Sakurai/pdf.js
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Zoom relative to cursor position via mouse wheel

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Before this patch, zooming in/out via the scroll wheel caused the page
to be zoomed relative to the upper-left corner of the page, i.e. the
upper-left corner of the page stays at a fixed position.

After this patch, the page is zoomed relative to the cursor position,
i.e. after zooming in/out, the part under the cursor 'has not moved'.

This only applies when the page does not fit in the viewport, because
pages smaller than the viewpoer are always centered.
This commit is contained in:
Rob Wu 2015-07-02 23:20:37 +02:00
parent 9ad6af4a3f
commit 2932f7c676
1 changed files with 18 additions and 1 deletions
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19
web/viewer.js
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@ -1811,14 +1811,31 @@ function handleMouseWheel(evt) {
evt.wheelDelta / MOUSE_WHEEL_DELTA_FACTOR;
var direction = (ticks < 0) ? 'zoomOut' : 'zoomIn';
if (PDFViewerApplication.pdfViewer.isInPresentationMode) {
var pdfViewer = PDFViewerApplication.pdfViewer;
if (pdfViewer.isInPresentationMode) {
evt.preventDefault();
PDFViewerApplication.scrollPresentationMode(ticks *
MOUSE_WHEEL_DELTA_FACTOR);
} else if (evt.ctrlKey || evt.metaKey) {
// Only zoom the pages, not the entire viewer.
evt.preventDefault();
var previousScale = pdfViewer.currentScale;
PDFViewerApplication[direction](Math.abs(ticks));
var currentScale = pdfViewer.currentScale;
if (previousScale !== currentScale) {
// After scaling the page via zoomIn/zoomOut, the position of the upper-
// left corner is restored. When the mouse wheel is used, the position
// under the cursor should be restored instead.
var scaleCorrectionFactor = currentScale / previousScale - 1;
var rect = pdfViewer.container.getBoundingClientRect();
var dx = evt.clientX - rect.left;
var dy = evt.clientY - rect.top;
pdfViewer.container.scrollLeft += dx * scaleCorrectionFactor;
pdfViewer.container.scrollTop += dy * scaleCorrectionFactor;
}
}
}