Added tooltips (if possible) to checkbox menu items

src/dorkbox/systemTray/Checkbox.java

@@ -32,6 +32,7 @@ class Checkbox extends Entry {
 
     private volatile boolean enabled = true;
     private volatile char mnemonicKey;
+    private volatile String tooltip;
 
     public
     Checkbox() {
@@ -195,4 +196,45 @@ class Checkbox extends Entry {
             ((CheckboxPeer) peer).setShortcut(this);
         }
     }
+
+    /**
+     * Specifies the tooltip text, usually this is used to brand the SystemTray icon with your product's name, or to provide extra
+     * information during mouse-over for menu entries.
+     * <p>
+     * NOTE: Maximum length is 64 characters long, and it is not supported on all Operating Systems and Desktop Environments.
+     * <p>
+     * For more details on Linux see https://bugs.launchpad.net/indicator-application/+bug/527458/comments/12.
+     *
+     * @param tooltipText the text to use as a mouse-over tooltip for the tray icon or menu entry, null to remove.
+     */
+    public
+    void setTooltip(final String tooltipText) {
+        if (tooltipText != null) {
+            // this is a safety precaution, since the behavior of really long text is undefined.
+            if (tooltipText.length() > 64) {
+                throw new RuntimeException("Tooltip text cannot be longer than 64 characters.");
+            }
+
+            if (!MenuItem.alreadyEmittedTooltipWarning) {
+                MenuItem.alreadyEmittedTooltipWarning = true;
+                SystemTray.logger.warn("Please disable tooltips, as they are not consistent across all platforms and tray types.");
+            }
+        }
+
+        this.tooltip = tooltipText;
+
+        if (peer != null) {
+            ((CheckboxPeer) peer).setTooltip(this);
+        }
+    }
+
+    /**
+     * Gets the mouse-over tooltip for the meme entry.
+     *
+     * NOTE: This is not consistent across all platforms and tray types.
+     */
+    public
+    String getTooltip() {
+        return this.tooltip;
+    }
 }

src/dorkbox/systemTray/MenuItem.java

@@ -33,7 +33,7 @@ import dorkbox.util.SwingUtil;
 @SuppressWarnings({"unused", "SameParameterValue", "WeakerAccess"})
 public
 class MenuItem extends Entry {
-    private static boolean alreadyEmittedTooltipWarning = false;
+    static boolean alreadyEmittedTooltipWarning = false;
 
     private volatile String text;
     private volatile File imageFile;

src/dorkbox/systemTray/peer/CheckboxPeer.java

@@ -31,5 +31,7 @@ interface CheckboxPeer extends EntryPeer {
 
     void setShortcut(Checkbox menuItem);
 
+    void setTooltip(Checkbox menuItem);
+
     void setChecked(Checkbox menuItem);
 }

src/dorkbox/systemTray/ui/awt/AwtMenuItemCheckbox.java

@@ -122,6 +122,12 @@ class AwtMenuItemCheckbox implements CheckboxPeer {
         });
     }
 
+    @Override
+    public
+    void setTooltip(final Checkbox menuItem) {
+        // no op. (awt menus cannot show tooltips)
+    }
+
     @Override
     public
     void setChecked(final Checkbox menuItem) {

src/dorkbox/systemTray/ui/gtk/GtkMenuItemCheckbox.java

@@ -268,6 +268,20 @@ class GtkMenuItemCheckbox extends GtkBaseMenuItem implements CheckboxPeer, GCall
         }
     }
 
+    @Override
+    public
+    void setTooltip(final Checkbox menuItem) {
+        GtkEventDispatch.dispatch(new Runnable() {
+            @Override
+            public
+            void run() {
+                // NOTE: this will not work for AppIndicator tray types!
+                // null will remove the tooltip
+                Gtk2.gtk_widget_set_tooltip_text(_native, menuItem.getTooltip());
+            }
+        });
+    }
+
     // this is pretty much ONLY for Ubuntu AppIndicators
     private
     void setCheckedIconForFakeCheckMarks() {

src/dorkbox/systemTray/ui/swing/SwingMenuItemCheckbox.java

@@ -173,4 +173,16 @@ class SwingMenuItemCheckbox extends SwingMenuItem implements CheckboxPeer {
             });
         }
     }
+
+    @Override
+    public
+    void setTooltip(final Checkbox menuItem) {
+        SwingUtil.invokeLater(new Runnable() {
+            @Override
+            public
+            void run() {
+                _native.setToolTipText(menuItem.getTooltip());
+            }
+        });
+    }
 }