Make begin_frame() set a rendering colorstate and depth, and provide it
to the renderers via gdk_draw_context_get_depth() and
gdk_draw_context_get_color_state().
This allows the draw contexts to define their own values, so that ie the
Cairo and GL renderer can choose different settings for rendering (in
particular, GL can choose GL_SRGB and do the srgb conversion; while
Cairo relies on the renderer).
That's basically the "undefined" value. We need that when drawing
nothing, which so far only happens with empty container nodes.
But empty container nodes can be children of other nodes, and that makes
things propagate. So instead of catching them, force the whole rest of
the code to deal with an undefined depth.
We also can't just set a random depth, because that will cause merging
to fail.
Make our visual selection code prefer fbconfigs that are
'srgb framebuffer capable', and mark the surface as 'is srgb'
in this case.
This arranges things so that GSK knows not to use an offscreen
for converting contents back to srgb in the end.
For GDK_MEMORY_U8_SRGB depth, try to create an SRGB surface.
This requires the EXT_KHR_gl_colorspace extension, which
isn't super-common in the wild (37%), so we fall back to regular U8 if
that fails.
But if we have the extension, create our egl surface with the
srgb colorspace, and report that fact in gdk_surface_gl_is_srgb().
We still only differentiate between high bit depth or not, but we now
choose at the end instead of the start, which makes it easier to adapt
to a different method of choosing.
This is an experiment for now, but it seems that encoding srgb inside
the depth makes sense, as we not just use depth to decide on the
GL fbconfigs/Vulkan formats to pick, depth also encodes how the [0...1]
color values are quantized when stored.
Let's see where this goes.
Returns the linear color state that renderers should render in when
this is the target color state.
We disable this function unless linear compositing is enabled and just
return @self by default.
This function checks if the colorstate uses an sRGB transfer function
as final operation. In that case, it is suitable for use with GL_SRGB
(and the Vulkan equivalents).
We disable this function (by always returning NULL) unless linear
compositing is enabled, because this function is used to transition
textures and framebuffers to their linear counterparts.
This is mostly an empty shell for now. We only have static instances
for srgb and srgb-linear, which we will use as markers during our
node processing.
In the future, this object may grow more instances, as well as the
ability to create them from and save them to icc profiles or cicp
data. And a color conversion API.
This is a temporary solution to allow testing how well linear rendering
already works while refactoring code.
This will be removed once linear rendering is the default.
We have code with proper error handling for dmabuf export, we can just
try to use it.
And if it doesn't work, we don't offload the texture like before.
But it does work - at least for me.
Instead of hardcoding which textures we presumably support, just try
creating a buffer and use the failure of that for the error message.
This makes the error message a bit less obvious, but it makes it
possible to refactor the get_buffer() code without having to deal with
the error path.
If we want to improve the debug message, we can start putting debug
messages into the get_buffer() function.
But I think this is good enough.
This allows handling them without ever needing to offscreen for losing
the clip, because the clip can always be transformed.
Also, all the optimizations keep working, like occlusion culling,
clears, and so on.
The main benefit of this work is the ability for offloading to now
handle dihedral transforms of the video buffer.
The other big advantage is that we can now start our rendering with a
dihedral transform from the compositor.
We are seeing posix_fallocate fail with ENOENT occasionally.
This shouldn't happen according to the docs, but it does. Fall back
to ftruncate if it does. It gives us less guarantees, but it makes
the ci not fail so much.
The unary (closure) annotation is for function pointer types; function
arguments that represent the user data to be passed to the callback are
annotated on the callback argument itself, with (closure arg-name).
