Modifying Layers inside the SurfaceFlinger

[Tez]

I am trying to modify the SurfaceFlinger to implement a set of custom transforms on surface data.

As a first step, I am trying to identify to whom a layer belongs (i.e which uid/pid).

As the second step, I am trying to overlay an image onto one of the target layers from within the surface flinger.

How can I get this done? I've been reading the SurfaceFlinger code and the render loop calls the onDraw function

of all the layers being composited. 

For example, one function is LayerBase::drawWithOpenGL. I have seen Jeff Sharkey's early example on alpha channel

hackery to reduce power consumption, but I'm not sure if I'm looking in the right place.

Any guidance is much appreciated.

PS: This is NOT for production or anything. Just personal experiments.

[Tez]

So I've just discovered that the name of the layer corresponds to the activity.

There seems to be one layer per activity.

Is there always one layer per activity?

Who sets the name? I've noticed transient names. For example, when the app is starting, I see a name

like "Starting packagename..." and later it changes to package name.

-Earlence

[Craig Mautner]

The surfaces you are looking at correspond to a window in the window manager. They are generally created when its activity is brought to the foreground and destroyed when the activity is hidden. The ones labeled "Starting..." are created by the window manager in order to display something while the activity is starting up. Once the activity has drawn into its window the Starting window fades out and is destroyed.

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Craig Mautner | Android Framework | cmau...@google.com | 858-361-2683

[Tez]

Hi Craig,

I think I've seen your name while reading the code (cmautner).

Thanks for the info.

Another question:

Is there a way (from within surfaceflinger or Window manager service) to enforce a particular Z order on layers (surfaces)?

What needs to be modified for me to ensure some specific Z order on, say, 2 layers in the layer stack?

-Earlence