Re: HTML5 apps compositing & opacity

[Jacobo Aragunde Pérez <jaragunde@xxxxxxxxxx>]

Hi Theo,

On 13/5/19 10:27, Theo BUENO via automotive-discussions wrote:
> Hi everyone,
> 
> I have been evaluating AGL's HTML5 platform with Chromium. I must say I
> am quite impressed by the level of support it currently has on AGL, and
> HTML5/WebGL apps run remarkably smoothly on Renesas H3.
> 
> I am interested into porting custom automotive graphical apps into
> WebGL/HTML5 and I am currently in the process of evaluating/benchmarking
> it against a native OpenGL ES solution.
> 

Thanks for testing the web application framework, please let us know of
any issues you encounter either here or in Jira.

> One thing I have noticed though is that there does not seem to be a way
> to gracefully handle background opacity of HTML5 apps. With current
> Qt/OpenGL demo apps, background opacity enables AGL to make use of
> Weston to create composite interfaces by stacking layers. This is how we
> are able to see the "wallpaper" behind apps such as homescreen or
> mediaplayer for instance. But with Chromium+WAM, a default background
> color seems to prevent this.
> 

We hadn't considered this requirement in this stage of the work, but we
have created a ticket to keep track of it, so it doesn't get lost:
https://jira.automotivelinux.org/browse/SPEC-2406

> I can see clues [1] in WAM's code that a background color can be set at
> this level, but I am unsure how this relates to this issue. With bare
> HTML documents, I was not able to get background opacity to "work"
> correctly. I can imagine that the way it could be addressed (if WAM
> really supports this) would be to add a custom AGL permission to set
> this behavior (something like "urn:AGL:html5:background-transparent" )
> at widget level.
> 
> Has this issue been addressed already ?
> 

I'm not sure if adding an AGL permission would be required, taking into
account there isn't an equivalent permission for native apps.
Nonetheless, the first step would be to clarify if it's possible to do
this with WAM/Chromium. At least, we know there is a concept of window
opacity in Chromium from:
https://chromium-review.googlesource.com/c/chromium/src/+/1520666

> [1]
> https://github.com/Igalia/webosose-wam/blob/master/src/core/WebPageBase.cpp#L383
> 
We'll keep the Jira ticket updated with any findings. Thanks for reporting!

Best,
-- 
Jacobo Aragunde
Software Engineer at Igalia
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