Issue #7061: Added a 'Turtle star' sidebar

5 files changed, 467 insertions, 0 deletions

diff --git a/Doc/includes/turtle-star.py b/Doc/includes/turtle-star.py
new file mode 100644
index 0000000..1a5db76
--- /dev/null
+++ b/Doc/includes/turtle-star.py
@@ -0,0 +1,10 @@
+from turtle import *
+color('red', 'yellow')
+begin_fill()
+while True:
+    forward(200)
+    left(170)
+    if abs(pos()) < 1:
+        break
+end_fill()
+done()
diff --git a/Doc/library/turtle-star.pdf b/Doc/library/turtle-star.pdf
new file mode 100644
index 0000000..e354073
--- /dev/null
+++ b/Doc/library/turtle-star.pdf
diff --git a/Doc/library/turtle-star.png b/Doc/library/turtle-star.png
new file mode 100644
index 0000000..caf36a3
--- /dev/null
+++ b/Doc/library/turtle-star.png
diff --git a/Doc/library/turtle-star.ps b/Doc/library/turtle-star.ps
new file mode 100644
index 0000000..46362cb
--- /dev/null
+++ b/Doc/library/turtle-star.ps
@@ -0,0 +1,447 @@
+%!PS-Adobe-3.0 EPSF-3.0
+%%Creator: Tk Canvas Widget
+%%For: Alexander Belopolsky
+%%Title: Window .4315905424
+%%CreationDate: Tue Nov  9 12:54:06 2010
+%%XBoundingBox: -172 -52 785 845
+%%BoundingBox: 290 290 520 520
+%%Pages: 1
+%%DocumentData: Clean7Bit
+%%Orientation: Portrait
+%%EndComments
+
+%%BeginProlog
+/CurrentEncoding [
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/exclam/quotedbl/numbersign/dollar/percent/ampersand/quotesingle
+/parenleft/parenright/asterisk/plus/comma/hyphen/period/slash
+/zero/one/two/three/four/five/six/seven
+/eight/nine/colon/semicolon/less/equal/greater/question
+/at/A/B/C/D/E/F/G
+/H/I/J/K/L/M/N/O
+/P/Q/R/S/T/U/V/W
+/X/Y/Z/bracketleft/backslash/bracketright/asciicircum/underscore
+/grave/a/b/c/d/e/f/g
+/h/i/j/k/l/m/n/o
+/p/q/r/s/t/u/v/w
+/x/y/z/braceleft/bar/braceright/asciitilde/space
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/space/space/space/space/space/space/space
+/space/exclamdown/cent/sterling/currency/yen/brokenbar/section
+/dieresis/copyright/ordfeminine/guillemotleft/logicalnot/hyphen/registered/macron
+/degree/plusminus/twosuperior/threesuperior/acute/mu/paragraph/periodcentered
+/cedilla/onesuperior/ordmasculine/guillemotright/onequarter/onehalf/threequarters/questiondown
+/Agrave/Aacute/Acircumflex/Atilde/Adieresis/Aring/AE/Ccedilla
+/Egrave/Eacute/Ecircumflex/Edieresis/Igrave/Iacute/Icircumflex/Idieresis
+/Eth/Ntilde/Ograve/Oacute/Ocircumflex/Otilde/Odieresis/multiply
+/Oslash/Ugrave/Uacute/Ucircumflex/Udieresis/Yacute/Thorn/germandbls
+/agrave/aacute/acircumflex/atilde/adieresis/aring/ae/ccedilla
+/egrave/eacute/ecircumflex/edieresis/igrave/iacute/icircumflex/idieresis
+/eth/ntilde/ograve/oacute/ocircumflex/otilde/odieresis/divide
+/oslash/ugrave/uacute/ucircumflex/udieresis/yacute/thorn/ydieresis
+] def
+
+50 dict begin
+% This is a standard prolog for Postscript generated by Tk's canvas
+% widget.
+% RCS: @(#) $Id$
+
+% The definitions below just define all of the variables used in
+% any of the procedures here.  This is needed for obscure reasons
+% explained on p. 716 of the Postscript manual (Section H.2.7,
+% "Initializing Variables," in the section on Encapsulated Postscript).
+
+/baseline 0 def
+/stipimage 0 def
+/height 0 def
+/justify 0 def
+/lineLength 0 def
+/spacing 0 def
+/stipple 0 def
+/strings 0 def
+/xoffset 0 def
+/yoffset 0 def
+/tmpstip null def
+
+
+/cstringshow {
+    {
+	dup type /stringtype eq
+	{ show } { glyphshow }
+	ifelse
+    }
+    forall
+} bind def
+
+
+
+/cstringwidth {
+    0 exch 0 exch
+    {
+	dup type /stringtype eq
+	{ stringwidth } { 
+	    currentfont /Encoding get exch 1 exch put (\001) stringwidth 
+        }
+	ifelse 
+	exch 3 1 roll add 3 1 roll add exch
+    }
+    forall
+} bind def
+
+% font ISOEncode font
+% This procedure changes the encoding of a font from the default
+% Postscript encoding to current system encoding.  It's typically invoked just
+% before invoking "setfont".  The body of this procedure comes from
+% Section 5.6.1 of the Postscript book.
