Author: Tomas Rutkauskas

Is there a built-in method for getting the absolute location of a control or do I 
need to step through the hierarchy? E.g.: Form1...Group1...Button1 means that the 
absolute left of Button1 is Form1.Left+Group1.Left+Button1.Left

Answer:

Solve 1:

You need to use the ClientToScreen and ScreenToClient methods, like this:


1   procedure TForm1.Button1Click(Sender: TObject);
2   var
3     P: TPoint;
4   begin
5     P := Point(Button1.Left, Button1.Top);
6     {Button1's coordinates are expressed relative to it's parent. Using 
7   Parent.ClientToScreen converts these client coordinates to screen coordinates, 
8   which are absolute, not relative.}
9     P := Button1.Parent.ClientToScreen(P);
10    {Using ScreenToClient here is the same as Self.ScreenToClient. Since Self is the 
11  current instance of TForm1, this statement converts the absolute screen coordinates 
12  back to coordinates relative to Self.}
13    P := ScreenToClient(P);
14    ShowMessage(Format('x: %d, y: %d', [P.X, P.Y]));
15  end;


Because this code uses the absolute screen coordinates in the conversion process, 
it will work regardless of how deeply nested the Button is. It could be on the 
form, on a group on the form, on a panel in a group on the form... it doesn't 
matter. The code will always return the same results, the coordinates expressed in 
the form's client system.


Solve 2:

I don't know if there is a simpler method, but this one works:


16  function GetScreenCoordinates(AControl: TControl): TPoint;
17  begin
18    if AControl.Parent <> nil then
19    begin
20      Result := AControl.Parent.ClientToScreen(Point(AContol.Left, AControl.Top));
21    end
22    else
23    begin
24      Result := Point(AContol.Left, AControl.Top);
25    end;
26  end;



The trick is: If a control has no parent, (Left, Top) should be the screen 
coordinates already (TForm). If it has a parent, the ClientToScreen function of the 
parent can be used to get it.


Solve 3:

Use TComponent.DesignInfo, which holds the Left and Top of the component. You can 
do this:


27  X := LongRec(MyComponent.DesignInfo).Lo;
28  Y := LongRec(MyComponent.DesignInfo).Hi;