扩展框架是一回事,绘制 Vista 主题(发光)文本是另一回事。使用 Canvas.TextOut 或 DrawText,输出会弄乱 alpha,这将产生您得到的效果。您需要使用 DrawThemeTextEx。以下是在玻璃上绘制文字的正确步骤:
uses Themes, UxTheme;
procedure DrawTextOnGlass(Canvas: TCanvas; Text: String; R: TRect);
var
memoryHdc: HDC;
b: TBitmap;
dttOpts: TDTTOpts;
DR: TRect;
bf: TBlendFunction;
begin
b := TBitmap.Create;
try
memoryHdc := CreateCompatibleDC(Canvas.Handle);
b.Handle := memoryHdc;
b.HandleType := bmDIB;
b.PixelFormat := pf32bit;
b.SetSize(R.Right - R.Left, R.Top - R.Bottom);
b.Canvas.Font := Canvas.Font;
DR := R;
OffsetRect(DR, -DR.Left, -DR.Top);
Inflaterect(dr, -5, -5);
b.Canvas.Brush.Color := clBlack;
b.Canvas.FillRect(DR);
dttOpts.dwSize := SizeOf(TDTTOpts);
dttOpts.iGlowSize := 8;
dttOpts.dwFlags := DTT_COMPOSITED or DTT_GLOWSIZE or DTT_TEXTCOLOR;
DrawThemeTextEx(ThemeServices.Theme[teWindow], b.Handle, WP_CAPTION, CS_ACTIVE, Text, -1,
DT_CENTER or DT_VCENTER or DT_SINGLELINE or DT_NOPREFIX, DR, dttOpts);
if GetLastError <> 0 then
RaiseLastOSError;
bf.BlendOp := AC_SRC_OVER;
bf.BlendFlags := 0;
bf.SourceConstantAlpha := 255;
bf.AlphaFormat := AC_SRC_ALPHA;
AlphaBlend(Canvas.Handle, R.Left, R.Top, R.Right - R.Left, R.Bottom - R.Top,
b.Canvas.Handle, 0, 0, R.Right - R.Left, R.Bottom - R.Top, bf);
finally
b.Free;
end;
end;