Title: How to create transparent menus (2000/XP)
var
hHookID: HHOOK;
// function to make the menu transparent
function MakeWndTrans(Wnd: HWND; nAlpha: Integer = 10): Boolean;
type
TSetLayeredWindowAttributes = function(hwnd: HWND; crKey: COLORREF; bAlpha: Byte;
dwFlags: Longint): Longint; stdcall;
const
// Use crKey as the transparency color.
LWA_COLORKEY = 1;
// Use bAlpha to determine the opacity of the layered window..
LWA_ALPHA = 2;
WS_EX_LAYERED = $80000;
var
hUser32: HMODULE;
SetLayeredWindowAttributes: TSetLayeredWindowAttributes;
i : Integer;
begin
Result := False;
// Here we import the function from USER32.DLL
hUser32 := GetModuleHandle('USER32.DLL');
if hUser32 0 then
begin
@SetLayeredWindowAttributes := GetProcAddress(hUser32,'SetLayeredWindowAttributes');
// If the import did not succeed, make sure your app can handle it!
if @SetLayeredWindowAttributes nil then
begin
// Check the current state of the dialog, and then add the WS_EX_LAYERED attribute
SetWindowLong(Wnd, GWL_EXSTYLE, GetWindowLong(Wnd, GWL_EXSTYLE) or WS_EX_LAYERED);
// The SetLayeredWindowAttributes function sets the opacity and
// transparency color key of a layered window
SetLayeredWindowAttributes(Wnd, 0, Trunc((255 / 100) * (100 - nAlpha)), LWA_ALPHA);
Result := True;
end;
end;
end;
// hook procedure
function HookCallWndProc(nCode: Integer; wParam, lParam: Longint): Longint; stdcall;
const
MENU_CLASS = '#32768';
N_ALPHA = 60;
var
cwps: TCWPStruct;
lRet: THandle;
szClass: array[0..8] of char;
begin
if (nCode = HC_ACTION) then
begin
CopyMemory(@cwps, Pointer(lParam), SizeOf(CWPSTRUCT));
case cwps.message of
WM_CREATE:
begin
GetClassName(cwps.hwnd, szClass, Length(szClass)-1);
// Window name for menu is #32768
if (lstrcmpi(szClass, MENU_CLASS) = 0) then
begin
MakeWndTrans(cwps.hwnd, N_ALPHA {Alphablending});
end;
end;
end;
end;
// Call the next hook in the chain
Result := CallNextHookEx(WH_CALLWNDPROC, nCode, wParam, lParam);
end;
// Install the hook in the OnCreate Handler
procedure TForm1.FormCreate(Sender: TObject);
var
tpid: DWORD;
begin
// Retrieve the identifier of the thread that created the specified window
tpid := GetWindowThreadProcessId(Handle, nil);
// The SetWindowsHookEx function installs an application-defined
// hook procedure into a hook chain
hHookID := SetWindowsHookEx(WH_CALLWNDPROC, HookCallWndProc, 0, tpid);
end;
// Stop the hook in the OnDestroy Handler
procedure TForm1.FormDestroy(Sender: TObject);
begin
if (hHookID 0) then
// Removes the hook procedure
UnhookWindowsHookEx(hHookID);
end;