widget-factory: add example on styling tooltip window

by using new api:
  gtk_tooltip_set_css_class()
  GtkWidget signals 'tooltip-show' and 'tooltip-hide'

Part of #5925

demos/widget-factory/widget-factory.c

@@ -153,6 +153,35 @@ get_busy (GSimpleAction *action,
   gtk_widget_set_sensitive (window, FALSE);
 }
 
+static void
+search_button_tooltip_show (GtkWidget  *self,
+                            GtkTooltip *tooltip)
+{
+  static int style = 0;
+
+  if (style == 0)
+    {
+       gtk_tooltip_set_css_class (tooltip, "red-tooltip");
+       style++;
+    }
+  else if (style == 1)
+    {
+       gtk_tooltip_set_css_class (tooltip, "yellow-tooltip");
+       style++;
+    }
+  else
+    {
+       style = 0;
+    }
+}
+
+static void
+search_button_tooltip_hide (GtkWidget  *self,
+                            GtkTooltip *tooltip)
+{
+  gtk_tooltip_set_css_class (tooltip, NULL);
+}
+
 static int current_page = 0;
 static gboolean
 on_page (int i)
@@ -2221,6 +2250,8 @@ activate (GApplication *app)
   gtk_builder_cscope_add_callback (scope, level_scale_value_changed);
   gtk_builder_cscope_add_callback (scope, transition_speed_changed);
   gtk_builder_cscope_add_callback (scope, reset_icon_size);
+  gtk_builder_cscope_add_callback (scope, search_button_tooltip_show);
+  gtk_builder_cscope_add_callback (scope, search_button_tooltip_hide);
   gtk_builder_set_scope (builder, scope);
   g_object_unref (scope);
   if (!gtk_builder_add_from_resource (builder, "/org/gtk/WidgetFactory4/widget-factory.ui", &error))

demos/widget-factory/widget-factory.css

@@ -6,3 +6,12 @@
 .toolbar {
   -gtk-icon-style: symbolic;
 }
+
+.red-tooltip {
+  background-color: red;
+}
+
+.yellow-tooltip {
+  background-color: yellow;
+  color: black;
+}

demos/widget-factory/widget-factory.ui

@@ -257,7 +257,9 @@
   </object>
   <object class="GtkTextBuffer" id="textbuffer1">
     <property name="tag-table">tags</property>
-    <property name="text">Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+    <property name="text">Search button above will display its tooltip in an alternating red, yellow and default style.
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit.
 Nullam fringilla, est ut feugiat ultrices, elit lacus ultricies nibh, id commodo tortor nisi id elit.
 Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
 Morbi vel elit erat. Maecenas dignissim, dui et pharetra rutrum, tellus lectus rutrum mi, a convallis libero nisi quis tellus.
@@ -1921,6 +1923,8 @@ microphone-sensitivity-medium-symbolic</property>
                                             <property name="icon-name">edit-find</property>
                                             <property name="action-name">win.search</property>
                                             <property name="tooltip-text" translatable="1">Search for it</property>
+                                            <signal name="tooltip-show" handler="search_button_tooltip_show"/>
+                                            <signal name="tooltip-hide" handler="search_button_tooltip_hide"/>
                                           </object>
                                         </child>
                                         <child>

gtk/gtktooltip.c

@@ -755,6 +755,8 @@ gtk_tooltip_show_tooltip (GdkDisplay *display)
 
   gtk_tooltip_position (tooltip, display, tooltip_widget, device);
 
+  g_signal_emit_by_name (tooltip_widget, "tooltip-show", tooltip);
+
   gtk_widget_set_visible (GTK_WIDGET (tooltip->window), TRUE);
 
   /* Now a tooltip is visible again on the display, make sure browse
@@ -771,6 +773,8 @@ gtk_tooltip_show_tooltip (GdkDisplay *display)
 static void
 gtk_tooltip_hide_tooltip (GtkTooltip *tooltip)
 {
+  GtkWidget *tooltip_widget;
+
   guint timeout = BROWSE_DISABLE_TIMEOUT;
 
   if (!tooltip)
@@ -785,6 +789,7 @@ gtk_tooltip_hide_tooltip (GtkTooltip *tooltip)
   if (!GTK_TOOLTIP_VISIBLE (tooltip))
     return;
 
+  tooltip_widget = tooltip->tooltip_widget;
   tooltip->tooltip_widget = NULL;
 
   /* The tooltip is gone, after (by default, should be configurable) 500ms
@@ -801,7 +806,10 @@ gtk_tooltip_hide_tooltip (GtkTooltip *tooltip)
     }
 
   if (tooltip->window)
-    gtk_widget_set_visible (tooltip->window, FALSE);
+    {
+      gtk_widget_set_visible (tooltip->window, FALSE);
+      g_signal_emit_by_name (tooltip_widget, "tooltip-hide", tooltip);
+    }
 }
 
 static int
@@ -1065,3 +1073,26 @@ gtk_tooltip_unset_surface (GtkNative *native)
   gtk_tooltip_set_surface (tooltip, NULL);
 }
 
