wxListBox's EnsureVisible not implemented in wxMSW

[jejackson]

I've tried using wxListBox's EnsureVisible to make sure that top element
of a list box is the displayed item.

However, if there is a selection that would be out-of-view, it always
scrolls to that one instead of what EnsureVisible is set to.

Code snippet: (wxPython)

listBox.SetSelection(10)
listBox.EnsureVisible(0)

always shows item 10, and not item 0.

It appears from looking at the sources that this was never implemented.

[leio]

From bug #836309:

Razvan Cojocaru:

EnsureVisible() doesn't scroll with the correct ammount
on wxGTK 2.5.1 and wxMac 2.5.1, so the wanted item is
not shown. I don't know if the problem exists on other
wxWindows flavours, but I've een it for myself on wxGTK
2.5.1 and it's been reported that it happens with wxMac
CVS HEAD.

[wojdyr]

wxListBox has EnsureVisible() in the base class, but it's not documented and it's not implemented in wxMSW.

[vadz]

I think we should document EnsureVisible() and support it. OTOH I don't know if the problem is still present in 2.8 or svn trunk, could someone please test this?

[wojdyr]

afaict it's not implemented on wxMSW and never was implemented. There is nothing to test, this function is just empty.

[oneeyeman]

The documentation for wxListBox::EnsureVisible() was added and it mentions that the function implemented only on GTK and Mac.

Probably worth changing the subject so that someone will implement that.

[vadz]

Considering that wxMSW does implement SetFirstItem(), it shouldn't be difficult to implement this one.

[oneeyeman]

Implementation patch

[oneeyeman]

Attached please find a patch that implements EnsureVisible for the listbox in wxMSW.
It also corrects the documentation.

[vadz]

Sorry, this is not the right implementation. If EnsureVisible() were the same as SetFirstItem(), what would be the point of having it?

EnsureVisible() is supposed to scroll just enough to make the item visible and, in particular, not scroll at all if it's already visible.