Change get_render_node to return nodes that are sized to the clip
area and expect to be placed at the clip position; change
gtk_container_propagate_render_node to place child render nodes
accordingly, and change gtk_css_gadget_get_render_node to return
nodes that are sized accordingly as well.
We store the vertices in (unscaled) window coords (but the item size
is still scaled to match the texture size). Also, the
projection/model-view multiplication order is switched so that the scale
is applied at the right place.
The renderer will always use nearest-neighbor filters because it renders
at 1:1 pixel to texel ratio.
On the other hand, render nodes may be scaled, so we need to offer a way
to control the minification and magnification filters.
If we already have a GL texture we definitely don't want to use
gdk_cairo_draw_from_gl() to draw on a Cairo context if we're going
to take the Cairo surface to which we draw and put it into an OpenGL
texture.
The details of the modelview and projection matrices are only useful for
the GL renderer; there's really no point in having those details
available in the generic API — especially as the Cairo fallback renderer
cannot really set up a complex modelview or a projection matrix.
Instead of using the background as the gadget's node, we add a
non-drawing node that can be used to apply offsets; all other nodes are
children of the "box" node.
Just like we reuse texture ids with the same size we can, at the expense
of a little memory, reuse vertex buffers if they reference the same
attributes and contain the same data.
Each VAO is marked as free at the end of the frame, and if it's not
reused in the following frame, it gets dropped.
The child-transform is useful only if we also provide clipping to the
parent nodes, otherwise children will just be drawn outside of the
parent's bounds.
We'll introduce child transforms either at a higher layer, or once we
add clipping support to GskRenderNode.
This is the first example of indirect rendering involving
a box gadget. For now, we iterate the child gadgets manually,
and rely on gtk_container_propagate_render_node for the
child widgets. Eventually, we may want a better solution
here.
...and implement it for GtkCssGadget and GtkCssCustomGadget.
This allows us to decide on a per-object basis if a custom
gadget needs a render node for content or not.
The custom gadget draw function has the side effect of informing
the gadget machinery wether to draw focus or not. Bring the
draw function back, just for its boolean return value. We may
want to find a better solution for this.
I don't think this should stay in the code long-term, but it
is useful for debugging. It helped me track down some suspicious
placements of render nodes.
Give all nodes the same detail about the owner widget.
This reveals that every GtkCssCustomGadget gets a
DrawGadgetContents node, even if their draw_func is NULL.
We may want to come up with a better solution for that.
When creating the GskRenderNodes for the gadgets we should not translate
the coordinates inside the Cairo context, but we should tweak the
coordinates of the anchor point.
This is still not enough to get an appropriate rendering, as the result
is still slightly offset to the left.
Instead of passing the size of the buffer, we should pass the number of
quads; we know what the size of a single quad structure is, so we can do
the multiplication internally when creating the VAO.
This allows us to print the quads for debugging purposes.
GtkWidget.create_render_node() sets up a GskRenderNode appropriate for
rendering the contents of a widget, including its bounds,
transformation, and anchor point.
The naming is consistent with other scene graph libraries, as it
represents an additional translation transformation applied on top of
the provided transformation matrices.
We can also simplify the implementation by applying the translation when
we compute the world matrix.
We keep the textures used inside a frame around until the end of the
following frame; whenever we need a texture with the same size, and
it's not marked in use, then we just reuse the existing texture.
We were allocating a surface thats big enough for the clip, and
we were setting the transform for that, but then GtkContainer
was overriding the transform with the one for the allocation.
Also, we were drawing at the clip position, not the allocation
position.
This was overwhelming other useful debug output, so make it
opt-in. We print the render items for both opengl and transforms,
since the matrices bleed into each other, otherwise.
