XQueryColor() failing on dual monitor system

[Mut...@dastardlyhq.com]

Hi

I'm hoping to write some code to save the contents of a window clicked on by
the mouse to a file and my plan was to get its image, save the pixels then
reload them into an image created by XCreateImage. However on one of the 3
systems I'm using the XQueryColor() call fails in the following code (but never
fails on the other 2). The only difference is the one it crashes on is a dual
monitor system:

:
:
screen = DefaultScreen(display);
cmap = DefaultColormap(display,screen);
:
:
win = event.xbutton.subwindow ?
event.xbutton.subwindow : event.xbutton.window;

XGetWindowAttributes(display,win,&att);
printf("Window %ld, width = %d, height = %d\n",
win,att.width,att.height);

puts("Grabbing image...");
oldimg = XGetImage(
display,win,
0,0,att.width,att.height,AllPlanes,XYPixmap);

puts("Pixels...");
for(x=0;x < att.width;++x)
{
for(y=0;y < att.height;++y)
{
printf("X,Y = %d,%d\n",x,y);
pixel = XGetPixel(oldimg,x,y);
col.pixel = pixel;
XQueryColor(display,cmap,&col);


$ ./a.out
Window 54532344, width = 786, height = 1037
Grabbing image...
Pixels...
:
:
X,Y = 12,26
X,Y = 12,27
X,Y = 12,28
X,Y = 12,29
X,Y = 12,30
X Error of failed request: BadValue (integer parameter out of range for operati
on)
Major opcode of failed request: 91 (X_QueryColors)
Value in failed request: 0x1000000
Serial number of failed request: 11
Current serial number in output stream: 11


Is there some obvious mistake I'm making?

Thanks for any help

[Marco Moock]

Am 27.10.2023 um 09:18:08 Uhr schrieb Mut...@dastardlyhq.com:

> I'm hoping to write some code to save the contents of a window
> clicked on by the mouse to a file and my plan was to get its image,
> save the pixels then reload them into an image created by
> XCreateImage.

Why don't use xwd to save the image of a window?

[Scott Lurndal]

Mut...@dastardlyhq.com writes:
>Hi
>
>I'm hoping to write some code to save the contents of a window clicked on by
>the mouse to a file

$ man 1 xwd

> and my plan was to get its image, save the pixels then
>reload them into an image created by XCreateImage.

$ man 1 convert (from the ImageMagick package)

I'd look at the sources for xwd (part of the X11 distribution)
to see how they handled the colormaps and/or direct color.

[Mut...@dastardlyhq.com]

Because I'm saving more than just the image of a window and I don't like
using system() or popen() to fork a utility that may or may not be available.

[Scott Lurndal]

Use the source, luke.

[Mut...@dastardlyhq.com]

Yes, I did. Looks complicated but I still don't know what I'm doing wrong.
Given I'm working with 24 bit colour I might just bypass XQueryColor() and
get the RGB values direct from the pixel.

[candycanearter07]

You could always try looking at the source code for xcolor and copy that.
--
user <candycane> is generated from /dev/urandom

[Spiros Bousbouras]

On Fri, 27 Oct 2023 09:18:08 -0000 (UTC)
Mut...@dastardlyhq.com wrote:
> Hi
>
> I'm hoping to write some code to save the contents of a window clicked on by
> the mouse to a file and my plan was to get its image, save the pixels then
> reload them into an image created by XCreateImage. However on one of the 3
> systems I'm using the XQueryColor() call fails in the following code (but never
> fails on the other 2). The only difference is the one it crashes on is a dual
> monitor system:

[...]

> Is there some obvious mistake I'm making?

The standard advice in such cases is to post full compilable code which
reproduces the problem and take it from there. If you are making an obvious
mistake , the effort to create such code may reveal the mistake.