Toolbar ideas

[James Henstridge <james daa com au>]

Anders asked me to post some ideas on what would be nice features to 
have in a new toolbar widget, so here is what I have so far:

While implementing the UI merging code for EggMenu, I ran into a number 
of issues that made implementing the toolbar merge code fairly 
difficult.  Most of these problems would probably be better solved by 
fixing the toolbar APIs.

Some of the problems in the current file selector code include:

   * Toolbar buttons are handled different to separators, which are
     handled different to other widgets.  It would be nice if all
     toolbar items had a common base type (GtkToolItem, mirroring
     GtkMenuItem, maybe?)  This would make handling in EggMenu and
     GtkItemFactory doable.
   * Pattern for creating toolbar buttons quite different to other
     child widgets; one function to construct and add to parent.  Can't
     easily remove a button from one toolbar and add to another (or
     move a button in the same toolbar).
   * No way to get some toolbar items to expand to fill available
     space. This is useful for things like the location bar in
     Mozilla/nautilus, and may also be useful to insert spacers (which
     would allow for putting items such as throbbers on the right edge
     of the toolbar).
   * No handling of overflow.  If the width of the toolbar exceeds the
     width of the window, then it would be nice to handle overflow in
     one of a number of ways:
         o Like BonoboToolbar: a button that pops up a panel with the
           extra items.
         o Like Windows/OSX: a button that pops up a menu with items
           representing the toolbar buttons
         o wrap round to a second line of buttons? (this is difficult
           with existing GTK+ geometry management, so can probably be
           ignored).


Ideas for the a better toolbar API:

   * children of toolbar are GtkToolItem objects (which may be a
     subclass of GtkItem; this would make it usable to GtkItemFactory).
   * Have tool items for various button types, separators, and one that
     can hold an arbitrary widget (good for entries, etc).
   * GtkToolItems track orientation, toolbar_style and icon_size
     properties of toolbar and are responsible for the consistant display.
   * Have a flag to specify whether a tool item should be used in the
     calculation of the size for toolbar buttons.
   * - tool items have a hook for creating a menu item proxy for use in
     overflow situations (if we decide to support that form of overflow
     handling).
   * Toolbar allows setting "expand" packing property. (to handle
     things like a location bar).
   * simple API to add and remove GtkToolItems from toolbar.


Do we want to build on top of the existing toolbar widget?

   * would probably want to deprecate half the APIs
   * constrained by existing struct layout.
         o no fields marked /*< public >*/, but children and
           num_children are documented in the reference docs.
         o GtkToolbarChild struct
   * how much of the internals are currently in use by applications?


or create a new widget?

   * no backward compatibility concerns if we create new widget
   * can't call new widget GtkToolbar if we go with new widget



Other toolbar APIs:

Mac OS X Cocoa:
 
http://developer.apple.com/techpubs/macosx/Cocoa/TasksAndConcepts/ProgrammingTopics/Toolbars/
 
http://developer.apple.com/techpubs/macosx/Cocoa/Reference/ApplicationKit/Java/Classes/NSToolbar.html  

 
http://developer.apple.com/techpubs/macosx/Cocoa/Reference/ApplicationKit/ObjC_classic/Classes/NSToolbarItem.html

.Net Windows Forms:
 
http://msdn.microsoft.com/library/en-us/cpref/html/frlrfSystemWindowsFormsToolBarClassTopic.asp
 
http://msdn.microsoft.com/library/en-us/cpref/html/frlrfsystemwindowsformstoolbarbuttonclasstopic.asp

Java Swing:
 http://java.sun.com/j2se/1.4/docs/api/javax/swing/JToolBar.html


James.

--
Email: james daa com au              | Linux.conf.au 2003 Call for Papers out
WWW:   http://www.daa.com.au/~james/ |   http://conf.linux.org.au/cfp.html