[gtk+/wip/colorchooser-v2: 20/40] Move color scales into separate widget

[Cosimo Cecchi <cosimoc src gnome org>]

commit 115cbda8f5101b5557893e40764a62c783dfe086
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Feb 2 00:58:26 2012 -0500

    Move color scales into separate widget

 gtk/Makefile.am      |    4 +-
 gtk/gtkcoloreditor.c |  241 +++-------------------------------------
 gtk/gtkcolorscale.c  |  297 ++++++++++++++++++++++++++++++++++++++++++++++++++
 gtk/gtkcolorscale.h  |   77 +++++++++++++
 4 files changed, 395 insertions(+), 224 deletions(-)
---
diff --git a/gtk/Makefile.am b/gtk/Makefile.am
index d775582..63e746d 100644
--- a/gtk/Makefile.am
+++ b/gtk/Makefile.am
@@ -416,6 +416,7 @@ gtk_private_h_sources =		\
 	gtkcolorswatch.h	\
 	gtkcoloreditor.h	\
 	gtkcolorplane.h		\
+	gtkcolorscale.h		\
 	gtkcolorchooserprivate.h	\
 	gtkcontainerprivate.h   \
 	gtkcsscomputedvaluesprivate.h \
@@ -600,7 +601,8 @@ gtk_base_c_sources = 		\
 	gtkcolorsel.c		\
 	gtkcolorseldialog.c	\
 	gtkcoloreditor.c	\
-	gtkcolorplane.c	\
+	gtkcolorplane.c		\
+	gtkcolorscale.c		\
 	gtkcolorswatch.c	\
 	gtkcolorchooser.c	\
 	gtkcolorchooserwidget.c	\
diff --git a/gtk/gtkcoloreditor.c b/gtk/gtkcoloreditor.c
index 99168b5..dcf1a40 100644
--- a/gtk/gtkcoloreditor.c
+++ b/gtk/gtkcoloreditor.c
@@ -18,7 +18,6 @@
  */
 
 /* TODO
- * - move out custom sliders
  * - pop-up entries
  */
 
@@ -27,9 +26,10 @@
 #include "gtkcolorchooserprivate.h"
 #include "gtkcoloreditor.h"
 #include "gtkcolorplane.h"
+#include "gtkcolorscale.h"
 #include "gtkcolorswatch.h"
 #include "gtkgrid.h"
-#include "gtkscale.h"
+#include "gtkorientable.h"
 #include "gtkaspectframe.h"
 #include "gtkdrawingarea.h"
 #include "gtkentry.h"
@@ -50,8 +50,6 @@ struct _GtkColorEditorPrivate
 
   GtkAdjustment *h_adj;
   GtkAdjustment *a_adj;
-  cairo_surface_t *h_surface;
-  cairo_surface_t *a_surface;
 
   GdkRGBA color;
   gdouble h, s, v;
@@ -146,12 +144,7 @@ h_changed (GtkAdjustment  *adj,
   gtk_color_plane_set_h (GTK_COLOR_PLANE (editor->priv->sv_plane), editor->priv->h);
   update_entry (editor);
   gtk_color_swatch_set_color (GTK_COLOR_SWATCH (editor->priv->swatch), &editor->priv->color);
-  gtk_widget_queue_draw (editor->priv->a_slider);
-  if (editor->priv->a_surface)
-    {
-      cairo_surface_destroy (editor->priv->a_surface);
-      editor->priv->a_surface = NULL;
-    }
+  gtk_color_scale_set_color (GTK_COLOR_SCALE (editor->priv->a_slider), &editor->priv->color);
   g_object_notify (G_OBJECT (editor), "color");
 }
 
@@ -167,12 +160,7 @@ sv_changed (GtkColorPlane  *plane,
                   &editor->priv->color.blue);
   update_entry (editor);
   gtk_color_swatch_set_color (GTK_COLOR_SWATCH (editor->priv->swatch), &editor->priv->color);
-  gtk_widget_queue_draw (editor->priv->a_slider);
-  if (editor->priv->a_surface)
-    {
-      cairo_surface_destroy (editor->priv->a_surface);
-      editor->priv->a_surface = NULL;
-    }
+  gtk_color_scale_set_color (GTK_COLOR_SCALE (editor->priv->a_slider), &editor->priv->color);
   g_object_notify (G_OBJECT (editor), "color");
 }
 
