screensaver and X11

[newelfik]

Hello,

I would like to draw a picture in X11 for screensaver.

So I started with excelent doc : http://tronche.com/gui/x/xlib/

And try to start with simpler thing like display text. So I've written that :



#include <stdio.h>
#include <X11/Xlib.h>
#include <stdlib.h>
#include <time.h>

#include "vroot.h"

Display *display;
Window root;
GC gc;


int main (argc, argv)
char *argv[];
int argc;
{
display = XOpenDisplay (getenv ("DISPLAY"));
if( display == NULL ){
printf("display = NULL");
}

printf("connection number : %d\n" , ConnectionNumber( display ) );

printf("height : %d\n", DisplayHeight(display , 0));
printf("width : %d\n", DisplayWidth(display , 0));

/* get the root window */
root = DefaultRootWindow (display);

gc = XCreateGC(display, root , 0 , NULL );

XTextItem *text = (XTextItem*)malloc(1 * sizeof(XTextItem));
text->chars = "Test TEST Test test TEST";
text->nchars = 24;
text->delta = 1;
text->font = None;

/* set foreground color */
XSetForeground(display, gc, WhitePixelOfScreen(DefaultScreenOfDisplay(display) ) );

/* draw something */
while (1)
{
/* draw a square */
XDrawText(display, root , gc , 100, 100, text , 1 );


/* once in a while, clear all */
if( random()%500<1 )
XClearWindow(display, root);


/* flush changes and sleep */
XFlush(display);
usleep (10);
}

XCloseDisplay( display );

printf("OK\n");
}


If I set the code as a screensaver and select [Preview], it's running.. I see the text.

If I launch screensaver in real conditions, I see only black screen ...

Have you got an idea ?

[pbrane]

I would recommend that you download the xscreensaver code and have a look at how it's done.

you can get it from the repos


sudo apt-get source xscreensaver