TAdvStringGrid or FormControlEditLink with a auto calculated ItemHeight ComboBox

[1111 (貴代 島田)]

Dear TMS Support,

Environment:

• C++Builder 12.3
• TMS VCL UI Pack: 13.5.5.0

I am using TAdvStringGrid with an external editor (a combo box control derived from TWinControl) by FormControlEditLink.
I noticed the following behavior:

• OwnerDraw = false
• DPI = 100%
• Skin/NativeStyle not used
• ItemHeight = 0 (auto calculation)
• RepositoryItem not used
• The issue occurs only when the combo box is used as a custom editor of TAdvStringGrid
• On the first use everything works fine, but from the second time with the same content,
  the clickable selection area of the second-last item in the drop-down becomes extremely narrow.
• I tried TComboBox and TAdvComboBox with fixed ItemHeight = 15 and it works fine. I updated my demo code.

My questions are:

1. Is this a known issue in TAdvStringGrid or TFormControlEditLink when reusing external editors?
2. If so, what is the root cause?
3. If the cause is identified, could you please advise the recommended fix or workaround?

My main goal is to understand the cause and, if possible, apply the proper solution or workaround.
TAdvStringGrid.zip (42.9 KB)

[brunofierens]

I'm trying to understand what you mean but I can't see a different editing behavior here on the first or second time (or even third , fourth time... etc)
Can you please provide more details on what exact steps you do and what exactly goes wrong?

[1111 (貴代 島田)]

It worked fine with TComboBox and TAdvComboBox, but did work well in my third-part ComboBox I can send you a video with my ComboBox. I hope that can be help.In that video item 4 and item 5 can't be selected.
2025-10-01 090117.zip (120.7 KB)

[brunofierens]

Without knowing details about this 3rd party combobox, it is very hard to tell what could be going wrong here.

[1111 (貴代 島田)]

Thank you very much for your feedback. I understand, and I will proceed with the investigation on my side.