completionlistbox: lock listmodel items during snapshotwip/chergert/fix-completion-snapshots

This avoids the GtkSourceCompletionContext (a GListModel) changes that
could come in during the snapshot cycle from messing with the rows that
we want to see snapshotted.

Related https://gitlab.gnome.org/GNOME/gnome-builder/-/issues/1840

1 files changed, 103 insertions, 29 deletions

diff --git a/gtksourceview/gtksourcecompletionlistbox.c b/gtksourceview/gtksourcecompletionlistbox.c
index a8f7d209..a7f6b810 100644
--- a/gtksourceview/gtksourcecompletionlistbox.c
+++ b/gtksourceview/gtksourcecompletionlistbox.c
@@ -27,12 +27,21 @@
 #include "gtksourcecompletionlistboxrow-private.h"
 #include "gtksourcecompletionproposal.h"
 #include "gtksourcecompletionprovider.h"
+#include "gtksourcelistsnapshot-private.h"
 #include "gtksourceview-private.h"
 
 struct _GtkSourceCompletionListBox
 {
 	GtkWidget parent_instance;
 
+	/* Used to snapshot a GListModel of the visible range during a
+	 * frame cycle, so that it cannot change underneath us. We hold()
+	 * and release() the snapshot from frame clock callbacks.
+	 */
+	GtkSourceListSnapshot *list_snapshot;
+	gulong update_handler;
+	gulong after_paint_handler;
+
 	/* The box containing the rows. */
 	GtkBox *box;
 
@@ -42,11 +51,6 @@ struct _GtkSourceCompletionListBox
 	/* The completion context that is being displayed. */
 	GtkSourceCompletionContext *context;
 
-	/* The handler for GtkSourceCompletionContext::items-chaged which should
-	 * be disconnected when no longer needed.
-	 */
-	gulong items_changed_handler;
-
 	/* The number of rows we expect to have visible to the user. */
 	guint n_rows;
 
@@ -116,12 +120,21 @@ enum {
 	N_SIGNALS
 };
 
-static void     gtk_source_completion_list_box_queue_update (GtkSourceCompletionListBox *self);
-static gboolean gtk_source_completion_list_box_update_cb    (GtkWidget                  *widget,
-                                                             GdkFrameClock              *frame_clock,
-                                                             gpointer                    user_data);
-static void     gtk_source_completion_list_box_do_update    (GtkSourceCompletionListBox *self,
-                                                             gboolean                    update_selection);
+static void     gtk_source_completion_list_box_queue_update     (GtkSourceCompletionListBox *self);
+static gboolean gtk_source_completion_list_box_update_cb        (GtkWidget                  *widget,
+                                                                 GdkFrameClock              *frame_clock,
+                                                                 gpointer                    user_data);
+static void     gtk_source_completion_list_box_after_update_cb  (GtkWidget                  *widget,
+                                                                 GdkFrameClock              *frame_clock);
+static void     gtk_source_completion_list_box_after_paint_cb   (GtkWidget                  *widget,
+                                                                 GdkFrameClock              *frame_clock);
+static void     gtk_source_completion_list_box_do_update        (GtkSourceCompletionListBox *self,
+                                                                 gboolean                    update_selection);
+static void     gtk_source_completion_list_box_items_changed_cb (GtkSourceCompletionListBox *self,
+                                                                 guint                       position,
+                                                                 guint                       removed,
+                                                                 guint                       added,
+                                                                 GListModel                 *model);
 
 G_DEFINE_TYPE_WITH_CODE (GtkSourceCompletionListBox, gtk_source_completion_list_box, GTK_TYPE_WIDGET,
                          G_IMPLEMENT_INTERFACE (GTK_TYPE_SCROLLABLE, NULL))
@@ -548,6 +561,42 @@ _gtk_source_completion_list_box_key_pressed_cb (GtkSourceCompletionListBox *self
 }
 
 static void
+gtk_source_completion_list_box_realize (GtkWidget *widget)
+{
+	GtkSourceCompletionListBox *self = GTK_SOURCE_COMPLETION_LIST_BOX (widget);
+	GdkFrameClock *frame_clock;
+
+	GTK_WIDGET_CLASS (gtk_source_completion_list_box_parent_class)->realize (widget);
+
+	frame_clock = gtk_widget_get_frame_clock (widget);
+
+	self->update_handler =
+		g_signal_connect_data (frame_clock,
+		                       "update",
+		                       G_CALLBACK (gtk_source_completion_list_box_after_update_cb),
+		                       self, NULL,
+		                       G_CONNECT_AFTER | G_CONNECT_SWAPPED);
+	self->after_paint_handler =
+		g_signal_connect_swapped (frame_clock,
+		                          "after-paint",
+		                          G_CALLBACK (gtk_source_completion_list_box_after_paint_cb),
+		                          self);
+}
+
+static void
+gtk_source_completion_list_box_unrealize (GtkWidget *widget)
+{
+	GtkSourceCompletionListBox *self = GTK_SOURCE_COMPLETION_LIST_BOX (widget);
+	GdkFrameClock *frame_clock;
+
+	frame_clock = gtk_widget_get_frame_clock (widget);
+	g_clear_signal_handler (&self->update_handler, frame_clock);
+	g_clear_signal_handler (&self->after_paint_handler, frame_clock);
+
+	GTK_WIDGET_CLASS (gtk_source_completion_list_box_parent_class)->unrealize (widget);
+}
+
+static void
 gtk_source_completion_list_box_constructed (GObject *object)
 {
 	GtkSourceCompletionListBox *self = (GtkSourceCompletionListBox *)object;
@@ -582,6 +631,7 @@ gtk_source_completion_list_box_dispose (GObject *object)
 		self->box = NULL;
 	}
 
