Use a fading icon button in genericDisplay

Add a new icon button in button.js that fades in/out with a short delay when the mouse enters/leaves its parent. Use it for the information button of genericDisplay.

js/ui/button.js

@@ -2,6 +2,11 @@
 
 const Big = imports.gi.Big;
 const Clutter = imports.gi.Clutter;
+const Lang = imports.lang;
+const Mainloop = imports.mainloop;
+
+const Shell = imports.gi.Shell;
+const Tweener = imports.ui.tweener;
 
 const DEFAULT_BUTTON_COLOR = new Clutter.Color();
 DEFAULT_BUTTON_COLOR.from_pixel(0xeeddcc66);
@@ -112,3 +117,105 @@ Button.prototype = {
         }
     }
 };
+
+/* Delay before the icon should appear, in seconds after the pointer has entered the parent */
+const SHOW_ICON_DELAY = 250; // 0.25 second
+const ANIMATION_TIME = 0.25;
+
+/* This is an icon button that fades in/out when mouse enters/leaves the parent.
+ * A delay is used before the fading starts. You can force it to be shown if needed.
+ *
+ * parent -- used to show/hide the button depending on mouse entering/leaving it
+ * size -- size in pixels of  both the button and the icon it contains
+ * texture -- optional, must be used if the texture for the icon is already created (else, use setIconFromName)
+ */
+function iconButton(parent, size, icon) {
+    this._init(parent, size, icon);
+}
+
+iconButton.prototype = {
+    _init : function(parent, size, texture) {
+        this._size = size;
+        if(texture)
+            this.actor = texture;
+        else
+            this.actor = new Clutter.Texture({ width: this._size, height: this._size });
+        this.actor.set_reactive(true);
+        this.actor.set_opacity(0);
+        parent.connect("enter-event", Lang.bind(this, function(actor, event) {
+            this._shouldHide = false;
+
+            // Nothing to do if the cursor has come back from a child of the parent actor
+            if(actor.get_children().indexOf(Shell.get_event_related(event)) != -1)
+                return;
+
+            this._sourceId = Mainloop.timeout_add(SHOW_ICON_DELAY,
+                                                  Lang.bind(this, this._fadeIn));
+        }));
+        parent.connect("leave-event", Lang.bind(this, function(actor, event) {
+            // Nothing to do if the cursor has merely entered a child of the parent actor
+            if(actor.get_children().indexOf(Shell.get_event_related(event)) != -1)
+                return;
+
+            // Remember that we should not be visible to hide the button if forceShow is unset
+            if(this._forceShow) {
+                this._shouldHide = true;
+                return;
+            }
+
+            this._fadeOut()
+        }));
+    },
+
+    /// Private methods ///
+
+    setIconFromName : function(iconName) {
+        let iconTheme = Gtk.IconTheme.get_default();
+        let iconInfo = iconTheme.lookup_icon(iconName, this._size, 0);
+        if (!iconInfo)
+            return;
+
+        let iconPath = iconInfo.get_filename();
+        this.actor.set_from_file(iconPath);
+    },
+
+    // Useful if we want to show the button immediately,
+    // e.g. in case the mouse is already in the parent when the button is created
+    show : function() {
+        this.actor.set_opacity(255);
+    },
+
+    // If show is true, prevents the button from fading out
+    forceShow : function(show) {
+        this._forceShow = show;
+        // Hide the button if it should have been hidden under normal conditions
+        if(!this._forceShow && this._shouldHide) {
+           this._fadeOut();
+        }
+    },
+
+    /// Private methods ///
+
+    _fadeIn : function() {
+        if(this._sourceId) {
+            Mainloop.source_remove(this._sourceId);
+            this._sourceId = null;
+        }
+        Tweener.removeTweens(this.actor);
+        Tweener.addTween(this.actor, { opacity: 255,
+                                       time: ANIMATION_TIME,
+                                       transition :"easeInQuad" });
+    },
+
+    _fadeOut : function() {
+        if(this._sourceId) {
+            Mainloop.source_remove(this._sourceId);
+            this._sourceId = null;
+        }
+        Tweener.removeTweens(this.actor);
+        Tweener.addTween(this.actor, { opacity: 0,
+                                       time: ANIMATION_TIME,
+                                       transition :"easeOutQuad" });
+    }
+};
+