1 <HTML><HEAD><TITLE>Using python to create Macintosh applications, part two</TITLE></HEAD> 2 <BODY> 3 <H1>Using python to create Macintosh applications, part two</H1> 4 <HR> 5 6 In this document we rewrite the application of the <A 7 HREF="example1.html">previous example</A> to use modeless dialogs. We 8 will use an application framework, and we will have a look at creating 9 applets, standalone applications written in Python. The <A 10 HREF="example2/dnslookup-2.py">source code</A> and 11 <A HREF="example2/dnslookup-2.rsrc">resource file</A> are available in the folder 12 <A HREF="example2">example2</A>. <p> 13 14 Again, we start with ResEdit to create our dialogs. Not only do we 15 want a main dialog this time but also an "About" dialog. This example is less 16 than complete since we do not provide a <A NAME="bundle">BNDL resource</A> 17 and related stuff that an application cannot be without. We are able to do this 18 when building a python applet since BuildApplet will substitute default resources 19 for BNDL, etc. when none are supplied (<A HREF="#no-bundle">See below</A>.) 20 "Inside Mac" or various 21 books on Macintosh programming will help here. Also, you can refer to 22 the resource files provided in the Python source distribution for some 23 of the python-specific points of BNDL programming: the 24 "appletbundle.rsrc" file is what is used for creating applets if you 25 don't provide your own resource file. <p> 26 27 When creating your own BNDL resouorces, keep in mind that the Finder gets 28 confused if you have more than one application with the same signature. This may be due 29 to some incorrectness on the side of "BuildApplet", I am not sure. There is one 30 case when you definitely need a unique signature: when you create an applet that 31 has its own data files and you want the user to be able to start your 32 applet by double-clicking one of the datafiles. <p> 33 34 Let's have a look at dnslookup-2.rsrc, our resource file. Dialog 512 is the 35 main window which has one button (Lookup), two labels and 36 two text entry areas, one of which is used for output only. The "Quit" 37 button has disappeared, because its function is handled by a menu choice. Here's 38 what it will look like at run time:<p> 39 <div align=center> 40 <img width=324 height=205 src="example2/dnslookup-2.gif" alt="dialog image"> 41 </div> 42 <p> 43 44 <H2>A modeless dialog application using FrameWork</H2> 45 46 On to the source code in <A 47 HREF="example2/dnslookup-2.py">dnslookup-2.py</A>. The 48 start is similar to our previous example program <A 49 HREF="example1/dnslookup-1.py">dnslookup-1.py</A>, with 50 one extra module being imported. To make life more simple we will use 51 the <CODE>FrameWork</CODE> module, a nifty piece of code that handles 52 all the gory Mac details of event loop programming, menubar 53 installation and all the other code that is the same for every Mac 54 program in the world. Like most standard modules, FrameWork will run 55 some sample test code when you invoke it as a main program, so try it 56 now. It will create a menu bar with an Apple menu with the about box 57 and a "File" menu with some pythonesque choices (which do nothing 58 interesting, by the way) and a "Quit" command that works. <p> 59 60 <BLOCKQUOTE> 61 If you have not used <code>FrameWork</code> before you may want to 62 first take a look at the <A HREF="textedit.html">Pathetic EDitor</A> 63 example, which builds a minimal text editor using FrameWork and TextEdit. 64 On the other hand: we don't use many features of FrameWork, so you could 65 also continue with this document. 66 </BLOCKQUOTE> 67 68 After the imports we get the definitions of resource-IDs in our 69 resource file, slightly changed from the previous version of our 70 program. The main program is also 71 similar to our previous version, with one important exception: we 72 first check to see whether our resource is available before opening 73 the resource file. Why is this? Because later, when we will have 74 converted the script to an applet, our resources will be available in 75 the applet file and we don't need the separate resource file 76 anymore. <p> 77 78 Next comes the definition of our main class, 79 <CODE>DNSLookup</CODE>, which inherits 80 <CODE>FrameWork.Application</CODE>. The Application class handles the 81 menu bar and the main event loop and event dispatching. In the 82 <CODE>__init__</CODE> routine we first let the base class