+/**
+ * gtk_tooltip_set_css_class:
+ * @tooltip: a #GtkTooltip
+ * @css_class: (allow-none): a css class name, or %NULL
+ *
+ * This function allows to add a single css class
+ * to @tooltip window, that means it will remove any
+ * css class previously added by this function before
+ * adding @css_class as the currently active one.
+ *
+ * if %NULL is passed then any active css class (which
+ * was added by this function) will be cleared.
+ *
+ * Since: 4.12
+ */
+void
+gtk_tooltip_set_css_class (GtkTooltip *tooltip,
+                           const char *css_class)
+{
+  g_return_if_fail (GTK_IS_TOOLTIP (tooltip));
+
+  gtk_tooltip_window_set_css_class (GTK_TOOLTIP_WINDOW (tooltip->window), css_class);
+}

gtk/gtktooltip.h

@@ -56,6 +56,9 @@ void gtk_tooltip_set_custom	         (GtkTooltip         *tooltip,
 GDK_AVAILABLE_IN_ALL
 void gtk_tooltip_set_tip_area            (GtkTooltip         *tooltip,
                                           const GdkRectangle *rect);
+GDK_AVAILABLE_IN_4_12
+void gtk_tooltip_set_css_class           (GtkTooltip *tooltip,
+                                          const char *css_class);
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GtkTooltip, g_object_unref)
 

gtk/gtktooltipwindow.c

@@ -59,6 +59,7 @@ struct _GtkTooltipWindow
   GtkWidget *image;
   GtkWidget *label;
   GtkWidget *custom_widget;
+  char      *css_class;
 };
 
 struct _GtkTooltipWindowClass
@@ -392,6 +393,7 @@ static void
 gtk_tooltip_window_init (GtkTooltipWindow *self)
 {
   gtk_widget_init_template (GTK_WIDGET (self));
+  self->css_class = NULL;
 }
 
 GtkWidget *
@@ -520,3 +522,30 @@ gtk_tooltip_window_position (GtkTooltipWindow *window,
 
   gtk_tooltip_window_relayout (window);
 }
+
+/* See gtk_tooltip_set_css_class() description */
+void
+gtk_tooltip_window_set_css_class (GtkTooltipWindow *window,
+                                  const char       *css_class)
+{
+  GtkWidget *wid = GTK_WIDGET (window);
+
+  if (g_strcmp0 (window->css_class, css_class) == 0)
+    return;
+
+  if (css_class)
+    {
+      if (window->css_class)
+        {
+          gtk_widget_remove_css_class (wid, window->css_class);
+          g_free (window->css_class);
+        }
+      window->css_class = g_strdup (css_class);
+      gtk_widget_add_css_class (wid, css_class);
+    }
+  else
+    {
+      gtk_widget_remove_css_class (wid, window->css_class);
+      g_clear_pointer (&window->css_class, g_free);
+    }
+}

gtk/gtktooltipwindowprivate.h

@@ -59,6 +59,8 @@ void            gtk_tooltip_window_position                     (GtkTooltipWindo
                                                                  GdkAnchorHints    anchor_hints,
                                                                  int               dx,
                                                                  int               dy);
+void            gtk_tooltip_window_set_css_class                (GtkTooltipWindow *window,
+                                                                 const char       *css_class);
 
 G_END_DECLS
 

gtk/gtkwidget.c

@@ -502,6 +502,8 @@ enum {
   MOVE_FOCUS,
   KEYNAV_FAILED,
   QUERY_TOOLTIP,
+  TOOLTIP_SHOW,
+  TOOLTIP_HIDE,
   LAST_SIGNAL
 };
 
@@ -1926,6 +1928,38 @@ gtk_widget_class_init (GtkWidgetClass *klass)
 
   gtk_widget_class_set_css_name (klass, I_("widget"));
   klass->priv->accessible_role = GTK_ACCESSIBLE_ROLE_WIDGET;
+
+  /**
+   * GtkWidget::tooltip-show:
+   * @widget: the object which received the signal.
+   *
+   * Emitted when a tooltip is about to be shown on @widget.
+   */
+  widget_signals[TOOLTIP_SHOW] =
+    g_signal_new (I_("tooltip-show"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_FIRST,
+                  0,
+                  NULL, NULL,
+                  NULL,
+                  G_TYPE_NONE, 1,
+                  GTK_TYPE_TOOLTIP);
+
+  /**
+   * GtkWidget::tooltip-hide:
+   * @widget: the object which received the signal.
+   *
+   * Emitted when a tooltip on @widget has just been hidden.
+   */
+  widget_signals[TOOLTIP_HIDE] =
+    g_signal_new (I_("tooltip-hide"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_FIRST,
+                  0,
+                  NULL, NULL,
+                  NULL,
+                  G_TYPE_NONE, 1,
+                  GTK_TYPE_TOOLTIP);
 }
 
 static void