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Moves watchScroll and getVisibleElements from PDFView

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This commit is contained in:
Yury Delendik 2014-09-12 13:39:23 -05:00
parent 12ec2a000b
commit bfefadb87c
2 changed files with 94 additions and 85 deletions
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85
web/ui_utils.js
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@ -138,6 +138,91 @@ function scrollIntoView(element, spot) {
parent.scrollTop = offsetY;
}
/**
* Helper function to start monitoring the scroll event and converting them into
* PDF.js friendly one: with scroll debounce and scroll direction.
*/
function watchScroll(viewAreaElement, callback) {
var debounceScroll = function debounceScroll(evt) {
if (rAF) {
return;
}
// schedule an invocation of scroll for next animation frame.
rAF = window.requestAnimationFrame(function viewAreaElementScrolled() {
rAF = null;
var currentY = viewAreaElement.scrollTop;
var lastY = state.lastY;
if (currentY > lastY) {
state.down = true;
} else if (currentY < lastY) {
state.down = false;
}
state.lastY = currentY;
// else do nothing and use previous value
callback(state);
});
};
var state = {
down: true,
lastY: viewAreaElement.scrollTop,
_eventHandler: debounceScroll
};
var rAF = null;
viewAreaElement.addEventListener('scroll', debounceScroll, true);
return state;
}
/**
* Generic helper to find out what elements are visible within a scroll pane.
*/
function getVisibleElements(scrollEl, views, sortByVisibility) {
var top = scrollEl.scrollTop, bottom = top + scrollEl.clientHeight;
var left = scrollEl.scrollLeft, right = left + scrollEl.clientWidth;
var visible = [], view;
var currentHeight, viewHeight, hiddenHeight, percentHeight;
var currentWidth, viewWidth;
for (var i = 0, ii = views.length; i < ii; ++i) {
view = views[i];
currentHeight = view.el.offsetTop + view.el.clientTop;
viewHeight = view.el.clientHeight;
if ((currentHeight + viewHeight) < top) {
continue;
}
if (currentHeight > bottom) {
break;
}
currentWidth = view.el.offsetLeft + view.el.clientLeft;
viewWidth = view.el.clientWidth;
if ((currentWidth + viewWidth) < left || currentWidth > right) {
continue;
}
hiddenHeight = Math.max(0, top - currentHeight) +
Math.max(0, currentHeight + viewHeight - bottom);
percentHeight = ((viewHeight - hiddenHeight) * 100 / viewHeight) | 0;
visible.push({ id: view.id, x: currentWidth, y: currentHeight,
view: view, percent: percentHeight });
}
var first = visible[0];
var last = visible[visible.length - 1];
if (sortByVisibility) {
visible.sort(function(a, b) {
var pc = a.percent - b.percent;
if (Math.abs(pc) > 0.001) {
return -pc;
}
return a.id - b.id; // ensure stability
});
}
return {first: first, last: last, views: visible};
}
/**
* Event handler to suppress context menu.
*/