ksnapshot: Problem with offscreen pieces of windows

Bug #204358 reported by Some Thing on 2008-03-20
This bug affects 1 person
Affects Status Importance Assigned to Milestone
KDE Graphics
kdegraphics (Ubuntu)

Bug Description

Binary package hint: ksnapshot


The problem is in window capturing mode. If the window hangs out from the screen, then ksnapshot bugs in the way that can be seen on the attached image. (Okay, i do that for fun, capturing webpages can be done with Screengrab (https://addons.mozilla.org/en-US/firefox/addon/1146), but it isn't solves ksnapshot's problem.)


Qt: 3.3.7
KDE: 3.5.8
KSnapshot: 0.7

Version: 0.7 (using KDE KDE 3.3.1)
Installed from: RedHat RPMs
OS: Linux

My KMix window is about twice the width of my screen. When taking a snapshot (to submit a bug report about it), I ended up with this:


This was using "window under cursor" mode. I was not surprised that it couldn't get the contents of the window that were not visible on screen, but it seems like it should handle this more gracefully - perhaps by clipping the final image, or just filling in the remaining space with black.

I don't see garbage (just black sections - probably a change to Qt), but it is still wrong (because we are using QPixmap::grabRegion(), and that has a warning that it isn't safe to grab off screen regions).

I've got a patch that just trims to the current screen size:
--- ksnapshot.cpp 11 Dec 2004 21:40:39 -0000 1.78
+++ ksnapshot.cpp 29 Jan 2005 22:23:59 -0000
@@ -498,8 +498,20 @@ void KSnapshot::performGrab()
                y = newy;

+ XWindowAttributes rootAttributes;
+ if ( XGetWindowAttributes( qt_xdisplay(), root, &rootAttributes ) ) {
+ if ( ( x + w ) > rootAttributes.width ) {
+ // then the window is partly off the screen
+ w = rootAttributes.width - x;
+ }
+ if ( ( y + h ) > rootAttributes.height ) {
+ // then the window is partly off the screen
+ h = rootAttributes.height - y;
+ }
+ }
        snapshot = QPixmap::grabWindow( qt_xrootwin(), x, y, w, h );


Is that OK to commit?

That is committed now.

Some Thing (something) wrote :
Harald Sitter (apachelogger) wrote :

Thank you very much for helping us improving Kubuntu :-)
This issue is caused by KDE itself, therefor it would be very cool if you could report this issue on bugs.kde.org otherwise it might take some time until someone finds the time to do it.

Changed in kdegraphics:
importance: Undecided → Low
status: New → Confirmed
Some Thing (something) wrote :

Looks that it was solved a hundred year ago...


Harald Sitter (apachelogger) wrote :

Doesn't look like that on my KDE 4 machine ;-)

Please reopen the KDE bug.

Changed in kdegraphics:
status: New → Unknown
Changed in kdegraphics:
status: Unknown → Fix Released

According to https://bugs.launchpad.net/ubuntu/+source/kdegraphics/+bug/204358 this is still/again a problem in KDE 3.5 and KDE 4.0

Yes, this still is an issue in KDE 4.1.1. Please reopen the bug.

Jonathan Thomas (echidnaman) wrote :

I reopened the upstream bug.

Changed in kdegraphics:
status: Confirmed → Triaged

Still a problem in KDE 4.1.85, reopening.

Changed in kdegraphics:
status: Fix Released → New

Here's an adaptation of the patch for KDE 4.3:

Index: kdegraphics-4.2.90/ksnapshot/windowgrabber.cpp
--- kdegraphics-4.2.90.orig/ksnapshot/windowgrabber.cpp 2009-06-12 23:16:28.000000000 -0400
+++ kdegraphics-4.2.90/ksnapshot/windowgrabber.cpp 2009-06-12 23:37:00.000000000 -0400
@@ -140,6 +140,18 @@
 QPixmap grabWindow( Window child, int x, int y, uint w, uint h, uint border,
       QString *title=0, QString *windowClass=0 )
+ XWindowAttributes rootAttributes;
+ if ( XGetWindowAttributes( QX11Info::display(), QX11Info::appRootWindow(), &rootAttributes ) ) {
+ if ( ( x + w ) > rootAttributes.width ) {
+ // then the window is partly off the screen
+ w = rootAttributes.width - x;
+ }
+ if ( ( y + h ) > rootAttributes.height ) {
+ // then the window is partly off the screen
+ h = rootAttributes.height - y;
+ }
+ }
     QPixmap pm( QPixmap::grabWindow( QX11Info::appRootWindow(), x, y, w, h ) );

     KWindowInfo winInfo( findRealWindow(child), NET::WMVisibleName, NET::WM2WindowClass );

Changed in kdegraphics:
importance: Unknown → Medium
Maarten Bezemer (veger) wrote :

I can confirm this is still an issue on KDE 4.7.4

Can't reproduce this anymore on KDE 4.10 RC1 (4.9.95).
IIRC since KDE 4.5 the window screenshot is grabbed from kwin directly to:
* also include the window decoration's shadow
* create screenshots of windows which are (partially) covered by other windows
* create screenshots of (partially) offscreen windows

It even works when disabling compositing.

I don't know what would happen when using a different WM than kwin, but I don't think that really counts here.

So I'd vote for closing this bug. Any objections?

Created attachment 88044

Ubuntu 14.04 (KDE 4.13.2)

Hello! Sorry to be the bearer of bad news, but this project has been unmaintained for many years and I will be closing this bug. Spectacle is the replacement for ksnapshot now. Please test again and file a new bug for Spectacle if you still have issues. Thank you!

Changed in kdegraphics:
status: New → Unknown
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