Add api to ellipsize labels to multiple lines

When setting the lines property, the label will be ellipsized
to that many lines, with the ellipsis only appearing in the
last line. This is different from how ellipsization of multi-line
labels normally works in GTK+.

docs/reference/gtk/gtk3-sections.txt

@@ -2055,6 +2055,7 @@ gtk_label_set_width_chars
 gtk_label_set_max_width_chars
 gtk_label_set_line_wrap
 gtk_label_set_line_wrap_mode
+gtk_label_set_lines
 gtk_label_get_layout_offsets
 gtk_label_get_mnemonic_keyval
 gtk_label_get_selectable
@@ -2073,6 +2074,7 @@ gtk_label_get_label
 gtk_label_get_layout
 gtk_label_get_line_wrap
 gtk_label_get_line_wrap_mode
+gtk_label_get_lines
 gtk_label_get_mnemonic_widget
 gtk_label_get_selection_bounds
 gtk_label_get_use_markup

gtk/gtklabel.c

@@ -265,6 +265,7 @@ struct _GtkLabelPrivate
 
   gint     width_chars;
   gint     max_width_chars;
+  gint     lines;
 };
 
 /* Notes about the handling of links:
@@ -355,7 +356,8 @@ enum {
   PROP_SINGLE_LINE_MODE,
   PROP_ANGLE,
   PROP_MAX_WIDTH_CHARS,
-  PROP_TRACK_VISITED_LINKS
+  PROP_TRACK_VISITED_LINKS,
+  PROP_LINES
 };
 
 /* When rotating ellipsizable text we want the natural size to request 
@@ -961,6 +963,26 @@ gtk_label_class_init (GtkLabelClass *class)
                                                          P_("Whether visited links should be tracked"),
                                                          TRUE,
                                                          GTK_PARAM_READWRITE));
+
+  /**
+   * GtkLabel:lines:
+   *
+   * The number of lines to which an ellipsized, wrapping label
+   * should be limited. This property has no effect if the
+   * label is not wrapping or ellipsized. Set this property to
+   * -1 if you don't want to limit the number of lines.
+   *
+   * Since: 3.10
+   */
+  g_object_class_install_property (gobject_class,
+                                   PROP_LINES,
+                                   g_param_spec_int ("lines",
+                                                     P_("Number of lines"),
+                                                     P_("The desired number of lines, when ellipsizing a wrapping label"),
+                                                     -1,
+                                                     G_MAXINT,
+                                                     -1,
+                                                     GTK_PARAM_READWRITE));
   /*
    * Key bindings
    */
@@ -1138,6 +1160,9 @@ gtk_label_set_property (GObject      *object,
     case PROP_TRACK_VISITED_LINKS:
       gtk_label_set_track_visited_links (label, g_value_get_boolean (value));
       break;
+    case PROP_LINES:
+      gtk_label_set_lines (label, g_value_get_int (value));
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -1209,6 +1234,9 @@ gtk_label_get_property (GObject     *object,
     case PROP_TRACK_VISITED_LINKS:
       g_value_set_boolean (value, gtk_label_get_track_visited_links (label));
       break;
+    case PROP_LINES:
+      g_value_set_int (value, gtk_label_get_lines (label));
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -3432,6 +3460,8 @@ gtk_label_ensure_layout (GtkLabel *label)
       pango_layout_set_ellipsize (priv->layout, priv->ellipsize);
       pango_layout_set_wrap (priv->layout, priv->wrap_mode);
       pango_layout_set_single_paragraph_mode (priv->layout, priv->single_line_mode);
+      if (priv->lines > 0)
+        pango_layout_set_height (priv->layout, - priv->lines);
 
       gtk_label_update_layout_width (label);
     }
@@ -6533,3 +6563,52 @@ _gtk_label_get_selection_bound (GtkLabel *label)
 
   return 0;
 }
+
+/**
+ * gtk_label_set_lines:
+ * @label: a #GtkLabel
+ * @lines: the desired number of lines, or -1
+ *
+ * Sets the number of lines to which an ellipsized, wrapping label
+ * should be limited. This has no effect if the label is not wrapping
+ * or ellipsized. Set this to -1 if you don't want to limit the
+ * number of lines.
+ *
+ * Since: 3.10
+ */
+void
+gtk_label_set_lines (GtkLabel *label,
+                     gint      lines)
+{
+  GtkLabelPrivate *priv;
+
+  g_return_if_fail (GTK_IS_LABEL (label));
+
+  priv = label->priv;
+
+  if (priv->lines != lines)
+    {
+      priv->lines = lines;
+      g_object_notify (G_OBJECT (label), "lines");
+      gtk_widget_queue_resize (GTK_WIDGET (label));
+    }
+}
+
+/**
+ * gtk_label_get_lines:
+ * @label: a #GtkLabel
+ *
+ * Gets the number of lines to which an ellipsized, wrapping
+ * label should be limited. See gtk_label_set_lines().
+ *
+ * Returns: The number of lines
+ *
+ * Since: 3.10
+ */
+gint
+gtk_label_get_lines (GtkLabel *label)
+{
+  g_return_if_fail (GTK_IS_LABEL (label));
+
+  return label->priv->lines;
+}

gtk/gtklabel.h

@@ -155,6 +155,11 @@ void     gtk_label_set_max_width_chars    	  (GtkLabel         *label,
 					  	   gint              n_chars);
 GDK_AVAILABLE_IN_ALL
 gint     gtk_label_get_max_width_chars  	  (GtkLabel         *label);
+GDK_AVAILABLE_IN_3_10
+void     gtk_label_set_lines                      (GtkLabel         *label,
+                                                   gint              lines);
+GDK_AVAILABLE_IN_3_10
+gint     gtk_label_get_lines                      (GtkLabel         *label);
 GDK_AVAILABLE_IN_ALL
 void     gtk_label_set_pattern                    (GtkLabel         *label,
 						   const gchar      *pattern);