X Server & OpenGL Render

OpenGL
1

How to be capable to grab the display of an application that is running in the background (no focus) and convert it into a texture for OpenGL?

2

What do you mean ? Be very more precise. Is it a GL program running in background ? Or is it a simple X program ? Do you want to make ‘real-time’ texture creation ?

3

What I’m doing is… I got a display (:1) that is running with Xvfb, and on my display (:0) I got an OpenGL application that is running… Now in example I start xterm on the display :1, what I want to do is to grab the display of xterm and load it as a texture in my OpenGL application. I guess is pretty much as you said, ‘real-time’ texture creation.

I just don’t get it how to grab the display (pixmap or x window dump) of (ie) xterm running on my display :1 and load it as a texture in my OpenGL program running on my display :0, except by passing by xwd and convert it into jpeg, but its really slow, what are my other options since I need to do this operation in memory to speed up the whole thing?

Tks in advance…

4

Unfortunately I can’t help you. You will effectively need to take a screenshot from one program and translate it into your another program. But you might use networking for that (just a guess since I don’t know how you do that translation) and that you use 2 different displays (so 2 distinct X clients). glCopyTexSubImage (or so) should help you.

Also, I can remember VNV, do you know it, maybe you should look at how it is done, that might help you a bit.

5

Do you have the address of the website? Can’t find it…

6

Ok well, I’ve done some research and come out with this sample code, now my problem is how to be capable to convert the Ximage/ZPixmap to a format that OpenGL understand, and load it as a texture…

#include <stdlib.h>
#include <stdio.h>

#include <GL/glu.h>
#include <X11/Xlib.h>
#include <X11/Xmu/WinUtil.h>

int main (int argc, char **argv)
{
	Display *dpy;
	dpy = XOpenDisplay(":1.0");
	
	if (dpy == NULL) 
	{ printf("Cannot connect to X server ':1.0'
");
      exit(1); }
	
	Window target_win;
	target_win = 0x400016; // In example...
  
	  
    XWindowAttributes win_info;

    int absx, absy, x, y;
	XImage *image;
	unsigned width, height;
    Window dummywin;
		
	XGetWindowAttributes(dpy, target_win, &win_info);
	XTranslateCoordinates(dpy, target_win, RootWindow(dpy, 0), 0, 0,  &absx, &absy, &dummywin);

	win_info.x = absx;
    win_info.y = absy;
    width = win_info.width;
    height = win_info.height;	
    x = absx - win_info.x;
    y = absy - win_info.y;		
	
	XMapRaised(dpy, target_win);
	XSync(dpy, 0);
	XSetInputFocus(dpy, target_win, RevertToPointerRoot, CurrentTime);

	image = XGetImage(dpy, target_win, x, y, width, height, AllPlanes, ZPixmap);
	if(!image) printf("Unable to create image...
");		
		
	printf("%d %d", image->width, image->height);
	
	
	GLuint texture;
    glGenTextures(1, &texture);
	glBindTexture(GL_TEXTURE_2D, texture);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,  GL_LINEAR);
	
    gluBuild2DMipmaps (GL_TEXTURE_2D, GL_RGB,
                       image->width, image->height,
                       GL_RGB, GL_UNSIGNED_BYTE,
                       image->data); // Exit with segmentation fault...
	
	XDestroyImage(image);
	XCloseDisplay(dpy);
	exit(0);	
}
7

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