themes sub-directory found in tree-widget-themes-load-path.
(tree-widget-themes-directory, tree-widget-theme): Doc fix.
(tree-widget--locate-sub-directory): Return all occurrences.
(tree-widget-themes-path): New function. Replace
tree-widget-themes-directory, and return a list of directories.
(tree-widget-set-parent-theme)
(tree-widget-lookup-image): Use it.
(tree-widget-theme-name): Ignore parent themes.
(tree-widget-set-parent-theme): New function.
(tree-widget-set-theme): Use it.
(tree-widget-set-image-properties): Move definition. Does nothing
if image properties have already been set.
(tree-widget-image-properties): Move definition. Receive an image
name. Set the :pointer property.
(tree-widget-lookup-image): Doc fix. Search in parent themes.
Don't set the :pointer image property.
(tree-widget-convert-widget): New function. Handle :dynargs
compatibility here.
(tree-widget): Use it to :convert-widget. Add the :expander-p
predicate to control when the :expander function is entered.
Thanks to Ken Manheimer <ken.manheimer@gmail.com> for the idea.
(tree-widget-value-create): Handle :expander-p. widget-apply
:expander.
(tree-widget-expander-p): New function. Default value of the
:expander-p property.
(tree-widget-themes-directory): Doc fix.
(tree-widget-image-formats) [Emacs]: Doc fix.
(tree-widget--locate-sub-directory): New function.
(tree-widget-themes-directory): Use it.
(tree-widget-theme): Doc fix.
(tree-widget-space-width): New option.
(tree-widget-image-properties): Look up in the default theme too.
(tree-widget--cursors): Only for images with arrow pointer shape.
(tree-widget-lookup-image): Pointer shape is hand by default.
(tree-widget-icon): Generic icon widget renamed from
`tree-widget-control'.
(tree-widget-*-icon): Rename from `tree-widget-*-control' and
derive from `tree-widget-icon'.
(tree-widget-handle): Improve default look and feel of the text
representation.
(tree-widget): Rename :*-control properties to :*-icon properties.
Add :action and :help-echo properties.
(tree-widget-after-toggle-functions): Move.
(tree-widget-close-node, tree-widget-open-node): Remove.
(tree-widget-before-create-icon-functions): New hook.
(tree-widget-value-create): Update to allow customization of icons
and nodes at run-time via that new hook.
(tree-widget-icon-create, tree-widget-leaf-node-icon-p)
(tree-widget-icon-action, tree-widget-icon-help-echo)
(tree-widget-action, tree-widget-help-echo): New functions.
