How do I display opaque text on a translucent window? - delphi

Question

Can you give me the names of the functions needed for this purpose? I'm using Delphi XE 5. I want to get this effect:
Window: half transparent
Font: fully visible.
I will use "System" font (zero problems with AA)
What do I look on MSDN? What functions (name) do I need to use?

Answer 1

This is basically the same idea as in Marcus' answer, but with some enhancements. You might have to adjust this to your needs, but the principle is the following:
Create form1 with the following properties:
AlphaBlend := True;
AlphaBlendValue := 128;
BorderStyle := bsNone;
Create form2 with the controls as desired and the following properties:
Color := clFuchsia; // or whatever color is not used
TransparentColor := true;
TransparentColorValue := Color;
Declare a Boolean field in form1 named AllowMove.
In TForm1.FormShow call the following code:
begin
form2.BorderStyle := bsNone;
form2.SetBounds(0, 0, ClientWidth, ClientHeight);
form2.Show;
AllowMove := true;
end;
Declare a Boolean field in form1 named AllowMove and a message handler for WM_MOVE:
procedure WMMOVE(var Message: TMessage); message WM_MOVE;
procedure TForm1.WMMOVE(var Message: TMessage);
begin
inherited;
if AllowMove then begin
Form2.Left := Message.LParamLo;
Form2.Top := Message.LParamHi;
end;
Message.Result := 0;
end;

Answer 2

The only way that I know to get that kind of effect is to render the window contents to an in-memory bitmap, then apply the desired alpha values to the non-font pixels, and then use UpdateLayeredWindow() to display the bitmap on a window. You cannot achieve that affect with a TForm as it relies on SetLayeredWindowAttributes() instead.
Create a 32bit bitmap and draw the desired background on it with alpha values, using a separate array to keep track of the current pixel values in the spots you are going to draw text on, then draw the actual text and use the array to detect which pixels were changed so you can clear the alpha values from just those pixels. Then display the bitmap.

Answer 3

You can get something close by layering two forms over each other. Set the bottom form's color to blue, enable AlphaBlend, and set AlphaBlend to something like 100. That just provides the blue background.
On second form, set TransparentColor to clBtnFace, and put your label there. Set the label font's quality to fqAntialiased.
Set both form's BorderStyle to bsNone.
Lay the second form over the first form, and there you go.
This might be workable if you don't plan on letting the user move the forms, or you move them together.