[gtk/docs-work: 1/4] docs: Restructure a bit

[Matthias Clasen <matthiasc src gnome org>]

commit bc7da45902d9bbd7917a937aaa1293b348bb3b87
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Apr 19 13:15:05 2020 -0400

    docs: Restructure a bit
    
    Split the overview sections off into its own "concepts part.

 docs/reference/gtk/drawing-model.xml | 14 +++++++-------
 docs/reference/gtk/gtk4-docs.xml     |  6 +++++-
 2 files changed, 12 insertions(+), 8 deletions(-)
---
diff --git a/docs/reference/gtk/drawing-model.xml b/docs/reference/gtk/drawing-model.xml
index 5a4dd781df..27cf247aef 100644
--- a/docs/reference/gtk/drawing-model.xml
+++ b/docs/reference/gtk/drawing-model.xml
@@ -203,12 +203,12 @@
       <title>Hierarchical drawing</title>
 
       <para>
-        During the Paint phase GTK receives a single ::render signal on the toplevel
-        window. The signal handler will create a snapshot object (which is a
-        helper for creating a scene graph) and emit a GtkWidget::snapshot() signal,
-        which will propagate down the widget hierarchy. This lets each widget
-        snapshot its content at the right place and time, correctly handling things
-        like partial transparencies and overlapping widgets.
+        During the Paint phase GTK receives a single #GdkSurface::render signal on
+        the toplevel surface. The signal handler will create a snapshot object
+        (which is a helper for creating a scene graph) and call the
+        #GtkWidget::snapshot() vfunc, which will propagate down the widget hierarchy. 
+        This lets each widget snapshot its content at the right place and time,
+        correctly handling things like partial transparencies and overlapping widgets.
       </para>
 
       <para>
@@ -217,7 +217,7 @@
         the render nodes of children, and grandchildren, and so on), and will reuse
         that node during the Paint phase. Invalidating a widget (by calling
         gtk_widget_queue_draw()) discards the cached render node, forcing the widget
-        to regenerate it the next time it needs to handle a ::snapshot.
+        to regenerate it the next time it needs to produce a snapshot.
       </para>
     </refsect2>
 
diff --git a/docs/reference/gtk/gtk4-docs.xml b/docs/reference/gtk/gtk4-docs.xml
index cca756c355..a01508c54d 100644
--- a/docs/reference/gtk/gtk4-docs.xml
+++ b/docs/reference/gtk/gtk4-docs.xml
@@ -19,11 +19,15 @@
   </bookinfo>
 
   <part id="gtk">
-    <title>GTK Overview</title>
+    <title>Introduction</title>
     <xi:include href="overview.xml"/>
     <xi:include href="xml/getting_started.xml"/>
     <xi:include href="resources.xml" />
     <xi:include href="xml/question_index.xml" />
+  </part>
+
+  <part id="concepts">
+    <title>GTK Concepts</title>
     <xi:include href="xml/drawing-model.xml" />
     <xi:include href="xml/input-handling.xml" />
     <xi:include href="xml/actions.xml" />