@@ -185,193 +173,11 @@ a_changed (GtkAdjustment  *adj,
   g_object_notify (G_OBJECT (editor), "color");
 }
 
-static cairo_pattern_t *
-get_checkered_pattern (void)
-{
-  /* need to respect pixman's stride being a multiple of 4 */
-  static unsigned char data[8] = { 0xFF, 0x00, 0x00, 0x00,
-                                   0x00, 0xFF, 0x00, 0x00 };
-  static cairo_surface_t *checkered = NULL;
-  cairo_pattern_t *pattern;
-
-  if (checkered == NULL)
-    checkered = cairo_image_surface_create_for_data (data,
-                                                     CAIRO_FORMAT_A8,
-                                                     2, 2, 4);
-
-  pattern = cairo_pattern_create_for_surface (checkered);
-  cairo_pattern_set_extend (pattern, CAIRO_EXTEND_REPEAT);
-  cairo_pattern_set_filter (pattern, CAIRO_FILTER_NEAREST);
-
-  return pattern;
-}
-
-static cairo_surface_t *
-create_h_surface (GtkWidget *widget)
-{
-  cairo_t *cr;
-  cairo_surface_t *surface;
-  gint width, height, stride;
-  cairo_surface_t *tmp;
-  guint red, green, blue;
-  guint32 *data, *p;
-  gdouble h;
-  gdouble r, g, b;
-  gdouble f;
-  gint x, y;
-
-  if (!gtk_widget_get_realized (widget))
-    return NULL;
-
-  width = gtk_widget_get_allocated_width (widget);
-  height = gtk_widget_get_allocated_height (widget);
-
-  surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
-                                               CAIRO_CONTENT_COLOR,
-                                               width, height);
-
-  if (width == 1 || height == 1)
-    return surface;
-
-  stride = cairo_format_stride_for_width (CAIRO_FORMAT_RGB24, width);
-
-  data = g_malloc (height * stride);
-
-  f = 1.0 / (height - 1);
-  for (y = 0; y < height; y++)
-    {
-      h = CLAMP (y * f, 0.0, 1.0);
-      p = data + y * (stride / 4);
-      for (x = 0; x < width; x++)
-        {
-          gtk_hsv_to_rgb (h, 1, 1, &r, &g, &b);
-          red = CLAMP (r * 255, 0, 255);
-          green = CLAMP (g * 255, 0, 255);
-          blue = CLAMP (b * 255, 0, 255);
-          p[x] = (red << 16) | (green << 8) | blue;
-        }
-    }
-
-  tmp = cairo_image_surface_create_for_data ((guchar *)data, CAIRO_FORMAT_RGB24,
-                                             width, height, stride);
-  cr = cairo_create (surface);
-
-  cairo_set_source_surface (cr, tmp, 0, 0);
-  cairo_paint (cr);
-
-  cairo_destroy (cr);
-  cairo_surface_destroy (tmp);
-  g_free (data);
-
-  return surface;
-}
-
-static gboolean
-h_draw (GtkWidget *widget,
-        cairo_t   *cr,
-        GtkColorEditor *editor)
-{
-  cairo_surface_t *surface;
-  gint width, height;
-
-  width = gtk_widget_get_allocated_width (widget);
-  height = gtk_widget_get_allocated_height (widget);
-
-  if (!editor->priv->h_surface)
-    editor->priv->h_surface = create_h_surface (widget);
-  surface = editor->priv->h_surface;
-
-  cairo_save (cr);
-
-  cairo_rectangle (cr, 1, 1, width - 2, height - 2);
-  cairo_clip (cr);
-  cairo_set_source_surface (cr, surface, 0, 0);
-  cairo_paint (cr);
-
-  cairo_restore (cr);
-
-  return FALSE;
-}
-
-static cairo_surface_t *
-create_a_surface (GtkWidget *widget,
-                  GdkRGBA   *color)
-{
-  cairo_t *cr;
-  cairo_surface_t *surface;
-  cairo_pattern_t *pattern;
-  cairo_matrix_t matrix;
-  gint width, height;
-
-  if (!gtk_widget_get_realized (widget))
-    return NULL;
-
-  width = gtk_widget_get_allocated_width (widget);
-  height = gtk_widget_get_allocated_height (widget);
-
-  surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
-                                               CAIRO_CONTENT_COLOR,
-                                               width, height);
-
-  if (width == 1 || height == 1)
-    return surface;
-
-  cr = cairo_create (surface);
-
-  cairo_set_source_rgb (cr, 0.33, 0.33, 0.33);
-  cairo_paint (cr);
-  cairo_set_source_rgb (cr, 0.66, 0.66, 0.66);
-
-  pattern = get_checkered_pattern ();
-  cairo_matrix_init_scale (&matrix, 0.125, 0.125);
-  cairo_pattern_set_matrix (pattern, &matrix);
-  cairo_mask (cr, pattern);
-  cairo_pattern_destroy (pattern);
-
-  pattern = cairo_pattern_create_linear (0, 0, width, 0);
-  cairo_pattern_add_color_stop_rgba (pattern, 0, color->red, color->green, color->blue, 0);
-  cairo_pattern_add_color_stop_rgba (pattern, width, color->red, color->green, color->blue, 1);
-  cairo_set_source (cr, pattern);
-  cairo_paint (cr);
-  cairo_pattern_destroy (pattern);
-
-  cairo_destroy (cr);
-
-  return surface;
-}
-
-static gboolean
-a_draw (GtkWidget *widget,
-        cairo_t   *cr,
-        GtkColorEditor *editor)
-{
-  cairo_surface_t *surface;
-  gint width, height;
-
-  width = gtk_widget_get_allocated_width (widget);
-  height = gtk_widget_get_allocated_height (widget);
-
-  if (!editor->priv->a_surface)
-    editor->priv->a_surface = create_a_surface (widget, &editor->priv->color);
-  surface = editor->priv->a_surface;
-
-  cairo_save (cr);
-
-  cairo_rectangle (cr, 1, 1, width - 2, height - 2);
-  cairo_clip (cr);
-  cairo_set_source_surface (cr, surface, 0, 0);
-  cairo_paint (cr);
-
-  cairo_restore (cr);
-
-  return FALSE;
-}
-
 static void
 gtk_color_editor_init (GtkColorEditor *editor)
 {
   GtkWidget *grid;
-  GtkAdjustment *adj;
+  GtkWidget *slider;
 
