diff options
| author | Jack Jansen <jack.jansen@cwi.nl> | 1996-04-19 15:56:08 (GMT) |
|---|---|---|
| committer | Jack Jansen <jack.jansen@cwi.nl> | 1996-04-19 15:56:08 (GMT) |
| commit | 08365425f6ec63335951d831918b5fa5ec4934c1 (patch) | |
| tree | 87e2523aec71a77f7715ed4583d333a39f27ecaa /Mac/Demo/textedit.html | |
| parent | 8444507faf45eb14bc19be4371a766c05d684aa2 (diff) | |
| download | cpython-08365425f6ec63335951d831918b5fa5ec4934c1.zip cpython-08365425f6ec63335951d831918b5fa5ec4934c1.tar.gz cpython-08365425f6ec63335951d831918b5fa5ec4934c1.tar.bz2 | |
Added documentation on FrameWork, TextEdit and Waste
Updated minor things in the other documents (pathnames, etc)
Diffstat (limited to 'Mac/Demo/textedit.html')
| -rw-r--r-- | Mac/Demo/textedit.html | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/Mac/Demo/textedit.html b/Mac/Demo/textedit.html new file mode 100644 index 0000000..d56ea0b --- /dev/null +++ b/Mac/Demo/textedit.html @@ -0,0 +1,152 @@ +<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. We will improve +on ped later, in a <A HREF="waste.html">waste-based example</A>. <p> + +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. +Quitting itself is also a bit strange: you raise <code>self</code> to break out of the main loop. This bit +of idiom was invented by Guido, so blame him:-). <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> |