Basic X Routines Summary
There are many other routines that are available at the Back to table of contentsBasic Xlib Routines/Macros
XOpenDisplay Connect to X server
DefaultScreen Returns the default screen of a given display
WhitePixel Returns white value for a given screen and display
BlackPixel Returns black value for a given screen and display
Xcreate SimpleWindow Create a simple window
DefaultRootWindow Returns the default root of a display
XMapRaised Map a window to a screen
XFlush Flush the request queue to the server
XDestroyWindow Destroys a window along with its related data structures
XCloseDisplay Disconnect from X server
XSelectInput Choose which type of event to be looked for
XNextEvent Wait for the next event specified by XSelectInput
XDrawArc Draw an arc
XFillArc Similar to XDrawArc but is filled
XDrawLine Draw line
XDrawRectangle Draws rectangle
XFillRectangle Similar to XDrawRectangle but is filled
XWarpPointer Moves mouse pointer
XLookupString Look up which key is pressed on keyboard
XRefreshKeyboard Mapping Changes key mapping to default value
XQueryPointer Returns the position of mouse pointer with status
of keys/buttons
GC Routines
XCreateGC Creates graphics context
XSetForeground Sets foreground attribute of a given GC
XSetBackground Sets background attribute of a given GC
XSetLineAttributes Sets the attribute of line of a given GC
XSetDashes Sets the dash attribute of line of a given GC
DisplayPlanes Returns color depth of a screen
Defaultcolormap Returns the default colormap of a given screen and
display
XAllocNamedColor Allocates a color of a given color name
XAllocColor Allocates a color of a given RGB attribute
This following program simply creates a window with white background for
5 seconds, then self-destruct.
Examples Example 1 - a easy start
%(1) cat xprog1.c
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
main ()
{
Display *display;
Window window;
int screen;
unsigned long foreground, background;
/* connect to the X server */
display = XOpenDisplay ("");
if (display == NULL) {
fprintf (stderr, "cannot connect to server\n");
exit (EXIT_FAILURE);
}
/* get default screen */
screen = DefaultScreen (display);
/* get black and white representation on current screen */
background = WhitePixel (display, screen);
foreground = BlackPixel (display, screen);
/* Create window at (100,50), width 350, height 250, border width
2, in default root */
window = XCreateSimpleWindow (display,
DefaultRootWindow(display), 100, 50, 350, 250, 2,
foreground, background);
if (window == NULL) {
fprintf (stderr, "cannot open window\n");
exit (EXIT_FAILURE);
}
/* pop this window up on the screen */
XMapRaised (display, window);
/* flush X request queue to server */
XFlush (display);
sleep (5);
XDestroyWindow(mydisplay, mywindow);
XCloseDisplay (mydisplay);
exit (EXIT_SUCCESS);
}
Back to table of contents
%(4)
Example 2 - drawing graphics
The following programs draws a red rectangle on black background
%(1) cat xprog2.c
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
main ()
{
Display *xdisplay;
Window xwindow;
int xscreen;
unsigned long xforeground, xbackground;
XEvent xevent;
GC xgc;
Colormap cmap;
XColor color, colorrgb;
/* connect to the X server */
xdisplay = XOpenDisplay ("");
if (xdisplay == NULL) {
fprintf (stderr, "cannot connect to server\n");
exit (EXIT_FAILURE);
}
/* get default screen */
xscreen = DefaultScreen (xdisplay);
/* get black and white representation on current screen */
xbackground = BlackPixel (xdisplay, xscreen);
xforeground = WhitePixel (xdisplay, xscreen);
/* Create window at (100,50), width 350, height 250, border width
2, in default root */
xwindow = XCreateSimpleWindow (xdisplay,
DefaultRootWindow(xdisplay), 100, 50, 350, 250, 2,
xforeground, xbackground);
if (xwindow == NULL) {
fprintf (stderr, "cannot open window\n");
exit (EXIT_FAILURE);
}
/* ask for exposure event */
XSelectInput(xdisplay, xwindow, ExposureMask);
/* pop this window up on the screen */
XMapRaised (xdisplay, xwindow);
/* wait for the window showing up before continuing */
XNextEvent (xdisplay, &xevent);
/* set graphics context of rectangle to red */
xgc= XCreateGC (xdisplay, xwindow, 0, 0);
if (DisplayPlanes (xdisplay, xscreen) != 1) {
cmap = DefaultColormap (xdisplay, xscreen);
if (XAllocNamedColor (xdisplay, cmap, "red", &color, &colorrgb))
XSetForeground (xdisplay, xgc, color.pixel);
}
/* Draw rectangle at (25,25), width 300, height, 200 */
XFillRectangle (xdisplay, xwindow, xgc, 25, 25,
300, 200);
/* flush X request queue to server */
XFlush (xdisplay);
sleep (10);
XDestroyWindow(xdisplay, xwindow);
XCloseDisplay (xdisplay);
return 0;
}
Note that if you are on a black and white xterminal, the red rectangle would
show up as black.
%(4)
Example 3 - event loops
%(1) cat xprog3.c
#include <stdio.h>
#include <stdlib.hgt;
#include <X11/Xlib.h>
main ()
{
Display *xdisplay;
Window xwindow;
int xscreen;
unsigned long xforeground, xbackground;
XEvent xevent;
GC xgc;
Colormap cmap;
XColor color, colorrgb;
/* connect to the X server */
xdisplay = XOpenDisplay ("");
if (xdisplay == NULL) {
fprintf (stderr, "cannot connect to server\n");
exit (EXIT_FAILURE);
}
/* get default screen */
xscreen = DefaultScreen (xdisplay);
/* get black and white representation on current screen */
xbackground = BlackPixel (xdisplay, xscreen);
xforeground = WhitePixel (xdisplay, xscreen);
/* Create window at (100,50), width 350, height 250, border width
2, in default root */
xwindow = XCreateSimpleWindow (xdisplay,
DefaultRootWindow(xdisplay), 100, 50, 350, 250, 2,
xforeground, xbackground);
if (xwindow == NULL) {
fprintf (stderr, "cannot open window\n");
exit (EXIT_FAILURE);
}
/* ask for exposure event */
XSelectInput(xdisplay, xwindow, ButtonPressMask | ExposureMask);
/* pop this window up on the screen */
XMapRaised (xdisplay, xwindow);
/* set graphics context of rectangle to red */
xgc= XCreateGC (xdisplay, xwindow, 0, 0);
cmap = DefaultColormap (xdisplay,xscreen);
while (1) {
/* wait for next event */
XNextEvent (xdisplay, &xevent);
switch (xevent.type) {
/* ignore this event */
case Expose:
break;
case ButtonPress:
/* if mouse button is down inside rectangle.. */
if ((xevent.xbutton.x>=25)&&(xevent.xbutton.x<=325)
&&(xevent.xbutton.y>=25)&&(xevent.xbutton.y<=225)) {
/* change color */
if (color.red == 0xffff)
color.red =0x0;
else if (color.green == 0xfff)
color.green=0x0;
else if (color.blue == 0xffff)
color.blue=0x0;
else {
color.red+=0x1000;
color.green+=0x2000;
color.blue += 0x3000;
}
/* allocate color and redraw rectangle */
if (XAllocColor (xdisplay,cmap, &color))
XSetForeground (xdisplay, xgc,
color.pixel);
XFillRectangle(xdisplay,xwindow,xgc,25,25,
300,200);
}
break;
}
}
return 0;
}
%(2) cc -lX11 xprog3.c
%(3) a.out