CANVAS

Description

The CANVAS element lets you draw your own shapes using the Kt::Graphics scripting API.

Inherited Attributes

See the Widgets element.

Specific Attributes

Name	Value Type	Default Value	Description	Comment	V.	Exp.
render_script	script	empty	inline script that draws onto the current Graphics context.	You can access the current graphics context object in the script using the Kt::Graphics::GetCurrentContext() function.	2.6	No
requires	list of ';' separated identifiers or wildcards	Empty.	List of objects expected by the script.	Forces the KUIML engine to expose the listed objects to the scripting engine. for example: 'my_object.*;my_string'	2.0	No
script_handles_opacity	boolean	false	if true, the render script should handle the opacity of the widget.		2.6	No

Examples

Skin file:

<?xml version="1.0" encoding="utf-8" ?>
<SKIN author="Blue Cat Audio" name="2D Canvas Script" background_color="#000000" margin="2">
<!-- Includes -->
<SCRIPT src="demoCanvas.cxx"/>

<!-- The Canvas -->
<CANVAS id="shapes" requires="shapes.width;shapes.height" render_script="renderShapes(this.width,this.height)" width="300" height="300" opacity=".8"/>
</SKIN>

Render script file (demoCanvas.cxx):

void renderShapes(double w,double h)
{
    Kt::Graphics::Context@ ctx=Kt::Graphics::GetCurrentContext();
    if(@ctx!=null)
    {
      double r=.5;
      double g=1;
      double b=1;
      
      // setup transforms
      double lineW=3*2/sqrt(w*w+h*h);

      // draw lines and outer circle
      ctx.transform.Scale(w/2,h/2);
      ctx.transform.Translate(1,1);
      ctx.settings.lineWidth=lineW;
      ctx.source.SetRGBA(r,g,b,1);
      ctx.path.Clear();
      ctx.path.MoveTo(-.7,-.7);
      ctx.path.LineTo(.7,.7);
      ctx.path.MoveTo(.7,-.7);
      ctx.path.LineTo(-.7,.7);
      ctx.path.MoveTo(-1,0);
      ctx.path.LineTo(1,0);
      ctx.path.NewSubPath();
      ctx.path.Arc(0,0,1-lineW/2,0,360);
      ctx.StrokePath();

      // draw gradient
      Kt::Graphics::GradientDrawPattern@ gradient=ctx.patterns.NewRadialGradient(0,0,0,0,0,1);
      gradient.AddColorStopRGBA(0,r,g,b,0);
      gradient.AddColorStopRGBA(1,r,g,b,.3);
      gradient.SelectAsSource();
      ctx.FillPath();
      
      ctx.path.MoveTo(0,0);
      ctx.transform.Scale(.05,.05);
      ctx.path.Clear();

      Kt::Graphics::DrawPattern@ rgba=ctx.patterns.NewRGBA(1,1,1,.8);
      rgba.SelectAsSource();

      ctx.font.SelectFontFace("Georgia");
      ctx.font.SetFontSize(9);
      ctx.path.Text("ABC");
      ctx.FillPath();
    }
}