initialize 83 itself, then we create our modeless dialog and finally we jump into 84 the main loop. The main loop continues until we call <CODE>self._quit</CODE>, 85 which we will do when the user selects "Quit". When we create 86 the instance of <CODE>MyDialog</CODE> (which inherits 87 <CODE>DialogWindow</CODE>, which inherits <CODE>Window</CODE>) we pass 88 a reference to the application object, this reference is used to tell 89 Application about our new window. This enables the event loop to keep 90 track of all windows and dispatch things like update events and mouse 91 clicks. <p> 92 93 The <CODE>makeusermenus()</CODE> method (which is called sometime 94 during the Application <CODE>__init__</CODE> routine) creates a File 95 menu with a Quit command (shortcut command-Q), which will callback to 96 our quit() method. <CODE>Quit()</CODE>, in turn, calls <CODE>_quit</CODE> which 97 causes the mainloop to terminate at a convenient time. <p> 98 99 Application provides a standard about box, but we override this by 100 providing our own <CODE>do_about()</CODE> method which shows an about 101 box from a resource as a modal dialog. This piece of code should look 102 familiar to you from the previous example program. That do_about is 103 called when the user selects About from the Apple menu is, again, 104 taken care of by the __init__ routine of Application. <p> 105 106 The <CODE>MyDialog</CODE> class is the container for our main 107 window. Initialization is again done by first calling the base class 108 <CODE>__init__</CODE> function and finally setting the local variable 109 "parent." <p> 110 111 <CODE>Do_itemhit()</CODE> is called when an item is selected in this 112 dialog by the user. We are passed the item number (and the original 113 event structure, which we normally ignore). The code is similar to the 114 main loop of our previous example program: a switch depending on the 115 item selected. <CODE>Dnslookup()</CODE> is quite similar to our previous 116 example. <p> 117 118 <H2><IMG SRC="html.icons/mkapplet.gif"><A NAME="applets">Creating applets</A></H2> 119 120 Now let us try to turn the python script into an applet, a standalone 121 application. This will <em>not</em> work if you have the "classic 68k" 122 Python distribution, only if you have the cfm68k or PPC distribution. 123 124 <blockquote> 125 Actually, "standalone" is probably not the correct term here, since an 126 applet does still depend on a lot of the python environment: the 127 PythonCore shared library, the Python Preferences file, the python Lib 128 folder and any other modules that the main module depends on. It is 129 possible to get rid of all these dependencies and create true standalone 130 applications in Python, but this is a bit difficult. See <a href="freezing.html"> 131 Standalone Applications in Python</a> for details. For this 132 document, by standalone we mean here that 133 the script has the look-and-feel of an application, including the 134 ability to have its own document types, be droppable, etc. 135 </blockquote> 136 137 The easiest way to create an applet is to take your source file and 138 drop it onto "BuildApplet", located in the Python home 139 folder. This will create an applet with the same name as your python 140 source with the ".py" stripped. Also, if a resource file with the same 141 name as your source but with ".rsrc" extension is available the 142 resources from that file will be copied to your applet too. If there 143 is no resource file for your script a set of default resources will be 144 used, and the applet will have the default creator 'Pyt0'. The latter 145 also happens if you do have a resource file but without the BNDL 146 combo. <A NAME="no-bundle">Actually</A>, as in the present example. 147 <p> 148 149 If you need slightly more control over the BuildApplet process you can 150 double-click it, and you will get dialogs for source and 151 destination of the applet. The rest of the process, including locating 152 the resource file, remains the same. <p> 153 154 Note that though our example application completely bypasses the 155 normal python user interface this is by no means necessary. Any python 156 script can be turned into an applet, and all the usual features of the 157 interpreter still work. <p> 158 159 That's all for this example, you may now return to the <A HREF="index.html"> 160 table of contents</A> to pick another topic. <p> 161 </BODY> 162 </HTML> 163
