Gestures event issue - No offsets management

[ystreibel]

Hi,

When we try to use the x, y coordinates given by gestures event, we have noticed that the values do not take offsets in account.

You can find a sample code at https://github.com/ystreibel/my-canvas and the working demo http://ystreibel.github.io/my-canvas/components/my-canvas/demo/

This issue seems quite important, Could you please fix it up as soon as possible ?

Thanks.

[dfreedm]

I don't understand what you mean by "offsets". Can you explain a bit more?

[ystreibel]

Yes, try to draw on the yellow my-canvas components at http://ystreibel.github.io/my-canvas/components/my-canvas/demo/
Click down and move to the top. You can see a difference between your pointer position and the drawing point.
This difference is due to the first my-canvas conponents heigth (=offsets).

[dfreedm]

Ah I see. What I would recommend you do is use downEvent.sourceEvent.offsetX and offsetY to find your starting point and use offsetX + trackEvent.detail.dx and offsetY + trackEvent.detail.dy to draw your line.

[ystreibel]

I don't understand why the x,y coordinates are not computed by the topleft corner of the component.
More other, why they are not the sourceEvent on the trackEvent ?

[dfreedm]

sourceEvent was missing on the track events, I added them here: 5fb2ef3

Making x/y the topleft of a node requires using getBoundingClientRect, which will can cause a synchronous layout and be very expensive and slow.

[ystreibel]

Cool for sourceEvent on trackEvent, thanks !
Ok, I understand for getBoundingClientRect.

[kevinpschaaf]

Closing, with @azakus's sourceEvent fix there is enough information to calculate the screen position.