[librsvg: 19/48] Some documentation for XmlState

[Federico Mena Quintero <federico src gnome org>]

commit ad725cc1acb43c05984a93d5adb769120b04a40c
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Sep 7 15:05:57 2018 -0500

    Some documentation for XmlState

 rsvg_internals/src/xml.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/rsvg_internals/src/xml.rs b/rsvg_internals/src/xml.rs
index fa49f5a0..5e005fad 100644
--- a/rsvg_internals/src/xml.rs
+++ b/rsvg_internals/src/xml.rs
@@ -132,6 +132,18 @@ struct Context {
 // A *const RsvgXmlState is just the type that we export to C
 pub enum RsvgXmlState {}
 
+/// Holds the state used for XML processing
+///
+/// These methods are called when an XML event is parsed out of the XML stream: `start_element`,
+/// `end_element`, `characters`.
+///
+/// When an element starts, we push a corresponding `Context` into the `context_stack`.  Within
+/// that context, all XML events will be forwarded to it, and processed in one of the `XmlHandler`
+/// trait objects. Normally the context refers to a `NodeCreationContext` implementation which is
+/// what creates normal graphical elements.
+///
+/// When we get to a `<style>` element, we push a `StyleContext`, which processes its contents
+/// specially.
 struct XmlState {
     tree: Option<Box<Tree>>,