Getting Started With Lighthouse

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Getting started with Lighthouse (a.k.a. QPA)


You need a Unix-like system, a reasonably modern C++ compiler, and an up-to-date version of git (1.6 or newer recommended). (If you do not have git, there is a way to download tarballs from, but I'm not going to show you how: You really want to use git, especially if you are ever going to update to newer versions.)

Clone the Lighthouse repository

First choose some convenient place to put the code. For the purpose of this document I will use ~/dev/.

mkdir -p~/dev
cd ~/dev

Now clone the Lighthouse repository into ~/dev/lighthouse:

git clone git://

Configure and build

We will use shadow builds for this. Shadow building means building outside the source directory tree. It is of course possible to build Lighthouse inside the source tree, but use shadow builds anyway. You will thank me later: With shadow builds you can have several different build configurations side by side.

The only limitation is that the shadow build directory has to be outside the source tree; otherwise Qt's build system will be fatally confused. Apart from that you could put the build directory anywhere, but here I'll put it next to the source directory.

Create a build directory, and cd into it.

cd ~/dev
mkdir build-lighthouse
cd build-lighthouse

Running the configure script from inside the build directory sets up the shadow build:

../qt-lighthouse/configure -qpa -developer-build

(The -embedded-lite option is what makes this a Lighthouse build instead of making just another Qt/X11 binary; -developer-build makes a library that does not need to be installed somewhere else, as well as setting some other developer-friendly options.)

Now compile Lighthouse. To save time, we'll just compile src, and skip the tools and examples for now:

make -C src

Run some examples

We didn't compile any examples in the previous step, so we have to compile them as we need them. We'll choose the industrial standard example for Qt testing:

cd examples/widgets/wiggly/

If we don't specify a backend, Lighthouse will just complain at us, so we use the -platform command line argument, and choose minimal.

./wiggly -platform minimal

Note: you have to press Ctrl-C to stop the program, otherwise your file system will fill up with images.

Now you can use your favorite image viewer to look at the images (outputxxxx.png). You probably want to clean up afterwards:

rm output*.png

If you are running an X11 server, and have the necessary header files installed, you can also try out the testlite backend. It's not compiled by default, so you'll have to do that first:

cd ../../../src/plugins/platforms/testlite/

Go back to the example,


and run it with the new backend:

./wiggly -platform testlite

Now you can start on the advanced stuff

The short version: Look at the files in qtbase/src/plugins/platforms/minimal/. That should show what needs to be implemented to get a new plugin off the ground. The long version might get written up as Writing Your Own Lighthouse Backend.