qt

Writing cross-platform applications with Git, Qt and CMake

I've been working a lot on the new fwbackups branch, where my main goal was to make it faster, more versatile and cross-platform. I decided to write it in C++ and use Qt for the interface, since when combined with CMake it would be very easy to have it compiling on all platforms. Stick the code into a git repo and you've got cross-platform building with cross-platform revision control! If you're looking for a way to setup a cross-platform application, I've listed the steps I took below:

Step 1: Install the Dependencies

Before we begin, you'll have to install a few dependencies:

Step 2: Create the git repository

Now that you have Git installed, it's time to create the Git repository which will host your project. Open up a command line and type:

  • Linux (Applications Menu > System Tools > Terminal), Unix or Mac OS X (Macintosh HD > Applications > Utilities > Terminal):

    mkdir -p ~/development/ProjectName
    cd ~/development/ProjectName
    git init
  • Microsoft Windows (Start > Run, type "cmd"):
    mkdir "My Documents"
    mkdir "My Documents\development"
    mkdir "My Documents\development\ProjectName"
    cd "My Documents\development\ProjectName"
    git init

This will initialize a git repository called ProjectName inside the "development" folder in your home. You can replace ProjectName with whatever you'd like, but just remember to replace all further instances of it in this tutorial with the same name.

If you'd like to share the project and authorize with other developers to commit to the Git repository, be sure to check out gitosis.

Step 3: Directory Layout

While it's not required, I chose to use an out-of-source build to help keep the source directories clean and keep the build files for each platform separate. Inside your newly-created ProjectName folder, create the following directory tree:

  • build/
  • build/mingw/
  • build/linux/
  • build/osx/
  • build/unix/
  • pixmaps/
  • src/
  • translations/

Step 4: Configure CMake

The last step is to configure CMake. When CMake is invoked, it reads the CMakeLists.txt file and then automatically generates Makefiles for your platform. Use this template CMakeLists.txt file and save it in the ProjectName directory created earlier:

# Name of the project
project( ProjectName )

# Essentially, just split up your project version numbers by the dot.
# These variables map version 0.0.1 of ProjectName.
set( VERSION_MAJOR "0" )
set( VERSION_MINOR "0" )
set( VERSION_PATCH "1" )

if( APPLE )
  # If we're running OS X, we need CMake 2.6.0
  cmake_minimum_required(VERSION 2.6.0)
  set( CMAKE_OSX_ARCHITECTURES "ppc;i386" )
else( APPLE )
  # Otherwise, CMake 2.4.8 is fine
  cmake_minimum_required( VERSION 2.4.8 )
endif( APPLE )

# This project requires Qt4 and Gettext
# If your project does not use Qt or Gettext, simpy remove these lines.
find_package( Qt4 REQUIRED )
find_package( Gettext REQUIRED )

# Enable all compiler warnings
add_definitions( -Wall )

# Process the "src" subdirectory
add_subdirectory(src)

If you're using gettext for translations (as many open-source projects do) then all you need to change is the ProjectName at the beginning and the version number. You'll notice that "add_subdirectory(src)" is called, so the next step is to create the CMakeLists.txt in the ProjectName/src directory:

# All cpp files go here
set(SRC_FILES
    main.cpp
    ProjectName.cpp
   )

# Headers with signal/slot definitions go here
# Remove me if not using Qt
set(MOC_HDRS
    ProjectName.h
    )

# Qt designer interface files go here
# Remove me if not using Qt
set(UI_FILES
    interface/ProjectName.ui
    )

# Qt RC files go here, uncomment if applicable
# Remove me if not using Qt
#set(RC_FILES ProjectName.qrc)

# Remove me if not using Qt
qt4_wrap_ui( UI_HDRS ${UI_FILES} )
qt4_wrap_cpp( MOC_SRCS ${MOC_HDRS} )
# If you're using Qt RC files, uncomment this too
#qt4_add_resources( RC_SRC_FILES ${RC_FILES} )
# Includes the standard Qt libraries
include( ${QT_USE_FILE} )

# Include your headers in the build and source directories
# If you need to include more directories, add them here
include_directories( ${ProjectName_BINARY_DIR}/src
                     ${ProjectName_SOURCE_DIR}/src
                     )

if( APPLE )
  # Define some settings for the Bundle
  set( MACOSX_BUNDLE_BUNDLE_NAME ProjectName )
  set( MACOSX_BUNDLE_GUI_IDENTIFIER "ProjectName" )
  set( MACOSX_BUNDLE_ICON_FILE ProjectName.icns )
  set( MACOSX_BUNDLE_INFO_STRING ""${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}",
                                 Copyright 2008 ProjectName team" )
  set( MACOSX_BUNDLE_SHORT_VERSION_STRING "${VERSION_MAJOR}.${VERSION_MINOR}" )
  set( MACOSX_BUNDLE_LONG_VERSION_STRING "${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}" )
  set( MACOSX_BUNDLE_BUNDLE_VERSION "${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}" )
  set( MACOSX_BUNDLE_COPYRIGHT "(C) 2005-2008 Stewart Adam" )
  # create a bundle with an icon too!
  # If you're not using Qt, uncomment the next line and comment the line below it:
  #add_executable( ProjectName MACOSX_BUNDLE ${SRC_FILES} )
  add_executable( ProjectName MACOSX_BUNDLE ${SRC_FILES} ${MOC_SRCS} ${RC_SRC_FILES} ${UI_HDRS} )
  
