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Bug 1643508 - Disable touch-based pinch zooming on pdf.js. #12212

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merged 1 commit into from
Aug 16, 2020
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Bug 1643508 - Disable touch-based pinch zooming on pdf.js. #12212

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20 changes: 20 additions & 0 deletions web/app.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1760,6 +1760,9 @@ const PDFViewerApplication = {

window.addEventListener("visibilitychange", webViewerVisibilityChange);
window.addEventListener("wheel", webViewerWheel, { passive: false });
window.addEventListener("touchstart", webViewerTouchStart, {
passive: false,
});
window.addEventListener("click", webViewerClick);
window.addEventListener("keydown", webViewerKeyDown);
window.addEventListener("keyup", webViewerKeyUp);
Expand Down Expand Up @@ -1822,6 +1825,9 @@ const PDFViewerApplication = {

window.removeEventListener("visibilitychange", webViewerVisibilityChange);
window.removeEventListener("wheel", webViewerWheel, { passive: false });
window.removeEventListener("touchstart", webViewerTouchStart, {
passive: false,
});
window.removeEventListener("click", webViewerClick);
window.removeEventListener("keydown", webViewerKeyDown);
window.removeEventListener("keyup", webViewerKeyUp);
Expand Down Expand Up @@ -2519,6 +2525,20 @@ function webViewerWheel(evt) {
}
}

function webViewerTouchStart(evt) {
if (evt.touches.length > 1) {
// Disable touch-based zooming, because the entire UI bits gets zoomed and
// that doesn't look great. If we do want to have a good touch-based
// zooming experience, we need to implement smooth zoom capability (probably
// using a CSS transform for faster visual response, followed by async
// re-rendering at the final zoom level) and do gesture detection on the
// touchmove events to drive it. Or if we want to settle for a less good
// experience we can make the touchmove events drive the existing step-zoom
// behaviour that the ctrl+mousewheel path takes.
evt.preventDefault();
}
}

function webViewerClick(evt) {
// Avoid triggering the fallback bar when the user clicks on the
// toolbar or sidebar.
Expand Down