REM. Demonstration of anti-aliased graphics library for BBC BASIC for SDL 2.0
      INSTALL @lib$ + "aagfxlib"
      
      LineEndTriangle = 1
      LineEndRound = 2
      LineEndArrow = 3
      
      LineStartTriangle = &100
      LineStartRound = &200
      LineStartArrow = &300
      
      LineDot = &10000
      LineDash = &20000
      LineDashDot = &30000
      
      ON ERROR OSCLI "REFRESH ON" : IF ERR = 17 CHAIN @lib$+"../examples/tools/touchide" ELSE REPORT : END
      
      VDU 23,22,640;480;8,16,16,128
      OFF
      
      *REFRESH OFF
      REPEAT
        angle += 0.01
        
        CLS
        
        REM Near-horizontal line to demonstrate antialiasing
        pencolour% = &FF0000FF : REM. Opaque red
        penstyle% = LineStartArrow + LineEndArrow
        penwidth = 4.0
        PROC_aaline(0, 200, 1280, 210, penwidth, pencolour%, penstyle%)
        
        REM Near vertical line to demonstrate antialiasing
        pencolour% = &FF008000 : REM. Opaque dark green
        penstyle% = LineEndTriangle + LineDashDot
        penwidth = 2.5
        PROC_aaline(200, 0, 210, 960, penwidth, pencolour%, penstyle%)
        
        REM Thick lines to illustrate end-point options
        pencolour% = &FF0080C0 : REM brown
        penstyle% = LineEndRound + LineStartArrow
        penwidth = 16.0
        PROC_aaline(100, 400, 90, 800, penwidth, pencolour%, penstyle%)
        pencolour% = &50FF0000 : REM translucent blue
        penstyle% = LineEndTriangle
        PROC_aaline(500, 100, 900, 90, penwidth, pencolour%, penstyle%)
        
        REM Cubic Bezier curve from four control points
        pencolour% = &FFFF0000 : REM. Opaque blue
        penstyle% = LineStartRound + LineEndArrow
        penwidth = 5.0
        PROC_aabezier(20, 20, 200, 200, 400, 600, 800, 600, penwidth, pencolour%, penstyle%)
        
        REM Ellipse made from 360-degree arc
        pencolour% = &A00080FF : REM. Translucent orange
        penstyle% = LineStartArrow + LineEndArrow
        penwidth = 3.0
        PROC_aaarc(500, 500, 150, 100, DEG(angle), 360, penwidth, pencolour%, penstyle%)
        LINE 500, 500, 500, 500
        
        REM Filled sector, 3/4 of an ellipse
        brushcolour% = &FFFF00FF : REM. Opaque magenta
        PROC_aasector(900, 800, 100, 150, 90+DEG(angle), 270, brushcolour%)
        LINE 900, 800, 900, 800
        
        REM Filled five-pointed star (alternate)
        brushcolour% = &FF808080 : REM. Opaque grey
        DIM X(4), Y(4)
        X() = 1100,900,1060,1000,940
        Y() = 430,430,320,500,320
        PROC_aapolygon(5, X(), Y(), brushcolour%)
        
        REM Square drawn with polyline
        pencolour% = &FF000000 : REM. Opaque black
        penstyle% = LineEndArrow + LineStartArrow
        penwidth = 6.0
        DIM xx(4), yy(4)
        x = 600 : y = 800
        FOR I% = 0 TO 3
          xx(I%) = x + 80 * COS(I% * PI / 2 + angle / 2)
          yy(I%) = y + 80 * SIN(I% * PI / 2 + angle / 2)
        NEXT
        xx(4) = xx(0) : yy(4) = yy(0)
        PROC_aapolyline(5, xx(), yy(), penwidth, pencolour%, penstyle%)
        
        REM Angled outline ellipse
        pencolour% = &FF00C000 : REM. Opaque bright green
        penwidth = 2.0
        PROC_aaellipse(350, 800, 70, 100, penwidth, -angle, pencolour%)
        x = 70 * COS(2 * angle) : y = 100 * SIN(2 * angle)
        xx = x * COS(angle) + y * SIN(angle) : yy = y * COS(angle) - x * SIN(angle)
        PROC_aaline(350, 800, 350 + xx, 800 + yy, 2.5, &80C000C0, &20202)
        
        REM Angled solid ellipse
        brushcolour% = &C0808000 : REM. Cyan
        PROC_aaellipsefill(1100, 600, 50, 140, angle, brushcolour%)
        
        REM Heart shape from polybezier
        pencolour% = &FF2B39C0 : REM. opaque red
        brushcolour% = &200000FF : REM. pink
        penstyle% = LineEndTriangle + LineStartTriangle
        penwidth = 3.0
        x = 750 : y = 330
        DIM x(12), y(12)
        x() = x, x,    x-100, x-100, x-100, x,    x,     x,    x+100, x+100, x+100, x,    x
        y() = y, y+60, y+60,  y,     y-60,  y-70, y-110, y-70, y-60,  y,     y+60,  y+60, y
        PROC_aafillbezier(13, x(), y(), brushcolour%)
        PROC_aapolybezier(13, x(), y(), penwidth, pencolour%, penstyle%)
        
        *REFRESH
        
      UNTIL FALSE
      END