MATLAB Function Reference

Hgtransform Properties

You can set and query graphics object properties using the set and get commands.

To change the default values of properties, see Setting Default Property Values.

See Group Objects for general information on this type of object.

Hgtransform Property Descriptions

This section provides a description of properties. Curly braces { } enclose default values.

This object is being deleted. The BeingDeleted property provides a mechanism that you can use to determine whether objects are in the process of being deleted. MATLAB sets the BeingDeleted property to on when the object's delete function callback is called (see the DeleteFcn property). It remains set to on while the delete function executes, after which the object no longer exists.

For example, an object's delete function might call other functions that act on a number of different objects. These functions might not need to perform actions on objects if the objects are going to be deleted, and therefore can check the object's BeingDeleted property before acting.

Callback routine interruption. The BusyAction property enables you to control how MATLAB handles events that potentially interrupt executing callback functions. If there is a callback executing, callbacks invoked subsequently always attempt to interrupt it.

If the Interruptible property of the object whose callback is executing is set to on (the default), then interruption occurs at the next point where the event queue is processed. If the Interruptible property is off, the BusyAction property (of the object owning the executing callback) determines how MATLAB handles the event. The choices are

• cancel -- Discard the event that attempted to execute a second callback routine.
• queue -- Queue the event that attempted to execute a second callback routine until the current callback finishes.

Button press callback function. A callback that executes whenever you press a mouse button while the pointer is within the extent of the hgtransform object, but not over another graphics object. The extent of an hgtransform object is the smallest rectangle that encloses all the children. Note that you cannot execute the hgtransform object's button down function if it has no children.

This property can be

• A string that is a valid MATLAB expression
• The name of an M-file
• A function handle

The expression executes in the MATLAB workspace.

See Function Handle Callbacks for information on how to use function handles to define the callbacks.

Children of the hgtransform object. An array containing the handles of all graphics objects parented to the hgtransform object (whether visible or not).

The graphics objects that can be children of an hgtransform are images, lights, lines, patches, rectangles, surfaces, and text. You can change the order of the handles and thereby change the stacking of the objects on the display.

Note that if a child object's HandleVisibility property is set to callback or off, its handle does not show up in the hgtransform Children property unless you set the Root ShowHiddenHandles property to on.

This property has no effect on hgtransform objects.

Callback executed during object creation. This property defines a callback routine that executes when MATLAB creates an hgtransform object. You must define this property as a default value for hgtransform objects. For example, the statement

• set(0,'DefaultHgtransformCreateFcn',@myCreateFcn)
  

defines a default value on the root level that applies to every hgtransform object created in a MATLAB session. Whenever you create an hgtransform object, the function associated with the function handle @myCreateFcn executes.

MATLAB executes the callback after setting all the hgtransform object's properties. Setting the CreateFcn property on an existing hgtransform object has no effect.

The handle of the object whose CreateFcn is being executed is accessible only through the Root CallbackObject property, which can be queried using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

Callback executed during object deletion. A callback that executes when the hgtransform object is deleted (e.g., this might happen when you issue a delete command on the hgtransform object, its parent axes, or the figure containing it). MATLAB executes the callback before destroying the object's properties so the callback routine can query these values.

The handle of the object whose DeleteFcn is being executed is accessible only through the Root CallbackObject property, which can be queried using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

See the BeingDeleted property for related information.

Erase mode. This property controls the technique MATLAB uses to draw and erase hgtransform child objects (light objects have no erase mode). Alternative erase modes are useful for creating animated sequences, where control of the way individual objects are redrawn is necessary to improve performance and obtain the desired effect.

• normal -- Redraw the affected region of the display, performing the three-dimensional analysis necessary to ensure that all objects are rendered correctly. This mode produces the most accurate picture, but is the slowest. The other modes are faster, but do not perform a complete redraw and are therefore less accurate.
• none -- Do not erase objects when they are moved or destroyed. While the objects are still visible on the screen after erasing with EraseMode none, you cannot print these objects because MATLAB stores no information about their former locations.
• xor-- Draw and erase the object by performing an exclusive OR (XOR) with each pixel index of the screen behind it. Erasing the object does not damage the color of the objects behind it. However, the color of the erased object depends on the color of the screen behind it and it is correctly colored only when it is over the axes background color (or the figure background color if the axes Color property is set to none). That is, it isn't erased correctly if there are objects behind it.
• background -- Erase the graphics objects by redrawing them in the axes background color, (or the figure background color if the axes Color property is set to none). This damages other graphics objects that are behind the erased object, but the erased object is always properly colored.

Set the axes background color with the axes Color property. Set the figure background color with the figure Color property.

Printing with Nonnormal Erase Modes

MATLAB always prints figures as if the EraseMode of all objects is normal. This means graphics objects created with EraseMode set to none, xor, or background can look different on screen than on paper. On screen, MATLAB can mathematically combine layers of colors (e.g., performing an XOR operation on a pixel color and the pixel behind it) and ignore three-dimensional sorting to obtain greater rendering speed. However, these techniques are not applied to the printed output.