+
+/ISOEncode {
+    dup length dict begin
+	{1 index /FID ne {def} {pop pop} ifelse} forall
+	/Encoding CurrentEncoding def
+	currentdict
+    end
+
+    % I'm not sure why it's necessary to use "definefont" on this new
+    % font, but it seems to be important; just use the name "Temporary"
+    % for the font.
+
+    /Temporary exch definefont
+} bind def
+
+% StrokeClip
+%
+% This procedure converts the current path into a clip area under
+% the assumption of stroking.  It's a bit tricky because some Postscript
+% interpreters get errors during strokepath for dashed lines.  If
+% this happens then turn off dashes and try again.
+
+/StrokeClip {
+    {strokepath} stopped {
+	(This Postscript printer gets limitcheck overflows when) =
+	(stippling dashed lines;  lines will be printed solid instead.) =
+	[] 0 setdash strokepath} if
+    clip
+} bind def
+
+% desiredSize EvenPixels closestSize
+%
+% The procedure below is used for stippling.  Given the optimal size
+% of a dot in a stipple pattern in the current user coordinate system,
+% compute the closest size that is an exact multiple of the device's
+% pixel size.  This allows stipple patterns to be displayed without
+% aliasing effects.
+
+/EvenPixels {
+    % Compute exact number of device pixels per stipple dot.
+    dup 0 matrix currentmatrix dtransform
+    dup mul exch dup mul add sqrt
+
+    % Round to an integer, make sure the number is at least 1, and compute
+    % user coord distance corresponding to this.
+    dup round dup 1 lt {pop 1} if
+    exch div mul
+} bind def
+
+% width height string StippleFill --
+%
+% Given a path already set up and a clipping region generated from
+% it, this procedure will fill the clipping region with a stipple
+% pattern.  "String" contains a proper image description of the
+% stipple pattern and "width" and "height" give its dimensions.  Each
+% stipple dot is assumed to be about one unit across in the current
+% user coordinate system.  This procedure trashes the graphics state.
+
+/StippleFill {
+    % The following code is needed to work around a NeWSprint bug.
+
+    /tmpstip 1 index def
+
+    % Change the scaling so that one user unit in user coordinates
+    % corresponds to the size of one stipple dot.
+    1 EvenPixels dup scale
+
+    % Compute the bounding box occupied by the path (which is now
+    % the clipping region), and round the lower coordinates down
+    % to the nearest starting point for the stipple pattern.  Be
+    % careful about negative numbers, since the rounding works
+    % differently on them.
+
+    pathbbox
+    4 2 roll
+    5 index div dup 0 lt {1 sub} if cvi 5 index mul 4 1 roll
+    6 index div dup 0 lt {1 sub} if cvi 6 index mul 3 2 roll
+
+    % Stack now: width height string y1 y2 x1 x2
+    % Below is a doubly-nested for loop to iterate across this area
+    % in units of the stipple pattern size, going up columns then
+    % across rows, blasting out a stipple-pattern-sized rectangle at
+    % each position
+
+    6 index exch {
+	2 index 5 index 3 index {
+	    % Stack now: width height string y1 y2 x y
+
+	    gsave
+	    1 index exch translate
+	    5 index 5 index true matrix tmpstip imagemask
+	    grestore
+	} for
+	pop
+    } for
+    pop pop pop pop pop
+} bind def
+
+% -- AdjustColor --
+% Given a color value already set for output by the caller, adjusts
+% that value to a grayscale or mono value if requested by the CL
+% variable.
+
+/AdjustColor {
+    CL 2 lt {
+	currentgray
+	CL 0 eq {
+	    .5 lt {0} {1} ifelse
+	} if
+	setgray
+    } if
+} bind def
+
+% x y strings spacing xoffset yoffset justify stipple DrawText --
+% This procedure does all of the real work of drawing text.  The
+% color and font must already have been set by the caller, and the
+% following arguments must be on the stack:
+%
+% x, y -	Coordinates at which to draw text.
+% strings -	An array of strings, one for each line of the text item,
+%		in order from top to bottom.
+% spacing -	Spacing between lines.
+% xoffset -	Horizontal offset for text bbox relative to x and y: 0 for
+%		nw/w/sw anchor, -0.5 for n/center/s, and -1.0 for ne/e/se.
+% yoffset -	Vertical offset for text bbox relative to x and y: 0 for
+%		nw/n/ne anchor, +0.5 for w/center/e, and +1.0 for sw/s/se.
+% justify -	0 for left justification, 0.5 for center, 1 for right justify.
+% stipple -	Boolean value indicating whether or not text is to be
+%		drawn in stippled fashion.  If text is stippled,
+%		procedure StippleText must have been defined to call
+%		StippleFill in the right way.
