Created attachment 5162 [details]
test program to demonstrate bug
The dropdown list for a ComboBox can be clipped if the control is too close to the bottom of the screen. This makes items on the list inaccessible. Windows/.Net behavior in such cases is to move the listbox to display above the ComboBox's textbox instead of below.
I'm attaching a demo program that demonstrates the problem, and a proposed patch which implements behavior similar to that observed in Windows/.Net.
Created attachment 5163 [details]
proposed fix (diff against 2.10.9 code)
The bug probably exists in the 3.x code since the code in master appears to be the same as that in 2.10.9 in the relevant places in ComboBox.cs.
This is probably the same as https://bugzilla.xamarin.com/show_bug.cgi?id=4712 but with more details to explain why it's important and with a proposed fix.
Setting priority to lowest, since Windows.Forms is no longer being developed actively.
suggested fix is part of PR #943.