How to convert Delphi TPageControl "tab index" to "page index"?

Question

I'm using a TPageControl, where certain pages are not visible.

This breaks the normal 1:1 mapping of the TabIndex and ActivePageIndex properties.

In most places I can use ActivePageIndex (or ActivePage itself) to get the current page, but I want a dynamic tooltip hint which requires me to determine which page is associated with a specific tab index.

If I call pageControl.IndexOfTabAt(X, Y), I get a Tab Index back, but I can't directly use that as an index into the Pages[] array, as some page tabs aren't visible.

I could explicity iterate through the pages, ignoring the visible ones, but it feels like there should be something in the VCL that does this for me already...?

Answer 1

I you look in the source for TPageControl (ComCtrls.pas), there is a private method:

function TPageControl.PageIndexFromTabIndex(TabIndex: Integer): Integer;

that does what you want. But you can't call it (D2007), so (unfortunately) you have to copy the code.

Answer 2

Here is an old article that deals with dragging & dropping pages. It has some logic to obtain the index of a page from an (X, Y) position, perhaps you can use it. Something like this (untested):

function TMyPageControl.GetPageIndexAtPos(X, Y: Integer) : Integer;
const
   TCM_GETITEMRECT = $130A;
var
   TabRect: TRect;
   j: Integer;    
begin
   for j := 0 to PageCount - 1 do
   begin
     Perform(TCM_GETITEMRECT, j, LParam(@TabRect)) ;
     if PtInRect(TabRect, Point(X, Y)) then
     begin
       Result := j;
       exit;
     end;
   end;
   Result := -1;
end;