There are lots of reasons to using C++’s bit field feature. Perhaps you need a more compact way to represent your data structures, maybe you need to use them interact with hardware, or if you’re writing an emulator, maybe you want to use them to efficiently represent the hardware that you’re emulating. The list goes on…
A few years ago, I was asked to add “theme” to a Qt project of mine. I wasn’t fully aware of the power of Qt’s style system, so I did it the hard way. I created a configuration file which contained the theme-able attributes of just about everything I could think of. And when the application started, I parsed it, and applied the colors, fonts, etc. After a short bit, I noticed things I had overlooked and added them. It wasn’t amazingly hard, but it sure could have been easier. Today I’d like to discuss the easy way :-).
As developers, we all have an editor of choice. We all have one that we consider to be “perfect for our way of working” and no others will do. Sure, in a bind we can make do with alternatives, but they never seem to “feel” right. For me, this editor is nedit. I guess it’s because it was the graphical editor suggested by my professor in school. But I often feel crippled when I have to use something else. Unfortunately, nedit is showing its age. It was made in a time before Unicode was even a concept, using a widget toolkit that has simply not kept up with the times.
Sadly the developers do not seem to be working on it anymore, the last update was version 5.5 in 2004, nearly a decade ago :-(. Often I am still able to make use of nedit on my Linux install, but I’d love to see a spiritual successor developed using a modern toolkit. I’ve looked, nothing quite fits the bill. gedit comes close, but I find its keyboard bindings awkward and it is completely lacking some advanced features such as regular expression based search and replace, and rectangular selection. So I’ve decided in my spare time time to try to develop an editor using Qt, that is a work-alike for nedit and a spiritual successor. For now, the working title is “nedit2“. I make no promises on timeline, but I plan to do my best to create modern maintainable code resulting in an editor that any nedit user will feel comfortable using.
So why I am talking so much and not showing code yet? Well, this task is all about the details. In my initial tests I encountered something which was driving me a bit batty, and I wanted to share with you my findings :-).
Qt has a wonderful way of dealing with memory management. The core idea is simple. Most objects have a parent, and when the parent gets destroyed, it will first destroy all its children. Using this technique, you can often write your Qt applications with little to no concern for memory management. Often, you literally don’t have to have a single
delete in your entire application. That’s pretty sweet!
In addition, since Qt 4.5
QSharedPointer was introduced, which is very similar in concept to
boost::shared_ptr (and thus
std::tr1::shared_ptr). I have long been a huge fan of the idea of smart pointers. They solve the need to worry about memory management for almost all usual cases. Unfortunately, when you combine these two concepts, sometimes you can go awry. I was surprised by this one, so I figured I’d shared my findings :-).
Qt is a fantastically designed library. However, every now and then I think of something that I wish they offered that they don’t. It’s almost always something small and easily worked around, but it would be nice if it were just there. This time around, that feature is the ability to connect a signal to a function which is not a member of a class/struct. Specifically, I think it would be really cool if I could connect it to a c++0x lambda! Especially now that the ISO C++ committee approved the C++0x final draft.
I recently submitted a bug report to Qt software, the results were less than impressive. One thing I’d like to make clear though is that Qt is an amazing library that I would recommend to any c++ software developer, I truly mean that. It is well designed, well documented and generally works as advertised. On top of all of this, it is portable! It really just gets better and better. Which is why I found the handling of my bug report so… underwhelming.
So I’ve been working on my graphing code for EDB. I was eventually able create a Qt widget which natively renders a graphviz graph layout. It actually works quite nicely, you can create an ordinary graphviz graph either in memory or from a file like usual. The code can simply create a “GraphWidget” and the code will display the graph perfectly (there are some constructs which it doesn’t support, but the basics are there) with nice things such as zooming and rotating.
All of this works great, except for the fact that graphviz decided to change some of the structures used to represent the layed out graph.
I tend to frequent the website stackoverflow.com. It’s a fantastic website. It allows knowledge to be shared in a unique way. The only problem is, some people have no idea what they are talking about. If there are enough people who agree with these misguided notions, well then these incorrect answers get up-votes. And the cycle of mis-information repeats. It isn’t too dissimilar from the various types of incorrect information regarding 32-bit machines and 4GB of RAM. Continue reading