How to correctly maximize a window

Problem/Question/Abstract:

I have some forms with the property WindowState set to wsMaximized. The problem is that some forms are hiding the taskbar. I can't find the problem since some others forms are working fine.

Answer:

Solve 1:

If I'm right, the only way to get correctly maximized windows (regarding the taskbar and other "taskbar like" windows) is using API functions:


var
  x: pointer;
  r: TRect;
begin
  x := Addr(r);
  SystemParametersInfo(SPI_GETWORKAREA, 0, x, 0);
  Left := 0;
  Width := r.Right;
  Top := 0;
  Height := r.Bottom;
  { ... }


Solve 2:

This seems to be a particular problem when you do it in the forms OnCreate event. To fix it add a handler for the WM_GETMINMAXINFO message:


private
{ Private declarations }

procedure wmGetMinMaxInfo(var msg: TWMGetMinMaxInfo); message WM_GETMINMAXINFO;

  procedure TForm1.wmGetMinMaxInfo(var msg: TWMGetMinMaxInfo);
  var
    r: TRect;
  begin
    SystemParametersInfo(SPI_GETWORKAREA, 0, @r, 0);
    with msg.MinMaxInfo^ do
    begin
      ptMaxSize := r.BottomRight;
      ptMaxPosition := r.TopLeft;
    end;
  end;


If your form is set to Position := poDesigned and WindowState := wsMaximized, then don't set any value for Constraints. Otherwise the form won't maximize correctly at runtime, if the Windows taskbar is resized.