   editor->priv = G_TYPE_INSTANCE_GET_PRIVATE (editor,
                                               GTK_TYPE_COLOR_EDITOR,
@@ -396,13 +202,13 @@ gtk_color_editor_init (GtkColorEditor *editor)
   g_signal_connect (editor->priv->entry, "focus-out-event",
                     G_CALLBACK (entry_focus_out), editor);
 
-  adj = gtk_adjustment_new (0, 0, 1, 0.01, 0.1, 0);
-  g_signal_connect (adj, "value-changed", G_CALLBACK (h_changed), editor);
-  editor->priv->h_slider = gtk_scale_new (GTK_ORIENTATION_VERTICAL, adj);
-  editor->priv->h_adj = adj;
-  g_signal_connect (editor->priv->h_slider, "draw", G_CALLBACK (h_draw), editor);
+  editor->priv->h_slider = slider = gtk_color_scale_new ();
+  gtk_orientable_set_orientation (GTK_ORIENTABLE (slider), GTK_ORIENTATION_VERTICAL);
+  gtk_color_scale_set_type (GTK_COLOR_SCALE (slider), GTK_COLOR_SCALE_HUE);
+  gtk_style_context_add_class (gtk_widget_get_style_context (slider), GTK_STYLE_CLASS_SCALE_HAS_MARKS_BELOW);
+  editor->priv->h_adj = gtk_range_get_adjustment (GTK_RANGE (slider));
+  g_signal_connect (editor->priv->h_adj, "value-changed", G_CALLBACK (h_changed), editor);
 
-  gtk_scale_set_draw_value (GTK_SCALE (editor->priv->h_slider), FALSE);
   editor->priv->sv_plane = gtk_color_plane_new ();
   gtk_widget_set_size_request (editor->priv->sv_plane, 300, 300);
   gtk_widget_set_hexpand (editor->priv->sv_plane, TRUE);
@@ -410,12 +216,12 @@ gtk_color_editor_init (GtkColorEditor *editor)
 
   g_signal_connect (editor->priv->sv_plane, "changed", G_CALLBACK (sv_changed), editor);
 
