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= Notes on Pd's source from notes.txt Pd 0.37.1 =

You can see the current version of this file in git: pd/src/notes.txt

--------------------- source notes --------------------------

  1. structure definition roadmap. First, the containment tree of things that can be sent messages ("pure data"). (note that t_object and t_text, and t_graph and t_canvas, should be unified...)

------------ BFFORE 0.35: --------- m_pd.h t_pd anything with a class t_gobj "graphic object" t_text text object g_canvas.h t_glist list of graphic objects g_canvas.c t_canvas Pd "document"

------------ AFTER 0.35: --------- m_pd.h t_pd anything with a class t_gobj "graphic object" t_text patchable object, AKA t_object g_canvas.h t_glist list of graphic objects, AKA t_canvas

... and other structures: g_canvas.h t_selection -- linked list of gobjs t_editor -- editor state, allocated for visible glists m_imp.h t_methodentry -- method handler t_widgetbehavior -- class-dependent editing behavior for gobjs t_parentwidgetbehavior -- objects' behavior on parent window t_class -- method definitions, instance size, flags, etc.

  1. C coding style. The source should pass most "warnings" of C compilers (-Wall on linux, for instance; see the makefile.) Some informalities are intentional, for instance the loose use of function prototypes (see below) and uncast conversions from longer to shorter numerical formats. The code doesn't respect "const" yet.
  2. 1. Prefixes in structure elements. The names of structure elements always have a K&R-style prefix, as in ((t_atom)x)->a_type, where the "a_" prefix indicates "atom." This is intended to enhance readability (although the convention arose from a limitation of early C compilers.) Common prefixes are "w_" (word), "a_" (atom), "s_" (symbol), "ob_" (object), "te_" (text object), "g_" (graphical object), and "gl_" (glist, a list of graphical objects). Also, global symbols sometimes get prefixes, as in "s_float" (the symbol whose string is "float). Typedefs are prefixed by "t_". Most private structures, i.e., structures whose definitions appear in a ".c" file, are prefixed by "x_".
  3. 2. Function arguments. Many functions take as their first argument a pointer named "x", which is a pointer to a structure suggested by the function prefix; e.g., canvas_dirty(x, n) where "x" points to a canvas (t_canvas *x).
  4. 3. Function Prototypes. Functions which are used in at least two different files (besides where they originate) are prototyped in the appropriate include file. Functions which are provided in one file and used in one other are prototyped right where they are used. This is just to keep the size of the ".h" files down for readability's sake.
  5. 4. Whacko private terminology. Some terms are lifted from other historically relevant programs, notably "ugen" (which is just a tilde object; see d_ugen.c.)
  6. 5. Spacing. Tabs are 8 spaces; indentation is 4 spaces. Indenting curly brackets are by themselves on their own lines, as in:

    if (x) { x = 0; }

Lines should fit within 80 spaces.

  1. Max patch-level compatibility. "Import" and "Export" functions are provided which aspire to strict compatibility with 0.26 patches (ISPW version), but which don't get anywhere close to that yet. Where possible, features appearing on the Mac will comeday also be provided; for instance, the connect message on the Mac offers segmented patch cords; these will devolve into straight lines in Pd. Many, many UI objects in Opcode Max will not appear in Pd, at least at first.
  2. Compatibility with Max 0.26 "externs", i.e., source-level compatibility. Pd objects follow the style of 0.26 objects as closely as possible, making exceptions in cases where the 0.26 model is clearly deficient. These are:
  3. 1. Anything involving the MacIntosh "Handle" data type is changed to use char or void instead.
  4. 2. Pd passes true single-precision floating-point arguments to methods; Max uses double. Typedefs are provided: t_floatarg, t_intarg for arguments passed by the message system t_float, t_int for the "word" union (in atoms, for example.)
  5. 3. Badly-named entities got name changes:

    w_long --> w_int (in the "union word" structure)

  6. 4. Many library functions are renamed and have different arguments; I hope to provide an include file to alias them when compiling Max externs.
  7. Function name prefixes. Many function names have prefixes which indicate what "package" they belong to. The exceptions are: typedmess, vmess, getfn, gensym (m_class.c) getbytes, freebytes, resizebytes (m_memory.c) post, error, bug (s_print.c) which are all frequently called and which don't fit into simple categories. Important packages are: (pd-gui:) pdgui -- everything (pd:) pd -- functions common to all "pd" objects obj -- fuctions common to all "patchable" objects ala Max sys -- "system" level functions binbuf -- functions manipulating binbufs class -- functions manipulating classes (other) -- functions common to the named Pd class
  8. Source file prefixes. PD: s system interface m message system g graphics stuff d DSP objects x control objects z other

PD-GUI: t TK front end

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