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symbian-qemu-0.9.1-12/python-2.6.1/Mac/Demo/textedit.html
changeset 1 2fb8b9db1c86 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/symbian-qemu-0.9.1-12/python-2.6.1/Mac/Demo/textedit.html	Fri Jul 31 15:01:17 2009 +0100
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+<HTML><HEAD><TITLE>Using FrameWork and TextEdit</TITLE></HEAD>
+<BODY>
+<H1>Using FrameWork and TextEdit</H1>
+<HR>
+
+In this document we use the <CODE>FrameWork</CODE> and <CODE>TextEdit</CODE>
+modules to create a simple text editor. The functionality
+of the editor is very basic: you can open multiple files, type text and use
+cut/copy/paste. The main intention is to explain the use of FrameWork, really. <p>
+
+<H2>FrameWork</H2>
+
+The FrameWork module provides you with a skeleton application. It declares a
+number of classes suitable for subclassing in your application, thereby
+releaving you of the burden of doing all event handling, etc. yourself. For a
+real understanding you will have to browse the source. Here is a short overview
+of the classes and what functionality they provide.
+
+<dl>
+<dt> <CODE>Application</CODE>
+<dd>
+This is the toplevel class you will override. It maintains the menu bar and contains
+the main event handling code. Normal use is to override the <code>__init__</code> routine
+to do your own initializations and override <code>makeusermenus</code> to create your menus
+(your menu callback routines may be here too, but this is by no means necessary).
+The event handling code can be overridden at various levels, from very low-level (the
+<code>dispatch</code> method) to intermedeate level (<code>do_keyDown</code>, for instance)
+to high-level (<code>do_key</code>). The application class knows about the <code>Window</code>
+objects you create, and will forward events to the appropriate window (So, normally you
+would have a <code>do_key</code> method in your window object, not your application object).
+
+<dt> <CODE>MenuBar</CODE>, <CODE>Menu</CODE> and <CODE>MenuItem</CODE>
+<dd>
+These classes (and a few friends like <CODE>SubMenu</CODE>) handle your menus. You would not
+normally override them but use them as-is. The idiom for creating menus is a bit strange,
+see the test code at the bottom of FrameWork for sample use. The apple menu is handled for you
+by <CODE>MenuBar</CODE> and <CODE>Application</CODE>.
+
+<dt> <CODE>Window</CODE>
+<dd>
+The basic window. Again, a class that you normally subclass in your application, possibly
+multiple times if you have different types of windows. The init call instantiates the data
+structure but actually opening the window is delayed until you call <code>open</code>. Your
+open method should call <code>do_postopen</code> to let the base class handle linking in to
+the application object. Similarly with <code>close</code> and <code>do_postclose</code>. The
+rest of the code is mainly event-oriented: you override <code>do_postresize</code>,
+<code>do_contentclick</code>, <code>do_update</code>, <code>do_activate</code>
+and <code>do_key</code> to "do your thing". When these methods are called the relevant environment
+has been setup (like <code>BeginDrawing</code> has been called for updates, etc).
+
+<dt> <CODE>windowbounds</CODE>
+<dd>
+Not a class but a function: you pass it a width and height and it will return you a rectangle
+you can use to create your window. It will take care of staggering windows and it will try
+to fit the window on the screen (but the resulting rect will <em>always</em> have the size you
+specify).
+
+<dt> <CODE>ControlsWindow</CODE>
+<dd>
+A subclass of Window which automatically handles drawing and clicking for controls. You override
+the same methods as for Window (if you need to: control-related things are done automatically) and
+<code>do_controlhit</code>.
+
+<dt> <CODE>ScrolledWindow</CODE>
+<dd>
+A subclass of ControlsWindow, a window with optional scrollbars. If you override <code>do_activate</code>
+or <code>do_postresize</code> you must call the ScrolledWindow methods at the end of your override.
+You call <code>scrollbars</code> to enable/disable scrollbars and <code>updatescrollbars</code> to
+update them. You provide <code>getscrollbarvalues</code> to return the current x/y values (a helper
+method <code>scalebarvalues</code> is available) and <code>scrollbarcallback</code> to update your
+display after the user has used the scrollbars.
+
+<dt> <CODE>DialogWindow</CODE>
+<dd>
+A modeless dialog window initialized from a DLOG resource. See the
+<A HREF="example2.html">second Interslip example</A> for its useage.
+</dl>
+
+<H2>A sample text editor</H2>
+
+Let us have a look at <A HREF="textedit/ped.py">ped.py</A> (in the Demo:textedit folder), the Pathetic
+EDitor. It has multiple windows, cut/copy/paste and keyboard input, but that is about all. It looks
+as if you can resize the window but it does not work. Still, it serves as an example. 
