`MouseEvent.pointerId` is `undefined` so that `setPointerCapture(undefined)`
means `setPointerCapture(0)` and it captures both click of mouse and first
touch of touch input devices. Therefore, for getting correct `pointerId`,
it needs to listen to `pointerdown`. Then, we make it listen to `pointerdown`
and `pointerup` events because `mousedown` and `mouseup` are always fired after
`pointerdown` and `pointerup` (`mousemove` and `pointermove` are really
different, therefore, it needs to keep listening to `mousemove`). Finally,
they are handling a drag during a button press. Therefore, they are designed
only for mouse devices. Therefore, this patch makes the `pointerdown` listener
start to handle a drag only when the device type is "mouse".
Note that the pointer capture will be released when all pointers of the device
are inactivated. Therefore, it does not need explicitly to release the capture.
Depends on D217215
Differential Revision: https://phabricator.services.mozilla.com/D217216
This adds an authoring tool similar to the one we have for cubic bezier.
A swatch is added next to `linear()` functions and clicking on it will show
the widget.
Modifying the line in the widget will update the value of the `linear()` function
in the rule view.
Differential Revision: https://phabricator.services.mozilla.com/D153333
Masayuki Nakano