Bug 168893 - Resizing panels is extremely slow and ramps up a single CPU core
Summary: Resizing panels is extremely slow and ramps up a single CPU core
Status: UNCONFIRMED
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: UI (show other bugs)
Version:
(earliest affected)
25.8.1.1 release
Hardware: All Linux (All)
: medium normal
Assignee: Not Assigned
URL:
Whiteboard:
Keywords: perf
Depends on:
Blocks:
 
Reported: 2025-10-16 11:30 UTC by postix
Modified: 2025-10-20 13:23 UTC (History)
2 users (show)

See Also:
Crash report or crash signature:

Attachments
Screenrecording of LO Impress 25.8.1.1 (941.22 KB, video/mp4)
2025-10-16 11:30 UTC, postix 		Details
Flamegraph (Plasma 6.4.5 Wayland) (725.24 KB, image/png)
2025-10-16 12:56 UTC, postix 		Details
Flamegraph TopDown (Plasma 6.4.5 Wayland) (2.00 MB, image/png)
2025-10-16 12:57 UTC, postix 		Details
Screenshot of Hotspot TopDown (1.00 MB, image/png)
2025-10-16 12:58 UTC, postix 		Details
View All Add an attachment (proposed patch, testcase, etc.)

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Description postix 2025-10-16 11:30:52 UTC 
Created attachment 203365 [details]
Screenrecording of LO Impress 25.8.1.1

Resizing panels in Impress by dragging them with the cursor is very slow and happens with a delay of a second or more.

While constantly resizing (i.e. dragging a panel's edge to left/right), one CPU core goes up to 100% and the fans turn on.

Please see the screen recording. On the left you can see the CPU usage.

Haven't tested it under X11 though.

---

Version: 25.8.1.1 (X86_64) / LibreOffice Community
Build ID: 580(Build:1)
CPU threads: 24; OS: Linux 6.17; UI render: default; VCL: kf6 (cairo+wayland)
Locale: en-US (en_US.UTF-8); UI: en-US
Calc: threaded

Operating System: openSUSE Tumbleweed 20251013
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.17.1-1-default (64-bit)
Graphics Platform: Wayland
Graphics Processor: AMD Radeon RX 580 Series
CPU: AMD 5900X
Comment 1 postix 2025-10-16 11:56:40 UTC 
Just confirmed again on 

Version: 25.8.2.2 (X86_64) / LibreOffice Community
Build ID: 580(Build:2)

Also, when having more slides, the UI actually freezes for a few seconds when trying to resize a panel ...
Comment 2 BogdanB 2025-10-16 12:55:42 UTC 
No problem on
Version: 25.8.2.2 (X86_64)
Build ID: d401f2107ccab8f924a8e2df40f573aab7605b6f
CPU threads: 4; OS: Windows 10 X86_64 (build 19045); UI render: Skia/Raster; VCL: win
Locale: ro-RO (en_US); UI: en-US
Calc: threaded
Comment 3 postix 2025-10-16 12:56:57 UTC 
Created attachment 203367 [details]
Flamegraph (Plasma 6.4.5 Wayland)
Comment 4 postix 2025-10-16 12:57:24 UTC 
Created attachment 203368 [details]
Flamegraph TopDown (Plasma 6.4.5 Wayland)
Comment 5 postix 2025-10-16 12:58:22 UTC 
Created attachment 203369 [details]
Screenshot of Hotspot TopDown

I've recorded some perf stats with hotspot, while resizing constantly a panel.