added convenience actions isabelle.increase-font-size and isabelle.decrease-font-size;

--- a/NEWS	Sun Nov 25 15:17:01 2012 +0100
+++ b/NEWS	Sun Nov 25 17:15:21 2012 +0100
@@ -82,7 +82,11 @@
 
 * Improved editing support for control styles: subscript, superscript,
 bold, reset of style -- operating on single symbols or text
-selections.  Cf. keyboard short-cuts C+e DOWN/UP/RIGHT/LEFT.
+selections.  Cf. keyboard shortcuts C+e DOWN/UP/RIGHT/LEFT.
+
+* Actions isabelle.increase-font-size and isabelle.decrease-font-size
+adjust the main text area font size, and its derivatives for output,
+tooltips etc.  Cf. keyboard shortcuts C-PLUS and C-MINUS.
 
 * Uniform Java 7 platform on Linux, Mac OS X, Windows: recent updates
 from Oracle provide better multi-platform experience.  This version is

--- a/src/Tools/jEdit/src/Isabelle.props	Sun Nov 25 15:17:01 2012 +0100
+++ b/src/Tools/jEdit/src/Isabelle.props	Sun Nov 25 17:15:21 2012 +0100
@@ -27,6 +27,10 @@
 options.isabelle-rendering.code=new isabelle.jedit.Isabelle_Options2();
 
 #actions
+isabelle.increase-font-size.label=Increase font size
+isabelle.increase-font-size.shortcut=C+PLUS
+isabelle.decrease-font-size.label=Decrease font size
+isabelle.decrease-font-size.shortcut=C+MINUS
 isabelle.check-buffer.label=Commence full proof checking of current buffer
 isabelle.check-buffer.shortcut=C+e SPACE
 isabelle.cancel-execution.label=Cancel current proof checking process

--- a/src/Tools/jEdit/src/actions.xml	Sun Nov 25 15:17:01 2012 +0100
+++ b/src/Tools/jEdit/src/actions.xml	Sun Nov 25 17:15:21 2012 +0100
@@ -42,6 +42,16 @@
 			wm.addDockableWindow("isabelle-symbols");
 		</CODE>
 	</ACTION>
+	<ACTION NAME="isabelle.increase-font-size">
+	  <CODE>
+	    isabelle.jedit.Isabelle_Actions.increase_font_size(view);
+	  </CODE>
+	</ACTION>
+	<ACTION NAME="isabelle.decrease-font-size">
+	  <CODE>
+	    isabelle.jedit.Isabelle_Actions.decrease_font_size(view);
+	  </CODE>
+	</ACTION>
 	<ACTION NAME="isabelle.check-buffer">
 	  <CODE>
 	    isabelle.jedit.Isabelle_Actions.check_buffer(buffer);

--- a/src/Tools/jEdit/src/isabelle_actions.scala	Sun Nov 25 15:17:01 2012 +0100
+++ b/src/Tools/jEdit/src/isabelle_actions.scala	Sun Nov 25 17:15:21 2012 +0100
@@ -9,12 +9,28 @@
 
 import isabelle._
 
-import org.gjt.sp.jedit.Buffer
+import org.gjt.sp.jedit.{jEdit, View, Buffer}
 import org.gjt.sp.jedit.textarea.JEditTextArea
 
 
 object Isabelle_Actions
 {
+  /* font size */
+
+  def change_font_size(view: View, change: Int => Int)
+  {
+    val FONT_SIZE = "view.fontsize"
+    val size = change(jEdit.getIntegerProperty(FONT_SIZE, 12)) max 5
+    jEdit.setIntegerProperty(FONT_SIZE, size)
+    jEdit.propertiesChanged()
+    jEdit.saveSettings()
+    view.getStatus.setMessageAndClear("Text font size: " + size)
+  }
+
+  def increase_font_size(view: View): Unit = change_font_size(view, i => i + ((i / 10) max 1))
+  def decrease_font_size(view: View): Unit = change_font_size(view, i => i - ((i / 10) max 1))
+
+
   /* full checking */
 
   def check_buffer(buffer: Buffer)