Hello All,
I have a simple code which I'll paste below which I think should display
a black or blank 512x512 pixel image however it segfaults according to
GDB at XPutImage(). I can't find any documentation as to why this is
occurring and I am hoping someone my have some insight. This is my first
exposure to X so I'm not sure what is going wrong and the documentation
has not been very helpful. Here is the code:
#include <X11/Xlib.h>
#include <X11/Xutil.h>
main(int argc, char *argv[])
{
Display *Monitor;
Window ImageWindow;
GC ImageGC;
XWindowAttributes Atts;
XImage *Picture;
int ROWS,COLS;
unsigned char *displaydata;
/* ... */
ROWS = COLS = 512;
Monitor=XOpenDisplay(NULL);
if (Monitor == NULL)
{
printf("Unable to open graphics display\n");
exit(0);
}
ImageWindow=XCreateSimpleWindow(Monitor,RootWindow(Monitor,0),
50,10, /* x,y on screen */
COLS,ROWS, /* width, height */
2, /* border width */
BlackPixel(Monitor,0),
WhitePixel(Monitor,0));
ImageGC=XCreateGC(Monitor,ImageWindow,0,NULL);
XMapWindow(Monitor,ImageWindow);
XFlush(Monitor);
while(1)
{
XGetWindowAttributes(Monitor,ImageWindow,&Atts);
if (Atts.map_state == IsViewable /* 2 */)
break;
}
unsigned char *dispalydata;
displaydata = (unsigned char *)calloc(ROWS*COLS*2, sizeof(unsigned char));
Picture=XCreateImage(Monitor,DefaultVisual(Monitor,0),
DefaultDepth(Monitor,0),
ZPixmap, /* format */
0, /* offset */
(char*)displaydata,/* the data */
COLS,ROWS, /* size of the image data */
16, /* pixel quantum (8, 16 or 32) */
0); /* bytes per line (0 causes compute) */
XPutImage(Monitor,ImageWindow,ImageGC,Picture,
0,0,0,0, /* src x,y and dest x,y offsets */
COLS,ROWS); /* size of the image data */
XFlush(Monitor);
sleep(2);
XCloseDisplay(Monitor);
}
Thanks in advance to anyone who can help.
-Richard
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