Fast filled circle

[CharlieJV]

I ran into issues with Paint and transparency; they don't get along very well.
So I created my own filled circle routine:

Code: (Select All)

Sub fCircle (x%, y%, r%, c~&)
  'Filled Circle: Transparency OK & >4x faster then Paint
  r2& = r% * r%
  xx% = Sqr(r2& - y2&): Line (x% - xx%, y%)-(x% + xx%, y%), c~&
  For yy% = 1 To r%
    y2& = yy% * yy%: xx% = Sqr(r2& - y2&)
    Line (x% - xx%, y% - yy%)-(x% + xx%, y% - yy%), c~&
    Line (x% - xx%, y% + yy%)-(x% + xx%, y% + yy%), c~&
  Next yy%
End Sub

It runs a lot faster then Circle & Paint and also works well with transparent colors!

That is very cool and very fast.  Side-question/observation:

Playing around with CIRCLE in GW-BASIC, the CIRCLE statement produces pretty perfect circles in every screen mode.  Drawing a square box (with LINE statement using the B parameter) in GW-BASIC will result in rectangles in different screen modes.  So the CIRCLE command in GW-BASIC must be doing something special to overcome the different pixel width to height ratios to always result in a circle instead of an oval.

For the code above, I would expect that same code to produce ovals in GW-BASIC when in screen modes that don't have 1 to 1 for pixel width to pixel height ratios.

Testing that out in QB64, the code above produces a perfect circle in every screen mode.

Just to understand the evolution of screen modes from GW-BASIC to QBASIC to QB64(pe), at which point did the varying pixel width to height ratios (as existing in GW-BASIC) go away?