Can overriding the CreateParams procedure allow me to still have full access to the WS_SYSMENU? - windows

Question

Complete source code can be found here:
http://www.eyeClaxton.com/download/delphi/SkinProject.zip
I'm trying to create a skinned form with no "Caption or Borders", but still leaving me with the full access to System Menu (I.E: Move, Minimize, Maximize, Restore and Size). I can achieve all of the menu items by overriding the CreateParams procedure by using WS_SYSMENU, WS_MAXIMIZEBOX, WS_MINIMIZEBOX. Using the WS_SIZEBOX gives me access to the menu "Size" command but paints a border I do not want. I have included a complete (Delphi 7) example in the link above. If more information is needed, please feel free to ask.
procedure TMainFrm.CreateParams(var Params: TCreateParams);
begin
FormStyle := fsNormal;
try
if (BorderIcons <> []) then BorderIcons := [];
if (BorderStyle <> bsNone) then BorderStyle := bsNone;
inherited CreateParams(Params);
Params.ExStyle := (Params.ExStyle and (not WS_EX_WINDOWEDGE)
and (not WS_EX_STATICEDGE) and (not WS_EX_DLGMODALFRAME) and (not WS_EX_CLIENTEDGE));
Params.Style := (Params.Style and (not WS_CAPTION) and (not DS_MODALFRAME)
and (not WS_DLGFRAME) and (not WS_THICKFRAME));
Params.Style := (Params.Style or WS_SYSMENU or WS_MAXIMIZEBOX or WS_MINIMIZEBOX or WS_SIZEBOX);
finally
Position := poScreenCenter;
end;
end;
SOLUTION:
unit WndProcUnit;
interface
uses
Windows, Messages, Classes, Controls, Forms, SysUtils;
type
EWndProc = class(Exception);
TWndProcMessages = class(TComponent)
private
{ Private declarations }
FOwnerWndProc: TFarProc;
FNewWndProc: TFarProc;
protected
{ Protected declarations }
procedure WndProc(var theMessage: TMessage); virtual;
public
{ Public declarations }
constructor Create(theOwner: TComponent); override;
destructor Destroy(); override;
procedure DefaultHandler(var theMessage); override;
end;
TWndProc = class(TWndProcMessages)
private
{ Private declarations }
protected
{ Protected declarations }
procedure Loaded(); override;
public
{ Public declarations }
constructor Create(theOwner: TComponent); override;
destructor Destroy(); override;
published
{ Published declarations }
end;
implementation
{ TWndProcMessages }
constructor TWndProcMessages.Create(theOwner: TComponent);
var
X, I: Integer;
begin
inherited Create(theOwner);
if (not (Owner is TForm)) then
raise EWndProc.Create('TWndProc parent must be a form!');
I := 0;
for X := 0 to (Owner.ComponentCount - 1) do
begin
if (Owner.Components[X] is TWndProc) then Inc(I);
if (I > 1) then Break;
end;
if (I > 1) then
begin
raise EWndProc.Create('The form already contains a TWndProc!');
end
else begin
FOwnerWndProc := TFarProc(GetWindowLong((Owner as TForm).Handle, GWL_WNDPROC));
FNewWndProc := Classes.MakeObjectInstance(WndProc);
if (not (csDesigning in ComponentState)) then
SetWindowLong((Owner as TForm).Handle, GWL_WNDPROC, LongInt(FNewWndProc));
end;
end;
destructor TWndProcMessages.Destroy();
begin
if Assigned(FNewWndProc) then
try
Classes.FreeObjectInstance(FNewWndProc);
finally
if (Pointer(FNewWndProc) <> nil) then Pointer(FNewWndProc) := nil;
end;
if Assigned(FOwnerWndProc) then Pointer(FOwnerWndProc) := nil;
inherited Destroy();
end;
procedure TWndProcMessages.DefaultHandler(var theMessage);
begin
if ((Owner as TForm).Handle <> 0) then
begin
case TMessage(theMessage).Msg of
WM_DESTROY:
SetWindowLong((Owner as TForm).Handle, GWL_WNDPROC, LongInt(FOwnerWndProc));
WM_INITMENU:
EnableMenuItem(TMessage(theMessage).WParam, SC_SIZE, MF_BYCOMMAND or MF_ENABLED);
else
with TMessage(theMessage) do
Result := CallWindowProc(FOwnerWndProc, (Owner as TForm).Handle, Msg, WParam, LParam);
end;
end
else
inherited DefaultHandler(theMessage);
end;
procedure TWndProcMessages.WndProc(var theMessage: TMessage);
begin
Dispatch(theMessage);
end;
{ TWndProc }
constructor TWndProc.Create(theOwner: TComponent);
begin
inherited Create(theOwner);
end;
destructor TWndProc.Destroy();
begin
inherited Destroy();
end;
procedure TWndProc.Loaded();
begin
inherited Loaded();
if (not (csDesigning in ComponentState)) then
GetSystemMenu((Owner as TForm).Handle, False);
end;
end.
Complete "updated" source code can be found here:
http://www.eyeClaxton.com/download/delphi/SkinProject.zip

Answer 1

Instead of having a border-less form and faking borders and caption all in the client area, the correct way to do this would be to handle WM_NCPAINT and draw your caption and border in the non-client area. Then, you wouldn't have to use an undocumented message to show the system menu on a caption-less window, or try to have the 'size' system menu item enabled on a window without a sizing border.
Anyway, if you want a quick workaround, enable the item yourself:
type
TMainFrm = class(TForm)
[...]
procedure FormCreate(Sender: TObject);
private
procedure WmInitMenuPopup(var Msg: TWMInitMenuPopup); message WM_INITMENUPOPUP;
[...]
procedure TMainFrm.FormCreate(Sender: TObject);
begin
GetSystemMenu(Handle, False); // force a copy of the system menu
[...]
end;
procedure TMainFrm.WmInitMenuPopup(var Msg: TWMInitMenuPopup);
begin
inherited;
if Msg.SystemMenu then
EnableMenuItem(Msg.MenuPopup, SC_SIZE, MF_BYCOMMAND or MF_ENABLED);
end;
PS:
In the code sample in the question, you're excluding WS_THICKFRAME, but including WS_SIZEBOX. They're, in fact, the same flag.
You've got a bit of a weird try-finally in your CreateParams. Form positioning have got nothing to do with the preceding code, you can put the 'Position := ' statement just before or after setting 'FormStyle' and drop the try-finally.