Spreadsheet with many Hidden Rows/Columns = 100% CPU and very sluggish performance

[Tex2002ans]

Describe the Bug

Huge 100% CPU spikes whenever you try to do anything in a spreadsheet with LOTS of hidden rows/columns.

Steps to Reproduce

In Calc:

1. Open LO.24.2.2.-.Many.Hidden.Columns.Rows[Only.4x10.Showing].ods
   • Only has Columns A-D + Rows 1-10 showing. All others are Hidden.
2. Click in any cell or try to adjust any formula.

Expected Behavior

Clicking or changing a cell should be instant.

Actual Behavior

Takes 3+ seconds to highlight after clicking.

Takes 3+ seconds after changing a formula for new number to appear.

100% CPU is taken up while trying to do any sort of action in example spreadsheet.

• LO 24.2 = instant
• Excel 365 = instant
• Collabora 24.04.4 = 100% CPU slowdown for ~3 seconds on every action.

Desktop

• Collabora version: 24.04.4.2
• OS and version: Linux Mint 21.3
• Browser and version: Firefox 127.0

COOLWSD version: 24.04.4.2 (git hash: 967b85ec)
LOKit version: Collabora Office 24.04.4.2 (git hash: 586d953)
Served by: Linux Mint 21.3
Server ID: 86706693

Also tested in:

Version: 24.2.4.2 (X86_64) / LibreOffice Community
Build ID: 51a6219feb6075d9a4c46691dcfe0cd9c4fff3c2
CPU threads: 8; OS: Windows 10.0 Build 22631; UI render: Skia/Raster; VCL: win
Locale: en-US (en_US); UI: en-US
Calc: CL threaded

Additional Context

SafeLamp, a user at the Collabora Forums, brought this use-case up.

Google Sheets seems to have a feature where you can "Delete" extra columns/rows.