Re: custom zig zag sidebars

[mf <massifr@fastwebnet.it>]

Il 28/04/21 17:53, Hans Hagen ha scritto:
> On 4/28/2021 5:27 PM, mf wrote:
>> Hello,
>>
>> I made an experiment to add alternatives to sidebars (see attachment).
>>
>> I discovered the sidebar is drawn by anch_sidebars_draw in 
>> metapost/context/base/mpiv/mp-apos.mpiv.
>>
>> I've redefined it locally to add alternatives.
>>
>> To make fancy, zig zag bars I defined a macro, draw_pattern_bar, that 
>> draws a bar repeating a pattern which is a path connecting (0,0) and 
>> (1,0).
>>
>> The macro has 3 parameters (actually it has more params, but the 
>> remainder are anch_sidebars_draw params):
>>
>> - a pattern, which is a path from (0,0) to (1,0) that should have a 
>> vertical size = 1; it's a sort of waveform
>>
>> - a pattern length, by which the pattern is xsized
>>
>> - a pattern width, by which the pattern is ysized
>>
>> Then the pattern is rotated along the bar direction (so -90 degrees) 
>> and drawn many times until it covers the bar length.
>>
>> A proposal and a question:
>>
>> - patternlength and patternwidth could become \setupsidebar params; 
>> alternative (=2,3,4...) could be used to specify the pattern (a sort 
>> of waveform); currently alternative=0 is a solid bar and alternative=1 
>> is a dashed one
>>
>> - in case of long patterns (a patternlength spanning more lines of 
>> text) the last replica of the pattern should be clipped not to exceed 
>> the last line of the sidebarred text (see the last example): how can 
>> that be done?
> how about
> 
> def draw_pattern_bar(expr a, b, pattern, patternlength, patternheight, 
> linewidth, linecolor) =
>     draw image (
>         begingroup ;
>             save p, q, stp ;
>             pair p, q, stp ;
>             stp := ( ( b - a ) / arclength( a -- b ) ) * patternlength ;
>             path q ; q := pattern xscaled patternlength yscaled 
> patternheight rotated (angle(stp)) ;
>             p := a ;
>             forever :
>                 draw
>                     q shifted p
>                     withpen pencircle scaled linewidth
>                     withcolor linecolor ;
>                 p := p + stp ;
>                 exitif arclength( a -- p ) > arclength( a -- b ) ;
>             endfor ;
>         endgroup ;
>         clip currentpicture to
>             (xpart llcorner currentpicture, ypart b) --
>             (xpart lrcorner currentpicture, ypart b) --
>             (xpart urcorner currentpicture, ypart a) --
>             (xpart ulcorner currentpicture, ypart a) -- cycle ;
>     ) ;
> enddef ;
> 
> 
Thank you, Hans.

To save this example, I wikified \setupsidebar, \definesidebar and 
\startsidebar...\stopsidebar.

If you do something on alternatives, let me know.

Massi
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