Screen capturing based on Windows Magnification API fails on Windows 7 64 bit With Aero theme disabled











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I'm trying to capture the desktop screen using Windows Magnification APIs based on code sample given in https://www.codeproject.com/Articles/607288/Screenshot-using-the-Magnification-library?msg=5570528#xx5570528xx.



The program (32bit executable) works pretty good on Windows8 and Windows10 but fails on Windows7 OS. I compiled the program into 64bit and the behavior is same even for the sample program mentioned in the above codeproject thread.



After debugging I figured out that the MagImageScalingCallback function returns image width and height as 4*4 instead of my monitor's size and that causes the program to crash or capture a blank screen on Windows7 machines (reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/ns-magnification-tagmagimageheader).



All the API calls (MagInitialize, CreateWindow, MagSetWindowFilterList & MagSetWindowSource) are successful. There are no API call failures or mistakes in the code flow in terms of Initializing creating, setting desktop area & assigning filter list.



DWM (Aero theme) is turned off (as per reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback)



I couldn't find any resources related to this topic even after researching for about 3 days. I have to use Magnification APIs because I have the need to capture windows that stays behind other windows on the desktop.



Any help would be appreciated.



Update 1:



I figured out that the application is able to capture the screen only when Aero theme is enabled and that contradicts with the statement in https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback.



I'm not sure how could I make it work on Operating systems with Aero theme disabled or not available by default.










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  • 1




    Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
    – Hans Passant
    Nov 14 at 10:54










  • @HansPassant you are absolutely right. This should be the answer, thanks.
    – Ram
    Nov 15 at 12:51















up vote
1
down vote

favorite
3












I'm trying to capture the desktop screen using Windows Magnification APIs based on code sample given in https://www.codeproject.com/Articles/607288/Screenshot-using-the-Magnification-library?msg=5570528#xx5570528xx.



The program (32bit executable) works pretty good on Windows8 and Windows10 but fails on Windows7 OS. I compiled the program into 64bit and the behavior is same even for the sample program mentioned in the above codeproject thread.



After debugging I figured out that the MagImageScalingCallback function returns image width and height as 4*4 instead of my monitor's size and that causes the program to crash or capture a blank screen on Windows7 machines (reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/ns-magnification-tagmagimageheader).



All the API calls (MagInitialize, CreateWindow, MagSetWindowFilterList & MagSetWindowSource) are successful. There are no API call failures or mistakes in the code flow in terms of Initializing creating, setting desktop area & assigning filter list.



DWM (Aero theme) is turned off (as per reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback)



I couldn't find any resources related to this topic even after researching for about 3 days. I have to use Magnification APIs because I have the need to capture windows that stays behind other windows on the desktop.



Any help would be appreciated.



Update 1:



I figured out that the application is able to capture the screen only when Aero theme is enabled and that contradicts with the statement in https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback.



I'm not sure how could I make it work on Operating systems with Aero theme disabled or not available by default.










share|improve this question




















  • 1




    Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
    – Hans Passant
    Nov 14 at 10:54










  • @HansPassant you are absolutely right. This should be the answer, thanks.
    – Ram
    Nov 15 at 12:51













up vote
1
down vote

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up vote
1
down vote

favorite
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I'm trying to capture the desktop screen using Windows Magnification APIs based on code sample given in https://www.codeproject.com/Articles/607288/Screenshot-using-the-Magnification-library?msg=5570528#xx5570528xx.



The program (32bit executable) works pretty good on Windows8 and Windows10 but fails on Windows7 OS. I compiled the program into 64bit and the behavior is same even for the sample program mentioned in the above codeproject thread.



After debugging I figured out that the MagImageScalingCallback function returns image width and height as 4*4 instead of my monitor's size and that causes the program to crash or capture a blank screen on Windows7 machines (reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/ns-magnification-tagmagimageheader).



All the API calls (MagInitialize, CreateWindow, MagSetWindowFilterList & MagSetWindowSource) are successful. There are no API call failures or mistakes in the code flow in terms of Initializing creating, setting desktop area & assigning filter list.



DWM (Aero theme) is turned off (as per reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback)



I couldn't find any resources related to this topic even after researching for about 3 days. I have to use Magnification APIs because I have the need to capture windows that stays behind other windows on the desktop.



Any help would be appreciated.



Update 1:



I figured out that the application is able to capture the screen only when Aero theme is enabled and that contradicts with the statement in https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback.



I'm not sure how could I make it work on Operating systems with Aero theme disabled or not available by default.










share|improve this question















I'm trying to capture the desktop screen using Windows Magnification APIs based on code sample given in https://www.codeproject.com/Articles/607288/Screenshot-using-the-Magnification-library?msg=5570528#xx5570528xx.



The program (32bit executable) works pretty good on Windows8 and Windows10 but fails on Windows7 OS. I compiled the program into 64bit and the behavior is same even for the sample program mentioned in the above codeproject thread.



After debugging I figured out that the MagImageScalingCallback function returns image width and height as 4*4 instead of my monitor's size and that causes the program to crash or capture a blank screen on Windows7 machines (reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/ns-magnification-tagmagimageheader).



All the API calls (MagInitialize, CreateWindow, MagSetWindowFilterList & MagSetWindowSource) are successful. There are no API call failures or mistakes in the code flow in terms of Initializing creating, setting desktop area & assigning filter list.



DWM (Aero theme) is turned off (as per reference: https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback)



I couldn't find any resources related to this topic even after researching for about 3 days. I have to use Magnification APIs because I have the need to capture windows that stays behind other windows on the desktop.



Any help would be appreciated.



Update 1:



I figured out that the application is able to capture the screen only when Aero theme is enabled and that contradicts with the statement in https://docs.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetimagescalingcallback.



I'm not sure how could I make it work on Operating systems with Aero theme disabled or not available by default.







visual-c++ screenshot screen-capture dwm magnification-api






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edited Nov 14 at 10:15

























asked Nov 14 at 8:31









Ram

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  • 1




    Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
    – Hans Passant
    Nov 14 at 10:54










  • @HansPassant you are absolutely right. This should be the answer, thanks.
    – Ram
    Nov 15 at 12:51














  • 1




    Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
    – Hans Passant
    Nov 14 at 10:54










  • @HansPassant you are absolutely right. This should be the answer, thanks.
    – Ram
    Nov 15 at 12:51








1




1




Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
– Hans Passant
Nov 14 at 10:54




Win7 is the new XP in many ways. "need to capture windows that stays behind..." is the killer detail. That can't work with the DWM disabled.
– Hans Passant
Nov 14 at 10:54












@HansPassant you are absolutely right. This should be the answer, thanks.
– Ram
Nov 15 at 12:51




@HansPassant you are absolutely right. This should be the answer, thanks.
– Ram
Nov 15 at 12:51

















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