diff options
| author | Federico Mena Quintero <federico@gnome.org> | 2023-01-11 10:35:28 -0600 |
|---|---|---|
| committer | Marge Bot <marge-bot@gnome.org> | 2023-03-23 01:41:14 +0000 |
| commit | 55a788ba118c3ada2cd59c27d8db16f4a3615dd1 (patch) | |
| tree | 9b09497401c99079443056ab787290f9efbc703c | |
| parent | 3ba2872c4abfcc580ecc29293bdf5e78c310a50a (diff) | |
| download | librsvg-55a788ba118c3ada2cd59c27d8db16f4a3615dd1.tar.gz | |
render_tree.rst: Describe the render model; add some links
Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/816>
| -rw-r--r-- | devel-docs/render_tree.rst | 34 |
1 files changed, 24 insertions, 10 deletions
diff --git a/devel-docs/render_tree.rst b/devel-docs/render_tree.rst index ffebfbce..cbc9d2a1 100644 --- a/devel-docs/render_tree.rst +++ b/devel-docs/render_tree.rst @@ -125,14 +125,23 @@ That is where much of the complexity of librsvg's code flow comes from: Summary of the SVG rendering model ---------------------------------- -FIXME: - -paint -clip -mask -filter -composite - +In the SVG2 spec, this has been offloaded to the "`Order of graphical +operations +<https://www.w3.org/TR/compositing/#compositingandblendingorder>`_" +section of the Compositing and Blending Level 1 spec. Once the render +tree is resolved, each node is painted like this, conceptually to a +transparent, temporary surface: + +- Paint the shape/text/etc. +- Filters. +- Clip paths. +- Masks. +- Blend/composite the temporary surface onto the result. + +The most critical function in librsvg is probably +`DrawingCtx::with_discrete_layer +<https://gnome.pages.gitlab.gnome.org/librsvg/internals/librsvg/drawing_ctx/struct.DrawingCtx.html#method.with_discrete_layer>`_; +it implements this drawing model. Current state ------------- @@ -143,7 +152,9 @@ Current state - A primitive for text. -- A stacking context, which indicates each layer's opacity/clip/mask/filters. +- A `stacking context + <https://www.w3.org/TR/SVG2/render.html#EstablishingStackingContex>`_, + which indicates each layer's opacity/clip/mask/filters. - Various ancillary structures that try to have only user-space coordinates (e.g. a number of CSS pixels instead of ``5cm``) and no @@ -180,7 +191,10 @@ yet). Elements that establish a viewport (``svg``, ``symbol``, ``image``, ``marker``, ``pattern``) need to carry information about this -viewport, which is a ``viewBox`` plus ``preserveAspectRatio``. See #298. +viewport, which is a ``viewBox`` plus ``preserveAspectRatio``. See +`#298 <https://gitlab.gnome.org/GNOME/librsvg/-/issues/298>`_ for a +somewhat obsolete description of the refactoring work needed to unify +this logic. The ``layout::StackingContext`` struct should contain another field, probably called ``layer``, with something like this: |