This commit adds the basic infrastructure for paths.
The public APIs consists of GskPath, GskPathPoint and
GskPathBuilder.
GskPath is a data structure for paths that consists
of contours, which in turn might contain Bézier curves.
The Bezier data structure is inspired by Skia, with separate
arrays for points and operations. One advantage of this
arrangement is that start and end points are shared
between adjacent curves.
A GskPathPoint represents a point on a path, which can
be queried for various properties.
GskPathBuilder is an auxiliary builder object for paths.
A GskGLShader is an abstraction of a GLSL fragment shader that
can produce pixel values given inputs:
* N (currently max 4) textures
* Current arguments for the shader uniform
Uniform types are: float,(u)int,bool,vec234)
There is also a builder for the uniform arguments which are
passed around as immutable GBytes in the built form.
A GskGLShaderNode is a render node that renders a GskGLShader inside a
specified rectangular bounds. It renders its child nodes as textures
and passes those as texture arguments to the shader. You also pass it
a uniform arguments object.
Don't install headers for code that we don't build.
And don't include those headers in gsk.h.
Just as we do in gdk, require applications to include
the backend-specific headers they need explicitly.
Update the one affected demo, gtk4-node-editor.
GSK is conceptually split into two scene graphs:
* a simple rendering tree of operations
* a complex set of logical layers
The latter is built on the former, and adds convenience and high level
API for application developers.
The lower layer, though, is what gets transformed into the rendering
pipeline, as it's simple and thus can be transformed into appropriate
rendering commands with minimal state changes.
The lower layer is also suitable for reuse from more complex higher
layers, like the CSS machinery in GTK, without necessarily port those
layers to the GSK high level API.
This lower layer is based on GskRenderNode instances, which represent
the tree of rendering operations; and a GskRenderer instance, which
takes the render nodes and submits them (after potentially reordering
and transforming them to a more appropriate representation) to the
underlying graphic system.
