[Shotwell] Improve Shotwell Slideshow - Weekly Report #10 & #11

[Alexandre Rosenfeld]

Hey guys,

I had some issues these two weeks, since I changed to a new notebook and
shortly afterwards I moved to a new country and in the process lost more
then a week of work when I tried to install the wireless driver, broke my
Ubuntu installation and reinstalled everything but forgot I didnt redo the
backup of my data. And the worst is that I cant make Ubuntu to work with my
wireless, so I started using a virtual machine but I had issues with the 3D
driver. Now I'm running Ubuntu with a network cable so I can get up to speed
in development and redo the work I lost.

So far I resumed my idea of creating an abstraction of a stage, so that I
can still use Clutter for compositing, but use Cairo to do the drawing and
effects. This appear to be working well, but I havent tested everything yet,
so I'm not sure how the performance will be (I'm afraid doing too much
drawing in Cairo will slow everything down). Still my plan is to include the
export video code I created outside Shotwell, but it won't work until the
Stage backend for Cairo is made (which means do the compositing in Cairo, so
that the Cairo surface is exported to video), which I believe wont be ready
in the end of Summer of Code, so exporting a video will probably not work.
It's a bit more complicated this way, but this allow the slideshow to use
the hardware acceleration for the slideshow in the screen and the software
renderer using Cairo anywhere else it's needed (themes preview as well).
Also all the slideshows will still use the Clutter animation framework,
which can save a lot of code in Shotwell.

*Alexandre Rosenfeld*