It will be completely possible to implement subsystem with only include/freerdp/server/shadow.h and libfreerdp-shadow.
Details as following:
1. Exported surface structure as subsystem implementations deeply depend on it to send image update
2. Export capture APIs. They are actually indepent APIs to help compare and calculate image difference.
3. Introduce API to trigger client frame update. Conceal details in subsystem->updateEvent
4. Pass client to client callbacks. Subsystem implementation may need to know 'which client' send the interaction event as well as the authentication request.
Add this support in callback definition before anyone really use shadow framework APIs to implement a custom subsystem.
Also added callback for client capability exchange
5. Remove X11_ShadowSubsystem Mac_ShadowSubsystem Win_ShadowSubsystem from libfreerdp-shadow.
Discard FREERDP_API mark on ShadowSubsystemEntry functions and make them be compiled together with shadow.c in CMakeLists.txt.
This is required from PR #2751.
Now subsystem implementations and shadow.c could be regarded as an example for shadow framework.
Detail fixes:
1. Add resize support in shadow framework layer
2. Enhance X11 implementation to detect desktop resolution change
3. Fix the subRect feature.
It seems not completely finished and it looks incompatible in different source code.
Fix it to be consistent in all source code as following:
a. The subRect is only awared in framework layer, subsystem implementation should not be aware of it. It only take effect at shadow_client and corresponding shadow_input.
b. The screen and surface should only represent a monitor screen. They don't need to consider subRect feature.
4. A lobby should be alternative image shown to client when the client is not 'mayView'.
We don't need to have seperate lobby for each client, move it into server structure as 'another surface'
5. Fix display handle leak in enum monitor of X11
6. Suppress BadMatch Error while capturing the image
