color-cycle: add color generator helper

We need a simple helper to choose colors for visualizers so
they do not overlap. This is just a simple cycle using some
predefined colors.

We should come up with something more unique in the future or
possibly do this with CSS and :nth-child(n) once we have access
to CSS nodes.

lib/Makefile.am

@@ -159,6 +159,8 @@ libsysprof_ui_@API_VERSION@_la_SOURCES = \
 	$(uiheaders_DATA) \
 	sp-callgraph-view.c \
 	sp-cell-renderer-percent.c \
+	sp-color-cycle.c \
+	sp-color-cycle.h \
 	sp-cpu-visualizer-row.c \
 	sp-empty-state-view.c \
 	sp-failed-state-view.c \

lib/sp-color-cycle.c

@@ -0,0 +1,122 @@
+/* sp-color-cycle.c
+ *
+ * Copyright (C) 2016 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/>.
+ */
+
+#define G_LOG_DOMAIN "sp-color-cycle"
+
+#include "sp-color-cycle.h"
+
+G_DEFINE_BOXED_TYPE (SpColorCycle, sp_color_cycle, sp_color_cycle_ref, sp_color_cycle_unref)
+
+static const gchar *default_colors[] = {
+  "#73d216",
+  "#f57900",
+  "#3465a4",
+  "#ef2929",
+  "#75507b",
+  "#ce5c00",
+  "#c17d11",
+  "#cc0000",
+  "#edd400",
+  "#555753",
+  "#4e9a06",
+  "#204a87",
+  "#5c3566",
+  "#a40000",
+  "#c4a000",
+  "#8f5902",
+  "#2e3436",
+  "#8ae234",
+  "#729fcf",
+  "#ad7fa8",
+  "#fce94f",
+  "#fcaf3e",
+  "#e9b96e",
+  "#888a85",
+  NULL
+};
+
+struct _SpColorCycle
+{
+  volatile gint ref_count;
+  GdkRGBA *colors;
+  gsize n_colors;
+  guint position;
+};
+
+static void
+sp_color_cycle_destroy (SpColorCycle *self)
+{
+  g_free (self->colors);
+  g_slice_free (SpColorCycle, self);
+}
+
+SpColorCycle *
+sp_color_cycle_new (void)
+{
+  SpColorCycle *self;
+
+  self = g_slice_new0 (SpColorCycle);
+  self->ref_count = 1;
+  self->n_colors = g_strv_length ((gchar **)default_colors);
+  self->colors = g_new0 (GdkRGBA, self->n_colors);
+
+  for (guint i = 0; default_colors[i]; i++)
+    {
+      if G_UNLIKELY (!gdk_rgba_parse (&self->colors[i], default_colors[i]))
+        g_warning ("Failed to parse color %s into an RGBA", default_colors[i]);
+    }
+
+  return self;
+}
+
+SpColorCycle *
+sp_color_cycle_ref (SpColorCycle *self)
+{
+  g_return_val_if_fail (self != NULL, NULL);
+  g_return_val_if_fail (self->ref_count > 0, NULL);
+  g_atomic_int_inc (&self->ref_count);
+  return self;
+}
+
+void
+sp_color_cycle_unref (SpColorCycle *self)
+{
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (self->ref_count > 0);
+  if (g_atomic_int_dec_and_test (&self->ref_count))
+    sp_color_cycle_destroy (self);
+}
+
+void
+sp_color_cycle_next (SpColorCycle *self,
+                     GdkRGBA      *rgba)
+{
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (self->position < self->n_colors);
+
+  *rgba = self->colors[self->position];
+
+  /*
+   * TODO: Adjust color HSV/etc
+   *
+   * We could simply adjust the brightness/etc after we dispatch
+   * a color so that we get darker as we go.
+   */
+
+  self->position = (self->position + 1) % self->n_colors;
+}

lib/sp-color-cycle.h

@@ -0,0 +1,39 @@
+/* sp-color-cycle.h
+ *
+ * Copyright (C) 2016 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/>.
+ */
+
+#ifndef SP_COLOR_CYCLE_H
+#define SP_COLOR_CYCLE_H
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define SP_TYPE_COLOR_CYCLE (sp_color_cycle_get_type())
+
+typedef struct _SpColorCycle SpColorCycle;
+
+GType         sp_color_cycle_get_type (void);
+SpColorCycle *sp_color_cycle_ref      (SpColorCycle *self);
+void          sp_color_cycle_unref    (SpColorCycle *self);
+SpColorCycle *sp_color_cycle_new      (void);
+void          sp_color_cycle_next     (SpColorCycle *self,
+                                       GdkRGBA      *rgba);
+
+G_END_DECLS
+
+#endif /* SP_COLOR_CYCLE_H */