Title: Using AlphaBlending on Forms with Delphi 5
Question: There are new properties on Delphi 6 Forms that allows to use alpha blending options. How to do it on Delphi 5?
Answer:
To enable alpha blending on Delphi 5 TForms, just use the following lines:
----------%unit Unit1;
interface
type
TForm1 = class(TForm)
... members here ...
public
constructor Create(AOwner : TComponent); override;
end;
implementation
{-------------------------------------------------------
ALPHA_VALUE determines the level of transparency.
0 = full transparency,
255 = opaque
--------------------------------------------------------}
const ALPHA_VALUE = 128;
{-------------------------------------------------------
Missing Win32 Constants & Functions
-------------------------------------------------------}
const WS_EX_LAYERED = $00080000;
const LWA_ALPHA = 2;
function SetLayeredWindowAttributes(Handle : HWND;
crKey : TColor;
bAlpha : Byte;
dwFlags : DWORD) : Boolean;
stdcall; external 'user32.dll';
constructor TForm1.Create(AOwner: TComponent);
var vi : _OSVERSIONINFO;
oldStyle : DWORD;
begin
inherited Create(AOwner);
GetVersionEx(vi);
if vi.dwMajorVersion = 5 then { Win2000 or superior?! }
begin
oldStyle := GetWindowLong(Self.Handle, GWL_EXSTYLE);
SetWindowLong(Self.Handle, GWL_EXSTYLE, oldStyle or WS_EX_LAYERED);
SetLayeredWindowAttributes(Self.Handle, clBlack, ALPHA_VALUE, LWA_ALPHA);
RedrawWindow(Self.Handle, nil, 0,
RDW_ERASE or RDW_INVALIDATE or RDW_FRAME or RDW_ALLCHILDREN);
end;
end;
end.
----------%
Notice that this will work only on Win2k or XP.