Here is a code sample of how to set the window region with shadow:
(Notes: The Form BorderStyle assumed to be bsNone, not re-sizable)
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
private
procedure CreateFlatRoundRgn;
protected
procedure CreateParams(var Params: TCreateParams); override;
public
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
procedure ExcludeRectRgn(var Rgn: HRGN; LeftRect, TopRect, RightRect, BottomRect: Integer);
var
RgnEx: HRGN;
begin
RgnEx := CreateRectRgn(LeftRect, TopRect, RightRect, BottomRect);
CombineRgn(Rgn, Rgn, RgnEx, RGN_OR);
DeleteObject(RgnEx);
end;
procedure TForm1.CreateFlatRoundRgn;
const
CORNER_SIZE = 6;
var
Rgn: HRGN;
begin
with BoundsRect do
begin
Rgn := CreateRoundRectRgn(0, 0, Right - Left + 1, Bottom - Top + 1, CORNER_SIZE, CORNER_SIZE);
// exclude left-bottom corner
ExcludeRectRgn(Rgn, 0, Bottom - Top - CORNER_SIZE div 2, CORNER_SIZE div 2, Bottom - Top + 1);
// exclude right-bottom corner
ExcludeRectRgn(Rgn, Right - Left - CORNER_SIZE div 2, Bottom - Top - CORNER_SIZE div 2, Right - Left , Bottom - Top);
end;
// the operating system owns the region, delete the Rgn only SetWindowRgn fails
if SetWindowRgn(Handle, Rgn, True) = 0 then
DeleteObject(Rgn);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
BorderStyle := bsNone;
CreateFlatRoundRgn;
end;
procedure TForm1.CreateParams(var Params: TCreateParams);
const
CS_DROPSHADOW = $00020000;
begin
inherited CreateParams(Params);
with Params do
begin
Style := WS_POPUP;
WindowClass.Style := WindowClass.Style or CS_DROPSHADOW;
end;
end;
Another way to draw a custom shadow would be to set Window WS_EX_LAYERED and use UpdateLayeredWindow
Here is a very good example of how it's done (sources are in C++ but very easy to understand)
For more complicated shapes you can use a PNG image on the form and Alpha Blend it.
EDIT:
Resizing a WS_POPUP Window is a world of pain...
You have a few options:
NOTE that you need to re-create the Window region when you re-size it (e.g OnResize event).
