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8<H2>
9The XsMDICanvas Class
10</H2>
11
12<P>
13This section describes how to build and manipulate an MDI using the
14<I>XsMDICanvas</I> class. Minimally, you must perform the following actions
15to build and display an MDI canvas:
16
17<OL>
18<LI>Create the <I>XsMDICanvas</I> object.</LI>
19<LI>Create the documents as instances of subclasses of <I>XsMDIWindow</I>.</LI>
20<LI>Add the documents to the canvas</LI>
21<LI>Show the canvas</LI>
22</OL>
23
24<P>
25<B>Constructor and Destructor:</B>
26
27<P>
28The <I>XsMDICanvas</I> accepts two arguments:
29
30<DL>
31<DD>XsMDICanvas (const char *name, Widget parent)</DD>
32</DL>
33
34<P>
35The <I>name</I> parameter specifies the name of the canvas and is used
36as the widget name for the underlying implementation. The <I>parent</I>
37parameter specifies the widget that is to be used as the parent of the
38canvas.
39
40<P>
41The <I>XsMDICanvas</I> destructor destroys the canvas, but it <B>does not</B>
42destroy any of the underlying documents. It is up to the application to
43destroy these.
44
45<P>
46<B>Adding and removing documents:</B>
47
48<P>
49After the documents are created, they must be added to the canvas. The
50<I>XsMDICanvas::add()</I> member-function adds documents to the canvas:
51
52<DL>
53<DD>virtual void add (XsMDIWindow *window)</DD>
54</DL>
55
56<P>
57The behavior of adding the same document to the canvas more than once
58is undefined. Documents can be removed from the canvas by using:
59
60<DL>
61<DD>virtual void remove (XsMDIWindow *window)</DD>
62</DL>
63
64<P>
65Additionally, all documents can be removed from the canvas with:
66
67<DL>
68<DD>void removeAll ( )</DD>
69</DL>
70
71<P>
72The number of documents currently installed in the canvas can be
73retrieved with:
74
75<DL>
76<DD>int numWindows ( ) const</DD>
77</DL>
78
79<P>
80<B>Showing the canvas:</B>
81
82<P>
83In order to show (manage) the canvas call the <I>show</I> member function:
84
85<DL>
86<DD>virtual void show ( )</DD>
87</DL>
88
89This member-function is responsible for cycling all of the installed documents
90and calling their respective <I>XsMDIWindow::_buildClientArea()</I>
91member-functions. After each document has been created, <I>show</I> will then
92manage each document and, finally, itself.
93
94<P>
95<B>Window Placement:</B>
96
97<P>
98The current implementation of <I>XsMDICanvas</I> uses a very simple algorithm
99to place the documents on the canvas. In order to implement a more specific
100placement algorithm, derive a class from <I>XsMDICanvas</I> and override
101the member-function:
102
103<DL>
104<DD>virtual void _placeWindow (XsMDIWindow *win)</DD>
105</DL>
106
107<P>
108This member-function is called for each document in the canvas to compute
109the location of the document. Please refer to the code (<I>XsMDICanvas.C</I>)
110for more details.
111
112<P>
113<B>Canvas Behavior:</B>
114
115<P>
116The <I>XsMDICanvas</I> is implemented as an <I>XmScrolledWindow</I> with an
117<I>XmDrawingArea</I> work-window. The instance name for the work-window
118is <I>canvas</I>. Internal callbacks in the canvas class force the work-window
119to be at-least the size of the clip-window. This prevents documents from
120being clipped as they are moved around.
121
122<P>
123By default, the <I>XmDrawingArea</I> work-window has its <I>XmNresizePolicy</I>
124set to <I>XmRESIZE_GROW</I>. This will allow the work-area to grow to
125whatever size necessary, but it will not automatically shrink as windows
126are manipulated. If different behavior is desired, the <I>XmNresizePolicy</I>
127resource on the work-area can be set to <I>XmRESIZE_ANY</I>. This will
128force the work-window to recompute its size as windows are manipulated, and
129it will grow and shrink as necessary. However, the <I>XsMDICanvas</I> will
130still force the work-area to be at-least the size of the clip-window.
131
132<P>To change the default behavior, add the following resource:
133
134<DL>
135<DD>&ltXsMDICanvas name&gt*canvas.resizePolicy: XmRESIZE_ANY</DD>
136</DL>
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