[gnome-builder/wip/libide] libide: add rgba utils

[Christian Hergert <chergert src gnome org>]

commit 5c08937df5e5aea8bb698b0569aaee5e8c2a14ee
Author: Christian Hergert <christian hergert me>
Date:   Thu Mar 12 16:19:28 2015 -0700

    libide: add rgba utils

 libide/Makefile.am     |    2 +
 libide/util/ide-rgba.c |  217 ++++++++++++++++++++++++++++++++++++++++++++++++
 libide/util/ide-rgba.h |   32 +++++++
 3 files changed, 251 insertions(+), 0 deletions(-)
---
diff --git a/libide/Makefile.am b/libide/Makefile.am
index 6418999..c26381b 100644
--- a/libide/Makefile.am
+++ b/libide/Makefile.am
@@ -243,6 +243,8 @@ libide_1_0_la_SOURCES = \
        libide/util/ide-cairo.h \
        libide/util/ide-pango.c \
        libide/util/ide-pango.h \
+       libide/util/ide-rgba.c \
+       libide/util/ide-rgba.h \
        $(NULL)
 
 libide_1_0_la_includes = \
diff --git a/libide/util/ide-rgba.c b/libide/util/ide-rgba.c
new file mode 100644
index 0000000..0399cbd
--- /dev/null
+++ b/libide/util/ide-rgba.c
@@ -0,0 +1,217 @@
+/* ide-rgba.c
+ *
+ * Copyright (C) 2014 Christian Hergert <christian hergert me>
+ *
+ * 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/>.
+ */
+
+#include "ide-rgba.h"
+
+/*
+ * The following code is borrowed ultimately upstream through Clearlooks
+ * theme engine in 2.x days. It has been ported to use GdkRGBA. It exists
+ * all over the place, feel free to use this under any license compatible
+ * with upstream.
+ */
+
+/* Clearlooks - a cairo based GTK+ engine
+ * Copyright (C) 2006 Andrew Johnson <acjgenius earthlink net>
+ * Copyright (C) 2007 Benjamin Berg <benjamin sipsolutions net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+
+static void
+rgb_to_hls (gdouble *r,
+            gdouble *g,
+            gdouble *b)
+{
+  gdouble min;
+  gdouble max;
+  gdouble red;
+  gdouble green;
+  gdouble blue;
+  gdouble h, l, s;
+  gdouble delta;
+
+  red = *r;
+  green = *g;
+  blue = *b;
+  if (red > green)
+    {
+      if (red > blue)
+        max = red;
+      else
+        max = blue;
+      if (green < blue)
+        min = green;
+      else
+        min = blue;
+    }
+  else
+    {
+      if (green > blue)
+        max = green;
+      else
+        max = blue;
+      if (red < blue)
+        min = red;
+      else
+        min = blue;
+    }
+  l = (max + min) / 2;
+  s = 0;
+  h = 0;
+  if (max != min)
+    {
+      if (l <= 0.5)
+        s = (max - min) / (max + min);
+      else
+        s = (max - min) / (2 - max - min);
+      delta = max - min;
+      if (red == max)
+        h = (green - blue) / delta;
+      else if (green == max)
+        h = 2 + (blue - red) / delta;
+      else if (blue == max)
+        h = 4 + (red - green) / delta;
+      h *= 60;
+      if (h < 0.0)
+        h += 360;
+    }
+  *r = h;
+  *g = l;
+  *b = s;
+}
+
+static void
+hls_to_rgb (gdouble *h,
+            gdouble *l,
+            gdouble *s)
+{
+  gdouble hue;
+  gdouble lightness;
+  gdouble saturation;
+  gdouble m1, m2;
+  gdouble r, g, b;
+
+  lightness = *l;
+  saturation = *s;
+  if (lightness <= 0.5)
+    m2 = lightness * (1 + saturation);
+  else
+    m2 = lightness + saturation - lightness * saturation;
+  m1 = 2 * lightness - m2;
+  if (saturation == 0)
+    {
+      *h = lightness;
+      *l = lightness;
+      *s = lightness;
+    }
+  else
+    {
+      hue = *h + 120;
+      while (hue > 360)
+        hue -= 360;
+      while (hue < 0)
+        hue += 360;
+      if (hue < 60)
+        r = m1 + (m2 - m1) * hue / 60;
+      else if (hue < 180)
+        r = m2;
+      else if (hue < 240)
+        r = m1 + (m2 - m1) * (240 - hue) / 60;
+      else
+        r = m1;
+      hue = *h;
+      while (hue > 360)
+        hue -= 360;
+      while (hue < 0)
+        hue += 360;
+      if (hue < 60)
+        g = m1 + (m2 - m1) * hue / 60;
+      else if (hue < 180)
+        g = m2;
+      else if (hue < 240)
+        g = m1 + (m2 - m1) * (240 - hue) / 60;
+      else
+        g = m1;
+      hue = *h - 120;
+      while (hue > 360)
+        hue -= 360;
+      while (hue < 0)
+        hue += 360;
+      if (hue < 60)
+        b = m1 + (m2 - m1) * hue / 60;
+      else if (hue < 180)
+        b = m2;
+      else if (hue < 240)
+        b = m1 + (m2 - m1) * (240 - hue) / 60;
+      else
+        b = m1;
+      *h = r;
+      *l = g;
+      *s = b;
+    }
+}
+
+void
+ide_rgba_shade (const GdkRGBA *rgba,
+                GdkRGBA       *dst,
+                gdouble        k)
+{
+  gdouble red;
+  gdouble green;
+  gdouble blue;
+
+  red = rgba->red;
+  green = rgba->green;
+  blue = rgba->blue;
+
+  rgb_to_hls (&red, &green, &blue);
+
+  green *= k;
+
+  if (green > 1.0)
+    green = 1.0;
+  else if (green < 0.0)
+    green = 0.0;
+
+  blue *= k;
+
+  if (blue > 1.0)
+    blue = 1.0;
+  else if (blue < 0.0)
+    blue = 0.0;
+
+  hls_to_rgb (&red, &green, &blue);
+
+  dst->red = red;
+  dst->green = green;
+  dst->blue = blue;
+  dst->alpha = rgba->alpha;
+}
diff --git a/libide/util/ide-rgba.h b/libide/util/ide-rgba.h
new file mode 100644
index 0000000..cacd216
--- /dev/null
+++ b/libide/util/ide-rgba.h
@@ -0,0 +1,32 @@
+/* ide-rgba.h
+ *
+ * Copyright (C) 2014 Christian Hergert <christian hergert me>
+ *
+ * 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 IDE_RGBA_H
+#define IDE_RGBA_H
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+void ide_rgba_shade (const GdkRGBA *rgba,
+                     GdkRGBA       *dst,
+                     gdouble        k);
+
+G_END_DECLS
+
+#endif /* IDE_RGBA_H */