You can use the MATLAB getframe command or other screen capture applications to create an image of a figure containing nonnormal mode objects.

Control access to object's handle by command-line users and GUIs. This property determines when an object's handle is visible in its parent's list of children. HandleVisibility is useful for preventing command-line users from accidentally accessing the hgtransform object.

• on -- Handles are always visible when HandleVisibility is on.
• callback -- Setting HandleVisibility to callback causes handles to be visible from within callback routines or functions invoked by callback routines, but not from within functions invoked from the command line. This provides a means to protect GUIs from command-line users, while allowing callback routines to have access to object handles.
• off -- Setting HandleVisibility to off makes handles invisible at all times. This might be necessary when a callback invokes a function that might potentially damage the GUI (such as evaluating a user-typed string) and so temporarily hides its own handles during the execution of that function.

Functions Affected by Handle Visibility

When a handle is not visible in its parent's list of children, it cannot be returned by functions that obtain handles by searching the object hierarchy or querying handle properties. This includes get, findobj, gca, gcf, gco, newplot, cla, clf, and close.

Properties Affected by Handle Visibility

When a handle's visibility is restricted using callback or off, the object's handle does not appear in its parent's Children property, figures do not appear in the root's CurrentFigure property, objects do not appear in the root's CallbackObject property or in the figure's CurrentObject property, and axes do not appear in their parent's CurrentAxes property.

Overriding Handle Visibility

You can set the root ShowHiddenHandles property to on to make all handles visible regardless of their HandleVisibility settings (this does not affect the values of the HandleVisibility properties). See also findall.

Handle Validity

Handles that are hidden are still valid. If you know an object's handle, you can set and get its properties and pass it to any function that operates on handles.

Pickable by mouse click. HitTest determines whether the hgtransform object can become the current object (as returned by the gco command and the figure CurrentObject property) as a result of a mouse click within the limits of the hgtransform object. If HitTest is off, clicking the hgtransform picks the object behind it.

Callback routine interruption mode. The Interruptible property controls whether an hgtransform object callback can be interrupted by callbacks invoked subsequently. Only callbacks defined for the ButtonDownFcn property are affected by the Interruptible property. MATLAB checks for events that can interrupt a callback only when it encounters a drawnow, figure, getframe, or pause command in the routine. See the BusyAction property for related information.

Setting Interruptible to on allows any graphics object's callback to interrupt callback routines originating from an hgtransform property. Note that MATLAB does not save the state of variables or the display (e.g., the handle returned by the gca or gcf command) when an interruption occurs.

Transformation matrix applied to hgtransform object and its children. The hgtransform object applies the transformation matrix to all its children.

See Group Objects for more information and examples.

Parent of hgtransform object. This property contains the handle of the hgtransform object's parent object. The parent of an hgtransform object is the axes, hggroup, or hgtransform object that contains it.

See Objects That Can Contain Other Objects for more information on parenting graphics objects.

Is object selected? When you set this property to on, MATLAB displays selection handles on all child objects of the hgtransform if the SelectionHighlight property is also on (the default).

Objects are highlighted when selected. When the Selected property is on, MATLAB indicates the selected state by drawing selection handles on the objects parented to the hgtransform. When SelectionHighlight is off, MATLAB does not draw the handles.

User-specified object label. The Tag property provides a means to identify graphics objects with a user-specified label. This is particularly useful when you are constructing interactive graphics programs that would otherwise need to define object handles as global variables or pass them as arguments between callbacks.

For example, you might create an hgtransform object and set the Tag property:

• t = hgtransform('Tag','subgroup1')
  

When you want to access the hgtransform object to add another object, you can use findobj to find the hgtransform object's handle. The following statement adds a line to subgroup1 (assuming x and y are defined).

• line('XData',x,'YData',y,'Parent',findobj('Tag','subgroup1'))
  

Type of graphics object. This property contains a string that identifies the class of graphics object. For hgtransform objects, Type is set to 'hgtransform'. The following statement finds all the hgtransform objects in the current axes.

• t = findobj(gca,'Type','hgtransform');
  

Associate a context menu with the hgtransform object. Assign this property the handle of a uicontextmenu object created in the hgtransform object's figure. Use the uicontextmenu function to create the context menu. MATLAB displays the context menu whenever you right-click over the extent of the hgtransform object.

User-specified data. This property can be any data you want to associate with the hgtransform object (including cell arrays and structures). The hgtransform object does not set values for this property, but you can access it using the set and get functions.

Visibility of hgtransform object and its children. By default, hgtransform object visibility is on. This means all children of the hgtransform are visible unless the child object's Visible property is set to off. Setting an hgtransform object's Visible property to off also makes its children invisible.

hgtransform

hidden

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