiv.style.letterSpacing =
((textDivs[i].dataset.canvasWidth - textDivs[i].offsetWidth) / ((textDiv.dataset.canvasWidth - textDiv.offsetWidth) /
(textDivs[i].dataset.textLength - 1)) + 'px'; (textDiv.dataset.textLength - 1)) + 'px';
} }
finished = false;
} }
return finished;
} }
var textLayerQueue = this.textLayerQueue; var textLayerQueue = this.textLayerQueue;
textLayerQueue.push(renderTextLayer); textLayerQueue.push(renderTextLayer);
@ -347,12 +351,16 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
// Lazy textLayer rendering (to prevent UI hangs) // Lazy textLayer rendering (to prevent UI hangs)
// Only render queue if activity has stopped, where "no activity" == // Only render queue if activity has stopped, where "no activity" ==
// "no beginDrawing() calls in the last N ms" // "no beginDrawing() calls in the last N ms"
this.textLayerTimer = setTimeout(function renderTextLayerQueue() { this.textLayerTimer = setInterval(function renderTextLayerQueue() {
// Render most recent (==most relevant) layers first // Render most recent (==most relevant) layers first
for (var i = textLayerQueue.length - 1; i >= 0; i--) { for (var i = textLayerQueue.length - 1; i >= 0; i--) {
textLayerQueue.pop().call(); var finished = textLayerQueue[i].call();
if (finished)
textLayerQueue.splice(i,1);
} }
}, 500); if (textLayerQueue.length == 0)
clearInterval(this.textLayerTimer);
}, 1);
}, },
// Graphics state // Graphics state