XChangeProperty () always fails

Question

I am studying the use of xlib and I cannot get XChangeProperty() to work for me.

I have a simple program that successfully displays a window. But calls to XChangeProperty() always fail with error code error 1 (BadRequest) .

Can someone tell me what I'm doing wrong?

Here is my code to change the property.

 static void change_prop(Display *display, Window window) { unsigned char some_text[40] = "hello world!"; int retval; Atom my_atom; my_atom = XInternAtom(display, "PERSONAL_PROPERTY", False); if (my_atom == None) { printf("### failed to create atom with name PERSONAL_PROPERTY\n"); return; } retval = XChangeProperty(display, /* connection to x server */ window, /* window whose property we want to change */ my_atom, /* property name */ XA_STRING, /* type of property */ 8, /* format of prop; can be 8, 16, 32 */ PropModeReplace, some_text, /* actual data */ 10 /* number of elements */ ); printf("###### XChangeProperty() reted %d\n", retval); } 

Answer 1

Most xlib functions always return 1, and you should use error handlers to check for errors. See XChangeProperty implementation - note return 1 at the end.

Your code works very well:

 #include <stdio.h> #include <stdlib.h> #include <X11/Xlib.h> #include <X11/Xutil.h> #include <X11/Xos.h> #include <X11/Xatom.h> #include <X11/keysym.h> static void change_prop(Display *display, Window window) { unsigned char some_text[40] = "hello world!"; int retval; Atom my_atom; my_atom = XInternAtom(display, "PERSONAL_PROPERTY", False); if (my_atom == None) { printf("### failed to create atom with name PERSONAL_PROPERTY\n"); return; } retval = XChangeProperty(display, /* connection to x server */ window, /* window whose property we want to change */ my_atom, /* property name */ XA_STRING, /* type of property */ 8, /* format of prop; can be 8, 16, 32 */ PropModeReplace, some_text, /* actual data */ 10 /* number of elements */ ); printf("###### XChangeProperty() reted %d\n", retval); } int main() { Display *dis; Window win; dis = XOpenDisplay(NULL); win = XCreateSimpleWindow(dis, RootWindow(dis, 0), 1, 1, 500, 500, \ 0, BlackPixel (dis, 0), BlackPixel(dis, 0)); XMapWindow(dis, win); printf("window %i\n", (int)win); change_prop(dis, win); XFlush(dis); sleep(50); return(0); } 

result:

 09:48 tmp $ g++ prop.cpp /usr/X11/lib/libX11.dylib 09:48 tmp $ ./a.out window 6291457 ###### XChangeProperty() reted 1 

xprop result:

 09:48 tmp $ xprop -id 6291457 WM_STATE(WM_STATE): window state: Normal icon window: 0x0 _NET_WM_STATE(ATOM) = _NET_WM_ALLOWED_ACTIONS(ATOM) = _NET_WM_ACTION_MOVE, _NET_WM_ACTION_RESIZE, _NET_WM_ACTION_MINIMIZE, _NET_WM_ACTION_MAXIMIZE_HORZ, _NET_WM_ACTION_MAXIMIZE_VERT, _NET_WM_ACTION_FULLSCREEN, _NET_WM_ACTION_CLOSE PERSONAL_PROPERTY(STRING) = "hello worl"