+ Mostly undocumented.
+
+* Menu:
+
+* Lucid Widget Library:: An interface to various widget sets.
+
+\1f
+File: internals.info, Node: Lucid Widget Library, Up: Interface to the X Window System
+
+Lucid Widget Library
+====================
+
+ Lwlib is extremely poorly documented and quite hairy. The author(s)
+blame that on X, Xt, and Motif, with some justice, but also sufficient
+hypocrisy to avoid drawing the obvious conclusion about their own work.
+
+ The Lucid Widget Library is composed of two more or less independent
+pieces. The first, as the name suggests, is a set of widgets. These
+widgets are intended to resemble and improve on widgets provided in the
+Motif toolkit but not in the Athena widgets, including menubars and
+scrollbars. Recent additions by Andy Piper integrate some "modern"
+widgets by Edward Falk, including checkboxes, radio buttons, progress
+gauges, and index tab controls (aka notebooks).
+
+ The second piece of the Lucid widget library is a generic interface
+to several toolkits for X (including Xt, the Athena widget set, and
+Motif, as well as the Lucid widgets themselves) so that core XEmacs
+code need not know which widget set has been used to build the
+graphical user interface.
+
+* Menu:
+
+* Generic Widget Interface:: The lwlib generic widget interface.
+* Scrollbars::
+* Menubars::
+* Checkboxes and Radio Buttons::
+* Progress Bars::
+* Tab Controls::
+
+\1f
+File: internals.info, Node: Generic Widget Interface, Next: Scrollbars, Up: Lucid Widget Library
+
+Generic Widget Interface
+------------------------
+
+ In general in any toolkit a widget may be a composite object. In Xt,
+all widgets have an X window that they manage, but typically a complex
+widget will have widget children, each of which manages a subwindow of
+the parent widget's X window. These children may themselves be
+composite widgets. Thus a widget is actually a tree or hierarchy of
+widgets.
+
+ For each toolkit widget, lwlib maintains a tree of `widget_values'
+which mirror the hierarchical state of Xt widgets (including Motif,
+Athena, 3D Athena, and Falk's widget sets). Each `widget_value' has
+`contents' member, which points to the head of a linked list of its
+children. The linked list of siblings is chained through the `next'
+member of `widget_value'.
+
+ +-----------+
+ | composite |
+ +-----------+
+ |
+ | contents
+ V
+ +-------+ next +-------+ next +-------+
+ | child |----->| child |----->| child |
+ +-------+ +-------+ +-------+
+ |
+ | contents
+ V
+ +-------------+ next +-------------+
+ | grand child |----->| grand child |
+ +-------------+ +-------------+
+
+ The `widget_value' hierarchy of a composite widget with two simple
+ children and one composite child.
+
+ The `widget_instance' structure maintains the inverse view of the
+tree. As for the `widget_value', siblings are chained through the
+`next' member. However, rather than naming children, the
+`widget_instance' tree links to parents.
+
+ +-----------+
+ | composite |
+ +-----------+
+ A
+ | parent
+ |
+ +-------+ next +-------+ next +-------+
+ | child |----->| child |----->| child |
+ +-------+ +-------+ +-------+
+ A
+ | parent
+ |
+ +-------------+ next +-------------+
+ | grand child |----->| grand child |
+ +-------------+ +-------------+
+
+ The `widget_value' hierarchy of a composite widget with two simple
+ children and one composite child.
+
+ This permits widgets derived from different toolkits to be updated
+and manipulated generically by the lwlib library. For instance
+`update_one_widget_instance' can cope with multiple types of widget and
+multiple types of toolkit. Each element in the widget hierarchy is
+updated from its corresponding `widget_value' by walking the
+`widget_value' tree. This has desirable properties. For example,
+`lw_modify_all_widgets' is called from `glyphs-x.c' and updates all the
+properties of a widget without having to know what the widget is or
+what toolkit it is from. Unfortunately this also has its hairy
+properties; the lwlib code quite complex. And of course lwlib has to
+know at some level what the widget is and how to set its properties.
+
+ The `widget_instance' structure also contains a pointer to the root
+of its tree. Widget instances are further confi
+
+\1f
+File: internals.info, Node: Scrollbars, Next: Menubars, Prev: Generic Widget Interface, Up: Lucid Widget Library
+
+Scrollbars
+----------
+
+\1f
+File: internals.info, Node: Menubars, Next: Checkboxes and Radio Buttons, Prev: Scrollbars, Up: Lucid Widget Library
+
+Menubars
+--------
+
+\1f
+File: internals.info, Node: Checkboxes and Radio Buttons, Next: Progress Bars, Prev: Menubars, Up: Lucid Widget Library
+
+Checkboxes and Radio Buttons
+----------------------------
+
+\1f
+File: internals.info, Node: Progress Bars, Next: Tab Controls, Prev: Checkboxes and Radio Buttons, Up: Lucid Widget Library
+
+Progress Bars
+-------------
+
+\1f
+File: internals.info, Node: Tab Controls, Prev: Progress Bars, Up: Lucid Widget Library
+
+Tab Controls
+------------
projects / chise / xemacs-chise.git- / blobdiff