+%
+% Also, when this procedure is invoked, the color and font must already
+% have been set for the text.
+
+/DrawText {
+    /stipple exch def
+    /justify exch def
+    /yoffset exch def
+    /xoffset exch def
+    /spacing exch def
+    /strings exch def
+
+    % First scan through all of the text to find the widest line.
+
+    /lineLength 0 def
+    strings {
+	cstringwidth pop
+	dup lineLength gt {/lineLength exch def} {pop} ifelse
+	newpath
+    } forall
+
+    % Compute the baseline offset and the actual font height.
+
+    0 0 moveto (TXygqPZ) false charpath
+    pathbbox dup /baseline exch def
+    exch pop exch sub /height exch def pop
+    newpath
+
+    % Translate coordinates first so that the origin is at the upper-left
+    % corner of the text's bounding box. Remember that x and y for
+    % positioning are still on the stack.
+
+    translate
+    lineLength xoffset mul
+    strings length 1 sub spacing mul height add yoffset mul translate
+
+    % Now use the baseline and justification information to translate so
+    % that the origin is at the baseline and positioning point for the
+    % first line of text.
+
+    justify lineLength mul baseline neg translate
+
+    % Iterate over each of the lines to output it.  For each line,
+    % compute its width again so it can be properly justified, then
+    % display it.
+
+    strings {
+	dup cstringwidth pop
+	justify neg mul 0 moveto
+	stipple {
+	   
+ 
+	    % The text is stippled, so turn it into a path and print
+	    % by calling StippledText, which in turn calls StippleFill.
+	    % Unfortunately, many Postscript interpreters will get
+	    % overflow errors if we try to do the whole string at
+	    % once, so do it a character at a time.
+
+	    gsave
+	    /char (X) def
+	    {
+		dup type /stringtype eq {
+		    % This segment is a string.
+		    {
+		        char 0 3 -1 roll put
+		        currentpoint
+		        gsave
+		        char true charpath clip StippleText
+		        grestore
+		        char stringwidth translate
+		        moveto
+		    } forall
+		} {
+		    % This segment is glyph name
+		    % Temporary override
+		    currentfont /Encoding get exch 1 exch put
+		    currentpoint
+		    gsave (\001) true charpath clip StippleText
+		    grestore
+	            (\001) stringwidth translate
+		    moveto
+		} ifelse
+	    } forall
+	    grestore 
+	} {cstringshow} ifelse
+	0 spacing neg translate
+    } forall
+} bind def
+
+%%EndProlog
+%%BeginSetup
+/CL 2 def
+%%EndSetup
+
+%%Page: 1 1
+save
+306.0 396.0 translate
+0.9995 0.9995 scale
+4 -449 translate
+-483 898 moveto 475 898 lineto 475 0 lineto -483 0 lineto closepath clip newpath
+gsave
+grestore
+gsave
+0 445 moveto
+200 445 lineto
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+190.97697355474 411.325606868252 lineto
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+-1.70530256582424e-13 445 lineto
+0 445 lineto
+1.000 1.000 0.000 setrgbcolor AdjustColor
+eofill
+grestore
+gsave
+0 445 moveto
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+17.7718927978523 511.325606868252 lineto
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+74.0192308192062 550.710416955034 lineto
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+1 setlinecap
+1 setlinejoin
+1 setlinewidth
+[] 0 setdash
+1.000 0.000 0.000 setrgbcolor AdjustColor
+stroke
+grestore
+gsave
+grestore
+gsave
+-1.70530256582424e-13 445 moveto
+-9.00000000000019 450 lineto
+-7.00000000000017 445 lineto
+-9.00000000000015 440 lineto
+-1.70530256582424e-13 445 lineto
+1.000 1.000 0.000 setrgbcolor AdjustColor
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+-9.00000000000019 450 lineto
+-7.00000000000017 445 lineto
+-9.00000000000015 440 lineto
+-1.70530256582424e-13 445 lineto
+1 setlinejoin 1 setlinecap
+1 setlinewidth
+[] 0 setdash
+1.000 0.000 0.000 setrgbcolor AdjustColor
+stroke
+grestore
+restore showpage
+
+%%Trailer
+end
+%%EOF
+
diff --git a/Doc/library/turtle.rst b/Doc/library/turtle.rst
index efe9ae7..c2b9f41 100644
--- a/Doc/library/turtle.rst
+++ b/Doc/library/turtle.rst
@@ -23,6 +23,16 @@ command ``turtle.forward(15)``, and it moves (on-screen!) 15 pixels in the
 direction it is facing, drawing a line as it moves.  Give it the command
 ``turtle.left(25)``, and it rotates in-place 25 degrees clockwise.
 
+.. sidebar:: Turtle star
+
+   Turtle can draw intricate shapes using programs that repeat simple
+   moves.
+
+   .. image:: turtle-star.*
+      :align: center
+
+   .. literalinclude:: ../includes/turtle-star.py
+
 By combining together these and similar commands, intricate shapes and pictures
 can easily be drawn.