AlphaBlend in FireMonkey - delphi

Question

How can I change AlphaBlend value (of a form) in a FireMonkey Desktop Application? Well It's available in VCL Application but I couldn't find it in FireMonkey.
Screenshot:

Answer 1

To make your form background semitransparent you should set form Transparency property to true and use Fill.Color with alpha value like $AAFFFFFF(with Fill.Kind = bkSolid).
in this case form border becomes invisible (at least in Delphi XE2)
if you need to make all components at form semitransparent then place TLayout on form with Align = alContents and set its Opacity property to required value.
if you need semitransparent window with alpha blend as it was in VCL you can use the same methods (for Windows platform) as getWindowLong/SetWindowLong. Set transparency back to false and use code like this in form OnCreate event handler:
implementation
uses fmx.platform.win, winapi.windows;
{$R *.fmx}
procedure TMainForm.FormCreate(Sender: TObject);
var h : HWND;
aStyle : integer;
alphaValue : byte;
begin
h := WindowHandleToPlatform(self.Handle).Wnd;
AStyle := GetWindowLong(h, GWL_EXSTYLE);
SetWindowLong(h, GWL_EXSTYLE, AStyle or WS_EX_LAYERED);
AlphaValue := 125;
SetLayeredWindowAttributes(h, 0, alphaValue, LWA_ALPHA);
end;
of course all your components become trasparent too.

Answer 2

Since you are looking only for a Windows implementation you must add the WS_EX_LAYERED style to your form and then using the SetLayeredWindowAttributes method set the alpha value based in a value or a color.
Check this implementation, using a interposer class.
type
TForm = class(FMX.Forms.TForm)
private
FAlphaBlend: Boolean;
FAlphaBlendValue: Byte;
FTransparentColor: Boolean;
FTransparentColorValue: TColor;
procedure SetAlphaBlend(const Value: Boolean);
procedure SetAlphaBlendValue(const Value: Byte);
procedure SetLayeredAttribs;
procedure SetTransparentColor(const Value: Boolean);
procedure SetTransparentColorValue(const Value: TColor);
protected
property AlphaBlend: Boolean read FAlphaBlend write SetAlphaBlend default False;
property AlphaBlendValue: Byte read FAlphaBlendValue write SetAlphaBlendValue default 255;
property TransparentColor: Boolean read FTransparentColor write SetTransparentColor default False;
property TransparentColorValue: TColor read FTransparentColorValue write SetTransparentColorValue;
end;
TForm1 = class(TForm)
Button1: TButton;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.fmx}
uses
FMX.Platform.Win,
Winapi.Windows,
Vcl.Graphics;
type
TSetLayeredWindowAttributes = function (Hwnd: THandle; crKey: COLORREF;
bAlpha: Byte; dwFlags: DWORD): Boolean; stdcall;
var
SetLayeredWindowAttributes: TSetLayeredWindowAttributes = nil;
procedure TForm1.FormCreate(Sender: TObject);
begin
#SetLayeredWindowAttributes := GetProcAddress(GetModuleHandle(User32), 'SetLayeredWindowAttributes');
AlphaBlend:=True;
AlphaBlendValue:=200;
end;
{ TForm }
procedure TForm.SetAlphaBlend(const Value: Boolean);
begin
if FAlphaBlend <> Value then
begin
FAlphaBlend := Value;
SetLayeredAttribs;
end;
end;
procedure TForm.SetAlphaBlendValue(const Value: Byte);
begin
if FAlphaBlendValue <> Value then
begin
FAlphaBlendValue := Value;
SetLayeredAttribs;
end;
end;
procedure TForm.SetTransparentColor(const Value: Boolean);
begin
if FTransparentColor <> Value then
begin
FTransparentColor := Value;
SetLayeredAttribs;
end;
end;
procedure TForm.SetTransparentColorValue(const Value: TColor);
begin
if FTransparentColorValue <> Value then
begin
FTransparentColorValue := Value;
SetLayeredAttribs;
end;
end;
procedure TForm.SetLayeredAttribs;
const
cUseAlpha: array [Boolean] of Integer = (0, LWA_ALPHA);
cUseColorKey: array [Boolean] of Integer = (0, LWA_COLORKEY);
var
AStyle: Integer;
begin
if not (csDesigning in ComponentState) and
(Assigned(SetLayeredWindowAttributes)) then
begin
AStyle := GetWindowLong( WindowHandleToPlatform(Handle).Wnd, GWL_EXSTYLE);
if FAlphaBlend or FTransparentColor then
begin
if (AStyle and WS_EX_LAYERED) = 0 then
SetWindowLong(WindowHandleToPlatform(Handle).Wnd, GWL_EXSTYLE, AStyle or WS_EX_LAYERED);
SetLayeredWindowAttributes(WindowHandleToPlatform(Handle).Wnd, ColorToRGB(FTransparentColorValue), FAlphaBlendValue,
cUseAlpha[FAlphaBlend] or cUseColorKey[FTransparentColor]);
end
else
begin
SetWindowLong(WindowHandleToPlatform(Handle).Wnd, GWL_EXSTYLE, AStyle and not WS_EX_LAYERED);
RedrawWindow(WindowHandleToPlatform(Handle).Wnd, nil, 0, RDW_ERASE or RDW_INVALIDATE or RDW_FRAME or RDW_ALLCHILDREN);
end;
end;
end;