Re: [Lilypond-auto] Issue 3162 in lilypond: Patch: Eliminates pure-print-callbacks list

[lilypond]

Updates:
        Status: Fixed
        Labels: Fixed_2_17_13

Comment #15 on issue 3162 by address@hidden: Patch: Eliminates  
pure-print-callbacks list
http://code.google.com/p/lilypond/issues/detail?id=3162

commit 3222fb83fafa4c760ad76e10e2b602a854906a6e
Author: Mike Solomon <address@hidden>
Date:   Wed Feb 20 06:58:02 2013 +0100

    Removes pure-print-callbacks list.

    LilyPond currently hardcodes certain print functions as being able
    to be evaluated as 'pure', meaning that they should not result in calls
    to set_property, set_object, translate_axis or suicide.  This means  
that,
    for example, if one uses a custom stencil function, the Y-extent  
function
    for the grob must be wrapped in an unpure-pure-container in order
    to return a non-empty pure_height.

    The reading of these hardcoded lists results in difficult-to-maintain  
code.
    For example, several (but not all) flag modification functions are part  
of
    this list, causing spacing inconsistencies in certain regtests.
    Using unpure-pure-containers to signify all relationships between  
unpure and
    pure functions and eliminating the lists of pure functions in
    define-grobs.scm allows the code base to be more extensible, demanding  
the
    elaboration of unpure-pure relationships in the property-setting phase
    (either in define-grobs.scm or in an override) and not using hardcoded  
lists.

    Inversely, this also prevents deep that can creep up when a function
    signified as pure turns out not to be.  For example,  
ly:note-head::print,
    marked as pure, can be made unpure if its lookup of the style,
    duration-log or glyph-name properties trigger vertical alignment
    (which results in a call to translate_axis). Thus, users who wish to use
    this function as an unpure function now can because it is no longer
    hardcoded as pure.


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