42 lines
1.5 KiB
Plaintext
42 lines
1.5 KiB
Plaintext
#DEFINE WM_LBUTTONDOWN 513
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#DEFINE WM_CLOSE 16
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FBSLSETTEXT(ME, "Bresenham Circle") ' Set form caption
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FBSLSETFORMCOLOR(ME, RGB(0, 255, 255)) ' Cyan: persistent background color
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FBSL.GETDC(ME) ' Use volatile FBSL.GETDC below to avoid extra assignments
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RESIZE(ME, 0, 0, 220, 220)
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CENTER(ME)
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SHOW(ME)
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DIM Breadth AS INTEGER, Height AS INTEGER
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FBSL.GETCLIENTRECT(ME, 0, 0, Breadth, Height)
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BEGIN EVENTS ' Main message loop
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SELECT CASE CBMSG
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CASE WM_LBUTTONDOWN: MidpointCircle() ' Draw
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CASE WM_CLOSE: FBSL.RELEASEDC(ME, FBSL.GETDC) ' Clean up
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END SELECT
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END EVENTS
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SUB MidpointCircle()
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BresenhamCircle(Breadth \ 2, Height \ 2, 80, &HFF) ' Red: Windows stores colors in BGR order
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BresenhamCircle(Breadth \ 2, Height \ 2, 40, 0) ' Black
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SUB BresenhamCircle(cx, cy, radius, colour)
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DIM x = 0, y = radius, f = 1 - radius, dx = 0, dy = -2 * radius
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PSET(FBSL.GETDC, cx, cy + radius, colour)(FBSL.GETDC, cx, cy - radius, colour)
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PSET(FBSL.GETDC, cx + radius, cy, colour)(FBSL.GETDC, cx - radius, cy, colour)
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WHILE x < y
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IF f >= 0 THEN: DECR(y): INCR(dy, 2)(f, dy): END IF ' Try also "IF f THEN" :)
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INCR(x)(dx, 2)(f, dx + 1)
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PSET(FBSL.GETDC, cx + x, cy + y, colour)(FBSL.GETDC, cx - x, cy + y, colour)
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PSET(FBSL.GETDC, cx + x, cy - y, colour)(FBSL.GETDC, cx - x, cy - y, colour)
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PSET(FBSL.GETDC, cx + y, cy + x, colour)(FBSL.GETDC, cx - y, cy + x, colour)
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PSET(FBSL.GETDC, cx + y, cy - x, colour)(FBSL.GETDC, cx - y, cy - x, colour)
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WEND
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END SUB
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END SUB
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