+
+Ped creates two classes, <code>TEWindow</code> and <code>Ped</code>. Let us start with the latter one,
+which is a subclass of <code>FrameWork.Application</code> and our main application. The init function
+has little to do aside from the standard init: it remembers a window sequence number (for untitled windows),
+and sets things up for menu disable to work. Remember, the <code>makeusermenus</code> is called
+automatically. <p>
+
+<code>Makeusermenus</code> creates the <code>File</code> and <code>Edit</code> menus. It also initializes
+a couple of lists that are used later to correctly enable and disable menu items (and complete menus) depending
+on whether a window is open, text is selected, etc. The callback functions for the menu items are
+all methods of this class. <p>
+
+<code>Updatemenubar</code> handles greying out (and re-enabling) of menu items depending on whether there
+is a current window and its state. <p>
+
+The rest of the methods are all callbacks and simple to understand. They check whether there is an active
+window (and complain loudly if there is none: the corresponding menu entry should have been disabled
+in that case!) and call the appropriate window method. Only the <code>_open</code> method (the common code
+for <code>Open</code> and <code>New</code>) deserves some mention. It instantiates a <code>TEWindow</code>
+object and opens it with the title, filename and contents of the file to edit. Note that FrameWork takes
+care of remembering the window object. A minor note on opening the file in binary mode: this is because
+TextEdit expects MacOS style carriage-return terminated lines, not python/unix/C style newline-terminated
+lines. <p>
+
+Oh yes: the <code>quit</code> callback does a little magic too. It closes all windows, and only if this
+succeeds it actually quits. This gives the user a chance to cancel the operation if some files are unsaved.
+<p>
+
+Lastly, there is the <code>idle</code> method, called by the Application base class when no event
+is available. It is forwarded to the active window, so it can blink the text caret. <p>
+
+The <code>TEWindow</code> object handles a single window. Due to this structuring it is absolutely no
+problem to have multiple windows open at the same time (although a real application should exercise care when
+two windows refer to the same document). TEWindow uses the standard init code inherited from
+<code>ScrolledWindow</code>, and sets itself up at the time of the <code>open</code> call. It obtains screen
+coordinates, opens the window, creates rectangles for TextEdit to work in (the magical number <code>15</code>
+here is the size of a normal scroll bar: unfortunately there is no symbolic constant for it),
+creates the TextEdit object and initializes it with our data. Finally, the scroll bars are created (the
+initial values will be obtained automatically through <code>getscrollbarvalues</code>) and we activate
+ourselves (this is unfortunately not done automatically by the MacOS event handling code). <p>
+
+<code>Do_idle</code> simply calls the TextEdit routine that blinks the cursor. <code>Getscrollbarvalues</code>
+returns the current X and Y scrollbar values, scaled to <code>0..32767</code>. For X we return <code>None</code>,
+which means "no scrollbar, please", for Y we use the scaler provided by <code>ScrolledWindow</code>. <p>
+
+<code>Scrollbar_callback</code> is called when the user uses the scrollbar. It is passed a string <code>'x'</code>
+or <code>'y'</code>, one of <code>'set', '-', '--', '+', '++'</code> and (for <code>set</code>) an absolute
+value. Note that the sign of the value passed to <code>TEPinScroll</code> is counter-intuitive. <p>
+
+<code>do_activate</code> (de)activates the scrollbars and calls the relevant TextEdit routine. Moreover, it
+tells the application object if we are now the active window, and updates the menubar. The next few methods
+are update and menu callbacks, and pretty straightforward. Note that <code>do_close</code> can
+return without closing the window (if the document is changed and the users cancels out of the operation).
+Also note the "magic" in <code>menu_save_as</code>
+that set the correct window title. <p>
+
+Things get moderately interesting again at the cut/copy/paste handling, since the TextEdit scrap is
+separate from the desktop scrap. For that reason there are various calls to routines that move the scrap
+back and forth. <code>Have_selection</code> is called by the menubar update code to determine whether cut and
+copy should be enabled. <p>
+
+Understanding the main program is left as an exercise to the reader. <p>
+
+<hr>
+That's all for this example, you could now continue with the <A HREF="waste.html">next example</A>, where we use WASTE, a more-or-less
+TextEdit compatible library with more functionality, to rebuild our editor. Or you can
+return to the <A HREF="index.html">table of contents</A> to pick another topic. <p>
MCL/sf/adapt/qemu