Canvas class: hide std::list methods and do some cleanup

[rodolforg]

Although Canvas itself is (argh) a std::list of layers, it must always have a forced last list element: a null layer.
As a consequence, it must override some std::list methods to assure a programmer doesn't access or remove this special layer: like size() and end().

However, std containers are not supposed to be derived as they don't have virtual methods. A misplaced cast (like passing a Canvas as argument to a function that accepts std::list as parameter) may broken the list.
As original code was written way before C++11, some methods were added to std::list (and more may will be added). A distracted programmer could use those new methods and break the special behavior of this derived std::list. Example: push_back() with different signatures of the original - and they do exist now on C++11: current implementation only overrides one.

Therefore, it is best to just hide this ancestral class by making this inheritance private and make it available to programmer only via wrapped or customized methods.

[rodolforg]

OK. Autotools in my machine build.
Errors were in CMake. Any idea?

[ice0]

OK. Autotools in my machine build. Errors were in CMake. Any idea?

Checking now.

[ice0]

OK. Autotools in my machine build. Errors were in CMake. Any idea?

That's just a luck )
Same error with autotools build:

make[2]: *** [Makefile:1317: action_export_icon.png] Segmentation fault (core dumped)
make[2]: *** Deleting file 'action_export_icon.png'
make[2]: *** Waiting for unfinished jobs....
make[2]: *** [Makefile:1317: action_unexport_icon.png] Segmentation fault (core dumped)
make[2]: *** Deleting file 'action_unexport_icon.png'

it faults on different files, so you need to restart it several times to reproduce.
But for me it just hangs.

You can test it using this command:

./synfig ~/projects/synfig/synfig-studio/images/action_interpolate_interpolation_icon.sif -o ./test.png --time 0f

I noticed that it loops in remove_group_pair method, so I added debug output to canvas.cpp:

Canvas::remove_group_pair(String group, etl::handle<Layer> layer)
{
	static int counter = 0;
	std::cout << "Removed from: " << group << ++counter << std::endl;

and this is result:

Removed from: Shading13832
Removed from: Shading13833
Removed from: Shading13834
Removed from: Shading13835
Removed from: Shading13836
Removed from: Shading13837
Removed from: Shading13838

It hangs because layer inside group_db_ is NULL, so it never exits (I guess because of the recursive call).

[rodolforg]

That's just a luck )
Same error with autotools build:

Quite interesting. Here a I could build Synfig Studio, open it and even load some files... :)

[rodolforg]

Sorry - I was rebasing to master and accidentally included an additional commit.

I'll force push it again to fix it.

[rodolforg]

done

[ice0]

Merged. Thank you!