[solved] Need fast InvertRect for canvas
lazarus / 31-LCL

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AlexTP · 2015-03-09 18:36

My example of fast invert rect;
It's OK on Win, but bad on Linux/Gtk2: i see left edge of rect is
painted white. 1pix line at left and top. Bug? Other way to do fast
invert?

Quoteprocedure CanvasInvertRect(C: TCanvas; const R: TRect);
var
  N: TColor;
begin
  N:= C.Brush.Color;
  C.Pen.Color:= clWhite;
  C.Brush.Color:= clWhite;
  C.Pen.Width:= 1;
  C.Pen.Mode:= pmXor;
  C.Rectangle(R);
  C.Pen.Mode:= pmCopy;
  C.Rectangle(Rect(0, 0, 0, 0)); //update pen.mode
  C.Brush.Color:= N;
end;

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mm7 · 2015-03-10 21:21

May be brushed area overlaps with left side of the rectangle frame.
Try to draw smaller rectangle with just the brush and then draw
brushless rectangle with xor pen as frame.

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AlexTP · 2015-03-10 21:34

Tks. I fixed by SynEdit code

Code: [Select]procedure CanvasInvertRect(C: TCanvas; const R: TRect;
AColor: TColor);
var
  X: integer;
  AM: TAntialiasingMode;
begin
  if not Assigned(_Pen) then
    _Pen:= TPen.Create;

  AM:= C.AntialiasingMode;
  _Pen.Assign(C.Pen);

  X:= (R.Left+R.Right) div 2;
  C.Pen.Mode:= pmNotXor;
  C.Pen.Style:= psSolid;
  C.Pen.Color:= AColor;
  C.AntialiasingMode:= amOff;
  C.Pen.EndCap:= pecFlat;
  C.Pen.Width:= R.Right-R.Left;

  C.MoveTo(X, R.Top);
  C.LineTo(X, R.Bottom);

  C.Pen.Assign(_Pen);
  C.AntialiasingMode:= AM;
  C.Rectangle(0, 0, 0, 0); //apply pen
end;


solved..