Method ControlGetComboBox

source/script_gui.cpp:1671–1747

ResultType GuiType::ControlGetComboBox(ResultToken &aResultToken, GuiControlType &aControl, ValueModeType aMode)
{
	LRESULT index = SendMessage(aControl.hwnd, CB_GETCURSEL, 0, 0); // Get index of currently selected item.

	//   Problem #1:
	// It seems that any text put into a ComboBox's edit field by typing/pasting or via Ctrl.Text
	// always resets the current index to -1, even if that text exactly matches an existing item.

	//   Problem #2:
	// CB_GETCURSEL sometimes returns an index which doesn't match what's in the Edit control.
	// This typically happens as a result of typing/pasting while the drop-down window is visible
	// and then canceling the dropdown without making a selection.
	// Note that when the CBN_SELENDCANCEL notification is received, CB_GETCURSEL correctly returns -1,
	// but at some point after that the control restores the index to a possibly incorrect value.  This
	// appears to happen in other programs as well, and has been confirmed on Windows 10 and earlier.

	int edit_length = GetWindowTextLength(aControl.hwnd); // Zero is valid (the control may be empty).
	// For simplicity and in case the text is very large, use tmalloc() unconditionally
	// even though the text is probably very small.  This allocation may be returned below.
	LPTSTR edit_text = tmalloc(edit_length + 1);
	if (!edit_text)
		_o_throw_oom;
	edit_length = GetWindowText(aControl.hwnd, edit_text, edit_length + 1);
	if (index != CB_ERR)
	{
		// The control returned a valid index, so verify that it matches the edit text.
		// If a search beginning at the indicated item does not return that item, it must
		// not be a match.  This approach avoids retrieving the item's text, which reduces
		// code size.  Performance hasn't been measured, but at a guess, is probably better
		// when the item matches (as it would 99.9% of the time), and worse in other cases.
		if (!edit_length)
		{
			// A different approach is needed in this case since CB_FINDSTRINGEXACT can't
			// search for an empty string.  This preserves the ability to detect selection
			// of a specific empty list item, though for simplicity, clearing the edit text
			// will not match up to an empty list item.
			if (0 != SendMessage(aControl.hwnd, CB_GETLBTEXTLEN, (WPARAM)index, 0))
				index = CB_ERR;
		}
		else
		{
			if (index != SendMessage(aControl.hwnd, CB_FINDSTRINGEXACT, index - 1, (LPARAM)edit_text))
				index = CB_ERR;
		}
	}
	if (index == CB_ERR)
	{
		// Check if the Edit field contains text that exactly matches one of the items in the drop-list.
		// If it does, that item's position should be retrieved in AltSubmit mode (even for non-AltSubmit
		// mode, this should be done because the case of the item in the drop-list is usually preferable
		// to any varying case the user may have manually typed).
		index = SendMessage(aControl.hwnd, CB_FINDSTRINGEXACT, -1, (LPARAM)edit_text); // It's not case sensitive.
		if (index == CB_ERR && aMode != Value_Mode) // Text or Submit mode.
		{
			// edit_text does not match any of the list items, so just return the text.
			aResultToken.AcceptMem(edit_text, edit_length);
			return OK;
		}