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Archive for November, 2011

I use the Qt library in my day-to-day development work. I build my Qt libraries directly from the git repository and they are configured specifically for my projects. On the Mac OS X side, this is the command line I use:

The Windows one is similar:

You will notice that I am explicitly removing a whole bunch of stuff – SVG, WebKit, audio, etc.. The time it takes to build the Qt libraries is not insignificant and since I typically track the git repo, I don’t want to waste time building things I will not be using in my projects. The WebKit code takes an extraordinary amount of time to build, for example. I also don’t want to build things into the libs that I’m not going to be using for my commercial software – such as STL. One of the problems this poses, however, is how to handle build problems with other projects I want to build, for example the GUI for the open-source Cppcheck program.

For the most part the projects I’m interested in don’t use any of the capabilities I’m eliminating from my Qt build, but one option has been problematic for a couple of projects: -no-stl. This is because the projects use the functions QString::toStdString() and QString::fromStdString() which do not exist when you build Qt with the -no-stl option. While STL may be available to the source you are building, it was not compiled into the Qt libs, so this causes an error.

When I try to build Cppcheck using my own Qt build, I get errors like this:

../gui/mainwindow.cpp: In member function ‘Settings MainWindow::GetCppcheckSettings()’: ../gui/mainwindow.cpp:457: error: ‘class QString’ has no member named ‘toStdString’

../gui/threadresult.cpp: In member function ‘virtual void ThreadResult::reportOut(const std::string&)’: ../gui/threadresult.cpp:42: error: ‘fromStdString’ is not a member of ‘QString’

Solutions?

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COLLADA Files and SketchUp Component Hierarchies

posted by Andy Maloney

One of the formats my bloodstain pattern analysis software will export data to is COLLADA. COLLADA is an open format used to exchange 3D scene data between software packages. It is an XML format, meaning it’s readable in a text editor, but it is extremely verbose and not a simple thing to understand unless you know what you’re looking at [and even then…]. Before using it for my current work, I’d used COLLADA with an internal version of the Torque game engine at GarageGames, so I had some familiarity with the format before using it this time.

SketchUp is a powerful free modelling tool from Google. As with any software importing COLLADA, some of the concepts in the format map to concepts within the software, while others do not. One of the things that was not obvious to me when I started exporting COLLADA files for use in Google SketchUp was how to set up my COLLADA so it had hierarchical components upon import. My scenes always showed up as one monolithic component which meant that modifying parts of it to add textures or colours was not easy.

For the bloodstain analysis work, I only have to deal with simple scenes consisting of planar surfaces and lines.

SketchUp COLLADA Import Example

SketchUp COLLADA Import Example

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Cppcheck

posted by Andy Maloney

Cppcheck is an open source cool tool by Daniel Marjamäki used to statically analyse C/C++ code for errors, questionable code, and style. I’ve been tracking it for a number of months and, while it is still in active development, it is already a very useful tool. There are command line and GUI versions available for several platforms.

The Cppcheck wiki page gives a lot more information about it, and lists a couple of hundred checks that are performed on your code.

A git repository is available which makes it easy to keep up-to-date with the latest developments. The source also includes a Qt-based GUI which is quite straightforward to compile using Qt Creator. The GUI is functional, but could use a little bit of work to make it more friendly. In order to view error or warning in the source, for example, Cppcheck requires an external program. It really ought to show you the code in context in the main window, allowing you to correct things within the application.

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Running jpegtran From a Qt Application

posted by Andy Maloney

Continuing on with my obsession with smaller images, I thought I’d give an example of how to include jpegtran with your Qt app and how to call it using QProcess to optimize jpegs. Why do this? The use-case I had was that I was downloading images from the net from within my application and I wanted to ensure that they were optimized. I could have read them in and used my modifications to QImageWriter & co. to write them back out, but we are dealing with JPEG which is a lossy format, so I wanted a lossless way to optimize the images.

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qmake and the Info.plist File

posted by Andy Maloney

I use the Qt library and qmake to build my bloodstain pattern analysis software. qmake is a great tool for cross-platform development because it lets you use one relatively succinct description [a .pro file] to generate Xcode projects, MSVC projects, and makefiles. On the Mac OS X side of things, I use one qmake .pro file to generate three xcode projects: release, beta, and demo. My directory structure looks like this:

Example File Structure

Example File Structure

Overall this works well, but there’s an issue with the Info.plist file.

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WP-Syntax Style Sheet Order Fix

posted by Andy Maloney

I’m using Ryan McGeary‘s excellent WP-Syntax plugin for syntax highlighting of code in WordPress. [It is now maintained by Steve Zahm.]

Update [7 Apr 2014]: I’m, uh, no longer using Ryan’s WP-Syntax plugin… I switched to Crayon Syntax Highlighter so I could have more control over the layout. The examples below are using Crayon now.

Without the plugin, simply using the <code> tag, code looks like this:

/* Hello World program */

#include <stdio.h>

int main( int argc, char *argv[] ) { printf("Hello World");

return 0; }

With the WP-Syntax plugin, it is formatted to make it much more readable:

One problem with the plugin though is that the CSS style sheet for the plugin is being included after some external Javascript in the head element of the HTML document. This prevents some browsers from loading the CSS in parallel which can delay loading of the page. A good way to catch these kinds of things is to use Google’s Page Speed plugin.

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Techozoic Fluid Child Theme CSS

posted by Andy Maloney

So I’m using Jeremy Clark‘s Techozoic Fluid WordPress theme for this site. Kinda cool, eh?

I wanted to modify and minify the style.css file and make a couple of other changes. Given these other changes, I decided the best solution was to make a WordPress child theme. So I followed the instructions and expected that the header would reflect my new style.css file.

Alas, taking a look at the page source, it did not:

So I took a look at themes/techozoic-fluid/header.php, and found the problem on line 76:

It looked like get_template_directory_uri() was returning the main theme’s directory, not the child theme. Sure enough, the docs state:

In the event a child theme is being used, the parent theme directory URI will be returned, not the child theme directory URI

The fix was simple. Changing it to the following grabs the css file from the child theme:

Voilà!

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