Bug 396319

Summary:	KWin fails to accept large window icons leading to X11 errors and applications not starting
Product:	[Plasma] kwin	Reporter:	Kai Wb. <curan>
Component:	platform-x11-standalone	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal	Flags:	curan: X11+ curan: Gallium3D+ curan: Mesa+
Priority:	NOR
Version First Reported In:	5.12.5
Target Milestone:	---
Platform:	Debian testing
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Kai Wb. 2018-07-08 19:31:46 UTC

I came across a commercial application which tries to set a really large application icon (2100×1500 pixels). This leads to an X11 error with KWin:
> X Error of failed request:  BadLength (poly request too large or internal Xlib length error)
>  Major opcode of failed request:  146 ()
>  Minor opcode of failed request:  74
>  Serial number of failed request:  168
>  Current serial number in output stream:  168

With xtrace (and setting LIBGL_DRI3_DISABLE=true, without this xtrace was stuck before logging the error) I was able to dig out the following failing request:

> 003:<: Warning: buffer filled!
> 003:<: Warning: Waiting for rest of package (yet got 65524 of 17640036)!
>003:<: Warning: buffer filled!
>003:<:009d:17640036: Request(18): ChangeProperty mode=Replace(0x00) >window=0x07400005 property=0x152("_NET_WM_ICON") type=0x6("CARDINAL") data=0x00000834,0x00000834,0x00000000,0x0000000,[...]

Manually scaling the window icon file down, let me start the application.

Now, according to https://specifications.freedesktop.org/wm-spec/latest/ar01s05.html#idm139870829941264 it is the window managers job to scale the image down and that no maximum size is mandated by the spec for _NET_WM_ICON. This seems to indicate to me, that an application is actually free to set such a ridiculously large icon and the window manager should just scale it down.

[NB: I can trigger this bug also with the Windows version of the application, if I run it through Wine. This seems to indicate, that Wine isn't scaling the image down either and also expects the window manager to deal with it.]

Let me know if you need anything else.

Comment 1 Martin Flöser 2018-07-09 04:16:32 UTC

Is xprop able to retrieve the icon

Comment 2 Kai Wb. 2018-07-09 07:40:29 UTC

(In reply to Martin Flöser from comment #1)
> Is xprop able to retrieve the icon

I think I'm not following you: wouldn't I need a running application/window for xprop to work? With the shipped (large) icon file the application is not starting. I can just see the window border for a split second and then the application dies with that X error. Or do you mean "can xprop retrieve the manually scaled down icon"?

Comment 3 Martin Flöser 2018-07-09 14:58:08 UTC

Oh it's the application giving this error? That changes everything: the window manager cannot trigger this issue. This is an application bug.