ListTree Widget Programmer's Reference


NOTE!

This document isn't totally up-to-date with Version 3.1 yet. One of these days...


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This programmer's reference for the ListTree widget uses HTML3 tables, support for which is becoming very common among WWW browsers. Both Netscape and Mosaic (the most common browsers) support tables, and support for tables in Chimera (my browser of choice) will be included in version 2.0.


Usage

To use the ListTree widget in an application, include the three source code files ListTree.c, ListTree.h, and ListTreeP.h with the rest of the source code for the application. Include the object ListTree.o in the Makefile rule that compiles the application.

In source code that uses the ListTree widget, include the following two header files before references to the plot widget:

 #include <X11/Intrinsic.h>
 #include "ListTree.h"

To create the ListTree widget, use the following code as an example:

        tree=XmCreateScrolledListTree(parent,"tree",NULL,0);

This example creates an empty ListTree widget as the child of some container widget named parent. The ListTree widget now creates its own scrollbars and does not have to be placed in a scrolling container widget. It is also now dependent on the Motif widget set; I broke my rules about using Motif in non-free programs because the LessTif project is far enough along that the scrollbars are quite stable. Once LessTif is complete, there will be no reason to use any other toolkit.

List items must be added to the widget using convenience functions, because I couldn't think of a good way to add heirarchal items through resources. The convenience function method is also very easy, so this design decision wasn't difficult.

Adding items to the list is outlined below:

int i;
ListTreeItem *level1,*level2;

	level1=ListTreeAdd(tree,NULL,"Item 1");
	level1=ListTreeAdd(tree,NULL,"Item 2");
	level2=ListTreeAdd(tree,level1,"Item 3");

This adds three items to the ListTree widget tree, where Item 3 is a child of Item 2, and both Item 1 and Item 2 are root level items. See Public Functions below for descriptions of all of the convenience functions.

List Items

The following structure is returned from the ListTreeAdd convenience function, and is used whenever an item is referenced.

typedef struct _ListTreeItem {
  Boolean       open;
  Boolean       highlighted;
  char          *text;
  int           length;
  int           x,y,ytext;
  int           count;
  Dimension     height;
  ListTreeItemType type;
  struct _ListTreeItem  *parent,*firstchild,*prevsibling,*nextsibling;
  Pixmap        openPixmap,closedPixmap;
  XtPointer     user_data;
} ListTreeItem;

When this structure is returned for an item, the value points to the actual item, not a copy of the item. Do not modify any value in the structure except for the user_data entry, which is provided for your use. (Use the ListTreeRenameItem() public function to modify the text in the item.)

I'll rephrase this for emphasis: the items returned from the widget are the actual items the widget uses when it draws the tree. So, unless you want to Mess Things Up Real Good and crash your program, don't fiddle with the item structure.

OK, disclaimer out of the way, there is a lot of information available here that I didn't want to take away from you, gentle programmer. Stuff like open may be safely modified, but stay away from changing any of the positions or dimensions. Bad news to mess with those.

Really, Really, Really, don't modify parent, firstchild, prevsibling, or nextsibling.

I mean it, because it is possible to throw the widget into an infinite loop.

Trust me.


New Resources

The ListTree widget defines the following new resources:
NameClassTypeDefault
XtNbranchOpenPixmapXtCPixmapPixmapXtUnspecifiedPixmap
XtNbranchPixmapXtCPixmapPixmapXtUnspecifiedPixmap
XtNclickPixmapToOpenXtCBooleanBooleanTrue
XtNdoIncrementalHighlightCallbackXtCBooleanBooleanFalse
XtNfontXtCFontXFontStruct*XtDefaultFont
XtNforegroundXtCForegroundPixelXtDefaultForeground
XtNhighlightPathXtCBooleanBooleanFalse
XtNhorizontalSpacingXtCMarginDimension2
XtNindentXtCMarginDimension0
XtNleafOpenPixmapXtCPixmapPixmapXtUnspecifiedPixmap
XtNleafPixmapXtCPixmapPixmapXtUnspecifiedPixmap
XtNlineWidthXtCMarginDimension0
XtNmarginXtCMarginDimension2
XtNspacingXtCMarginDimension4
XtNverticalSpacingXtCMarginDimension0

