prog8/examples/line-circle-txt.p8

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%import textio
%import syslib
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%zeropage basicsafe
; Note: this program can be compiled for multiple target systems.
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main {
sub start() {
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txt.print("rectangles\nand circle\ndrawing.\n")
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ubyte r
for r in 3 to 12 step 3 {
circle(20, 12, r)
}
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txt.print("enter for disc:")
void cbm.CHRIN()
txt.nl()
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txt.clear_screen()
disc(20, 12, 12)
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txt.print("enter for rectangles:")
void cbm.CHRIN()
txt.nl()
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txt.clear_screen()
rect(4, 8, 37, 23, false)
rect(20, 12, 30, 20, true)
rect(10, 10, 10, 10, false)
rect(6, 0, 16, 20, true)
sub rect(ubyte x1, ubyte y1, ubyte x2, ubyte y2, bool fill) {
ubyte x
ubyte y
if fill {
for y in y1 to y2 {
for x in x1 to x2 {
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txt.setcc(x, y, 42, x+y)
}
}
} else {
for x in x1 to x2 {
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txt.setcc(x, y1, 42, 8)
txt.setcc(x, y2, 42, 8)
}
if y2>y1 {
for y in y1+1 to y2-1 {
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txt.setcc(x1, y, 42, 7)
txt.setcc(x2, y, 42, 7)
}
}
}
}
sub circle(ubyte xcenter, ubyte ycenter, ubyte radius) {
; Midpoint algorithm
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ubyte x = radius
ubyte y = 0
byte decisionOver2 = 1-x as byte
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while x>=y {
txt.setcc(xcenter + x, ycenter + y, 81, 1)
txt.setcc(xcenter - x, ycenter + y, 81, 2)
txt.setcc(xcenter + x, ycenter - y, 81, 3)
txt.setcc(xcenter - x, ycenter - y, 81, 4)
txt.setcc(xcenter + y, ycenter + x, 81, 5)
txt.setcc(xcenter - y, ycenter + x, 81, 6)
txt.setcc(xcenter + y, ycenter - x, 81, 7)
txt.setcc(xcenter - y, ycenter - x, 81, 8)
y++
if decisionOver2>=0 {
x--
decisionOver2 -= 2*x
}
decisionOver2 += 2*y
decisionOver2++
}
}
sub disc(ubyte cx, ubyte cy, ubyte radius) {
; Midpoint algorithm, filled
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ubyte x = radius
ubyte y = 0
byte decisionOver2 = 1-x as byte
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ubyte xx
while x>=y {
xx = cx-x
repeat 2*x+1 {
txt.setcc(xx, cy + y, 81, 11)
txt.setcc(xx, cy - y, 81, 12)
xx++
}
xx = cx-y
repeat 2*y+1 {
txt.setcc(xx, cy + x, 81, 13)
txt.setcc(xx, cy - x, 81, 14)
xx++
}
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y++
if decisionOver2>=0 {
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x--
decisionOver2 -= 2*x
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}
decisionOver2 += 2*y
decisionOver2++
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}
}
}
}