A Beginner's Guide to Using pyGTK and Glade
The theory behind using Glade and libglade is it wastes time to create your GUI using code. Sitting down and telling the Python interpreter where each widget goes, what color it is and what the defaults are is a huge time sink. Anyone who's programmed in Tcl/Tk has spent days doing this. Not only that, but changing a GUI created with code can be a massive undertaking at times. With Glade and libglade, instead of creating code, you create XML files and code links to those files wherever a button or an entry box or an output text buffer is located.
To start, you need Glade v2 if you don't have it already. Even if you do, you may want the latest version of it. Downloading and installing Glade v2 should be easy enough once you have GTK v2 development packages (the -devel RPMs) installed. However, for most people new to GUI development, the starting window for Glade is intimidatingly blank.
To begin your application, click the Window Icon. Now, you should have a big blank window on your screen (Figure 1).
The important thing to learn about GUI development is there are basically two types of objects: widgets, such as labels and entry boxes and other things you can see, and containers for those widgets. Most likely, you will use one of three kinds of containers, the vertical box, the horizontal box or the table. To create complex layouts, its easiest to nest these containers together in whatever order you need. For example, click on the horizontal box icon. Clicking on the hatched area in window1 inserts three more areas where you can add widgets. Your new window1 should look like Figure 2.
You now can select any of those three areas and further divide it with a vertical box. If you don't like the results, you always can go back and delete, cut and paste or change the number of boxes from the Properties menu (more on that later).
You can use these sorts of primitives to create almost any sort of layout. Now that we have a beginning layout, we can fill it with widgets that actually do something. In this case, I'll fill them with a label, a text entry, a spinbutton and a button. At first this looks pretty ugly (Figure 4).
Remember that GTK auto-adjusts the sizes of the finished product when it is displayed, so everything is packed together as tightly as possible. When the user drags the corner of the window, it's going to auto-expand as well. You can adjust these settings in the Properties window (go to the main Glade window and click View→Show Properties). The Properties window changes different values for different kinds of widgets. If the spinbutton is focused, for example, we see the options shown in Figure 5.
By changing the Value option, we can change what the spinbutton defaults to when displayed. Also important is to change the Max value. A common mistake is to change the Value to something high but forget the Max, which causes the spinbutton initially to display the default but then revert to the Max value when it is changed, confusing the user. In our case, we're going to use the spinbutton as a TCP port, so I'll set it to 65535, the minimum to 1 and the default to 80.
Then, focus on the label1 and change it to read Host:. By clicking on window1 in the main Glade window, you can focus on the entire window, allowing you to change its properties as well. You also can do this by bringing up the widget tree window and clicking on window1. Changing the name to serverinfo and the title to Server Info sets the titlebar and the internal Glade top-level widget name appropriately for this application.
If you go to the widget tree view and click on the hbox1, you can increase the spacing between Host: and the text-entry box. This may make it look a little nicer. Our finished GUI looks like Figure 6.
Normally, this would take only a few minutes to put together. After a bit of practice you'll find that putting together even the most complex GUIs using Glade can be accomplished in minutes. Compare that to the time it takes to type in all those Tk commands manually to do the same thing.
This GUI, of course, doesn't do anything yet. We need to write the Python code that loads the .glade file and does the actual work. In fact, I tend to write two Python files for each Glade-driven project. One file handles the GUI, and the other file doesn't know anything about that GUI. That way, porting from GTK v1 to GTK v2 or even to another GUI toolkit is easy.
Special Reports: DevOps
Have projects in development that need help? Have a great development operation in place that can ALWAYS be better? Regardless of where you are in your DevOps process, Linux Journal can help!
With deep focus on Collaborative Development, Continuous Testing and Release & Deployment, we offer here the DEFINITIVE DevOps for Dummies, a mobile Application Development Primer, advice & help from the experts, plus a host of other books, videos, podcasts and more. All free with a quick, one-time registration. Start browsing now...
- The Ubuntu Conspiracy
- A First Look at IBM's New Linux Servers
- Vigilante Malware
- Disney's Linux Light Bulbs (Not a "Luxo Jr." Reboot)
- Bluetooth Hacks
- System Status as SMS Text Messages
- Libreboot on an X60, Part I: the Setup
- Dealing with Boundary Issues
- Vagrant Simplified
- October 2015 Issue of Linux Journal: Raspberry Pi