[Bf-committers] Can someone please tell me what am I missing in this properties panel code

[Anthony Edlin]

>
> Yes, actually I would like to know why it doesn't work on the default
> outliner instance! Although, since I now know the code works, I will try to
> figure that out. But if you or Josh want to explain this than that would be
> extremely welcomed!!!!
>

Ok this may take a bit, so bear with me.  Remember that blender saves the
user interface data inside the .blend files, so old blend files and the
startup blend files do not have your extra region.  So for both factory
settings and old files you'll need to add your region in if you want it to
be available.

There are a couple of ways to approach this.  First you could just add the
area in when it's needed from the code.  I don't really recommend this but
there is precedent in the code for this, so I'll go over it and the issues
in your code for it first.

There is a function in your patch called outliner_has_buttons_region.  This
function is called whenever your properties region is toggled.  If the
region already exists it just returns it, but if the region does not exist
yet it adds it to the areas region list after the RGN_TYPE_WINDOW.  The
region list for your outliner area now goes like this: Header -> Main
Window -> Properties Buttons.  The problem with this is that order matters
on the region list.  To understand this you have to know that the regions
for the areas are setup using a function called region_rect_recursive which
loops over the regions from first to last and assigns space to each one.
In this case the Header takes some space along the top, then the main
window takes all the remaining space, and finally the new properties area
does not have any remaining space to take so it stays hidden all the time.

So the way to fix this is to change the RGN_TYPE_WINDOW to RGN_TYPE_HEADER
in the outliner_has_buttons_region function.  Now it inserts your new
region into the region list correctly (Header -> Properties Buttons -> Main
Window) and when you try to toggle your properties region on a factory
default outliner area it shows up.  Note that any files you've saved with
your patch previously and tried to toggle on your new region will always
fail now because it was inserted and saved in the wrong place, so make sure
to use a clean file.

It looks like you copied this has_buttons_region function from the
graph_has_button_regions function in the graph editor files.  I think it is
incorrect there also because I don't think you should ever insert a buttons
region after the main window region, but in that case the code is never run
because all blend files since 2.5 have had buttons regions already in the
correct order, so the function never gets to the part that inserts the
region.  If you look around you can see there is a _has_buttons_region
function for each space and most of them use RGN_TYPE_HEADER to insert the
region.

There are pluses and minuses to doing it this way though.  The good thing
is that you don't have to touch versioning code to test out your patch.
The bad part is that it doesn't account for everything.  If you load a file
with your patch it still doesn't indicate that your new area is there until
after you've fist tried to toggle it.  So for instance there will be no "+"
toggle icon on the side of the outliner area.  To fully fix this you
basically should go into the version code and there are basically two areas
you'll have to look at.

The first thing to consider is factory settings.  This loads a .blend file
that was compiled into the blender binary.  In the source directory it is
located at release/datafiles/startup.blend.  If you want to see how it
works look into "data_to_c" and the "datatoc" executable.  You can also
follow the WM_OT_read_factory_settings operator to see how it's loaded.
There is probably a process for updating this compiled in startup file but
I'm not sure of it.  I think in this case you can also look at
BLO_update_defaults_startup_blend function, it updates the factory settings
startup file when loaded without having to save and embed the file.

The second thing is old files.  When files are loaded there is a function
do_versions that is called to update data.  You can see this is split into
several more functions for different series.  You probably want
blo_do_versions_270.

Somewhere in both these functions you can loop through all areas and
spacelinks to find outliners and then add your new region in.  I'm not as
knowledgeable in the versioning code areas so I suggest looking around for
examples.

Hope that helps.