https://jsbin.com/teteluw/1/edit?html,js,output Try to drag the range slider. It won't move. Then, mouse up, and hover over the range thumb, it'll start moving with the mouse.
<rdar://problem/72336389>
Thanks for filing, I can reproduce this on Safari 13.1.3 as well as STP 117.
Instead of filing a separate bug, I'll suggest that this could be expanded to include number inputs as well. When setPointerCapture is used on a number input, clicking one of the "spinbutton"s will cause hovering over them to increment/decrement continuously as if the mouse/pointer/button was held down. Example at: https://lzlpc.csb.app/
Might be to merge this: https://chromium.googlesource.com/chromium/src.git/+/f4f29e883a0d68017e912d930b0070c3d76e8506 WebKit uses 'setCapturingMouseEventsElement': https://searchfox.org/wubkat/source/Source/WebCore/html/shadow/SliderThumbElement.cpp#293 It might need to use: `setPointerCapture`: https://searchfox.org/wubkat/rev/581e116dc6ce254811dbe2da9d1c1168762fc30c/Source/WebCore/dom/Element.cpp#4457