EditObject Widget Class
Overview
The EditObject widget class provides support for displaying, editing, and
storing/ retrieving graphic objects based on the Graphic object class. Any
widget class that is a subclass of the EditObject widget class inherits the
ability to display, edit, and store/ retrieve graphic objects.
The display and editing capabilities of the EditObject class are implemented
through a comprehensive set of actions, callbacks and convenience functions.
Editing capabilities include the ability to select one or more objects and
to move, size or shape objects. A set of convenience functions is provided for
saving and restoring objects to or from an ASCII file. A clipboard mechanism
provides cut and paste functionality inside an application or between two
different applications that use EditObject widgets (or widgets from a
subclass of the EditObject widget class).
Coordinate System
The EditObject class defines a linear coordinate system that is between 0 and
100, both horizontally and vertically. You can use the functions provided in
the CompBase widget class to do transformations between pixel values and the
EditObject coordinate system.
Object Selection
Once an object is created, it can be selected using BSelect. Handles are
displayed around the edges of a selected object (or group of objects) to
indicate it has been selected. Multiple selection and grouping/ungrouping of
objects is also supported.
Object Editing
Objects can be moved, sized and shaped interactively. Size and Shape operations
are identical for all rectangular Graphic objects (such as Oval and Text). For
objects instantiated using subclasses of the MultiPoint class (such as
PolyLine and Wavelet), the Shape operation is equivalent to a Move point
operation. The Move, Size and Shape operations are activated using BSelect
Drag and terminated using BSelect Release. A special operation, called Adjust,
combines the Shape and Move operations into one action. If the user performs
BSelect Drag close to a handle, a Shape operation will be performed, otherwise
a Move operation is performed. Finally, a specific set of actions is provided
to interactively add or remove points for MultiPoint based objects.
Objects can also be edited from the program, just like any other Motif widget,
using the XtSetValues or XtVaSetValues calls.
Object Display
Objects are displayed in the order they have been created. The object created
first is drawn first, while the object created last is drawn last and thus will
appear to be on top of the other objects. A set of convenience functions allows
the application to move objects forward or backward in the display order.
Input/Output
The EditObject widget class provides a set of convenience functions to write a
list of objects into a file and to retrieve them later on. The objects in an
object description file can be read by any widget created from a subclass of
the EditObject widget class.
Clipboard
A clipboard mechanism is implemented for Cut, Copy and Paste operations on
Graphic objects. The clipboard mechanism provides cut/copy/paste operations
among EditObject widgets inside the current application or between two
different applications. For example, it is possible to Cut an object from
an EditObject widget in one application and Paste it into an EditObject widget
belonging to another application.
Locator
The EditObject provides a callback and a set of actions that allow the
application to track the cursor location.
EditObject Widget Appearance
The EditObject widget appears as an empty rectangular window. In the
illustration below, a Chart object and various Graphic objects have been
created in an EditObject widget.
Figure 10: Example of an EditObject widget containing a Chart and various Graphic objects.