Linux C: get the screen resolution and window size
Happened to necessitate the retrieval of information about the screen of the canonical X window system (X11) in use while I am employing Fedora Linux release 14.
Some guys (or gals maybe) suggest achieving this by GTK calls like gdk_screen_get_resolution or the like, I will prefer to using the legacy routines of Xlib for accessing to the X window information. For at least one thing, the X window system is presumably more likely to be installed in Linux OS than is the GTK/GTK+ libraries in my view.
Actually it is quite simpler than it might be postulated to be:
// -----------------------------------------------------------
// Purpose : simply retrieve current X screen resolution and
// the size of current root window of the default
// screen of curent default window
// -----------------------------------------------------------
#include <X11/Xlib.h>
#include <stdio.h>
int getRootWindowSize(int *w, int *h)
{
Display* pdsp = NULL;
Window wid = 0;
XWindowAttributes xwAttr;
pdsp = XOpenDisplay( NULL );
if ( !pdsp ) {
fprintf(stderr, "Failed to open default display.\n");
return -1;
}
wid = DefaultRootWindow( pdsp );
if ( 0 > wid ) {
fprintf(stderr, "Failed to obtain the root windows Id "
"of the default screen of given display.\n");
return -2;
}
Status ret = XGetWindowAttributes( pdsp, wid, &xwAttr );
*w = xwAttr.width;
*h = xwAttr.height;
XCloseDisplay( pdsp );
return 0;
}
int getScreenSize(int *w, int*h)
{
Display* pdsp = NULL;
Screen* pscr = NULL;
pdsp = XOpenDisplay( NULL );
if ( !pdsp ) {
fprintf(stderr, "Failed to open default display.\n");
return -1;
}
pscr = DefaultScreenOfDisplay( pdsp );
if ( !pscr ) {
fprintf(stderr, "Failed to obtain the default screen of given display.\n");
return -2;
}
*w = pscr->width;
*h = pscr->height;
XCloseDisplay( pdsp );
return 0;
}
int main()
{
int w, h;
getScreenSize(&w, &h);
printf (" Screen: width = %d, height = %d \n", w, h);
getRootWindowSize(&w, &h);
printf (" Root Window: width = %d, height = %d \n", w, h);
return 1;
}
/* gcc -o $@ $< -lX11 */
/* set ts=4 sts=4 tw=100 sw=4 */
You can also retrieve more information about the X window system you are currently using, such as display name and the tag of vendor.
// -----------------------------------------------------------
// Purpose : simply retrieve current X windows information
// -----------------------------------------------------------
#define XLIB_ILLEGAL_ACCESS
#include <X11/Xlib.h>
#include <stdio.h>
int main()
{
Display* pdsp = XOpenDisplay(NULL);
Window wid = DefaultRootWindow(pdsp);
Screen* pwnd = DefaultScreenOfDisplay(pdsp);
int sid = DefaultScreen(pdsp);
XWindowAttributes xwAttr;
XGetWindowAttributes(pdsp,wid,&xwAttr);
printf (" name : %s\n vendor : %s\n", pdsp->display_name, pdsp->vendor);
printf (" pos : (%d, %d), width = %d, height = %d \n",
xwAttr.x, xwAttr.y, xwAttr.width, xwAttr.height);
XCloseDisplay( pdsp );
return 1;
}
/* gcc -o $@ $< -lX11 */
/* set ts=4 sts=4 tw=100 sw=4 */
Note that here "#define XLIB_ILLEGAL_ACCESS" was used for accessing to some of the data member in the Display structure in C.
For more data member accessible, see the definition/declarations in the header /usr/include/X11/Xlib.h.
PS: It is thankfully in the courtesy of
http://www.craftyfella.com/2010/01/syntax-highlighting-with-blogger-engine.html to make the code snippets I posted above have a highlighted effect and look organized more trimly (otherwise it is always bit of mangled!) Thanks to
craftyfella!
