UbuntuShape should support overlays

[Michał Sawicz]

As can be seen in the Carousel for People, the UbuntuShape needs to support a bottom bar of a certain height, color and opacity.

Important to note is that opacity will often be animated.

I can also imagine a top (maybe even left/right) bar might also be useful in the future.

I wouldn't allow different overlay colors as that could result in conflicts. The existing color property should be sufficient, as the overlay will most likely be used with images. I'm not even sure we should have separate opacities, for the same reason.

One more (possibly future) extension would be to blur the image for added readability.

I propose API additions as follows:

UbuntuShape {
  property int overlay.top: 0
  property int overlay.bottom: 0
  property int overlay.left: 0
  property int overlay.right: 0

  property real overlay.opacity: 1.0
  # or
  property real overlay.topOpacity: 1.0
  property real overlay.bottomOpacity: 1.0
  property real overlay.leftOpacity: 1.0
  property real overlay.rightOpacity: 1.0

  # potential future enhancement
  property real overlay.blur: 0.0
}

[Tim Peeters (tpeeters)]

when this bug is fixed - https://bugs.launchpad.net/ubuntu-ui-toolkit/+bug/1157712 then we don't need the ubuntushape to support overlays anymore because you can do it inside the Item that you put in the UbuntuShape.

[Michał Sawicz (saviq)]

That's arguable, if the shape supported an overlay internally, it would be a lot faster than blending an Image and a Rectangle together in an FBO, just to give it to the Shape for masking.

[Michał Sawicz (saviq)]

Isn't bug #1396170 a duplicate, one that's in progress, too?