-  adj = gtk_adjustment_new (1, 0, 1, 0.01, 0.1, 0);
-  editor->priv->a_slider = gtk_scale_new (GTK_ORIENTATION_HORIZONTAL, adj);
-  g_signal_connect (adj, "value-changed", G_CALLBACK (a_changed), editor);
-  gtk_scale_set_draw_value (GTK_SCALE (editor->priv->a_slider), FALSE);
-  editor->priv->a_adj = adj;
-  g_signal_connect (editor->priv->a_slider, "draw", G_CALLBACK (a_draw), editor);
+  editor->priv->a_slider = slider = gtk_color_scale_new ();
+  gtk_orientable_set_orientation (GTK_ORIENTABLE (slider), GTK_ORIENTATION_HORIZONTAL);
+  gtk_color_scale_set_type (GTK_COLOR_SCALE (slider), GTK_COLOR_SCALE_ALPHA);
+  gtk_style_context_add_class (gtk_widget_get_style_context (slider), GTK_STYLE_CLASS_SCALE_HAS_MARKS_ABOVE);
+  editor->priv->a_adj = gtk_range_get_adjustment (GTK_RANGE (slider));
+  g_signal_connect (editor->priv->a_adj, "value-changed", G_CALLBACK (a_changed), editor);
 
   gtk_grid_attach (GTK_GRID (grid), editor->priv->swatch,   1, 0, 1, 1);
   gtk_grid_attach (GTK_GRID (grid), editor->priv->entry,    2, 0, 1, 1);
@@ -495,13 +301,6 @@ gtk_color_editor_set_property (GObject      *object,
 static void
 gtk_color_editor_finalize (GObject *object)
 {
-  GtkColorEditor *editor = GTK_COLOR_EDITOR (object);
-
-  if (editor->priv->h_surface)
-    cairo_surface_destroy (editor->priv->h_surface);
-  if (editor->priv->a_surface)
-    cairo_surface_destroy (editor->priv->a_surface);
-
   G_OBJECT_CLASS (gtk_color_editor_parent_class)->finalize (object);
 }
 
@@ -554,13 +353,9 @@ gtk_color_editor_set_color (GtkColorChooser *chooser,
 
   gtk_adjustment_set_value (editor->priv->h_adj, h);
   gtk_adjustment_set_value (editor->priv->a_adj, color->alpha);
+  gtk_color_scale_set_color (GTK_COLOR_SCALE (editor->priv->a_slider), &editor->priv->color);
   update_entry (editor);
 
-  if (editor->priv->a_surface)
-    {
-      cairo_surface_destroy (editor->priv->a_surface);
-      editor->priv->a_surface = NULL;
-    }
   gtk_widget_queue_draw (GTK_WIDGET (editor));
 
