How to remove wsNormal fullscreen form title bar content offset?

Question

When maximizing a Form via WindowState:=wsMaximized, the title bar looks like this:

When setting the form to WindowState:=wsNormal and setting the form size manualy to a fullscreen state, the content of the frame is identical but the title bar is slightly moved.

The wsNormal form Rect on a 800*600 screen to simulate a wsMaxed form is TRect(-8,-8,808,608). (See this question why the difference of the size is necessary)

My Question: How can i fix the moved title bar content for the wsNormal window, so it would look correct like the following mock up?

Simple example form with one button, which reproduces both form states.

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
    FState: Integer;
  public
    { Public-Deklarationen }
    procedure WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo); message WM_GETMINMAXINFO;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  LBRect: TRect;
begin
  LBRect  := Screen.Monitors[0].BoundsRect;

  case FState of
    0:
    begin
      WindowState := wsMaximized;
    end;
    1:
    begin
      WindowState := wsNormal;
      LBRect := Screen.Monitors[0].WorkareaRect;
      LBRect.Inflate(8,8); //offset 8 for a form with bsSizeable
      BoundsRect := LBRect;
    end;
  end;

  Inc(FState);
  FState := FState mod 2;
end;

procedure TForm1.WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
begin
  //slightly smaller MaxTrackSize would prevent the wsNormal form the fully cover the screen on the right side
  Message.MinMaxInfo.ptMaxTrackSize := Message.MinMaxInfo.ptMaxSize;
end;

end.

Edit1:

To clarify why this might be usefull: We have a multi-monitor set up with identical resolution screens and want to span the form over this verly large "virtual screen. The desktop can not be unified to one large screen via e.g. AMDs Virtual Destkop settings.

The problem occurs because the title bar rect of a maximized Form has a slightly smaller height than a non-maximized form title bar.

Also, there is a need for the negative positions and enlarged size, caused by the (backwards compatible) way windows handles the border calculations and positioning. The actual offset/enlargement comes from the chosen borderstyle.

Answer 1

After some research, i found a way to reach the Goal for the described Scenario with minimal effort. This does not answer the question itself, it will only reach the goal.

When a form is created and also when it is maximized (by either the user or setting the forms WindowState to wsMaximized), the window message WM_GETMINMAXINFO gets send.

With sending WM_GETMINMAXINFO, the Form will be asked about its desired position and size in a maximized situation.

Here, we can override windows default positioning and e.g. span a maximized view over multiple screens by setting the values accordingly.

When analyzing the default values sent via WM_GETMINMAXINFO message, the values will have an offset of 8 in each dimension.

The offset was necessary on older Windows OS to tell the window manager to hide the borderstyle outside of the current screens view, and would also result in edge bleeding on multi-monitor setup. The edge bleeding also occurs nowadays, when the WindowState is is set to wsNormal.

The Offset will also tell Windows Window Manager to reduce the title bars size when it is docked to the top AND to render the title bar content correctly (which is the goal we searched for).

See the following example:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
    FState: Integer;
  public
    { Public-Deklarationen }
    procedure WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo); message WM_GETMINMAXINFO;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  case FState of
    0:
    begin
      WindowState := wsMaximized;
    end;
    1:
    begin
      WindowState := wsNormal;
      BoundsRect := TRect.Create(100,-8,300,192);
    end;
    2:
    begin
      WindowState := wsMaximized;
    end;
    3:
    begin
      WindowState := wsNormal;
      BoundsRect := TRect.Create(100,0,300,200);
    end;
    4:
    begin
      WindowState := wsMaximized;
    end;
    5:
    begin
      WindowState := wsNormal;
      BoundsRect := TRect.Create(100,100,300,300);
    end;
  end;

  Inc(FState);
  FState := FState mod 6;
end;

procedure TForm1.WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
begin
case FState of
  0, 1:
  begin
    Message.MinMaxInfo.ptMaxPosition.SetLocation(100,-8);
    Message.MinMaxInfo.ptMaxSize.SetLocation(200,200);
    Message.MinMaxInfo.ptMaxTrackSize := Message.MinMaxInfo.ptMaxSize;
    inherited;
  end;
  2, 3:
  begin
    Message.MinMaxInfo.ptMaxPosition.SetLocation(100,0);
    Message.MinMaxInfo.ptMaxSize.SetLocation(200,200);
    Message.MinMaxInfo.ptMaxTrackSize := Message.MinMaxInfo.ptMaxSize;
    inherited;
  end;
  4, 5:
  begin
    Message.MinMaxInfo.ptMaxPosition.SetLocation(100,100);
    Message.MinMaxInfo.ptMaxSize.SetLocation(200,200);
    Message.MinMaxInfo.ptMaxTrackSize := Message.MinMaxInfo.ptMaxSize;
    inherited;
  end;
end;

end;

end.

FYI: var Message: TWMGetMinMaxInfo seems to be persistent for the forms lifetime.

On state 0, the form is slightly moved into the top, which tells the window manager to render this forms title slightly smaller. This is the default behaviour for maximized forms and the optical result i searched for.

State 1 will show the problem i had, and the other states will show you that positioning a maximized form anywhere is possible AND that the title bar will have the default size when it is not cutting a screens edge.

If you want to know what offsets to pick for your TForm, you can ask windows by using AdjustWindowRectEx with your chosen styles and main menu informations. (See: VCL.Forms.pas, TCustomForm.GetClientRect implementation)

Answer 2

The standard caption of an API window is fixed, you cannot do anything to alter its position or size.