Re: [webkit-dev] enhancement - html hole element

[Julien Isorce]

Hi,

Thx for your replies!

We also had the solution based on plugin. But we prefer to not use plugins
if possible.

*Some details about our hole element implementation:

We have created a dedicated TextureMapperHoleBackingStore (which actually
could be integrated into TextureMapperSurfaceBackingStore).
So we call this GraphicsLayer::setContentsToPlatformLayer function from
RenderLayerBacking.cpp. I.e, we have put a new case: “if render().isHole()”
at the beginning of the existing black: “if render().isEmbeddedObject ()
else if render(). isVideo() else if render().isAcceleratedCanvas()” in
“RenderLayerBacking::updateGraphicsLayerConfiguration()”.
Note that the canvas case happens only if WEB_GL or ACCELERATED_2D_CANVAS
is enabled so moving the hole to video element is probably a better option.

We have validated it on upstream WebKitGtk and WebKitEfl, and the code we
put in WebKit is the same for both platforms.

* It makes sense to move this work to video. So instead of having a new
tag,  we suggest a new style value: video
style=”background=-webkit-hole;”
It will also simplify the diff a lot.

Comments are welcome.


On 19 September 2014 21:43, José Dapena Paz jdap...@igalia.com wrote:

 El jue, 18-09-2014 a las 12:07 -0700, Simon Fraser escribió:

  I don’t think it’s appropriate to add hole to WebKit.
 
  hole is really just adapting to a limitation of the platform’s
  compositing architecture. More powerful hardware like computers and
  smartphones are able to composite video above and below web content,
  which is achieved in WebCore via the accelerated compositing code
  path. I don’t think it’s appropriate to burden the platform with an
  element that only applies on power-limited hardware.
 
  The right solution for a WebKit implementation would be to solve this
  via the accelerated composting code. Just use a video or object in
  your markup, then implement the hole-punching via the GraphicsLayer
  subsystem.

 +1. Implementing punching hole with the integration of GraphicsLayer and
 MediaPlayer works well for the videos. Same for plugins.

 I see the punching hole is platform specific. No need for a new HTML
 tag.


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[webkit-dev] enhancement - html hole element

[Julien Isorce]

Hi,

A typical scenario when running WebKit in an embedded environment like a TV or 
STB is to punch through graphics to the video plane.

At Samsung Research UK we have developed a new hole element  that acts much 
like a canvas to

- Expose a rectangular hole in a web page.
- Support a mechanism to retrieve the position and size of the hole from 
JavaScript whenever its dimensions or location change.

We realise that there is currently no W3 specification for this element, but 
since our solution works we wanted to open the discussion to see if there is 
any wider interest, and if there is, to start the process of drafting a 
specification. Some details:

- Principle:

A hole is a rectangular area that behaves pretty much like a canvas, but 
everything in its area is transparent.
Every layer behind the hole is transparent in this rectangle.
In JavaScript you can register a handler which is notified when the hole 
position or size changes.

- Use case:

On TV this is useful to see the channel displayed behind the browser. 
Retrieving the hole's position and size
from JavaScript allows to rescale the TV channel plane to match the hole area 
whenever the hole changes.
Assume in JavaScript we have an object to control the TV channel plane.
This use case applies in many interactive TV applications, so it could be 
useful for a lot of people.

- Interfaces:

We have defined a new tag hole which  is similar to the canvas tag.
We have defined a geometrychanged JS event which is sent when the hole 
dimensions change.
This event contains the hole width, height and position in screen coordinates.

- Hole in canvas:

A hole tag has been defined to be less intrusive and having the feature in 
separate places in the code.
But we now think it may be better to actually put the hole capabilities under 
the canvas.
For example canvas style=background:hole;

Note that setting it as transparent is not enough to have a hole as the layers 
behind the canvas won't be necessarily transparent, and not only in its area.
The whole point of the hole capability is to make transparent every layers 
behind the hole and only in a specific rectangle.

- Next steps:

I would be very interested to hear if there are any other developers who need 
this functionality. If so, let's discuss the best way to share it, or possibly 
do it a better way.

Comments are welcome.

Julien

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