Using Bacon2D with Sailfish OS

Sailfish OS development for Jolla is quite versatile and you can use QML plugins to enhance your application. But if you’ve used a QML module which isn’t approved in Harbour and want to distribute your application via Jolla Store, you’ve to do some extra steps with it. Lately I ported Ubuntu Phone’s Falldown game for Sailfish OS and it uses Bacon2D framework to ease 2D game development. Bacon2D isn’t allowed in Harbour so I had to patch it to accept custom namespace and either package the dynamically linked library with my app’s RPM or use statically linked Bacon2D with my app. Here are my notes about it.

The examples will be with my Falldown game project and the code can be found on GitHub. The steps shown below are not the optimal way of doing things as you could streamline the process by including Bacon2D build to your project build and in RPM spec patch the needed files. Will see if I get around doing that and automate things.

Building Bacon2D for Sailfish OS

Bacon2D is a framework to ease 2D game development, providing ready-to-use QML elements representing basic game entities needed by most of games. Bacon2D uses Box2D, a 2D rigid body simulation engine for games. Box2D lets you make objects move in realistic ways and make the game world more interactive.

You can use Bacon2D in your Sailfish OS project by using it as dynamically or statically linked library. The easiest way is to just use the statically linked version so it’s statically compiled into your project. But it’s almost as easy to build the dynamically linked library.

The other issue is getting the Bacon2D built such way that you can use it in your project and submit your application to Jolla Store. As Bacon2D plugin isn’t allowed in Harbour you’ve to patch it to your own namespace, e.g harbour.falldown.bacon2d.

The next chapters cover the three different ways to build and use Bacon2D with Sailfish OS.

Get Bacon2D framework

Start with adding the Bacon2D repository to your project’s Git repository as submodule.

$ git submodule add https://github.com/Bacon2D/Bacon2D.git

Now the Bacon2D project files are in e.g. falldown/Bacon2D and falldown directory will be our base.

Now you’re ready to build and use Bacon2D with three optional ways:

After I got the needed things to work, I used the Option 3 way to get Bacon2D included in my application and hopefully it gets approved to Jolla Store.

Option 1: Using statically linked Bacon2D

In your project’s project file e.g. harbour-falldown.pro add to the top of the file include clause for including Bacon2D statically

include(./Bacon2D/src/Bacon2D-static.pri)

In your project’s main.cpp include plugins.h and register types before loading QML resources.

#include <plugins.h>
 
Plugins plugins;
plugins.registerTypes("Bacon2D");

Build your project in Qt Creator by selecting Build->Release, Deploy->Deploy as RPM Package and then running Build -> Clean, Build, Deploy.

Your Bacon2D powered app should now launch in your phone.

Option 2: Using dynamically linked Bacon2D

Open Bacon2D/Bacon2D.pro with Qt Creator and disable the test and examples subdirectories.

SUBDIRS += src

Build Bacon2D for Armv7: Select Kit – MerSDK-SailfishOS-armv7hl – Release – Deploy by copying binaries. The build will fail with “Error 127” but the libbacon2dplugin.so is built so you can use it now.

Copy the “build-Bacon2D-MerSDK_SailfishOS_armv7hl-Release/src/imports” directory which contains QML files and libbacon2dplugin.so to your project’s lib directory, e.g. falldown/lib.

$ cp -r build-Bacon2D-MerSDK_SailfishOS_armv7hl-Release/src/imports/Bacon2D lib

In e.g. harbour-falldown.pro add the lib directory to be added inside RPM.

DEPLOYMENT_PATH = /usr/share/$${TARGET}
lib.files += lib
lib.path = $${DEPLOYMENT_PATH}
INSTALLS += lib

In your main.cpp add import path to Bacon2D files.

view->engine()->addImportPath(SailfishApp::pathTo("qml/imports/").toLocalFile());

In Qt Creator select Build->Release, Deploy->Deploy as RPM Package. Run Build -> Clean, Build, Deploy.

