Discrepancy between command line XRandR and own code - c++

Question

I need to programatically get the refresh rate of a monitor.
When I type xrandr (1.4.1, opensuse 13) on the command line I get:
Screen 0: minimum 8 x 8, current 1920 x 1200, maximum 16384 x 16384
VGA-0 disconnected primary (normal left inverted right x axis y axis)
DVI-D-0 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
1920x1200 60.0*+
1920x1080 60.0
1680x1050 60.0
1600x1200 60.0
1280x1024 60.0
1280x960 60.0
1024x768 60.0
800x600 60.3
640x480 59.9
HDMI-0 disconnected (normal left inverted right x axis y axis)
This result is confirmed by nvidia-settings -q RefreshRate, among other things.
But ...
when I run the following code (origin: https://github.com/raboof/xrandr/blob/master/xrandr.c), compiled with g++ 4.8.1 (with -lX11 -lXext -lXrandr) :
int nsize;
int nrate;
short *rates;
XRRScreenSize *sizes;
Display *dpy = XOpenDisplay(NULL);
Window root = DefaultRootWindow(dpy);
XRRScreenConfiguration *conf = XRRGetScreenInfo(dpy, root);
printf ("Current rate: %d\n",XRRConfigCurrentRate(conf));
sizes = XRRConfigSizes(conf, &nsize);
printf(" SZ: Pixels Refresh\n");
for (int i = 0; i < nsize; i++) {
printf("%-2d %5d x %-5d", i, sizes[i].width, sizes[i].height);
rates = XRRConfigRates(conf, i, &nrate);
if (nrate)
printf(" ");
for (int j = 0; j < nrate; j++)
printf("%-4d", rates[j]);
printf("\n");
}
XRRFreeScreenConfigInfo(conf);
I get:
Current rate: 50
SZ: Pixels Refresh
0 1920 x 1200 50
1 1920 x 1080 51
2 1680 x 1050 52
3 1600 x 1200 53
4 1280 x 1024 54
5 1280 x 960 55
6 1024 x 768 56
7 800 x 600 57
8 640 x 480 58
9 1440 x 900 59
10 1366 x 768 60
11 1280 x 800 61
12 1280 x 720 62
Why am I getting this result?
What I am doing wrong?
The software uses OpenGL with GLEW. can this have any influence?
We do call glXQueryDrawable(dpy, drawable, GLX_SWAP_INTERVAL_EXT, &val) but afterwards, and I do not think this should have any influence.

Answer 1

I found the answer:
If the XRandR sever supports version 1.2 of the protocol, then the appropriate functions need to be used (wich I plan to do by copying snippets of code from https://github.com/raboof/xrandr/blob/master/xrandr.c where has_1_2 is true).
My code in the question uses functions for the version 1.1 of the protocol, and therefore only the metamodes are returned.
As a simple check, I tried the following two commands:
xrandr --q1
xrandr --q12.
And indeed the 1st one gives me the same result I programatically get.
Credits go to http://www.ogre3d.org/forums/viewtopic.php?f=4&t=65010&start=200