From 2932f7c6761fc523087c0d514b93488eb92e7236 Mon Sep 17 00:00:00 2001
From: Rob Wu <rob@robwu.nl>
Date: Thu, 2 Jul 2015 23:20:37 +0200
Subject: [PATCH] Zoom relative to cursor position via mouse wheel
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.
---
web/viewer.js | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/web/viewer.js b/web/viewer.js
index 1588ad605..c42545f21 100644
--- a/web/viewer.js
+++ b/web/viewer.js
@@ -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;
+ }
}
}