[gnome-builder] code: chain result for competing get_symbol_at_location

[Christian Hergert <chergert src gnome org>]

commit b83638be916cdfb1bcdb6366d84a4bec6ec426ed
Author: Christian Hergert <chergert redhat com>
Date:   Thu Oct 15 17:07:31 2020 -0700

    code: chain result for competing get_symbol_at_location
    
    If we get two requests to get the symbol at a given location, at the same
    time, without any changes to the buffer, then we want to reuse the result
    for both requests.
    
    This implements that to cut down on the overhead to show the hover window
    to users (which required usin this from at least two plugins).
    
    Also note we only show things after all hover providers have returned, so
    some work could be done to update those as results come in.
    
    Fixes #1313

 src/libide/code/ide-buffer.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)
---
diff --git a/src/libide/code/ide-buffer.c b/src/libide/code/ide-buffer.c
index 0afa3c12e..66e203729 100644
--- a/src/libide/code/ide-buffer.c
+++ b/src/libide/code/ide-buffer.c
@@ -84,6 +84,9 @@ struct _IdeBuffer
   GtkSourceFile          *source_file;
   GFile                  *readlink_file;
 
+  IdeTask                *in_flight_symbol_at_location;
+  gint                    in_flight_symbol_at_location_pos;
+
   /* Scalars */
   guint                   change_count;
   guint                   settling_source;
@@ -945,6 +948,7 @@ ide_buffer_class_init (IdeBufferClass *klass)
 static void
 ide_buffer_init (IdeBuffer *self)
 {
+  self->in_flight_symbol_at_location_pos = -1;
   self->source_file = gtk_source_file_new ();
   self->can_restore_cursor = TRUE;
   self->highlight_diagnostics = TRUE;
@@ -1873,6 +1877,9 @@ ide_buffer_changed (GtkTextBuffer *buffer)
 
   GTK_TEXT_BUFFER_CLASS (ide_buffer_parent_class)->changed (buffer);
 
+  g_clear_object (&self->in_flight_symbol_at_location);
+  self->in_flight_symbol_at_location_pos = -1;
+
   self->change_count++;
   g_clear_pointer (&self->content, g_bytes_unref);
   ide_buffer_delay_settling (self);
@@ -3321,6 +3328,7 @@ ide_buffer_get_symbol_at_location_cb (GObject      *object,
   g_autoptr(IdeTask) task = user_data;
   g_autoptr(GError) error = NULL;
   LookUpSymbolData *data;
+  IdeBuffer *self;
 
   g_assert (IDE_IS_MAIN_THREAD ());
   g_assert (IDE_IS_SYMBOL_RESOLVER (symbol_resolver));
@@ -3328,9 +3336,13 @@ ide_buffer_get_symbol_at_location_cb (GObject      *object,
   g_assert (IDE_IS_TASK (task));
 
   data = ide_task_get_task_data (task);
+  self = ide_task_get_source_object (task);
   g_assert (data->resolvers != NULL);
   g_assert (data->resolvers->len > 0);
 
+  g_clear_object (&self->in_flight_symbol_at_location);
+  self->in_flight_symbol_at_location_pos = -1;
+
   if ((symbol = ide_symbol_resolver_lookup_symbol_finish (symbol_resolver, result, &error)))
     {
       /*
@@ -3372,9 +3384,7 @@ ide_buffer_get_symbol_at_location_cb (GObject      *object,
     }
   else
     {
-      ide_task_return_pointer (task,
-                               g_steal_pointer (&data->symbol),
-                               g_object_unref);
+      ide_task_return_object (task, g_steal_pointer (&data->symbol));
     }
 }
 
@@ -3425,6 +3435,21 @@ ide_buffer_get_symbol_at_location_async (IdeBuffer           *self,
       return;
     }
 
+  /* If this query is the same as one in-flight, then try to chain
+   * to that query instead of competing and duplicating work.
+   */
+  if (self->in_flight_symbol_at_location_pos == (int)gtk_text_iter_get_offset (location) &&
+      self->in_flight_symbol_at_location != NULL)
+    {
+      ide_task_chain (self->in_flight_symbol_at_location, task);
+      return;
+    }
+  else
+    {
+      g_set_object (&self->in_flight_symbol_at_location, task);
+      self->in_flight_symbol_at_location_pos = gtk_text_iter_get_offset (location);
+    }
+
   _ide_buffer_sync_to_unsaved_files (self);
 
   line = gtk_text_iter_get_line (location);
@@ -3466,7 +3491,7 @@ ide_buffer_get_symbol_at_location_finish (IdeBuffer     *self,
   g_return_val_if_fail (IDE_IS_BUFFER (self), NULL);
   g_return_val_if_fail (IDE_IS_TASK (result), NULL);
 
-  return ide_task_propagate_pointer (IDE_TASK (result), error);
+  return ide_task_propagate_object (IDE_TASK (result), error);
 }
 
 /**