This patch has been generated by the following Coccinelle semantic patch:
// Remove useless checks for NULL before freeing
//
// free (NULL) is a no-op, so there is no need to avoid it
@@
expression E;
@@
+ free (E);
+ E = NULL;
- if (unlikely (E != NULL)) {
- free(E);
(
- E = NULL;
|
- E = 0;
)
...
- }
@@
expression E;
@@
+ free (E);
- if (unlikely (E != NULL)) {
- free (E);
- }
This adds a new GPU accelerated backend for Cairo based on the Cogl 3D
graphics API.
This backend aims to support Cairo in a way that translates as naturally
as possible to using a GPU, it does not strive to compete with the
anti-aliasing quality of the image backend if it can't be done
efficiently using the GPU - raw performance isn't the only metric of
concern, so is power usage.
As an overview of how the backend works:
- fills are handled by tessellating paths into triangles
- the backend has an extra fill_rectangle drawing operation so we have
a fast-path for drawing rectangles which are so common.
- strokes are also tessellated into triangles.
- stroke and fill tessellations are cached to avoid the cpu overhead
of tessellation and cost of upload given that its common for apps to
re-draw the same path multiple times. The tessellations can survive
translations and rotations increasing the probability that they can be
re-used.
- sources and masks are handled using multi-texturing.
- clipping is handled with a scissor and the stencil buffer which
we're careful to only update when they really change.
- linear gradients are rendered to a 1d texture using a triangle
strip + interpolating color attributes. All cairo extend modes
are handled by corresponding texture sampler wrap modes without
needing programmable fragment processing.
- antialiasing should be handled using Cogl's multisampling API
XXX: This is a work in progress!!
TODO:
- handle at least basic radial gradients (No need to handle full
pdf semantics, since css, svg and canvas only allow radial gradients
defined as one circle + a point that must lie within the first
circle.) - currently we fall back to pixman for radial gradients.
- support glyph rendering with a decent glyph cache design. The
current plan is a per scaled-font growable cache texture + a
scratch cache for one-shot/short-lived glyphs.
- decide how to handle npot textures when lacking hardware support.
Current plan is to add a transparent border to npot textures and use
CLAMP_TO_EDGE for the default EXTEND_NONE semantics. For anything else
we can allocate a shadow npot texture and scale the original to fit
that so we can map extend modes to texture sampler modes.