  # Allows for bundle re-creation just by running "make". Also installs bundle icon
  add_custom_target( osx_bundle_dirs
    COMMAND mkdir -p ${CMAKE_CURRENT_BINARY_DIR}/ProjectName.app/Contents/Resources
    COMMAND mkdir -p ${CMAKE_CURRENT_BINARY_DIR}/ProjectName.app/Contents/MacOS
    COMMAND cp ../../../pixmaps/${MACOSX_BUNDLE_ICON_FILE}
            ${CMAKE_CURRENT_BINARY_DIR}/ProjectName.app/Contents/Resources/${MACOSX_BUNDLE_ICON_FILE}
    # Qt translations - uncomment this line when you need to install them to the bundle
    #COMMAND cp *.qm ${CMAKE_CURRENT_BINARY_DIR}/ProjectName.app/Contents/Resources/
   )
  add_dependencies( ProjectName osx_bundle_dirs )
  # This tells cmake where to place files inside the bundle
  set_source_files_properties( ${ProjectName_RESOURCES} ${ProjectName_TRANSLATIONS}
    PROPERTIES MACOSX_PACKAGE_LOCATION Resources )
else( NOT APPLE )
  # Builds a binary for windows (without cmdline showing), regular for Linux
  # If you need the cmdline showing, remove the WIN32 attribute
  
  # If you're not using Qt, uncomment the next line and comment the line below it:
  #add_executable( ProjectName WIN32 ${SRC_FILES} )
  add_executable( ProjectName WIN32 ${SRC_FILES} ${MOC_SRCS} ${RC_SRC_FILES} ${UI_HDRS} )
endif( APPLE )

# Link Qt to the executable
target_link_libraries( ProjectName ${QT_LIBRARIES} ) 

Step 5: Build the project

Now that CMake is configured, you're good to go! To build the project, run:

cd ~/development/ProjectName/build/osx
cmake . ../../
make

If you'd like to build for Unix or Linux instead of Mac OS X, change the "build/osx" to "build/unix" or "build/linux" respectively. If you're running Windows, you need to reverse the slash direction and add an additional parameter to CMake:

cd "My Documents\development\ProjectName\build\mingw"
cmake . ..\..\ -G "MinGW Makefiles"
make
Rating: 

Qt, Drupal, iTunes, DRM and a bunch more

I saw this story on slashdot today and wanted to share it - this is exactly why I will never buy anything DRM-protected. If you missed the other article a while back, this is the second music store to shut down in the past few months and leave its users in the dark. I say "in the dark" because both Yahoo! and MSN took down their key servers along with the service, so any user who needs to authorize a new computer to play the music they legally purchased is unable to do so - forcing them to rebuy the songs they've already paid from for somewhere else. This is the perfect example of why I think DRM is a bad, bad technology. Another reason was something I read in a comment on slashdot (sorry, don't have the link this time): When you think about it, the users who pay are getting the short end of the stick. If you pay and recieve DRM content, you're getting a service that's worse than what you get from pirating that same content! For example, music. People who illegally download music are getting high-quality (320kbps) MP3 files without any content restrictions for free, while the users who pay to download music will typically get a 128kbps AAC or MP3 file, with DRM restrictions... Something has to change. Soon.

If you agree with me, try to opt for DRM-free music or simpy don't purchase DRM-encumbered music. While a CD will cost you a few more dollars, it has a much higher sound quality and it's not restricted in any way. Hopefully if the music industry sees the common trend of users moving towards DRM-free music, we can get rid of DRM once and for all. I've started purchasing from the iTunes store now that iTunes Plus is getting more popular, and I must admit I'm liking it. I can choose to purchase only select songs from an album, the prices are very reasonable ($0.99/song) and the sound quality is great - 256kbps AAC! What's best of all is that I can play the songs anywhere without the need for authorization - including on Linux or on other non-iPod media players (like Creative MuVos for example) since I can convert the song to any format: ogg, flac, mp3, etc.

Anyways, now that that rant is out of my system, I'll tell you what I've been up to recently. I've been creating a new website for the open-source section of Diffingo.com with the Drupal CMS. I still like Joomla since there's lots of support and community extensions available, but Drupal was recommended by a few friends so I figured I'd give it a shot. And I'm happy I did.

The first thing I noticed was that it was lightning-fast - at least twice or three times faster than Joomla. Not only that, but to my surprise it was much easier to use. I found the interface much cleaner and easier to look at... Everything faded nicely and there seems to be some pretty advanced Javascript stuff built right-in to the administator interface. The WYSIWYG "TinyMCE" editor packaged with Joomla is available for Drupal, so I felt right at home. Drupal also does away with the whole sections and category thing which is really nice. Instead, content items are created as "nodes" and you can cross-categorize nodes if you'd like to.

Blogging is also supported out-of-the-box, which was a big plus since I call this a "blog" but really it's just Joomla content items displayed on a homepage (this is going to be moved to Drupal soon, too). I found themeing Drupal to be a bit more difficult than theming Joomla, however that was made up by Drupal's wonderful access controls. Drupal supports creating user roles, and each role hasa set of permissions. This effetively lets my control who gets to what, when, where and how. I created three simple groups to start with (co-administrators, registered users and anonymous users), but there's a lot of potential in there that I'm hoping I can tap into later.

So, as I blogged about last time I'm also working on a new version of fwbackups. I've changed almost everything I could behind the scenes - from autotools to CMake, from GTK to Qt and from Python to C++. I plan on keeping the interface as similar to as it was before, but it's going to be much simpler and easier to use. It's also going to be much faster under the hood - I'm going to have more info about the next version soon, as soon as I get the new drupal site up ;)

One problem I had when making all these changes was how to set things up properly - it took me a few days, but right now the interface in Qt is done and the very little of the program that's been completed is C++ builds on Mac OS X (10.3.9 and later), Windows (MinGW required) and Linux of course. If you're looking for a way to do this with one of your projects, I'm going to blog about getting the structure for all that setup soon, so check back in a week or two!

Rating: