Qt Development on OS X Mountain Lion

1. October 2012 21:18 by Cameron in C++, Mac, Mac OS X, Qt  //  Tags: , , , , , ,   //   Comments

OS X Mountain Lion changes a few things on how XCode is installed. Xcode is now contained in an app bundle and the SDKs directory is part of the bundle contents, thus you will need to update your SDK paths in your project file like so:

MAC_SDK  = /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk
    if( !exists( $$MAC_SDK) ) {
        error("The selected Mac OSX SDK does not exist at $$MAC_SDK!")
    }
    QMAKE_MAC_SDK = $$MAC_SDK

If you want to support Snow Leopard as a target platform with your Qt applications, be sure to use the 10.7 SDK and not the default 10.8 SDK. Your app should work just fine in Snow Leopard provided that you don't make any calls to Lion specific features while using the 10.7 SDK.

Another important thing is to install the command line tools for GCC so that Qt can find the compiler during installation and successfully compile C/C++ applications from Qt Creator. If you do use the 10.8 SDK with any Qt version less than Qt 5.0, it will give warnings that OS X 10.8 is unsupported during compilation. These warnings can be safely ignored. Aside from that, everything else should be the same as before. Happy coding!

ODBC vs RESTful API

31. August 2012 00:55 by Cameron in C++, Qt  //  Tags: , , , , , , , , , ,   //   Comments

In the process of writing the IGA desktop application, I've been faced with several design decisions. One of the most challenging decisions I had to make was how I should most effectively interact with a database backend. To help with this decision, I weighed out the pros and cons of using ODBC and a RESTful web API. Each of these methods are very good for certain purposes.

ODBC

Pros

  • Cross platform support through C/C++ libraries
  • Secure using username and password (connection encrypted)

Cons

  • Some ISPs/Schools block port 1433 (used with SQL Server) or other database ports (MySQL, Postgre, etc)
  • Slow response time in some instances (running multiple queries can take a fair amount of time)

RESTful API

Pros

  • Fast response time
  • Abstracts data backend - i.e. allows for an easy switch of database servers or switch of web server languages
  • Easily allows for multiple desktop and mobile frontends by adhering the web API interface (ODBC isn't usually standard in mobile platforms)

Cons

  • Requires tighter security
  • All requests must be encrypted using SSL or  plain text is sent to the server
  • Requires some sort of authentication either by API key or other method to prevent arbitrary access to server

Ultimately, I decided to go with using a RESTful web API for maintaining separation of the database architecture from the IGA desktop application. This will allow me to change the database backend without breaking the application as long as I keep the API interface the same. Another huge factor in choosing a RESTful web API is that my school blocks port 1433 on its campus wireless networks. I want college students to be able to use the IGA desktop application while on campus so this was a necessary choice. Overall, both provide advantages and disadvantages and neither one is "better" than the other. I hope this helps people with the decision between ODBC and a RESTful API.

Improving speed of iterating a result set from a QSqlQuery

4. July 2012 16:22 by Cameron in C++, Qt  //  Tags: , , , , , , , ,   //   Comments

Today, I had to figure out why it was taking so long to iterate a result set using a QSqlQuery. A query that I ran in about 1 second from SQL Server Management Studio was taking 15 seconds to complete from my C++ application. I found that if you don't set ForwardOnly to true using setForwardOnly(true), it will drastically decrease performance of iterating through the query's results. You should also prepare the query before executing. After applying those changes, I got my query to run in under a second! Huge difference! You can see an example of how to connect to a SQL Server database and query a table using the QODBC3 driver. The speed improvements should also apply to SQLite databases.

QString connectionTemplate = "DRIVER={SQL SERVER};SERVER=server;DATABASE=Users;";
QSqlDatabase db = QSqlDatabase::addDatabase("QODBC3", "db");
db.setDatabaseName(connectionTemplate);
db.setUserName("sa");
db.setPassword("password");
if (db.open()) {
	qDebug() << "OK!";
	QSqlQuery * query = new QSqlQuery(db);
	query->setForwardOnly(true);
	query->prepare("SELECT [UserName]"
				   "  FROM [dbo].[Users]");
	QTime begin = QTime::currentTime();
	if(query->exec())      {
		while(query->next())
		{
			QString userName = query->value(0).toString();
			qDebug() << userName;
		}
		QTime end = QTime::currentTime();
		qDebug() << "finished in " + QVariant(end.second() - now.second()).toString() + " seconds";
	}
	db.close();
}
else {
	qDebug() << db.lastError().text();
}

Started Development of a Collapsible Frame Qt Widget

5. May 2012 22:14 by Cameron in C++, Qt  //  Tags: , ,   //   Comments

Today, I started development of a collapsible frame Qt widget. I needed a widget that could show/hide its contents by clicking on an open/close button but couldn't find a solution online so I decided to create my own. The code is still a work in progress, but the basis of the code involves the use of nested layouts to achieve the hide/show effect. I had to write a custom clickable label class and subclass QLabel as QLabel doesn't have a clicked() signal. I'm using style sheets to apply the icon to the QLabel so that it has the correct image based on open/close and hover over states. The code is available on github under the Apache 2.0 license. Feel free to check out the code and see if you'd like to fork it yourself and contribute.

https://github.com/pcmantinker/Qt-Collapsible-Panel

Qt Cross Platform Notification System

25. March 2012 16:30 by Cameron in C++, Qt  //  Tags: , , , , ,   //   Comments

I've been working on a cross-platform notification system built on Qt which is modeled after Mac OS X's Growl notification system. This is for use in a project that I'm currently working on. You may view the source code here: https://github.com/pcmantinker/Tray-Notification-System

I am still playing around with the window flags for the notification system as sometimes when a new notification is shown, within the Windows operating system, it steals focus from full screen applications. If you have any suggestions, feel free to let me know in the comments. Also, feel free to fork my repository and contribute to the code base if you're interested.

Qt Application Development in Mac OS X Lion

1. February 2012 01:52 by Cameron in Qt, Mac OS X, C++  //  Tags: , , , , ,   //   Comments

I've been working on some code using the QtSDK lately and I've been researching how to deploy applications for Mac OS X 10.6 and above. Luckily, it's pretty simple to deploy applications as the QtSDK includes a tool called macdeployqt. The tool copies all required Qt frameworks to the app bundle and re-assigns the library reference paths for the app to use the libraries within the app bundle and not the user's system directory (/usr/lib). It doesn't copy 3rd party libraries that aren't in the /usr/lib directory so you will have to manually add those.

Please note that macdeployqt on Qt 4.7.x doesn't seem to assign the correct library paths when linking against QtWebKit. This is a known bug that was fixed in Qt 4.8.0.

Also, if you want to insure that your app will not have problems on Snow Leopard, be sure to add this to your .pro file: 

macx:QMAKE_MAC_SDK=/Developer/SDKs/MacOSX10.6.sdk

This tells Qt to use the Snow Leopard SDK instead of the Lion SDK. If you build your application with the 10.6 SDK, it will work with Mac OS X 10.6 or higher.

One last thing is that there seems to be a problem with Xcode 4 and Qt Creator not being able to find g++-4.2 which is installed with older versions of Xcode. A work around for this until a new version of Qt Creator:

sudo ln -s /usr/bin/g++ /usr/bin/g++-4.2

sudo ln -s /usr/bin/gcc /usr/bin/gcc-4.2

I hope this helps anyone experiencing the same issues.

 

EDIT:
As of the February 1, 2012 QtSDK update, it appears as though the problems with g++ and using macdeployqt have been fixed. Please be sure to update to the latest SDK release. 

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