   g_object_notify (G_OBJECT (editor), "color");
diff --git a/gtk/gtkcolorscale.c b/gtk/gtkcolorscale.c
new file mode 100644
index 0000000..50c33f8
--- /dev/null
+++ b/gtk/gtkcolorscale.c
@@ -0,0 +1,297 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * 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 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "gtkcolorscale.h"
+#include "gtkhsv.h"
+#include "gtkstylecontext.h"
+#include "gtkintl.h"
+
+struct _GtkColorScalePrivate
+{
+  cairo_surface_t *surface;
+  gint width, height;
+  GdkRGBA color;
+  GtkColorScaleType type;
+};
+
+G_DEFINE_TYPE (GtkColorScale, gtk_color_scale, GTK_TYPE_SCALE)
+
+static cairo_pattern_t *
+get_checkered_pattern (void)
+{
+  /* need to respect pixman's stride being a multiple of 4 */
+  static unsigned char data[8] = { 0xFF, 0x00, 0x00, 0x00,
+                                   0x00, 0xFF, 0x00, 0x00 };
+  static cairo_surface_t *checkered = NULL;
+  cairo_pattern_t *pattern;
+
+  if (checkered == NULL)
+    checkered = cairo_image_surface_create_for_data (data,
+                                                     CAIRO_FORMAT_A8,
+                                                     2, 2, 4);
+
+  pattern = cairo_pattern_create_for_surface (checkered);
+  cairo_pattern_set_extend (pattern, CAIRO_EXTEND_REPEAT);
+  cairo_pattern_set_filter (pattern, CAIRO_FILTER_NEAREST);
+
+  return pattern;
+}
+
+static void
+create_h_surface (GtkColorScale *scale)
+{
+  GtkWidget *widget = GTK_WIDGET (scale);
+  cairo_t *cr;
+  cairo_surface_t *surface;
+  gint width, height, stride;
+  cairo_surface_t *tmp;
+  guint red, green, blue;
+  guint32 *data, *p;
+  gdouble h;
+  gdouble r, g, b;
+  gdouble f;
+  gint x, y;
+
+  if (!gtk_widget_get_realized (widget))
+    return;
+
+  width = gtk_widget_get_allocated_width (widget);
+  height = gtk_widget_get_allocated_height (widget);
+
+  if (width != scale->priv->width ||
+      height != scale->priv->height)
+    {
+      surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
+                                                   CAIRO_CONTENT_COLOR,
+                                                   width, height);
+      if (scale->priv->surface)
+        cairo_surface_destroy (scale->priv->surface);
+      scale->priv->surface = surface;
+      scale->priv->width = width;
+      scale->priv->height= height;
+    }
+  else
+    surface = scale->priv->surface;
+
+  if (width == 1 || height == 1)
+    return;
+
+  stride = cairo_format_stride_for_width (CAIRO_FORMAT_RGB24, width);
+
+  data = g_malloc (height * stride);
+
+  f = 1.0 / (height - 1);
+  for (y = 0; y < height; y++)
+    {
+      h = CLAMP (y * f, 0.0, 1.0);
+      p = data + y * (stride / 4);
+      for (x = 0; x < width; x++)
+        {
+          gtk_hsv_to_rgb (h, 1, 1, &r, &g, &b);
+          red = CLAMP (r * 255, 0, 255);
+          green = CLAMP (g * 255, 0, 255);
+          blue = CLAMP (b * 255, 0, 255);
+          p[x] = (red << 16) | (green << 8) | blue;
+        }
+    }
+
+  tmp = cairo_image_surface_create_for_data ((guchar *)data, CAIRO_FORMAT_RGB24,
+                                             width, height, stride);
+  cr = cairo_create (surface);
+
+  cairo_set_source_surface (cr, tmp, 0, 0);
+  cairo_paint (cr);
+
+  cairo_destroy (cr);
+  cairo_surface_destroy (tmp);
+  g_free (data);
+}
+
+static void
+create_a_surface (GtkColorScale *scale)
+{
+  GtkWidget *widget = GTK_WIDGET (scale);
+  cairo_t *cr;
+  cairo_surface_t *surface;
+  cairo_pattern_t *pattern;
+  cairo_matrix_t matrix;
+  GdkRGBA *color;
+  gint width, height;
+
+  if (!gtk_widget_get_realized (widget))
+    return;
+
+  width = gtk_widget_get_allocated_width (widget);
+  height = gtk_widget_get_allocated_height (widget);
+
+  if (!scale->priv->surface ||
+      width != scale->priv->width ||
+      height != scale->priv->height)
+    {
+      surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
+                                                   CAIRO_CONTENT_COLOR,
+                                                   width, height);
+      if (scale->priv->surface)
+        cairo_surface_destroy (scale->priv->surface);
+      scale->priv->surface = surface;
+      scale->priv->width = width;
+      scale->priv->height = height;
