Alternative circle routine

Circle.BI Include file or SUB to use when using PAINT with pie charts or arc slices:

 'CIRCLE.BI
'**
'** QB64 replacement CIRCLE command.
'**
'** The CIRCLE command in QB64 has a few issues:
'**
'** - radian end points are not calculate properly when creating arcs
'** - center line to radian end points do not close properly due to previous bug listed
'**
'** This circle command replacement works very similiarly to the native CIRCLE command:
'**
'** SYNTAX: CIRCLES x%, y%, radius!, color~&, start_radian!, end_radian!, aspect_ratio!
'**
'**   x%            - center X coordinate of circle
'**   y%            - center Y coordinate of circle
'**   radius!       - the radius of the circle
'**   color~&       - the circle's color
'**   start_radian! - the radian on circle curcunference to begin drawing at
'**   end_radian!   - the radian on circle circumference to end drawing at
'**   aspect_ratio! - the aspect ratio of the circle
'**
'** **NOTE: unlike the native CIRCLE command, all arguments MUST be supplied.** For example,
'**       with the native command this will draw a perfect circle with the default color,
'**       start radian, end radian and aspect ratio:
'**
'**       CIRCLE (319, 239), 100
'**
'**       To do the same thing with this replacement command you must supply everything:
'**
'**       CIRCLES 319, 239, 100, _RGB32(255, 255, 255), 0, 0, 0
'**
'** ACKNOWLEGEMENTS: The FOR/NEXT step formula was was written by Codeguy for Unseen
'**                  Machine's Visual library EllipseXS command. Specifically:
'**                         MinStep! = 1 / (2 * 3.1415926535 * Radius!)
'**
'**
'** Includes performance tweaks made by SMcNeill on 02/02/13 - specifically removing a few redundant * -1
'** statements and converting the FOR/NEXT loop to a DO loop for a ~3% increase in performance.
'**
'** Corrected bug in which variables being passed in were being modified and passed back - 02/02/13
'**
**SUB CIRCLES (cx%, cy%, r!, c~&, s!, e!, a!)**
DIM s%, e%, nx%, ny%, xr!, yr!, st!, en!, asp! '     local variables used

st! = s! '                                           copy start radian to local variable
en! = e! '                                           copy end radian to local variable
asp! = a! '                                          copy aspect ratio to local variable
IF asp! <= 0 THEN asp! = 1 '                         keep aspect ratio between 0 and 4
IF asp! > 4 THEN asp! = 4
IF asp! < 1 THEN xr! = r! * asp! * 4 ELSE xr! = r! ' calculate x/y radius based on aspect ratio
IF asp! > 1 THEN yr! = r! * asp! ELSE yr! = r!
IF st! < 0 THEN s% = -1: st! = -st! '                remember if line needs drawn from center to start radian
IF en! < 0 THEN e% = -1: en! = -en! '                remember if line needs drawn from center to end radian
IF s% THEN '                                         draw line from center to start radian?
    nx% = cx% + xr! * COS(st!) '                     yes, compute starting point on circle's circumference
    ny% = cy% + yr! * -SIN(st!)
    LINE (cx%, cy%)-(nx%, ny%), c~& '                draw line from center to radian
END IF
IF en! <= st! THEN en! = en! + 6.2831852 '           come back around to proper location (draw counterclockwise)
stepp! = 0.159154945806 / r!
c! = st! '                                           cycle from start radian to end radian
DO
    nx% = cx% + xr! * COS(c!) '                      compute next point on circle's circumfrerence
    ny% = cy% + yr! * -SIN(c!)
    PSET (nx%, ny%), c~& '                           draw the point
    c! = c! + stepp!
LOOP UNTIL c! >= en!
IF e% THEN LINE -(cx%, cy%), c~& '                   draw line from center to end radian if needed
**END SUB**