Bug 514518

Summary: Using the Breeze theme in Calibre removes the resize handles on the side panels
Product: [Plasma] Breeze Reporter: Mathis Paquet <mathispaquet362>
Component: generalAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED INTENTIONAL    
Severity: normal CC: mathispaquet362, nate, uhhadd
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Calibre with default theme, drag handle visible
Calibre with Breeze theme, drag handle missing

Description Mathis Paquet 2026-01-13 01:34:51 UTC
Created attachment 188464 [details]
Calibre with default theme, drag handle visible

SUMMARY
When using CALIBRE_USE_SYSTEM_THEME=1, Calibre will use the system QT theme. There are no visual issues and it does look very great, however, the left and right panels docked inside the application cannot be resized. Using any other QT theme allows to resize them. It seems like the resize handles either disappear or get a width of 0 pixels with Breeze, which is odd. 

STEPS TO REPRODUCE
1. Launch Calibre with CALIBRE_USE_SYSTEM_THEME=1 calibre
2. Try resizing the side panels

OBSERVED RESULT
Unable to resize the side panels. There are no handles visible and the cursor does not change to a double horizontal arrow when hovering over the vertical separator. 

EXPECTED RESULT
There should be a drag handle indicating the panel is resizable, and the panel should resize when dragged.

SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux 
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.22.0
Qt Version: 6.10.1
Kernel Version: 6.18.3-2-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 12 × Intel® Core™ i7-9750H CPU @ 2.60GHz
Memory: 16 GiB of RAM (15.5 GiB usable)
Graphics Processor 1: Intel® UHD Graphics 630
Graphics Processor 2: NVIDIA GeForce GTX 1660 Ti

ADDITIONAL INFORMATION
I have reported the issue on the side of Calibre, but they said they will not investigate it as they do not officially support system themes.
Comment 1 Mathis Paquet 2026-01-13 01:35:23 UTC
Created attachment 188465 [details]
Calibre with Breeze theme, drag handle missing
Comment 2 Nate Graham 2026-01-13 20:34:31 UTC
In breeze, the handles are intentionally invisible. You should be able to resize the sidebar from its line, though. If you can't, that's a Calibre bug.
Comment 3 Mathis Paquet 2026-01-13 20:53:52 UTC
Still cannot be resized with the separator. Definitely a Calibre bug, indeed. Sadly they won't fix it.