/Mac/Demo/example2.html

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  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. 

  6. In this document we rewrite the application of the <A
    7. 

  7. HREF="example1.html">previous example</A> to use modeless dialogs. We
    8. 

  8. will use an application framework, and we will have a look at creating
    9. 

  9. applets, standalone applications written in Python.  The <A
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  10. HREF="example2/dnslookup-2.py">source code</A> and 
    11. 

  11. <A HREF="example2/dnslookup-2.rsrc">resource file</A> are available in the folder 
    12. 

  12. <A HREF="example2">example2</A>. <p>
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  13. 

  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>.)
    20. 

  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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    27. 

  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. 

  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>
    39. 

  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. 

  44. <H2>A modeless dialog application using FrameWork</H2>
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  45. 

  46. On to the source code in <A
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  47. HREF="example2/dnslookup-2.py">dnslookup-2.py</A>.  The
    48. 

  48. start is similar to our previous example program <A
    49. 

  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. 

  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.
    64. 

  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. 
    66. 

  66. </BLOCKQUOTE>
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  67. 

  68. After the imports we get the definitions of resource-IDs in our
    69. 

  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
    72. 

  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. 

  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. 

  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. 

  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. 

  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. 

  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 
    116. 

  116. example. <p>
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  117. 

  118. <H2><IMG SRC="html.icons/mkapplet.gif"><A NAME="applets">Creating applets</A></H2>
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  119. 

  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. 

  124. <blockquote>
    125. 

  125. Actually, "standalone" is probably not the correct term here, since an
    126. 

  126. applet does still depend on a lot of the python environment: the
    127. 

  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. 

  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
    143. 

  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. 

  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. 

  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. 

  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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