#579 BITMAPTURTLE turtles are not drawn in correct position when zoomed

[David Costanzo]

Non-rotating bitmapped turtles (the ones created with BITMAPTURTLE with no optional inputs) are not drawn in the correct position when zoomed. Depending on the zoom factor and the scrollbar positions, they may be drawn in an incorrect location, disappear completely, or leave smudges on the screen when you scroll.

I have reproduced this in FMSLogo 8.2.0. It is reproducible as in FMSLogo 6.33.0 but not in FMSLogo 6.32.0. I introduced this regression when I was improving the behavior of rotating bitmaps.

How Reproducible:
Every Time

Steps to Reproduce:
Run the following program

:::text
; draw an arrow
clearscreen
setpensize [1 1]
setpencolor 0
fd 40
rt 135
fd 20
bk 20
rt 90
fd 20
bk 20
lt 45
fd 40
hideturtle

; cut the arrow
setturtle 1
penup
lt 90
fd 20
rt 90
setbitindex 1
bitcut 40 40

; move around as an arrow
bitmapturtle
pendown
setpensize [3 3]
setpencolor 4
fd 50

; zoom in to see the bug
zoom 2

What Happens:
The arrow shape of the turtle disappears when zoom 2 is run. If you zoom out again, you'll see where the arrow-shape should be.

Expected Result:
The arrow shape remains to the upper-right of the red line after zoom 2 is run. It's in the same position as seen before zoom 2 was run.

[David Costanzo]

This is fixed by [r5833]. The fix will be available in FMSLogo 8.3.0.