View source for Graphics and media/Collections of tips and tricks/Repetition of a text element to fill a bar using textext

= Repetition of a Text Element to Fill a Bar Using textext =

Imagine you want to create a frame which consists out of one glyph or a combination of different glyphs in order to make a decorative border. For this purpose a series of such elements should be placed on the bar as pictures, evenly spaced. Probably you want to have at the end of the bar a different glyph inserted as a picture too.

The following code is working but the last picture is not the expected glyph. One would expect 14 times the "?" and at the end of the bar a "*":

<context mode="mkiv" source="yes" text="Gives:">
\starttext
   \startMPpage
      picture PicA ; PicA := textext("*");
      picture PicB ; PicB := textext("?");

      numeric Step ; Step := 2cm div bbwidth(PicB)  ;

      for i = 1 upto Step :
         draw PicB shifted (i*5mm,0) ;
      endfor ;
      draw PicA ;
   \stopMPpage
\stoptext
</context>

What you get is 15 "?" but no "*"!

In order to get this corrected one needs to calculate the boundingbox of the "?" on beforehand. Hans Hagen provided this solution on 14-10-2014.

<context mode="mkiv" source="yes" text="Gives:">
\starttext
   \startMPcalculation
       path PicX ; PicX := boundingbox textext("?") ;
   \stopMPcalculation

   \startMPpage
      picture PicA ; PicA := textext("*");
      picture PicB ; PicB := textext("?");

      numeric Step ; Step := 2cm div bbwidth(PicX) ;
      % numeric Step ; Step := 2cm div bbwidth(PicB)  ;

      for i = 1 upto Step :
         draw PicB shifted (i*5mm,0) ;
      endfor ;
      draw PicA ;
   \stopMPpage
\stoptext

</context>

Now you get 14 "?" and the "*".

== A Full Example ==

<context mode="mkiv" source="yes" text="Gives:">
\setupbodyfont [8pt]

\defineoverlay[Myframe][\reuseMPgraphic{Frame}]

\setuppapersize[A8][A8]

\setuplayout
   [topspace=5mm,
    backspace=5mm,
    height=middle,
    width=middle,
    header=0pt,
    footer=0pt]

\starttext

% ======== Definition of the frame in Metafun ==========
\startMPcalculation
   path PicX ; PicX := boundingbox textext("= : =") ;
\stopMPcalculation	
   
\startreusableMPgraphic{Frame}
   numeric u,v,xshift,yshift,picwidth,remnant,nelements;

   u := OverlayWidth;
   v := OverlayHeight;
        
   path p,w;
   p := unitsquare xscaled u yscaled v;
   w := fullcircle scaled 8pt;
	
   picture Edgepic,Linepic[];
  
   color edgedotcolor,linelementcolorA;
  
   edgedotcolor       := blue;
   linelementcolorA := red;

   Linepic[1] := textext("\rotate[rotation=90]{= : =}");
   Linepic[2] :=  textext("= : =");
   Edgepic    := textext("o");
	
   %Calculations for the horizontal frame-element placement:
     % In order to make this work, the width of the line element needs to be calculated on beforehand.
     % path PicX; PicX := textext(")(");
   picwidth    := bbwidth(PicX);
   nelements := u div picwidth;
   remnant    := u mod picwidth;
   xshift        := picwidth + remnant/nelements;	 

   Linepic[3] := Linepic[2] shifted (0.5*picwidth,0);

   for a = llcorner p, ulcorner p :
      for i = 1 upto nelements :
         draw Linepic[3] shifted ((xpart a + (i-1)*xshift),ypart a) withcolor linelementcolorA;
      endfor;
   endfor;
	 			
   %Calculations for the vertical frame-element placement:
   picheight   := bbwidth(PicX);
   nelements := v div picheight;
   remnant    := v mod picheight;
   yshift        := picheight + remnant/nelements;
	 
   Linepic[4]:= Linepic[1] shifted (0,0.5*picheight);
	 
   for a = llcorner p, lrcorner p :
      for i = 1 upto nelements:
         draw Linepic[4] shifted (xpart a,ypart a + (i-1)*yshift) withcolor linelementcolorA;
      endfor;
   endfor;

   for i = llcorner p, lrcorner p,ulcorner p,urcorner p :
      fill w shifted (xpart i,ypart i) withcolor white;
        draw Edgepic shifted (xpart i,ypart i) withcolor edgedotcolor;
   endfor;

% For frame-element positioning checking:
%   draw p;
%
\stopreusableMPgraphic

% ==========

\startframedtext
   [width=0.8\textwidth,height=0.8\textheight,frame=off,background=Myframe, align={middle,lohi}]
      The butterfly counts not months but moments, and has time enough.
      \blank
      {\tfx Rabindranath Tagore}
\stopframedtext
\stoptext

</context>

There is one important remark: The MPcalculation and the drawing itself must be inside \starttext ... \stoptext.

[[Category:Graphics]]
[[Category:Programming and Databases]]