[maemo-developers] Howto grab all Maemo5 zoom key events in SDL/SDL_gles app?

[From: Eero Tamminen]

Hi,

Hamalainen Kimmo (Nokia-D/Helsinki) wrote:
> On Sun, 2010-05-02 at 13:26 +0200, ext Till Harbaum / Lists wrote:
>> i'd like to access the zoom keys in a SDL/SDL_gles app (the 3d globe
>> i uploaded to extras-devel).
>>
>> The odd thing is that my solution only partly works. Some key presses actually
>> reach my app as function key presses, but still most of them reach the volume
>> control. So when repeatedly pressing the zoom buttons my app zooms but also
>> the volume is changed.
>>
>> I am using the following code which is inspired by code from scummvm. I am 
>> calling this code once immediately after the SDL setup is done.
>>
>> Any idea why this still delivers some key events to the volume control?
> 
> It could be that _NET_ACTIVE_WINDOW or MB_CURRENT_APP_WINDOW on the root
> window does not correspond to your window.  The volume app is tracking
> one of these (I think _NET_ACTIVE_WINDOW) to determine the window whose
> ZOOM_KEY window property matters.

Maemo SDL doesn't seem to set all required window properties for
fullscreen windows for tracking of the topmost application to work
properly.  See this bug:
   https://bugs.maemo.org/show_bug.cgi?id=6175#c3

"xprop -root" produces this when there's a fullscreen SDL window:
_NET_ACTIVE_WINDOW(WINDOW): window id # 0x3e00002 

_MB_CURRENT_APP_WINDOW(WINDOW): window id # 0x3e00001

I.e. for SDL applications the value in these properties differ,
unlike for normal applications.

_MB_CURRENT_APP_WINDOW is the fullscreen SDL window and
_NET_ACTIVE_WINDOW is the non-fullscreen SDL window.

(I think SDL uses fullscreen window for output and non-fullscreen
one for input.)


	- Eero