C++/Linux: How can I find the screen resolution?

I would like to write some code to query the display and get the screen resolution on Linux.
If there are multiple monitors, I'd like to know the resolution for all the monitors.

Any ideas how?
rjsuratiAsked:
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arnoldConnect With a Mentor Commented:
I think that is handled through the OS/kernel/graphics
i.e. all you would see is the range of the arrangement of the monitors. If there are three in a row, the information you are looking for is a position as if the three were a single large display.0,0-1920,1080 for a single monitor would be 0,0-5760,3240 for a three monitor setup.
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arnoldCommented:
You are looking at system calls to the graphics API.
http://www.yolinux.com/TUTORIALS/LinuxTutorialC++.html
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denissieCommented:
Using QT:
http://www.qtforum.org/article/22414/read-screen-resolution.html

In X11, you'd need to call the Xlib's XGetWindowAttributes to get the various window info, including the size and position relative to parent:
Example: http://cvsweb.xfree86.org/cvsweb/xc/programs/xwininfo/xwininfo.c?rev=1.11&content-type=text/vnd.viewcvs-markup
Ref: http://efreedom.com/Question/1-1153052/Programmatically-Get-Resolution-Window-System-Linux

I hope it helps.
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expert_tanmayCommented:
you'd need to call the Xlib's XGetWindowAttributes to get the various window info, including the size and position relative to parent. you can man xwininfo to check its capabilities and also download the source xwininfo.c

just type xwininfo.c in google you will get the source..
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denissieCommented:
expert_tanmay, you've just copy/pasted the reference and what I wrote above :)
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expert_tanmayCommented:
denissie Oh yes I didn't realize that you have also written about xwininfo.c. I was writing code on getting live view of Nikon D90 on my desktop when I came across xwininfo.c by coincidence.

 
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rjsuratiAuthor Commented:
Guys, this is all great. But, I'm not sure how the multiple monitor case comes into play. Don't I need to enumerate each of the displays somehow?

I can call XGetWindowAttributes on a window, and then get the information of the root window. But how does that tell me how many monitors there are and which monitor has which coordinates?

I apologize -- I'm feeling a bit confused.
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arnoldCommented:
Oops, the range would be 0,0-5760,1080. (x,y)
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