Direct2D (14) : 画笔

画笔类 TDirect2DPen 的 Brush 属性是 TDirect2DBrush，现在的单色画笔其实是调用的实心画刷。
因为画刷的强大，所以让画笔丰富起来不是难事。

TDirect2DPen 的 StrokeStyle 属性是 ID2D1StrokeStyle 类型，它决定着线帽、拐角样式等；但遗憾的是该属性是只读的，基本无用。
但 TDirect2DPen 的 Style 属性还是巧妙实现了 psSolid, psDash, psDot, psDashDot, psDashDotDot。

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测试代码：

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uses Direct2D, D2D1;

procedure TForm1.FormPaint(Sender: TObject);
var
  cvs: TDirect2DCanvas;
  R: TRect;
begin
  cvs := TDirect2DCanvas.Create(Canvas, ClientRect);
  R := ClientRect;
  InflateRect(R, -ClientWidth div 6, -ClientHeight div 6);

  cvs.Pen.Color := clRed;
  cvs.Pen.Style := psDash;

  cvs.BeginDraw;
  cvs.Ellipse(R);
  cvs.EndDraw;
  cvs.Free;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  Repaint;
end;

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效果图：

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下面是较原始的实现方法(效果同上):

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uses Direct2D, D2D1;

procedure TForm1.FormPaint(Sender: TObject);
var
  cvs: TDirect2DCanvas;
  iBrush: ID2D1SolidColorBrush;
  iStrokeStyle: ID2D1StrokeStyle;
  rStrokeStyleProperties: TD2D1StrokeStyleProperties;
  R: TRect;
  rEllipse: TD2D1Ellipse;
begin
  cvs := TDirect2DCanvas.Create(Canvas, ClientRect);
  R := ClientRect;
  InflateRect(R, -ClientWidth div 6, -ClientHeight div 6);
  rEllipse := D2D1Ellipse(D2D1PointF((R.Right-R.Left)/2+R.Left, (R.Bottom-R.Top)/2+R.Top), (R.Right-R.Left)/2, (R.Bottom-R.Top)/2);

  cvs.BeginDraw;
  cvs.RenderTarget.CreateSolidColorBrush(D2D1ColorF(clRed), nil, iBrush);
  rStrokeStyleProperties := D2D1StrokeStyleProperties(); //获取 StrokeStyle 属性的默认值
  rStrokeStyleProperties.dashStyle := D2D1_DASH_STYLE_DASH;
  D2DFactory.CreateStrokeStyle(rStrokeStyleProperties, nil, 0, iStrokeStyle);
  cvs.RenderTarget.DrawEllipse(rEllipse, iBrush, 1, iStrokeStyle);
  cvs.EndDraw;
  cvs.Free;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  Repaint;
end;

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自定义虚线：

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uses Direct2D, D2D1;

procedure TForm1.FormPaint(Sender: TObject);
var
  cvs: TDirect2DCanvas;
  iBrush: ID2D1SolidColorBrush;
  iStrokeStyle: ID2D1StrokeStyle;
  rStrokeStyleProperties: TD2D1StrokeStyleProperties;
  R: TRect;
  rEllipse: TD2D1Ellipse;
  arrSingle: array[0..3] of Single;
begin
  cvs := TDirect2DCanvas.Create(Canvas, ClientRect);
  R := ClientRect;
  InflateRect(R, -ClientWidth div 6, -ClientHeight div 6);
  rEllipse := D2D1Ellipse(D2D1PointF((R.Right-R.Left)/2+R.Left, (R.Bottom-R.Top)/2+R.Top), (R.Right-R.Left)/2, (R.Bottom-R.Top)/2);

  cvs.BeginDraw;
  cvs.RenderTarget.CreateSolidColorBrush(D2D1ColorF(clRed), nil, iBrush);
  rStrokeStyleProperties := D2D1StrokeStyleProperties();

  rStrokeStyleProperties.dashStyle := D2D1_DASH_STYLE_CUSTOM;
  arrSingle[0] := 10;
  arrSingle[1] := 5;
  arrSingle[2] := 1;
  arrSingle[3] := 5;
  D2DFactory.CreateStrokeStyle(rStrokeStyleProperties, @arrSingle[0], Length(arrSingle), iStrokeStyle);

  cvs.RenderTarget.DrawEllipse(rEllipse, iBrush, 2, iStrokeStyle);
  cvs.EndDraw;
  cvs.Free;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  Repaint;
end;

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效果图：

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自定义拐角样式：

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uses Direct2D, D2D1;

procedure TForm1.FormPaint(Sender: TObject);
var
  cvs: TDirect2DCanvas;
  iBrush: ID2D1SolidColorBrush;
  iStrokeStyle: ID2D1StrokeStyle;
  rStrokeStyleProperties: TD2D1StrokeStyleProperties;
  R: TRect;
begin
  cvs := TDirect2DCanvas.Create(Canvas, ClientRect);
  R := ClientRect;
  InflateRect(R, -ClientWidth div 5, -ClientHeight div 5);

  cvs.BeginDraw;
  cvs.RenderTarget.CreateSolidColorBrush(D2D1ColorF(clGray), nil, iBrush);

  rStrokeStyleProperties := D2D1StrokeStyleProperties();
  rStrokeStyleProperties.lineJoin := D2D1_LINE_JOIN_BEVEL;
  D2DFactory.CreateStrokeStyle(rStrokeStyleProperties, nil, 0, iStrokeStyle);

  cvs.RenderTarget.DrawRectangle(R, iBrush, 25, iStrokeStyle);
  cvs.EndDraw;
  cvs.Free;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  Repaint;
end;

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效果图：

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