FILL x, y, colour

' Random Closed Shape Generator - MMBasic Subroutine
' Test harness and subroutine

Dim inx%, iny%
Option Explicit
If Instr(MM.DEVICE$,"VGA") Or Instr(MM.DEVICE$, "HDMI") Then MODE 2
FRAMEBUFFER create
FRAMEBUFFER write f
Do
CLS
shape inx%, iny%
Fill inx%, iny%, RGB(Rnd*255,Rnd*255,Rnd*255)
FRAMEBUFFER copy f,n
Pause 250
Loop

' Creates an interesting random closed polygon with convex and concave sections
' Returns coordinates of a point inside the shape via x% and y% parameters

Sub shape(x%, y%)
   Local margin, minX, maxX, minY, maxY
   Local centerX, centerY, numPoints
   Local baseRadius, i, angle, radiusVariation, radius
   Local x1, y1, x2, y2, dx, dy, sx, sy, err, px, py, e2
   Local foundInside
   Local pointX(50), pointY(50)  ' Maximum possible points is 32, so 50 is safe

   ' Get screen dimensions with margins
   margin = 30
   minX = margin
   maxX = MM.HRES - margin - 1
   minY = margin
   maxY = MM.VRES - margin - 1

   ' Calculate random center point within the screen bounds
   ' Ensure enough space for the shape around the center
   centerX = minX + margin + Rnd * (maxX - minX - 2 * margin)
   centerY = minY + margin + Rnd * (maxY - minY - 2 * margin)

   ' Generate random points around a circle with varying radii
   numPoints = 16 + Int(Rnd * 16)  ' Between 16 and 32 points

   ' Base radius (smaller of the two dimensions)
   If (maxX - minX) < (maxY - minY) Then
       baseRadius = (maxX - minX) / 3
   Else
       baseRadius = (maxY - minY) / 3
   End If

   ' Generate points at regular angular intervals with random radius variations
   For i = 0 To numPoints - 1
       angle = (i * 2 * 3.14159265) / numPoints

       ' Random radius variation creates convex and concave sections
       radiusVariation = 0.5 + Rnd * 0.8  ' Varies from 0.5 to 1.3 times base
       radius = baseRadius * radiusVariation

       ' Calculate point position
       pointX(i) = Int(centerX + radius * Cos(angle))
       pointY(i) = Int(centerY + radius * Sin(angle))
   Next i

   ' Draw the closed shape by connecting all points
   For i = 0 To numPoints - 1
       ' Get current and next point (wrap around to close the shape)
       x1 = pointX(i)
       y1 = pointY(i)

       If i = numPoints - 1 Then
           x2 = pointX(0)  ' Connect last point back to first
           y2 = pointY(0)
       Else
           x2 = pointX(i + 1)
           y2 = pointY(i + 1)
       End If

       ' Draw line between points using Bresenham's algorithm
       dx = Abs(x2 - x1)
       dy = Abs(y2 - y1)

       If x1 < x2 Then
           sx = 1
       Else
           sx = -1
       End If

       If y1 < y2 Then
           sy = 1
       Else
           sy = -1
       End If

       err = dx - dy
       px = x1
       py = y1

       Do
           ' Draw pixel
           Pixel px, py, RGB(WHITE)

           ' Check if we've reached the end point
           If px = x2 And py = y2 Then Exit Do

           ' Calculate next point
           e2 = 2 * err

           If e2 > -dy Then
               err = err - dy
               px = px + sx
           End If

           If e2 < dx Then
               err = err + dx
               py = py + sy
           End If
       Loop
   Next i

   ' Find a point inside the shape (use center as it's always inside)
   x% = Int(centerX)
   y% = Int(centerY)

   ' Verify it's not on the boundary by checking if it's a white pixel
   ' If it is, offset slightly
   foundInside = 0
   Do While foundInside = 0
       If Pixel(x%, y%) <> RGB(WHITE) Then
           foundInside = 1
       Else
           ' Move slightly in a random direction
           x% = x% + Int(Rnd * 5) - 2
           y% = y% + Int(Rnd * 5) - 2
       End If
   Loop
End Sub