[glib/test/gobjectnew: 2/3] GParamSpec: add g_param_spec_get_default_value()
- From: Ryan Lortie <ryanl src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib/test/gobjectnew: 2/3] GParamSpec: add g_param_spec_get_default_value()
- Date: Tue, 23 Apr 2013 19:51:32 +0000 (UTC)
commit c18462b5803a3dd57d3ccb67153ad7851cc8ce08
Author: Ryan Lortie <desrt desrt ca>
Date: Tue Apr 23 11:11:20 2013 -0400
GParamSpec: add g_param_spec_get_default_value()
The way of getting the default value out of a GParamSpec is to allocate
a GValue, initialise it, then call g_param_spec_set_default() to set the
default value into that GValue.
This is exactly how we handle setting the default value for all of the
construct properties that were not explicitly passed to g_object_new().
Instead of doing the alloc/init/store on all construct properties on
every call to g_object_new(), we can cache those GValues in the private
data of the GParamSpec itself and reuse them.
This patch does not actually make that change to g_object_new() yet, but
it adds the API to GParamSpec so that a future patch to GObject can make
the change.
https://bugzilla.gnome.org/show_bug.cgi?id=698056
docs/reference/gobject/gobject-sections.txt | 1 +
gobject/gparam.c | 62 +++++++++++++++++++++++++++
gobject/gparam.h | 3 +-
gobject/tests/param.c | 16 +++++++
4 files changed, 81 insertions(+), 1 deletions(-)
---
diff --git a/docs/reference/gobject/gobject-sections.txt b/docs/reference/gobject/gobject-sections.txt
index 9a190e0..d507f15 100644
--- a/docs/reference/gobject/gobject-sections.txt
+++ b/docs/reference/gobject/gobject-sections.txt
@@ -480,6 +480,7 @@ g_param_spec_ref
g_param_spec_unref
g_param_spec_sink
g_param_spec_ref_sink
+g_param_spec_get_default_value
g_param_value_set_default
g_param_value_defaults
g_param_value_validate
diff --git a/gobject/gparam.c b/gobject/gparam.c
index b5c3024..72bd855 100644
--- a/gobject/gparam.c
+++ b/gobject/gparam.c
@@ -80,6 +80,13 @@ static gchar* value_param_lcopy_value (const GValue *value,
GTypeCValue *collect_values,
guint collect_flags);
+typedef struct
+{
+ GValue default_value;
+} GParamSpecPrivate;
+
+static gint g_param_private_offset;
+#define PRIV(inst) (&G_STRUCT_MEMBER(GParamSpecPrivate, (inst), g_param_private_offset))
/* --- functions --- */
void
@@ -147,6 +154,9 @@ g_param_spec_class_init (GParamSpecClass *class,
class->value_set_default = NULL;
class->value_validate = NULL;
class->values_cmp = NULL;
+
+ g_type_class_add_private (class, sizeof (GParamSpecPrivate));
+ g_param_private_offset = g_type_class_get_instance_private_offset (class);
}
static void
@@ -168,6 +178,11 @@ g_param_spec_init (GParamSpec *pspec,
static void
g_param_spec_finalize (GParamSpec *pspec)
{
+ GParamSpecPrivate *priv = PRIV (pspec);
+
+ if (priv->default_value.g_type)
+ g_value_reset (&priv->default_value);
+
g_datalist_clear (&pspec->qdata);
if (!(pspec->flags & G_PARAM_STATIC_NICK))
@@ -1506,3 +1521,50 @@ g_value_dup_param (const GValue *value)
return value->data[0].v_pointer ? g_param_spec_ref (value->data[0].v_pointer) : NULL;
}
+
+/**
+ * g_param_get_default_value:
+ * @param: a #GParamSpec
+ *
+ * Gets the default value of @param as a pointer to a #GValue.
+ *
+ * The #GValue will remain value for the life of @param.
+ *
+ * Returns: a pointer to a #GValue which must not be modified
+ *
+ * Since: 2.38
+ **/
+const GValue *
+g_param_spec_get_default_value (GParamSpec *pspec)
+{
+ GParamSpecPrivate *priv = PRIV (pspec);
+
+ /* We use the type field of the GValue as the key for the once because
+ * it will be zero before it is initialised and non-zero after. We
+ * have to take care that we don't write a non-zero value to the type
+ * field before we are completely done, however, because then another
+ * thread could come along and find the value partially-initialised.
+ *
+ * In order to accomplish this we store the default value in a
+ * stack-allocated GValue. We then set the type field in that value
+ * to zero and copy the contents into place. We then end by storing
+ * the type as the last step in order to ensure that we're completely
+ * done before a g_once_init_enter() could take the fast path in
+ * another thread.
+ */
+ if (g_once_init_enter (&priv->default_value.g_type))
+ {
+ GValue default_value = G_VALUE_INIT;
+
+ g_value_init (&default_value, pspec->value_type);
+ g_param_value_set_default (pspec, &default_value);
+
+ /* store all but the type */
+ default_value.g_type = 0;
+ priv->default_value = default_value;
+
+ g_once_init_leave (&priv->default_value.g_type, pspec->value_type);
+ }
+
+ return &priv->default_value;
+}
diff --git a/gobject/gparam.h b/gobject/gparam.h
index ebdc91e..b35ad51 100644
--- a/gobject/gparam.h
+++ b/gobject/gparam.h
@@ -336,6 +336,8 @@ void g_value_take_param (GValue *value,
GLIB_DEPRECATED_FOR(g_value_take_param)
void g_value_set_param_take_ownership (GValue *value,
GParamSpec *param);
+GLIB_AVAILABLE_IN_2_36
+const GValue * g_param_spec_get_default_value (GParamSpec *param);
/* --- convenience functions --- */
typedef struct _GParamSpecTypeInfo GParamSpecTypeInfo;
@@ -421,7 +423,6 @@ GParamSpec** g_param_spec_pool_list (GParamSpecPool *pool,
guint *n_pspecs_p);
-
/* contracts:
*
* gboolean value_validate (GParamSpec *pspec,
diff --git a/gobject/tests/param.c b/gobject/tests/param.c
index 0c9edab..31515dc 100644
--- a/gobject/tests/param.c
+++ b/gobject/tests/param.c
@@ -786,6 +786,21 @@ test_param_implement (void)
}
}
+static void
+test_param_default (void)
+{
+ GParamSpec *param;
+ const GValue *def;
+
+ param = g_param_spec_int ("my-int", "My Int", "Blurb", 0, 20, 10, G_PARAM_READWRITE);
+ def = g_param_spec_get_default_value (param);
+
+ g_assert (G_VALUE_HOLDS (def, G_TYPE_INT));
+ g_assert_cmpint (g_value_get_int (def), ==, 10);
+
+ g_param_spec_unref (param);
+}
+
int
main (int argc, char *argv[])
{
@@ -798,6 +813,7 @@ main (int argc, char *argv[])
g_test_add_func ("/param/convert", test_param_convert);
g_test_add_func ("/param/implement", test_param_implement);
g_test_add_func ("/value/transform", test_value_transform);
+ g_test_add_func ("/param/default", test_param_default);
return g_test_run ();
}
[
Date Prev][
Date Next] [
Thread Prev][
Thread Next]
[
Thread Index]
[
Date Index]
[
Author Index]