<!DOCTYPE HTML> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width; initial-scale=1.0"> <title>Dragging the mouse on a scrollbar for a scrollframe inside nested transforms</title> <script type="application/javascript" src="apz_test_native_event_utils.js"></script> <script type="application/javascript" src="apz_test_utils.js"></script> <script src="/tests/SimpleTest/paint_listener.js"></script> <script type="text/javascript"> async function test() { var scrollableDiv = document.getElementById("scrollable"); let scrollPromise = new Promise(resolve => { scrollableDiv.addEventListener("scroll", resolve, {once: true}); }); // Scroll down a small amount (10px). The bug in this case is that the // scrollthumb "jumps" by an additional 40 pixels (height of the "gap" div) // and the scrollframe scrolls by a corresponding amount. So after doing this // drag we check the scroll position to make sure it hasn't scrolled by // too much. // Given the scrollable height of 2000px and scrollframe height of 400px, // the scrollthumb should be approximately 80px tall, and dragging it 10px // should scroll approximately 50 pixels. If the bug manifests, it will get // dragged 50px and scroll approximately 250px. var dragFinisher = await promiseVerticalScrollbarDrag(scrollableDiv, 10, 10); if (!dragFinisher) { ok(true, "No scrollbar, can't do this test"); return; } // the events above might be stuck in APZ input queue for a bit until the // layer is activated, so we wait here until the scroll event listener is // triggered. await scrollPromise; await dragFinisher(); // Flush everything just to be safe await promiseOnlyApzControllerFlushed(); // In this case we just want to make sure the scroll position moved from 0 // which indicates the thumb dragging worked properly. ok(scrollableDiv.scrollTop < 100, "Scrollbar drag resulted in a scroll position of " + scrollableDiv.scrollTop); } waitUntilApzStable() .then(test) .then(subtestDone, subtestFailed); </script> </head> <body> <div id="gap" style="min-height: 40px"></div> <div style="height: 400px; transform: translateZ(0)"> <div style="height: 100%; opacity: 0.9; will-change: opacity"> <div id="scrollable" style="height: 100%; overflow-y: auto; transform: translateZ(0)"> <div style="min-height: 2000px">Yay text</div> </div> </div> </div> </body> </html>