TSVGDocument.DrawElement(TSVGGraphicElement,TSVGMatrix,TSVGCanvas,TSVGRect) Method

Delphi

public
procedure DrawElement(Element: TSVGGraphicElement; aMatrix: TSVGMatrix; const Canvas: TSVGCanvas; aRect: TSVGRect);
reintroduce; overload; virtual;

Even though no ancestors or siblings are drawn, this method does call the Draw method of every ancestor and "older" sibling to ensure the transformation matrix and clipping rectangles are properly initialized before drawing the element and its children.

The following example uses the DrawBeforeElement, DrawElement, and DrawAfterElement methods to optimize the drawing of an svg where one element may be changed often (such as in an editor):

Delphi

procedure TfrmSVGEditor.PaintBox1Paint(Sender: TObject; Canvas: TCanvas);
var
   aRect: TSVGRect;
begin
   // do we need to update the background (elements before) and foreground (elements
   // after) the current Element.  By creating a bitmap of the background and
   // foreground, we can optimize the drawing of the SVG as the current Element
   // changes
   if UpdateBackground then
   begin
     // draw background and foreground
     Background.Canvas.BeginScene;
     try
       Background.Clear(TAlphaColorRec.Null);
       if Element is TSVGGraphicElement then
         SVG.DrawBeforeElement(TSVGGraphicElement(Element), Background.Canvas, RectF(0,0,Background.Width, Background.Height));
     finally
       Background.Canvas.EndScene;
     end;
     Foreground.Canvas.BeginScene;
     try
       Foreground.Clear(TAlphaColorRec.Null);
       if Element is TSVGGraphicElement then
         SVG.DrawAfterElement(TSVGGraphicElement(Element), Foreground.Canvas, RectF(0,0,Foreground.Width, Foreground.Height));
     finally
       Foreground.Canvas.EndScene;
     end;
     FUpdateBackground := False;
   end;
   if Element is TSVGGraphicElement then
   begin
     // if current Element is a graphical element, draw the background
     aRect := RectF(0, 0, Background.Width, Background.Height);
     Canvas.DrawBitmap(Background, aRect, aRect, 1);
     // draw the element
     SVG.DrawElement(TSVGGraphicElement(Element), Canvas, PaintBox1.ClipRect);
     // draw the foreground
     Canvas.DrawBitmap(Foreground, aRect, aRect, 1);
   end
   else
     // just draw the entire SVG without any background/foreground caching
     SVG.Draw(Canvas, PaintBox1.ClipRect);
   // draw the focus rectangle
   Canvas.DrawFocusRect(SelectRect);
end;

Reference

•Draw(TSVGCanvas,TSVGRect)

•Draw(TSVGMatrix,TCanvas,TRect)

•DrawElement(TSVGGraphicElement,TCanvas,TSVGRect)

•RSSVG.TSVGDocument.DrawAfterElement(TSVGGraphicElement,TSVGCanvas,TSVGRect,Boolean)

•RSSVG.TSVGDocument.DrawBeforeElement(TSVGGraphicElement,TSVGCanvas,TSVGRect,Boolean)

•TSVGDocument

•RSSVG