Hi,
I am having issues with getting correct alpha blending using QNX Screen. I am using QNX 6.6.0.  From the documentation:

There are 3 parameters that  control how transparency (alpha blending) is done in QNX Screen.
SCREEN_PROPERTY_TRANSPARENCY
SCREEN_PROPERTY_ALPHA_MODE
SCREEN_PROPERTY_GLOBAL_ALPHA   This value must be between 0 and 255.  If the global alpha value is 255 it is opaque

SCREEN_PROPERTY_TRANSPARENCY is set to SCREEN_TRANSPARENCY_SOURCE_OVER = 3 (typical alpha blending)

SCREEN_PROPERTY_ALPHA_MODE
     alpha-mode = pre-multipled
     alpha-mode = non-pre-multipled
SCREEN_NON_PRE_MULTIPLIED_ALPHA The non pre-multiplied alpha content. This is the default. In this case, the source 
blending is done using the equation: 
c(r,g,b) = s(r,g,b) * s(a) + d(r,g,b) * (1 - s(a)) 
SCREEN_PRE_MULTIPLIED_ALPHA The pre-multiplied alpha content. In this case, the source blending is done using the 
equation: 
c(r,g,b) = s(r,g,b) + d(r,g,b) * (1 - s(a))


I am trying to do a simple background (BG) and foreground (FG) blend.

I did few tests and it showed that s(a) in the SCREEN_PROPERTY_ALPHA_MODE equations proved to be controlled by the value
 set to SCREEN_PROPERTY_GLOBAL_ALPHA.

Tests:
1.)	SCREEN_PROPERTY_GLOBAL_ALPHA = 0
a.	SCREEN_PROPERTY_ALPHA_MODE was set to Non_pre_multipled and pre_multiplied: Only background was visible.
2.)	 SCREEN_PROPERTY_GLOBAL_ALPHA = 1 to 255
a.	SCREEN_PROPERTY_ALPHA_MODE was set to Non_pre_multipled and pre_multiplied: Only foreground was visible.

I didn’t get any blend between the FG & BG with any combination with above tests. 

what am I missing?  Is it possible that this is related to the hardware (i.MX6D)?

Any suggestions would be appreciated.

Dinu