XtNbranchOpenPixmap
Pixmap to use for an item that is open and has children.
XtNbranchOpenPixmap
Pixmap to use for an item that is closed and has children.
XtNclickPixmapToOpen
If True, a single click on the pixmap of an item is equivalent to a double click on the item's text.
XtNdoIncrementalHighlightCallback
Calls the highlight callback after each item is highlighted; otherwise only calls the callback after the button has been released and all items have been highlighted.
XtNfont
Font to use for items.
XtNforeground
Foreground color for text. Also used for the bitmap color, if any of the Pixmap resources is defined instead as a bitmap.
XtNhighlightPath
Highlights the item's parents when an item is opened.
XtNhorizontalSpacing
Pixel distance between the Pixmap and item text.
XtNindent
Pixel distance to indent a new level of items. Note that this distance is in addition to the width of the Pixmap.
XtNleafOpenPixmap
Pixmap to use for an item that is open and does not have children.
XtNleafPixmap
Pixmap to use for an item that is closed and does not have children.
XtNlineWidth
Specifies the line width used to draw the list heirarchy.
XtNmargin
Pixel distance between the border of the widget and any text or Pixmap.
XtNverticalSpacing
Pixel distance between neighboring items in the list.


Callbacks

Callback Resources

The ListTree widget defines the following callback resources:

XtNactivateCallback
Called when any item is opened or closed.
XtNhighlightCallback
Called when any item is highlighted.
XtNmenuCallback
Called when the right mouse button is pressed over an item.
XtNdestroyItemCallback
Called for each items that is deleted. This allows for the graceful freeing of anything allocated for user_data.

Activate Callback

This callback is called whenever an item is opened, or if an item is explicitly closed. The following structure is sent to the callback.

typedef struct _ListTreeActivateStruct {
        int             reason;
        ListTreeItem    *item;
        Boolean         open;
        ListTreeItem    **path;
        int             count;
} ListTreeActivateStruct;
reason
One of two constants, XtBRANCH or XtLEAF, indicating that the item has children or does not, respectively.
item
Pointer to the item selected (or unselected).
open
The state of the selected item.
path
The path from the root of the list to the selected item, including the selected item.
count
The number of items in path.

Highlight Callback

This callback is called whether the item is opened or closed, and is passed the following structure.

typedef struct _ListTreeMultiReturnStruct {
        ListTreeItem    **items;
        int             count;
} ListTreeMultiReturnStruct;
items
Pointer to a list of pointers that holds all of the highlighted items.
count
The number of highlighted items.

Menu Callback

This callback can be used to post a menu over the item, or some other application defined function may be implemented. It is passed the ItemReturn structure.

typedef struct _ListTreeItemReturnStruct {
  int		reason;
  ListTreeItem	*item;
  XEvent	*event;
} ListTreeItemReturnStruct;
reason
The constant XtMENU.
item
Pointer to the highlighted item.
event
The XEvent that triggered the callback (should be cast to a pointer to an XButtonEvent).

Item Destroy Callback

Called whenever an item is deleted, the callback function is passed the ItemReturn structure.

typedef struct _ListTreeItemReturnStruct {
  int		reason;
  ListTreeItem	*item;
  XEvent	*event;
} ListTreeItemReturnStruct;
reason
The constant XtDESTROY.
item
Pointer to the highlighted item.
event
This is not used and is assigned the value NULL.


Historical Callbacks

Three other callbacks did exist in previous versions of the widget, but I removed them. I warned ya! :)


Public Functions

All changes to the widget are reflected immediately, unless a call to ListTreeRefreshOff() is made before updating. ListTreeRefreshOn() must be called before the list will start to update itself again.

I could probably have gone on forever writing convenience functions for more and more generalized states, but I'd still be typing the source code, and not working on this here primo-excellent documentation. :) So, this is where the "batteries not included" phrase enters in: it is up to you to customize the widget for your own use. The entire tree of items contained in the widget is available for parsing by you by calling ListTreeFirstItem() and using the firstchild and nextsibling fields of the ListTreeItem structure.

Be careful not to copy over the text field of a ListTreeItem, because it is a malloced string. Use ListTreeRenameItem() if you need to change a name.



ListTree : Programmer's Reference