I'm trying to create a X11 window with a bit depth of 32 so that I can use ARGB colors. Here's what I do:
XVisualInfo vinfo; int depth = 32; XMatchVisualInfo(dpy, XDefaultScreen(dpy), depth, TrueColor, &vinfo); XCreateWindow(dpy, XDefaultRootWindow(dpy), 0, 0, 150, 100, 0, depth, InputOutput, vinfo.visual, 0, NULL);
Here's what happens:
X Error of failed request: BadMatch (invalid parameter attributes) Major opcode of failed request: 1 (X_CreateWindow) Serial number of failed request: 7 Current serial number in output stream: 7
Any pointers on why there is a BadMatch error?
The problem is this code in the X server http://cgit.freedesktop.org/xorg/xserver/tree/dix/window.c#n615
if (((vmask & (CWBorderPixmap | CWBorderPixel)) == 0) &&
(class != InputOnly) &&
(depth != pParent->drawable.depth))
{
*error = BadMatch;
return NullWindow;
}
i.e. "if depth isn't same as parent depth you have to set the border pixel or pixmap"
Here is a whole example
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/extensions/Xcomposite.h>
#include <stdio.h>
int main(int argc, char **argv)
{
Display *dpy;
XVisualInfo vinfo;
int depth;
XVisualInfo *visual_list;
XVisualInfo visual_template;
int nxvisuals;
int i;
XSetWindowAttributes attrs;
Window parent;
Visual *visual;
dpy = XOpenDisplay(NULL);
nxvisuals = 0;
visual_template.screen = DefaultScreen(dpy);
visual_list = XGetVisualInfo (dpy, VisualScreenMask, &visual_template, &nxvisuals);
for (i = 0; i < nxvisuals; ++i)
{
printf(" %3d: visual 0x%lx class %d (%s) depth %d\n",
i,
visual_list[i].visualid,
visual_list[i].class,
visual_list[i].class == TrueColor ? "TrueColor" : "unknown",
visual_list[i].depth);
}
if (!XMatchVisualInfo(dpy, XDefaultScreen(dpy), 32, TrueColor, &vinfo))
{
fprintf(stderr, "no such visual\n");
return 1;
}
printf("Matched visual 0x%lx class %d (%s) depth %d\n",
vinfo.visualid,
vinfo.class,
vinfo.class == TrueColor ? "TrueColor" : "unknown",
vinfo.depth);
parent = XDefaultRootWindow(dpy);
XSync(dpy, True);
printf("creating RGBA child\n");
visual = vinfo.visual;
depth = vinfo.depth;
attrs.colormap = XCreateColormap(dpy, XDefaultRootWindow(dpy), visual, AllocNone);
attrs.background_pixel = 0;
attrs.border_pixel = 0;
XCreateWindow(dpy, parent, 10, 10, 150, 100, 0, depth, InputOutput,
visual, CWBackPixel | CWColormap | CWBorderPixel, &attrs);
XSync(dpy, True);
printf("No error\n");
return 0;
}