| 1 | <HTML><HEAD><TITLE>Using python to create Macintosh applications, part two</TITLE></HEAD>
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| 2 | <BODY>
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| 3 | <H1>Using python to create Macintosh applications, part two</H1>
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| 4 | <HR>
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| 5 |
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| 6 | In this document we rewrite the application of the <A
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| 7 | HREF="example1.html">previous example</A> to use modeless dialogs. We
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| 8 | will use an application framework, and we will have a look at creating
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| 9 | applets, standalone applications written in Python. The <A
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| 10 | HREF="example2/dnslookup-2.py">source code</A> and
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| 11 | <A HREF="example2/dnslookup-2.rsrc">resource file</A> are available in the folder
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| 12 | <A HREF="example2">example2</A>. <p>
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| 13 |
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| 14 | Again, we start with ResEdit to create our dialogs. Not only do we
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| 15 | want a main dialog this time but also an "About" dialog. This example is less
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| 16 | than complete since we do not provide a <A NAME="bundle">BNDL resource</A>
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| 17 | and related stuff that an application cannot be without. We are able to do this
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| 18 | when building a python applet since BuildApplet will substitute default resources
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| 19 | for BNDL, etc. when none are supplied (<A HREF="#no-bundle">See below</A>.)
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| 20 | "Inside Mac" or various
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| 21 | books on Macintosh programming will help here. Also, you can refer to
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| 22 | the resource files provided in the Python source distribution for some
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| 23 | of the python-specific points of BNDL programming: the
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| 24 | "appletbundle.rsrc" file is what is used for creating applets if you
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| 25 | don't provide your own resource file. <p>
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| 26 |
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| 27 | When creating your own BNDL resouorces, keep in mind that the Finder gets
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| 28 | confused if you have more than one application with the same signature. This may be due
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| 29 | to some incorrectness on the side of "BuildApplet", I am not sure. There is one
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| 30 | case when you definitely need a unique signature: when you create an applet that
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| 31 | has its own data files and you want the user to be able to start your
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| 32 | applet by double-clicking one of the datafiles. <p>
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| 33 |
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| 34 | Let's have a look at dnslookup-2.rsrc, our resource file. Dialog 512 is the
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| 35 | main window which has one button (Lookup), two labels and
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| 36 | two text entry areas, one of which is used for output only. The "Quit"
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| 37 | button has disappeared, because its function is handled by a menu choice. Here's
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| 38 | what it will look like at run time:<p>
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| 39 | <div align=center>
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| 40 | <img width=324 height=205 src="example2/dnslookup-2.gif" alt="dialog image">
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| 41 | </div>
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| 42 | <p>
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| 43 |
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| 44 | <H2>A modeless dialog application using FrameWork</H2>
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| 45 |
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| 46 | On to the source code in <A
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| 47 | HREF="example2/dnslookup-2.py">dnslookup-2.py</A>. The
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| 48 | start is similar to our previous example program <A
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| 49 | HREF="example1/dnslookup-1.py">dnslookup-1.py</A>, with
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| 50 | one extra module being imported. To make life more simple we will use
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| 51 | the <CODE>FrameWork</CODE> module, a nifty piece of code that handles
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| 52 | all the gory Mac details of event loop programming, menubar
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| 53 | installation and all the other code that is the same for every Mac
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| 54 | program in the world. Like most standard modules, FrameWork will run
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| 55 | some sample test code when you invoke it as a main program, so try it
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| 56 | now. It will create a menu bar with an Apple menu with the about box
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| 57 | and a "File" menu with some pythonesque choices (which do nothing
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| 58 | interesting, by the way) and a "Quit" command that works. <p>
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| 59 |
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| 60 | <BLOCKQUOTE>
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| 61 | If you have not used <code>FrameWork</code> before you may want to
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| 62 | first take a look at the <A HREF="textedit.html">Pathetic EDitor</A>
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| 63 | example, which builds a minimal text editor using FrameWork and TextEdit.
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| 64 | On the other hand: we don't use many features of FrameWork, so you could
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| 65 | also continue with this document.
