libsysprof-gtk: add color iter for graph colors

src/libsysprof-gtk/meson.build

@@ -63,6 +63,7 @@ libsysprof_gtk_public_headers = [
 ]
 
 libsysprof_gtk_private_sources = [
+  'sysprof-color-iter.c',
   'sysprof-css.c',
   'sysprof-mark-chart-item.c',
   'sysprof-mark-chart-row.c',

src/libsysprof-gtk/sysprof-color-iter-private.h

@@ -0,0 +1,37 @@
+/* sysprof-color-iter-private.h
+ *
+ * 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
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+typedef struct _SysprofColorIter
+{
+  GdkRGBA *colors;
+  guint n_colors;
+  guint position;
+} SysprofColorIter;
+
+void           sysprof_color_iter_init (SysprofColorIter *iter);
+const GdkRGBA *sysprof_color_iter_next (SysprofColorIter *iter);
+
+G_END_DECLS

src/libsysprof-gtk/sysprof-color-iter.c

@@ -0,0 +1,70 @@
+/* sysprof-color-iter.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-color-iter-private.h"
+
+static GdkRGBA *colors;
+static guint n_colors;
+
+void
+sysprof_color_iter_init (SysprofColorIter *iter)
+{
+  if (g_once_init_enter (&colors))
+    {
+      static const char *color_strings[] = {
+        "#3584e4",
+        "#ff7800",
+        "#33d17a",
+        "#9141ac",
+        "#e5a50a",
+        "#63452c",
+      };
+      GdkRGBA *_colors;
+
+      n_colors = G_N_ELEMENTS (color_strings);
+      _colors = g_new0 (GdkRGBA, n_colors);
+
+      for (guint i = 0; i < n_colors; i++)
+        gdk_rgba_parse (&_colors[i], color_strings[i]);
+
+      g_once_init_leave (&colors, _colors);
+    }
+
+  iter->colors = colors;
+  iter->n_colors = n_colors;
+  iter->position = 0;
+}
+
+const GdkRGBA *
+sysprof_color_iter_next (SysprofColorIter *iter)
+{
+  const GdkRGBA *ret;
+
+  g_assert (iter->colors != NULL);
+  g_assert (iter->n_colors > 0);
+
+  ret = &iter->colors[iter->position % iter->n_colors];
+
+  iter->position++;
+
+  return ret;
+}