diff options
Diffstat (limited to 'generic')
| -rw-r--r-- | generic/tkOption.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/generic/tkOption.c b/generic/tkOption.c index 74fa344..d0cb8bc 100644 --- a/generic/tkOption.c +++ b/generic/tkOption.c @@ -11,7 +11,7 @@ * See the file "license.terms" for information on usage and redistribution * of this file, and for a DISCLAIMER OF ALL WARRANTIES. * - * RCS: @(#) $Id: tkOption.c,v 1.7 2000/05/27 02:11:37 ericm Exp $ + * RCS: @(#) $Id: tkOption.c,v 1.8 2000/05/30 17:35:19 ericm Exp $ */ #include "tkPort.h" @@ -26,6 +26,35 @@ * structures exists for each node or leaf in the option tree. It is * actually stored as part of the parent node, and describes a particular * child of the parent. + * + * The structure of the option db tree is a little confusing. There are + * four different kinds of nodes in the tree: + * interior class nodes + * interior name nodes + * leaf class nodes + * leaf name nodes + * + * All interior nodes refer to _window_ classes and names; all leaf nodes + * refer to _option_ classes and names. When looking for a particular option, + * therefore, you must compare interior node values to corresponding window + * values, and compare leaf node values to corresponding option values. + * + * The tree is actually stored in a collection of arrays; there is one each + * combination of WILDCARD/EXACT and CLASS/NAME and NODE/LEAF. The NODE arrays + * contain the interior nodes of the tree; each element has a pointer to an + * array of elements which are the leaves of the tree. The LEAF arrays, rather + * than holding the leaves of the tree, hold a cached subset of the option + * database, consisting of the values of all defined options for a single + * window, and some additional information about each ancestor of the window + * (since some options may be inherited from a parent), all the way back to the + * root window. + * + * Each time a call is made to Tk_GetOption, Tk will attempt to use the cached + * information to satisfy the lookup. If the call is for a window other than + * that for which options are currently cached, the portion of the cache that + * contains information for common ancestors of the two windows is retained and + * the remainder is discarded and rebuilt with new information for the new + * window. */ typedef struct Element { |