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| 66 | </BLOCKQUOTE>
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| 67 |
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| 68 | After the imports we get the definitions of resource-IDs in our
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| 69 | resource file, slightly changed from the previous version of our
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| 70 | program. The main program is also
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| 71 | similar to our previous version, with one important exception: we
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| 72 | first check to see whether our resource is available before opening
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| 73 | the resource file. Why is this? Because later, when we will have
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| 74 | converted the script to an applet, our resources will be available in
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| 75 | the applet file and we don't need the separate resource file
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| 76 | anymore. <p>
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| 77 |
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| 78 | Next comes the definition of our main class,
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| 79 | <CODE>DNSLookup</CODE>, which inherits
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| 80 | <CODE>FrameWork.Application</CODE>. The Application class handles the
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| 81 | menu bar and the main event loop and event dispatching. In the
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| 82 | <CODE>__init__</CODE> routine we first let the base class initialize
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| 83 | itself, then we create our modeless dialog and finally we jump into
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| 84 | the main loop. The main loop continues until we call <CODE>self._quit</CODE>,
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| 85 | which we will do when the user selects "Quit". When we create
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| 86 | the instance of <CODE>MyDialog</CODE> (which inherits
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| 87 | <CODE>DialogWindow</CODE>, which inherits <CODE>Window</CODE>) we pass
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| 88 | a reference to the application object, this reference is used to tell
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| 89 | Application about our new window. This enables the event loop to keep
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| 90 | track of all windows and dispatch things like update events and mouse
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| 91 | clicks. <p>
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| 92 |
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| 93 | The <CODE>makeusermenus()</CODE> method (which is called sometime
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| 94 | during the Application <CODE>__init__</CODE> routine) creates a File
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| 95 | menu with a Quit command (shortcut command-Q), which will callback to
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| 96 | our quit() method. <CODE>Quit()</CODE>, in turn, calls <CODE>_quit</CODE> which
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| 97 | causes the mainloop to terminate at a convenient time. <p>
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| 98 |
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| 99 | Application provides a standard about box, but we override this by
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| 100 | providing our own <CODE>do_about()</CODE> method which shows an about
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| 101 | box from a resource as a modal dialog. This piece of code should look
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| 102 | familiar to you from the previous example program. That do_about is
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| 103 | called when the user selects About from the Apple menu is, again,
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| 104 | taken care of by the __init__ routine of Application. <p>
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| 105 |
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| 106 | The <CODE>MyDialog</CODE> class is the container for our main
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| 107 | window. Initialization is again done by first calling the base class
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| 108 | <CODE>__init__</CODE> function and finally setting the local variable
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| 109 | "parent." <p>
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| 110 |
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| 111 | <CODE>Do_itemhit()</CODE> is called when an item is selected in this
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| 112 | dialog by the user. We are passed the item number (and the original
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| 113 | event structure, which we normally ignore). The code is similar to the
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| 114 | main loop of our previous example program: a switch depending on the
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| 115 | item selected. <CODE>Dnslookup()</CODE> is quite similar to our previous
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| 116 | example. <p>
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| 117 |
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| 118 | <H2><IMG SRC="html.icons/mkapplet.gif"><A NAME="applets">Creating applets</A></H2>
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| 119 |
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| 120 | Now let us try to turn the python script into an applet, a standalone
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| 121 | application. This will <em>not</em> work if you have the "classic 68k"
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| 122 | Python distribution, only if you have the cfm68k or PPC distribution.
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| 123 |
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| 124 | <blockquote>
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| 125 | Actually, "standalone" is probably not the correct term here, since an
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| 126 | applet does still depend on a lot of the python environment: the
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| 127 | PythonCore shared library, the Python Preferences file, the python Lib
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| 128 | folder and any other modules that the main module depends on. It is
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| 129 | possible to get rid of all these dependencies and create true standalone
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| 130 | applications in Python, but this is a bit difficult. See <a href="freezing.html">
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| 131 | Standalone Applications in Python</a> for details. For this
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| 132 | document, by standalone we mean here that
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| 133 | the script has the look-and-feel of an application, including the
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| 134 | ability to have its own document types, be droppable, etc.
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| 135 | </blockquote>
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| 136 |
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| 137 | The easiest way to create an applet is to take your source file and
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| 138 | drop it onto "BuildApplet", located in the Python home
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| 139 | folder. This will create an applet with the same name as your python
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| 140 | source with the ".py" stripped. Also, if a resource file with the same
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| 141 | name as your source but with ".rsrc" extension is available the
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| 142 | resources from that file will be copied to your applet too. If there
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| 143 | is no resource file for your script a set of default resources will be
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| 144 | used, and the applet will have the default creator 'Pyt0'. The latter
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| 145 | also happens if you do have a resource file but without the BNDL
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| 146 | combo. <A NAME="no-bundle">Actually</A>, as in the present example.
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| 147 | <p>
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| 148 |
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| 149 | If you need slightly more control over the BuildApplet process you can
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| 150 | double-click it, and you will get dialogs for source and
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| 151 | destination of the applet. The rest of the process, including locating
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| 152 | the resource file, remains the same. <p>
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| 153 |
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| 154 | Note that though our example application completely bypasses the
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| 155 | normal python user interface this is by no means necessary. Any python
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| 156 | script can be turned into an applet, and all the usual features of the
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| 157 | interpreter still work. <p>
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| 158 |
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| 159 | That's all for this example, you may now return to the <A HREF="index.html">
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| 160 | table of contents</A> to pick another topic. <p>
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| 161 | </BODY>
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| 162 | </HTML>
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