+	g_clear_object (&self->list_snapshot);
 	g_clear_object (&self->before_size_group);
 	g_clear_object (&self->typed_text_size_group);
 	g_clear_object (&self->after_size_group);
@@ -693,6 +743,9 @@ gtk_source_completion_list_box_class_init (GtkSourceCompletionListBoxClass *klas
 	object_class->get_property = gtk_source_completion_list_box_get_property;
 	object_class->set_property = gtk_source_completion_list_box_set_property;
 
+	widget_class->realize = gtk_source_completion_list_box_realize;
+	widget_class->unrealize = gtk_source_completion_list_box_unrealize;
+
 	properties [PROP_ALTERNATE] =
 		g_param_spec_int ("alternate",
 		                  "Alternate",
@@ -804,6 +857,13 @@ gtk_source_completion_list_box_init (GtkSourceCompletionListBox *self)
 	                          self);
 	gtk_widget_add_controller (GTK_WIDGET (self), key);
 
+	self->list_snapshot = gtk_source_list_snapshot_new ();
+	g_signal_connect_object (self->list_snapshot,
+	                         "items-changed",
+	                         G_CALLBACK (gtk_source_completion_list_box_items_changed_cb),
+	                         self,
+	                         G_CONNECT_SWAPPED);
+
 	self->box = g_object_new (GTK_TYPE_BOX,
 				  "orientation", GTK_ORIENTATION_VERTICAL,
 				  "visible", TRUE,
@@ -1158,25 +1218,10 @@ _gtk_source_completion_list_box_set_context (GtkSourceCompletionListBox *self,
 	g_return_if_fail (GTK_SOURCE_IS_COMPLETION_LIST_BOX (self));
 	g_return_if_fail (!context || GTK_SOURCE_IS_COMPLETION_CONTEXT (context));
 
-	if (self->context == context)
-		return;
-
-	if (self->context != NULL && self->items_changed_handler != 0)
-	{
-		g_signal_handler_disconnect (self->context, self->items_changed_handler);
-		self->items_changed_handler = 0;
-	}
-
-	g_set_object (&self->context, context);
-
-	if (self->context != NULL)
+	if (g_set_object (&self->context, context))
 	{
-		self->items_changed_handler =
-			g_signal_connect_object (self->context,
-			                         "items-changed",
-			                         G_CALLBACK (gtk_source_completion_list_box_items_changed_cb),
-			                         self,
-			                         G_CONNECT_SWAPPED);
+		gtk_source_list_snapshot_set_model (self->list_snapshot,
+		                                    G_LIST_MODEL (context));
 	}
 
 	gtk_source_completion_list_box_set_selected (self, -1);
@@ -1340,3 +1385,32 @@ _gtk_source_completion_list_box_set_show_icons (GtkSourceCompletionListBox *self
 
 	gtk_source_completion_list_box_queue_update (self);
 }
+
+static void
+gtk_source_completion_list_box_after_update_cb (GtkWidget     *widget,
+                                                GdkFrameClock *frame_clock)
+{
+	GtkSourceCompletionListBox *self = (GtkSourceCompletionListBox *)widget;
+	double lower;
+	double page_size;
+
+	g_assert (GTK_SOURCE_IS_COMPLETION_LIST_BOX (self));
+	g_assert (GDK_IS_FRAME_CLOCK (frame_clock));
+
+	lower = gtk_adjustment_get_lower (self->vadjustment);
+	page_size = gtk_adjustment_get_page_size (self->vadjustment);
+
+	gtk_source_list_snapshot_hold (self->list_snapshot, lower, lower + page_size);
+}
+
+static void
+gtk_source_completion_list_box_after_paint_cb (GtkWidget     *widget,
+					       GdkFrameClock *frame_clock)
+{
+	GtkSourceCompletionListBox *self = (GtkSourceCompletionListBox *)widget;
+
+	g_assert (GTK_SOURCE_IS_COMPLETION_LIST_BOX (self));
+	g_assert (GDK_IS_FRAME_CLOCK (frame_clock));
+
+	gtk_source_list_snapshot_release (self->list_snapshot);
+}