Bug 115405 – An iframe fling should not propagate to a parent iframe

• Status: NEW
• Component: UI Events

[Ryosuke Niwa]

We might want to back port https://chromium.googlesource.com/chromium/blink/+/fd480448cb8392b78999e056e51faf15d26b1b72

But I'm not sure how relevant this patch is to WebKit.

Fixed scrolling event handling to prevent bubbling up of touchscreen fling gestures when an iframe/div has become fully scrolled. This change affects only flings, regular gesture scrolling still bubbles up once the frame is fully scrolled. It also only affects flings from the touchscreen; touchpad flings retain the bubbling up behaviour.

[Antonio Gomes]

(In reply to comment #0)
> We might want to back port https://chromium.googlesource.com/chromium/blink/+/fd480448cb8392b78999e056e51faf15d26b1b72
> 
> But I'm not sure how relevant this patch is to WebKit.
> 
> Fixed scrolling event handling to prevent bubbling up of touchscreen fling gestures when an iframe/div has become fully scrolled. This change affects only flings, regular gesture scrolling still bubbles up once the frame is fully scrolled. It also only affects flings from the touchscreen; touchpad flings retain the bubbling up behaviour.

I am not sure if the ports in WebKit are still using this code path. Maybe Qt is still.

So back the at time, for the blackberry port, whenever a scrollable container (either a div or a frame) is being scrolled, it would not be possible to bubble it up to its scrollable parent. That was an usability decision. Instead, since both code paths were hardware accelerated, we over scroll the container, if it passes the scroll limits.

A scroll only gets propagated to its parent if at start of the gesture, you are at the say y:0 and one scrolls it downwards. In such cases, instead of over scrolling, we would look for the scrollable parent that would scroll in that direction.