Okay,
I am looking at the first issue, is there any way in my driver to say that
certain layers should not have a bg mode/color.
The crash is occuring as I try to GetDisplayLayer which in turn creates a
surface which in turn calls window stack functions and then accesses my null
ptr.
Therefore I have no chance in my application to call
layer->SetBackgroundMode(). So the only place I can see at the moment is to
make sure that I set the bgmode in my /etc/directfbrc file. is this correct
or should i be able to work some magic in my driver.
Dan
--------------------------------------------------
From: "Denis Oliver Kropp" <[EMAIL PROTECTED]>
Sent: Wednesday, September 03, 2008 4:32 PM
To: "Denis Oliver Kropp" <[EMAIL PROTECTED]>
Cc: "Daniel Laird" <[EMAIL PROTECTED]>; <directfb-dev@directfb.org>
Subject: Re: [directfb-dev] Virtual Video Surfaces Revisited.
> Denis Oliver Kropp wrote:
>> Daniel Laird wrote:
>>>> 1) Find out why the background is cleared at all, because
>>>> layers != PRIMARY should have no background color set,
>>>> or maybe it's black. The background mode for these layers
>>>> should be DLBM_DONTCARE to solve the issue.
>>>>
>>>> 2) Not create a window stack when the layer has a certain
>>>> capability, maybe add DLCAPS_NOWINDOWSTACK.
>>>>
>>>> 3) Allocate a dummy line of pixels in your surface pool and
>>>> keep the pitch at 0 :-)
>>>>
>>> Option 3 is probably the best but not the cleanest. I had a quick go
>>> with
>>> option 2.
>>
>> Option 3 is at least the one with the least impact or risks.
>>
>>> I modified dfb_layer_context_init in layer_context.c.
>>> I added
>>> /* Create the window stack if the layer supports it. */
>>> if (!D_FLAGS_IS_SET( shared->description.caps,
>>> DLCAPS_NOWINDOWSTACK ))
>>> {
>>> context->stack = dfb_windowstack_create( context );
>>> if (!context->stack) {
>>> dfb_layer_context_unref( context );
>>> return D_OOSHM();
>>> }
>>>
>>> /* Tell the window stack about its size. */
>>> dfb_windowstack_resize( context->stack,
>>> context->config.width,
>>> context->config.height );
>>> }
>>> This seemed to do the job rather nicely. Can you see any drawbacks?
>>> know of
>>> any hidden issues I might encounter.
>>
>>
>> The issues could be wherever context->stack is assumed to be non-NULL,
>> which should cause failing assertions, but some sites might just cause
>> a segmentation fault.
>>
>> So option 1 would be quite clean and somewhat safe, but at any time a
>> user might request to create a window or render to the layer surface
>> directly...
>>
>> I think I'd go for Option 1+3 which avoids filling the dummy line
>> multiple (height) times, but still has a fallback in case there's
>> another access.
>
> Ideally, option 2 would be the best, of course, but it also requires
> the biggest effort and caution :-)
>
> Denis
>
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