libsysprof-gtk: start on chart + layers

The goal here is to be able to connect data series such as
SysprofTimeSeries or SysprofXYSeries to various chart layers. Those
chart layers get stacked in a SysprofChart.

Some glue code will be necessary to go from frames into data series but
we can experiment with how to automate that later on.

src/libsysprof-gtk/sysprof-chart-layer.c

@@ -0,0 +1,131 @@
+/* sysprof-chart-layer.c
+ *
+ * Copyright 2023 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "config.h"
+
+#include "sysprof-chart-layer.h"
+
+typedef struct
+{
+  char *title;
+} SysprofChartLayerPrivate;
+
+enum {
+  PROP_0,
+  PROP_TITLE,
+  N_PROPS
+};
+
+G_DEFINE_ABSTRACT_TYPE (SysprofChartLayer, sysprof_chart_layer, GTK_TYPE_WIDGET)
+
+static GParamSpec *properties [N_PROPS];
+
+static void
+sysprof_chart_layer_dispose (GObject *object)
+{
+  SysprofChartLayer *self = (SysprofChartLayer *)object;
+  SysprofChartLayerPrivate *priv = sysprof_chart_layer_get_instance_private (self);
+
+  g_clear_pointer (&priv->title, g_free);
+
+  G_OBJECT_CLASS (sysprof_chart_layer_parent_class)->dispose (object);
+}
+
+static void
+sysprof_chart_layer_get_property (GObject    *object,
+                                  guint       prop_id,
+                                  GValue     *value,
+                                  GParamSpec *pspec)
+{
+  SysprofChartLayer *self = SYSPROF_CHART_LAYER (object);
+
+  switch (prop_id)
+    {
+    case PROP_TITLE:
+      g_value_set_string (value, sysprof_chart_layer_get_title (self));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+sysprof_chart_layer_set_property (GObject      *object,
+                                  guint         prop_id,
+                                  const GValue *value,
+                                  GParamSpec   *pspec)
+{
+  SysprofChartLayer *self = SYSPROF_CHART_LAYER (object);
+
+  switch (prop_id)
+    {
+    case PROP_TITLE:
+      sysprof_chart_layer_set_title (self, g_value_get_object (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+sysprof_chart_layer_class_init (SysprofChartLayerClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->dispose = sysprof_chart_layer_dispose;
+  object_class->get_property = sysprof_chart_layer_get_property;
+  object_class->set_property = sysprof_chart_layer_set_property;
+
+  properties[PROP_TITLE] =
+    g_param_spec_string ("title", NULL, NULL,
+                         NULL,
+                         (G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_STATIC_STRINGS));
+
+  g_object_class_install_properties (object_class, N_PROPS, properties);
+}
+
+static void
+sysprof_chart_layer_init (SysprofChartLayer *self)
+{
+}
+
+const char *
+sysprof_chart_layer_get_title (SysprofChartLayer *self)
+{
+  SysprofChartLayerPrivate *priv = sysprof_chart_layer_get_instance_private (self);
+
+  g_return_val_if_fail (SYSPROF_IS_CHART_LAYER (self), NULL);
+
+  return priv->title;
+}
+
+void
+sysprof_chart_layer_set_title (SysprofChartLayer *self,
+                               const char        *title)
+{
+  SysprofChartLayerPrivate *priv = sysprof_chart_layer_get_instance_private (self);
+
+  g_return_if_fail (SYSPROF_IS_CHART_LAYER (self));
+
+  if (g_set_str (&priv->title, title))
+    g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_TITLE]);
+}