https://learn.microsoft.com/zh-tw/dotnet/api/system.windows.forms.combobox.measureitem?view=netframework-4.8.1&viewFallbackFrom=windowsdesktop-10.0
ComboBox.MeasureItem Event (System.Windows.Forms) | Microsoft Learn
Occurs each time an owner-drawn ComboBox item needs to be drawn and when the sizes of the list items are determined.
event systemwindows formscomboboxmicrosoftlearn