[libshumate] map-layer: Queue idle relayout if grid needs recomputing

[Corentin Noël <corentinnoel src gnome org>]

commit 38e94a1f3d587b4c72ff43167327726a7d4d404d
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Fri Mar 5 18:09:36 2021 -0300

    map-layer: Queue idle relayout if grid needs recomputing
    
    Sometimes we legit need to recompute the grid using the new width and
    height passed by the allocator, but we can't really do that in that
    moment to not break the allocation model of GTK4.
    
    Queue an idle callback to recompute the grid in allocation.

 shumate/shumate-map-layer.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
---
diff --git a/shumate/shumate-map-layer.c b/shumate/shumate-map-layer.c
index 8d96121..009ddb9 100644
--- a/shumate/shumate-map-layer.c
+++ b/shumate/shumate-map-layer.c
@@ -30,6 +30,8 @@ struct _ShumateMapLayer
   guint required_tiles_x;
   guint required_tiles_y;
   GHashTable *tile_fill;
+
+  guint recompute_grid_idle_id;
 };
 
 G_DEFINE_TYPE (ShumateMapLayer, shumate_map_layer, SHUMATE_TYPE_LAYER)
@@ -193,6 +195,8 @@ grid_needs_recompute (ShumateMapLayer *self,
   guint required_tiles_x, required_tiles_y;
   guint tile_size;
 
+  g_assert (SHUMATE_IS_MAP_LAYER (self));
+
   tile_size = shumate_map_source_get_tile_size (self->map_source);
   required_tiles_x = (width / tile_size) + 2;
   required_tiles_y = (height / tile_size) + 2;
@@ -206,6 +210,8 @@ maybe_recompute_grid (ShumateMapLayer *self)
 {
   int width, height;
 
+  g_assert (SHUMATE_IS_MAP_LAYER (self));
+
   width = gtk_widget_get_width (GTK_WIDGET (self));
   height = gtk_widget_get_height (GTK_WIDGET (self));
 
@@ -213,6 +219,32 @@ maybe_recompute_grid (ShumateMapLayer *self)
     recompute_grid (self, width, height);
 }
 
+static gboolean
+recompute_grid_in_idle_cb (gpointer user_data)
+{
+  ShumateMapLayer *self = user_data;
+
+  g_assert (SHUMATE_IS_MAP_LAYER (self));
+
+  maybe_recompute_grid (self);
+
+  self->recompute_grid_idle_id = 0;
+  return G_SOURCE_REMOVE;
+}
+
+static void
+queue_recompute_grid_in_idle (ShumateMapLayer *self)
+{
+  g_assert (SHUMATE_IS_MAP_LAYER (self));
+
+  if (self->recompute_grid_idle_id > 0)
+    return;
+
+  self->recompute_grid_idle_id = g_idle_add (recompute_grid_in_idle_cb, self);
+  g_source_set_name_by_id (self->recompute_grid_idle_id,
+                           "[shumate] recompute_grid_in_idle_cb");
+}
+
 static void
 on_view_longitude_changed (ShumateMapLayer *self,
                            GParamSpec      *pspec,
@@ -297,6 +329,7 @@ shumate_map_layer_dispose (GObject *object)
   while ((child = gtk_widget_get_first_child (GTK_WIDGET (object))))
     gtk_widget_unparent (child);
 
+  g_clear_handle_id (&self->recompute_grid_idle_id, g_source_remove);
   g_clear_pointer (&self->tile_fill, g_hash_table_unref);
   g_clear_pointer (&self->tiles_positions, g_ptr_array_unref);
   g_clear_object (&self->map_source);
@@ -406,6 +439,12 @@ shumate_map_layer_size_allocate (GtkWidget *widget,
       child_allocation.x += tile_size;
       tile_x++;
     }
+
+  /* We can't recompute while allocating, so queue an idle callback to run
+   * the recomputation outside the allocation cycle.
+   */
+  if (grid_needs_recompute (self, width, height))
+    queue_recompute_grid_in_idle (self);
 }
 
 static void