The primary goal here was to cleanup the current GL renderer to make
maintenance easier going forward. Furthermore, it tracks state to allow
us to implement more advanced renderer features going forward.
Reordering
This renderer will reorder batches by render target to reduce the number
of times render targets are changed.
In the future, we could also reorder by program within the render target
if we can determine that vertices do not overlap.
Uniform Snapshots
To allow for reordering of batches all uniforms need to be tracked for
the programs. This allows us to create the full uniform state when the
batch has been moved into a new position.
Some care was taken as it can be performance sensitive.
Attachment Snapshots
Similar to uniform snapshots, we need to know all of the texture
attachments so that we can rebind them when necessary.
Render Jobs
To help isolate the process of creating GL commands from the renderer
abstraction a render job abstraction was added. This could be extended
in the future if we decided to do tiling.
Command Queue
Render jobs create batches using the command queue. The command queue
will snapshot uniform and attachment state so that it can reorder
batches right before executing them.
Currently, the only reordering done is to ensure that we only visit
each render target once. We could extend this by tracking vertices,
attachments, and others.
This code currently uses an inline array helper to reduce overhead
from GArray which was showing up on profiles. It could be changed to
use GdkArray without too much work, but had roughly double the
instructions. Cycle counts have not yet been determined.
GLSL Programs
This was simplified to use XMACROS so that we can just extend one file
(gskglprograms.defs) instead of multiple places. The programs are added
as fields in the driver for easy access.
Driver
The driver manages textures, render targets, access to atlases,
programs, and more. There is one driver per display, by using the
shared GL context.
Some work could be done here to batch uploads so that we make fewer
calls to upload when sending icon theme data to the GPU. We'd need
to keep a copy of the atlas data for such purposes.
When we are rendering a texture node to an offscreen,
and we have a clip, we must force the offscreen rendering.
Otherwise, the code will notice: Hey, it already is a texture
node, so no need to render it to a texture again. But when
clipping is involved, that is exactly what we want to do.
Testcase included.
Fixes: #3651
There isn't any state to modify in the type so we can use const here.
Doing so allows some of the renderer code to use const across a
number of functions so that repeated calls are elided if inlined.
These do not do modify anything so they can be marked as pure to
potentially ellide calls. Since they do dereference, I do not believe
we can make them const although that is unclear since we could technically
just return a pointer + offset. Therefore it *might* be possible to also
make these G_GNUC_CONST.
This also removes the return if fail macros from these as a good portion
of them didn't have them anyway. I think it's fair to say that access to
these incorrectly is a programmer error.
It significantly reduces the amount of code generated into generally a
movss,ret.
According to OpenGL spec, a shader object will only be flagged
for deletion unless it has been detached; when a program object
is deleted, those shader objects attached to it will be detached
but not deleted unless they have already been flagged for deletion.
So we shall detach a shader object before it is deleted, and delete
it before the program object is deleted best.
Here is a command to reproduce this testcase:
GDK_DEBUG=gl-gles gtk4-demo --run gears
Without this patch, Mesa throws this compile error:
0:130(13): error: no matching function for call to `mod(error, float)'; candidates are:
This is caused by `u_rotation - 90` being of type error since
`u_rotation` is a float and it’s illegal to subtract it with an integer.
The special case for ASCII glyphs is unfortunately not
working very well, because of an oversight in pango:
When I added subpixel positioning, I made pango_shape()
default to not rounding, and make PangoLayout call
pango_shape_with_flags() and pass the rounding information
down. The upshot is that we need to use the _with_flags
variant here and tell it to round position, so it matches
what the text node contains.
This way we can render the first frame of tests/testoutsetshadowdrawing
in 153 ops instead of 183.
And the first frame of gtk4-demo in 260 instead of 300.
