[evince] Document presentation mode shortcuts

[Germán Poo-Caamaño <gpoo src gnome org>]

commit 2a00397bd8eb3efdf497edaa268ac1409423ce89
Author: Jason Crain <jason inspiresomeone us>
Date:   Fri Nov 22 18:18:12 2019 -0700

    Document presentation mode shortcuts
    
    Add documentation for 'B' and '.', for showing a black screen in
    presentation mode, and 'W', for showing a white screen.
    
    Fixes #1302

 help/C/presentations.page |  8 ++++++++
 help/C/shortcuts.page     | 14 ++++++++++++++
 shell/help-overlay.ui     | 21 +++++++++++++++++++++
 3 files changed, 43 insertions(+)
---
diff --git a/help/C/presentations.page b/help/C/presentations.page
index bbd5eda5..caa5a804 100644
--- a/help/C/presentations.page
+++ b/help/C/presentations.page
@@ -59,6 +59,14 @@
  </p>
 </section>
 
+<section id="blank-screen">
+<title>Showing a blank screen</title>
+<p>Press <key>B</key> or <key>.</key> to show a black screen.</p>
+<p>Press <key>W</key> to show a white screen.</p>
+<p>Press <key>B</key>, <key>.</key>, or <key>W</key> again to show the
+slide.</p>
+</section>
+
 <section id="file-formats">
 <title>Supported presentation file formats</title>
 <p>
diff --git a/help/C/shortcuts.page b/help/C/shortcuts.page
index 98743d1f..1900922c 100644
--- a/help/C/shortcuts.page
+++ b/help/C/shortcuts.page
@@ -252,6 +252,20 @@ arrow</key></keyseq></p></td>
 </table>
 </section>
 
+<section id="presentation">
+    <title>Presentation mode</title>
+<table frame="all" rules="cols" shade="rows">
+    <tr>
+        <td><p>Toggle black screen.</p></td>
+        <td><p><key>B</key> / <key>.</key></p></td>
+    </tr>
+    <tr>
+        <td><p>Toggle white screen.</p></td>
+        <td><p><key>W</key></p></td>
+    </tr>
+</table>
+</section>
+
 <section id="annotate">
     <title>Annotate the document</title>
 <table frame="all" rules="cols" shade="rows">
diff --git a/shell/help-overlay.ui b/shell/help-overlay.ui
index e3220d71..8f6ea08c 100644
--- a/shell/help-overlay.ui
+++ b/shell/help-overlay.ui
@@ -308,6 +308,27 @@
           </object>
         </child>
 
+        <child>
+          <object class="GtkShortcutsGroup">
+            <property name="visible">True</property>
+            <property name="title" translatable="yes" context="shortcut window">Presentation mode</property>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">True</property>
+                <property name="title" translatable="yes" context="shortcut window">Toggle black 
screen</property>
+                <property name="accelerator">b period</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">True</property>
+                <property name="title" translatable="yes" context="shortcut window">Toggle white 
screen</property>
+                <property name="accelerator">w</property>
+              </object>
+            </child>
+          </object>
+        </child>
+
         <child>
           <object class="GtkShortcutsGroup">
             <property name="visible">True</property>