docs: Rename SGML files

We've been using XML for ages.

docs/reference/gtk/building.xml

@@ -516,7 +516,3 @@ How to compile GTK itself
   </refsect1>
 
 </refentry>
-
-<!-- Local Variables: -->
-<!-- sgml-parent-document: ("gtk-docs.sgml" "chapter" "refentry")  -->
-<!-- End: -->

docs/reference/gtk/drawing-model.xml

@@ -224,10 +224,3 @@
   </refsect1>
 
 </refentry>
-
-<!--
-Local variables:
-mode: xml
-sgml-parent-document: ("gtk-docs.sgml" "book" "part" "refentry")
-End:
--->

docs/reference/gtk/glossary.xml

@@ -364,10 +364,3 @@
     </glossdef>
   </glossentry>
 </glossary>
-
-<!--
-Local variables:
-mode: sgml
-sgml-parent-document: ("gtk-docs.sgml" "book" "glossary")
-End:
--->

docs/reference/gtk/gtk4-docs.xml

@@ -22,8 +22,8 @@
     <title>GTK Overview</title>
     <xi:include href="overview.xml"/>
     <xi:include href="xml/getting_started.xml"/>
-    <xi:include href="resources.sgml" />
-    <xi:include href="xml/question_index.sgml" />
+    <xi:include href="resources.xml" />
+    <xi:include href="xml/question_index.xml" />
     <xi:include href="xml/drawing-model.xml" />
     <xi:include href="xml/input-handling.xml" />
     <xi:include href="xml/actions.xml" />
@@ -168,7 +168,7 @@
 
     <chapter id="TextWidgetObjects">
       <title>Multiline Text Editor</title>
-      <xi:include href="xml/text_widget.sgml" />
+      <xi:include href="xml/text_widget.xml" />
       <xi:include href="xml/gtktextiter.xml" />
       <xi:include href="xml/gtktextmark.xml" />
       <xi:include href="xml/gtktextbuffer.xml" />
@@ -179,7 +179,7 @@
 
     <chapter id="TreeWidgetObjects">
       <title>Tree, List and Icon Grid Widgets</title>
-      <xi:include href="xml/tree_widget.sgml" />
+      <xi:include href="xml/tree_widget.xml" />
       <xi:include href="xml/gtktreemodel.xml" />
       <xi:include href="xml/gtktreeselection.xml" />
       <xi:include href="xml/gtktreeviewcolumn.xml" />
@@ -407,12 +407,12 @@
 
   <part id="platform-support">
     <title>GTK Platform Support</title>
-    <xi:include href="building.sgml" />
-    <xi:include href="xml/compiling.sgml" />
-    <xi:include href="running.sgml" />
-    <xi:include href="x11.sgml" />
-    <xi:include href="windows.sgml" />
-    <xi:include href="osx.sgml" />
+    <xi:include href="building.xml" />
+    <xi:include href="xml/compiling.xml" />
+    <xi:include href="running.xml" />
+    <xi:include href="x11.xml" />
+    <xi:include href="windows.xml" />
+    <xi:include href="osx.xml" />
     <xi:include href="broadway.xml" />
     <xi:include href="wayland.xml" />
   </part>

docs/reference/gtk/meson.build

@@ -342,8 +342,8 @@ images = [
 content_files = [
   'actions.xml',
   'broadway.xml',
-  'building.sgml',
-  'compiling.sgml',
+  'building.xml',
+  'compiling.xml',
   'css-overview.xml',
   'css-properties.xml',
   'drawing-model.xml',
@@ -361,31 +361,31 @@ content_files = [
   'input-handling.xml',
   'migrating-2to4.xml',
   'migrating-3to4.xml',
-  'osx.sgml',
-  'other_software.sgml',
+  'osx.xml',
+  'other_software.xml',
   'overview.xml',
-  'question_index.sgml',
-  'resources.sgml',
-  'running.sgml',
-  'text_widget.sgml',
-  'tree_widget.sgml',
+  'question_index.xml',
+  'resources.xml',
+  'running.xml',
+  'text_widget.xml',
+  'tree_widget.xml',
   'visual_index.xml',
   'wayland.xml',
-  'windows.sgml',
-  'x11.sgml',
+  'windows.xml',
+  'x11.xml',
 ]
 
 expand_content_files = [
   'actions.xml',
-  'compiling.sgml',
+  'compiling.xml',
   'drawing-model.xml',
   'glossary.xml',
   'input-handling.xml',
   'migrating-2to4.xml',
   'migrating-3to4.xml',
-  'question_index.sgml',
-  'text_widget.sgml',
-  'tree_widget.sgml',
+  'question_index.xml',
+  'text_widget.xml',
+  'tree_widget.xml',
 ]
 
 types_conf = configuration_data()