Issue is way less eminent without debug info but still it takes a noticeable time (~500ms on a fast machine) with 10 comments. And it might be an issue with real data.

Steps to reproduce:
1. Open Calc
2. Insert a comment in a A1
3. Copy A1
4. Paste it in A1:A40
5. Select A1
6. Ctrl -
7. Ctrl + 

-> Hang

also reproduced in

Version: 7.3.0.0.alpha1+ / LibreOffice Community
Build ID: 229123ccc6f90ebf66b3e659bebbd53f8a9bdd3a
CPU threads: 8; OS: Linux 6.1; UI render: default; VCL: gtk3
Locale: fr-FR (es_ES.UTF-8); UI: en-US
Calc: threaded

It's much slower with Gtk3 Than with gen so I believe accessibility might be involved

If the comment is on the end (not just the last row) it is as fast as without.

Also with
Version: 7.1.8.0.0+ (x64) / LibreOffice Community
Build ID: a94b58277c7aeaa83ce14347cd0b8f7137969d03
CPU threads: 4; OS: Windows 6.3 Build 9600; UI render: default; VCL: win
Locale: nl-NL (nl_NL); UI: en-US
Calc: CL

fine with
Version: 7.0.7.0.0+ (x64)
Build ID: 626ea4e62a3e5005fe9825923a1c0c5bdb61cc08
CPU threads: 4; OS: Windows 6.3 Build 9600; UI render: default; VCL: win
Locale: nl-NL (nl_NL); UI: en-US
Calc: CL

Created attachment 192030 [details]
hotspot flamegraph with gtk3 debug build

(In reply to Xisco Faulí from comment #2)
> Steps to reproduce:
> 1. Open Calc
> 2. Insert a comment in a A1
> 3. Copy A1
> 4. Paste it in A1:A40
> 5. Select A1
> 6. Ctrl -
> 7. Ctrl + 
> 
> -> Hang

I've used steps 1-5 as described, then

6. Ctrl+Down

(Ctrl - bring up a dialog asking what to remove, doesn't hang for me).

(In reply to Xisco Faulí from comment #4)
> It's much slower with Gtk3 Than with gen so I believe accessibility might be
> involved

I see nothing that looks directly a11y-related in the attached hotspot flamegraph (taken with gtk3 debug build. I've waited more than a minute after step 6).

Most of the time seems to be spent calculating row heights (ScDocument::GetRowHeight).
It's similar in a flamegraph for kf5.

Version: 24.8.0.0.alpha0+ (X86_64) / LibreOffice Community
Build ID: 3e9a700091872480dd085f0928d1d30b7d74cfd7
CPU threads: 12; OS: Linux 6.5; UI render: default; VCL: gtk3
Locale: en-US (en_GB.UTF-8); UI: en-US
Calc: threaded

Jumping to the end is instant, but Calc hangs after that when I click on a different cell. Same on Windows. Bibisected that behaviour with linux-64-6.3 to d464d505fbf6e53a38afdd3661d320fac8c760d6, which is also blamed for bug 125619 (and two others which are not perf issues).

Also, this does not repro with an existing file with comments. You need to go through the steps from scratch.

I'm wondering about Telesto's result with 7.0 vs. 7.1 in comment 6.

Heiko, Xisco and Michael are invited to check with bibisect repos.

(In reply to Buovjaga from comment #8)
> I'm wondering about Telesto's result with 7.0 vs. 7.1 in comment 6.

1. Open Calc
2. Insert a comment in a A1
3. Copy A1
4. Paste it in A1:A40
5. Select A1
6. Press CTRL+Arrow Down

> Comment 8
> Also, this does not repro with an existing file with comments. You need to go through the steps from scratch.

Certainly, i did not reproduce it in the existing documentation.

--- --- --- ---
Most of the posted glitches are reproducible, but oddly enough, when the mouse cursor is off the sheet, it moves briskly.
For example, if the mouse cursor is over a sheet label (ex. [A] [1]), it moves briskly.
I hope you find it useful.
(by TexTra)

Version: 24.8.0.0.alpha1+ (X86_64) / LibreOffice Community
Build ID: fbe57382eef1138999f63e01b6152d4d05749807
CPU threads: 4; OS: Windows 10 X86_64 (10.0 build 10240); UI render: Skia/Raster; VCL: win
Locale: ja-JP (ja_JP); UI: ja-JP
Calc: threaded

(In reply to Telesto from comment #9)
> (In reply to Buovjaga from comment #8)
> > I'm wondering about Telesto's result with 7.0 vs. 7.1 in comment 6.
> 
> 1. Open Calc
> 2. Insert a comment in a A1
> 3. Copy A1
> 4. Paste it in A1:A40
> 5. Select A1
> 6. Press CTRL+Arrow Down

Sure, that's what I did, but are you really seeing a delay before you are moved to the end? I could see not any such effect in 7.0 or 7.1 bibisect repos or anywhere else.

> are you really seeing a delay before you are
> moved to the end?

FWIW, after [CTRL]+[down_arrow], the move itself doesn't _seem_ to be delayed, but there are other symptoms of such. For example, the Name box takes some time to update the new active cell A1048576.

When starting from cell A1, if instead of [CTRL]+[down_arrow] I press [CTRL]+[END] (going to cell A40), there is no delay. So maybe the delay is related to the row number (but not related to the amount of displacement of rows)?

(In reply to Buovjaga from comment #8)
> Jumping to the end is instant, but Calc hangs after that when I click on a
> different cell.

In my case, after cell A1048576 is the new active cell, I can click on some other cell and I experience a clear delay, which could be called a "hang" until Calc finally reacts – not every user would be so tolerant, perhaps killing Calc before it reacts. Here the row displacement is not big (from cell A1048576 to – say – cell E1048563, a difference of 10-30 rows or so), but the row number is still near the max.

After that, Calc reaction's time might vary. From cell E1048563, [CTRL]+[END] or [CTRL]+[HOME] takes some time. But from cell A1048576, the same [CTRL]+[END] or [CTRL]+[HOME] is quicker to react. Same column? First column? First displayed column?

Version: 24.8.0.0.alpha1+ (X86_64) / LibreOffice Community
Build ID: 1071db05c2b5a5a9974ec9ece12f60217ab86db6
CPU threads: 4; OS: Windows 10 X86_64 (10.0 build 19045); UI render: Skia/Raster; VCL: win
Locale: en-US (es_AR); UI: en-US
Calc: CL threaded