Your Bacon2D powered app for Sailfish OS should now launch in Jolla.

Option 3: Using statically linked Bacon2D the Harbour way

Including statically linked Bacon2D to be built with you Sailfish OS application can be done different ways and I chose not to write my own plugins.cpp to register QML types and just patched the plugins.cpp which Bacon2D provides.

In harbour-falldown.pro add to the top of the file include clause for including Bacon2D statically

include(./Bacon2D/src/Bacon2D-static.pri)

Patch Bacon2D Bacon2D/src/plugins.cpp to accept e.g. harbour.falldown.bacon2d namespace. Change every qmlRegisterType line from “Bacon2D” to your namespace.

qmlRegisterType<Layer>("harbour.falldown.bacon2d", 1, 0, "Layer");

In your project’s src/main.cpp include plugins.h and register types before loading QMLresources.

#include <plugins.h>
 
Plugins plugins;
plugins.registerTypes("harbour.falldown.bacon2d");

Put Bacon2D QML files under e.g. qml/components and change them to import e.g. harbour.falldown.bacon2d 1.0. Somehow I didn’t get the Bacon2D type to work which defines enums.

Build your project in Qt Creator by selecting Build->Release, Deploy->Deploy as RPM Package and then running Build -> Clean, Build, Deploy.

Your Bacon2D powered app should now launch in your phone.

Option 4: Using dynamically linked Bacon2D the Harbour way

You can link against shared libraries which ships with your Sailfish OS app in the RPM but because of Harbour rules you have to install the library under e.g. /usr/share/harbour-falldown/lib.

But before you can use the dynamically linked Bacon2D for Sailfish OS app intended to be distributed via Jolla Harbour you have to patch Bacon2D to accept e.g. harbour.falldown.bacon2d namespace and build the library.

In Bacon2D project change the following files.

Bacon2D/Bacon2D.pro

PROJECT_NAME = harbour.falldown.bacon2d

Bacon2D/src/src.pro

TARGETPATH = harbour/falldown/bacon2d
DESTDIR = $$OUT_PWD/imports/harbour/falldown/bacon2d/

Bacon2D/src/plugins.cpp

qmlRegisterType<Layer>("harbour.falldown.bacon2d", 1, 0, "Layer");

Bacon2D/src/qmldir

module harbour.falldown.bacon2d

In Bacon2D/src directory change every QML file to import e.g. harbour.falldown.bacon2d 1.0

Build Bacon2D with Qt Creator for Armv7: Kit – MerSDK-SailfishOS-armv7hl – Release – Deploy by copying binaries

Copy Bacon2D QML files and libbacon2dplugin.so under lib directory and to the structure which match you import namespace, e.g.: lib/harbour/falldown/bacon2d/.

$ cp -r build-Bacon2D-MerSDK_SailfishOS_armv7hl-Release/src/imports/harbour lib

In your project’s project file, e.g. harbour-falldown.pro add the lib directory to be added inside RPM

DEPLOYMENT_PATH = /usr/share/$${TARGET}
lib.files += lib
lib.path = $${DEPLOYMENT_PATH}
INSTALLS += lib

In your spec file, e.g. rpm/harbour-falldown.spec add following exclude as Harbour RPM packages should not provide anything.

# >> macros
%define __provides_exclude_from ^%{_datadir}/.*$
# << macros

Also to use QML modules which ships together with the application but you have to prefix the name of the imports with e.g. “harbour.falldown.bacon2d”. And you have to install them under /usr/share/harbour-falldown (loadable QML plugins or the QML files).

In src/main.cpp add import path to Bacon2D QML files and plugin before loading qml resources.

view->engine()->addImportPath(SailfishApp::pathTo("lib/").toLocalFile());

Build your project in Qt Creator by selecting Kit – MerSDK-SailfishOS-armv7hl – Release – Deploy – Deploy as RPM Package and then running Clean, Build, Deploy.

Your Bacon2D powered app should now launch in your phone.