Add keepBorder <theme> option and enable it by default

With the new keepBorder option enabled, the
ToggleDecorations action now has 3 states:

- the first time only disables the titlebar
- the second time disables the whole SSD
- the third time enables the whole SSD again

When the keepBorder action is disabled, the old 2-state
behavior is restored, e.g. the ToggleDecorations action
only toggles between on and off.

Fixes #813

docs/labwc-actions.5.scd

@@ -80,6 +80,14 @@ Actions are used in menus and keyboard/mouse bindings.
 *<action name="ToggleDecorations" />*
 	Toggle decorations of focused window.
 
+	This is a 3-state action which can be executed multiple times:
+	- Only the titlebar will be hidden, borders and resize area are kept
+	- Remaining decorations will be disabled
+	- Decorations will be shown normally
+
+	By disabling the theme configuration 'keepBorder' the first step
+	will be removed and the action only toggles between on and off.
+
 *<action name="ToggleFullscreen" />*
 	Toggle fullscreen state of focused window.
 

docs/labwc-config.5.scd

@@ -218,6 +218,10 @@ Therefore, where multiple objects of the same kind are required (for example
 *<theme><cornerRadius>*
 	The radius of server side decoration top corners. Default is 8.
 
+*<theme><keepBorder>* [yes|no]
+	Even when disabling server side decorations via ToggleDecorations,
+	keep a small border (and resize area) around the window. Default is yes.
+
 *<theme><font place="">*
 	The font to use for a specific element of a window, menu or OSD.
 	Places can be any of:

docs/rc.xml.all

@@ -18,6 +18,7 @@
   <theme>
     <name></name>
     <cornerRadius>8</cornerRadius>
+    <keepBorder>yes</keepBorder>
     <font place="ActiveWindow">
       <name>sans</name>
       <size>10</size>