%!PS-Adobe-2.0
%%Pages: 1
%%BoundingBox: 0 0 595 841
%%DocumentPaperSizes: A4
%%EndComments

% Protractor by Tom Quetchenbach, 2009
% http://wombatula.com/wombats/protractor.php
% You may use, modify, reproduce, distribute, transmit, build upon,
% etc, with no restrictions.

% I don't actually know how DSC works, but the above seems to be ok.

% Options passed by PHP script:
% TYPE="180" METRIC="false" OFFSET="90" CENTER_BOTTOM_EDGE="false"
% MIRROR="false" OUTER="4 inch" THICKNESS="1 inch" FONTSIZE="12"
% PAPER_HEIGHT="841" PAPER_WIDTH="595" PAPER_NAME="A4"

/inch {72 mul} bind def
/cm {72 2.54 div mul} bind def

% user definitions
% type must be one of 90, 180, or 360; anything else is undefined
/type 180 def
% ruler in metric
/metric false def
% offet of center point; useful values are 0 and 90
/offset 90 def
% whether to place the center point on the bottom edge
/center_bottom_edge false def
% if set, 0 degrees is on the left and increases clockwise
/mirror false def
% font size in points
/fontsize 12 def
% height of the page including margins
/page_height 841 def
% width of the page including margins
/page_width 595 def
% major tick mark interval in degrees
/major 10 def
% minor tick mark interval in degrees
/minor 5 def
% in addition there are even smaller tick marks every degree
% outer radius of the protractor. Note that the width of the protractor is outer
% if center_bottom_edge is set; otherwise outer + thickness / 2
/outer 4 inch def
% thickness (outer radius - inner radius) of the protractor
/thickness 1 inch def

% end user definitions

type 360 eq {
    /center_bottom_edge true def
    /offset 0 def
} if

/inner outer thickness sub def
/tick_len outer inner sub 4 div def

% syntax: x h arcsin -- computes arcsin (x/h)
/arcsin { /hv exch def /xv exch def xv hv dup mul xv dup mul sub sqrt atan } bind def

% temp string for int->str conversion
/tmp 3 string def

% set up font
/Helvetica findfont
12 scalefont
setfont

/bottom_edge center_bottom_edge { 0 } { thickness -2 div } ifelse def

type 360 eq {
    /inner_angle 0 def
    /amax 270 def
    outer 2 div 0 translate
} {
    /inner_angle thickness bottom_edge add inner arcsin def
    type 90 eq {
        /amax 0 def
        0 outer 2 div translate
    } {
        /amax 90 def
    } ifelse
} ifelse

% move protractor to center of page
page_width outer sub bottom_edge neg add 2 div page_height 2 div translate

% outer arc

bottom_edge outer neg moveto
0 0 outer -90 amax arc
center_bottom_edge not {
    amax 90 add dup rotate
    thickness 2 div 0 rlineto
    neg rotate
} if

bottom_edge type 180 eq {outer} {0} ifelse type 90 eq {bottom_edge neg add}if lineto
bottom_edge outer neg lineto

% inner arc
type 360 eq {
    0 0 moveto
    0 0 inner -90 270 arc
} {
    bottom_edge thickness add  type 90 eq {thickness bottom_edge add neg} {0} ifelse 2 copy moveto
    0 0 inner -90 inner_angle add amax inner_angle sub arc
    lineto
} ifelse

% crosshair, or if center is on bottom edge just a long tick mark and
% half-circle
center_bottom_edge {
    type 360 eq {
        tick_len 2 mul 0 moveto
        tick_len 2 mul neg 0 lineto
        tick_len 4 div 0 moveto
        0 0 tick_len 4 div 0 360 arc
    } {
        bottom_edge 0 moveto
        tick_len 2 mul 0 rlineto
        0 tick_len 4 div neg moveto
        0 0 tick_len 4 div 270 amax arc
    } ifelse
} {
    bottom_edge 0 moveto
    tick_len 0 rlineto
    type 90 eq {
        0 thickness 2 div moveto
        0 tick_len neg rlineto
    } if
    tick_len 2 div dup dup dup 0 exch moveto
    0 exch neg lineto
    0 moveto
    neg 0 lineto
    tick_len 4 div 0 moveto
    0 0 tick_len 4 div 0 360 arc
} ifelse

% big tick-marks at 0 and 180
amax rotate
inner 0 moveto
outer 0 lineto
amax neg rotate
0 outer neg moveto
0 inner neg lineto

% the rest of the tick-marks
-89 1 amax 1 sub {
    /angle exch def
    angle rotate
    % select tick-mark length based on angle
    angle major mod 0 eq {
        % major tick-mark labels, rotated to be parallel with long edge of page
        outer tick_len 2 mul sub 0 translate
        angle neg 90 sub rotate
        0 0 moveto
        angle mirror not {neg} if offset exch sub tmp cvs dup stringwidth
        pop -2 div 0 moveto show
        angle 90 add rotate
        
        outer tick_len 2 mul sub neg 0 translate
        tick_len
    } {
        angle minor mod 0 eq {
            tick_len 2 div
        } {
            tick_len 4 div
        } ifelse
    } ifelse

    % draw tick on outer edge and inner edge if adjacent
    dup outer exch sub 0 moveto
    outer 0 lineto
    inner add 0 moveto
    amax angle sub inner_angle gt angle 90 add inner_angle gt and{
        inner 0 lineto
    } if

    angle neg rotate
} for

% ruler on bottom edge

metric {
    /unit 0.1 cm def
    /ticks1 10 def
    /ticks2 5 def
    /ticks3 1 def
    /ticks4 1 def
} {
    /unit .0625 inch def
    /ticks1 16 def
    /ticks2 8 def
    /ticks3 4 def
    /ticks4 2 def
} ifelse

1 1 outer unit div {
    /i exch def
    /x i unit mul neg def
    i ticks1 mod 0 eq {
        -90 rotate
        /num_text i ticks1 div cvi tmp cvs def
        /num_width num_text stringwidth pop def
        x num_width -2 div sub dup neg bottom_edge tick_len 4 add add moveto
        num_width -2 div add outer neg gt {
            num_text show
            amax 90 sub dup rotate
            num_width -2 div x add fontsize neg thickness 2 div bottom_edge add add moveto
            num_text show
            neg rotate
        } if
        90 rotate
        tick_len
    } {
        i ticks2 mod 0 eq {
            tick_len 2 div
        } {
            i ticks3 mod 0 eq {
                tick_len 4 div
            } {
                i ticks4 mod 0 eq {
                    tick_len 8 div
                } {
                    tick_len 16 div
                } ifelse
            } ifelse
        } ifelse
    } ifelse

    bottom_edge x moveto
    dup 0 rlineto
    amax 90 sub rotate
    bottom_edge x neg moveto
    0 rlineto
    90 amax sub rotate
} for

% done!
stroke

showpage