Here's the shortest description of the bug I can come up with:
When computing values, we have 3 kinds of dependencies:
(1) other properties ("currentColor" or em values)
(2) inherited properties ("inherit")
(3) generic things from the theme (@keyframes or @define-color)
Previously, we passed the GtkStyleContext as an argument, because it
provided these 3 things using:
(1) _gtk_style_context_peek_property()
(2) _gtk_style_context_peek_property(gtk_style_context_get_parent())
(3) context->priv->cascade
However, this makes it impossible to lookup values other than the ones
accessible via _gtk_style_context_peek_property(). And this is exactly
what we are doing in gtk_style_context_update_cache(). So when the cache
updates encountered case (1), they were looking up the values from the
wrong style data.
So this large patch essentially does nothing but replace the
context argument in all compute functions with new arguments for the 3
cases above:
(1) values
(2) parent_values
(3) provider
We apparently have a lot of computing code.
Also, in places where we're computing a new CssValue based on an
old one, make sure that if nothing changes we're returning a reference
to the old one, rather than creating a new identical instance.
We now use the GtkStleProviderPrivate interface, which hopefully is
faster and more conformant to CSS. Long term, it definitely should be
both.
I would have liked to split this up into multiple commits, but couldn't
find a way.
We want to move to a world where getting style properties can
allocate a new value, depending on the style property context.
In this world we can't expose "peeking" a property, as we neet
to return a ref to the property that is newly created.
So, we move the peek code into get_property and use get_property
from get_valist.
At the toplevel we have _gtk_theming_engine_get, which lets us pass
in a property context with (atm) the size to get the property for.
Then there is a lot of plumbing to push this down into the lower
layers of the style property code until finally hitting
the property resolvers.
I need this because I will be adding a property resolver for win32
theme parts, and they render differently depending on the size
(i.e. they don't scale linearly). The idea is that the code
to get the background properties will pass in the final size
and we will resolve the theme part specification to that particular
size.
If the old non-context calls are used we just hardcode a size
of 100x100.
