Mega Code Archive
How to make a Form semi C transparent
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Title: How to make a Form semi C transparent
TMyForm = class (TForm);
TrackBar1: TTrackBar;
//..
private
FColorKey: TCOLOR;
end;
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 = $80000;
implementation
{$R *.DFM}
// The SetLayeredWindowAttributes function sets the opacity and transparency
// color key of a layered window.
// Note : This function is only available with Windows 2000 and XP!
function SetLayeredWindowAttributes(
// Handle to the layered window.
Wnd: hwnd;
// Pointer to a COLORREF value that specifies the transparency
// color key to be used when composing the layered window
crKey: ColorRef;
// Alpha value used to describe the opacity of the layered window
Alpha: Byte;
// Specifies an action to take
// LWA_COLORKEY or LWA_ALPHA
// This parameter can be one or more of the following values:
dwFlags: DWORD): Boolean;
stdcall; external 'user32.dll';
procedure TMyForm.TrackBar1Change(Sender: TObject);
// Trackbar.Position must run at range 1-255...
begin
SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYERED);
SetLayeredWindowAttributes(Handle, ColorToRGB(FColorKey), TrackBar1.Position, LWA_ALPHA);
end;
{******************************************************************}
{ To load the SetLayeredWindowAttributes() function dynamically, use this function:}
function MakeWindowTransparent(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;
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