MagImageScalingCallback doesn't work in secondary monitor

Question

Hi, I'm using Magnification API to capture screenshoot, and I have some problems.
When I set up my magnifier window rect same as Secondary Monitor rect (such (1920,0,3840,1080)) , I can't get rgb data from MagImageScalingCallback.
Actually , MagImageScalingCallback can work normally on the primary monitor which rect is (0,0,1920,1080).
I can't find any doc to introduce how MagImageScalingCallback working on.
Can anybody tell me how to get rgb data from Secondary Monitor with Magnification API?
ps: my magnifier host window is showed as hidden.

Answer 1

From this documentation its noted that the MagImageScalingCallback was deprecated in Windows 7 and there is no replacement.

https://learn.microsoft.com/en-us/windows/win32/api/magnification/nc-magnification-magimagescalingcallback

Answer 2

Well, I wanna get the rgb data from magnifier window that show with SW_HIDE command. But I can't get data from this callback at secondary monitor

Answer 3

@JunPing Li Did you get any fix for this ? Only way I see is like you have to capture secondary screen as parts and stich it.

Answer 4

Hey,

I test the code of webrtc screen_capturer_win_magnifier.cc, find that if you want use magnification API to capture sub screen, maybe you should satisfy following conditions:

• make sure that the sum of left of host_window_ and magnifier_window_ is zero
• make sure that the sum of top of host_window_ and magnifier_window_ is zero
• make sure that the native_rect of MagSetWindowSource() equals to sub screen's position