+    }
+  else
+    return;
+
+  if (width == 1 || height == 1)
+    return;
+
+  cr = cairo_create (surface);
+
+  cairo_set_source_rgb (cr, 0.33, 0.33, 0.33);
+  cairo_paint (cr);
+  cairo_set_source_rgb (cr, 0.66, 0.66, 0.66);
+
+  pattern = get_checkered_pattern ();
+  cairo_matrix_init_scale (&matrix, 0.125, 0.125);
+  cairo_pattern_set_matrix (pattern, &matrix);
+  cairo_mask (cr, pattern);
+  cairo_pattern_destroy (pattern);
+
+  color = &scale->priv->color;
+
+  pattern = cairo_pattern_create_linear (0, 0, width, 0);
+  cairo_pattern_add_color_stop_rgba (pattern, 0, color->red, color->green, color->blue, 0);
+  cairo_pattern_add_color_stop_rgba (pattern, width, color->red, color->green, color->blue, 1);
+  cairo_set_source (cr, pattern);
+  cairo_paint (cr);
+  cairo_pattern_destroy (pattern);
+
+  cairo_destroy (cr);
+}
+
+static void
+create_surface (GtkColorScale *scale)
+{
+  switch (scale->priv->type)
+    {
+    case GTK_COLOR_SCALE_HUE:
+      create_h_surface (scale);
+      break;
+    case GTK_COLOR_SCALE_ALPHA:
+      create_a_surface (scale);
+      break;
+    }
+}
+
+static gboolean
+scale_draw (GtkWidget *widget,
+            cairo_t   *cr)
+{
+  GtkColorScale *scale = GTK_COLOR_SCALE (widget);
+  gint width, height;
+
+  width = gtk_widget_get_allocated_width (widget);
+  height = gtk_widget_get_allocated_height (widget);
+
+  create_surface (scale);
+
+  cairo_save (cr);
+
+  cairo_rectangle (cr, 1, 1, width - 2, height - 2);
+  cairo_clip (cr);
+  cairo_set_source_surface (cr, scale->priv->surface, 0, 0);
+  cairo_paint (cr);
+
+  cairo_restore (cr);
+
+  GTK_WIDGET_CLASS (gtk_color_scale_parent_class)->draw (widget, cr);
+
+  return FALSE;
+}
+
+static void
+gtk_color_scale_init (GtkColorScale *scale)
+{
+  scale->priv = G_TYPE_INSTANCE_GET_PRIVATE (scale,
+                                             GTK_TYPE_COLOR_SCALE,
+                                             GtkColorScalePrivate);
+
+  scale->priv->type = GTK_COLOR_SCALE_HUE;
+}
+
+static void
+scale_finalize (GObject *object)
+{
+  GtkColorScale *scale = GTK_COLOR_SCALE (object);
+
+  if (scale->priv->surface)
+    cairo_surface_destroy (scale->priv->surface);
+
+  G_OBJECT_CLASS (gtk_color_scale_parent_class)->finalize (object);
+}
+
+static void
+gtk_color_scale_class_init (GtkColorScaleClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  object_class->finalize = scale_finalize;
+
+  widget_class->draw = scale_draw;
+
+  g_type_class_add_private (class, sizeof (GtkColorScalePrivate));
+}
+
+void
+gtk_color_scale_set_color (GtkColorScale *scale,
+                           const GdkRGBA *color)
+{
+  scale->priv->color.red = color->red;
+  scale->priv->color.green = color->green;
+  scale->priv->color.blue = color->blue;
+  scale->priv->color.alpha = color->alpha;
+  if (scale->priv->surface)
+    {
+      cairo_surface_destroy (scale->priv->surface);
+      scale->priv->surface = NULL;
+    }
+  create_surface (scale);
+  gtk_widget_queue_draw (GTK_WIDGET (scale));
+}
+
+void
+gtk_color_scale_set_type (GtkColorScale     *scale,
+                          GtkColorScaleType  type)
+{
+  scale->priv->type = type;
+  cairo_surface_destroy (scale->priv->surface);
+  scale->priv->surface = NULL;
+  create_surface (scale);
+  gtk_widget_queue_draw (GTK_WIDGET (scale));
+}
+
+GtkWidget *
+gtk_color_scale_new (void)
+{
+  return (GtkWidget *) g_object_new (GTK_TYPE_COLOR_SCALE,
+                                     "adjustment", gtk_adjustment_new (0, 0, 1, 0.01, 0.1, 0),
+                                     "draw-value", FALSE,
+                                     NULL);
+}
diff --git a/gtk/gtkcolorscale.h b/gtk/gtkcolorscale.h
new file mode 100644
index 0000000..385706a
--- /dev/null
+++ b/gtk/gtkcolorscale.h
@@ -0,0 +1,77 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * 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 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#ifndef __GTK_COLOR_SCALE_H__
+#define __GTK_COLOR_SCALE_H__
+
+#include <gtk/gtkscale.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_COLOR_SCALE            (gtk_color_scale_get_type ())
+#define GTK_COLOR_SCALE(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), GTK_TYPE_COLOR_SCALE, GtkColorScale))
+#define GTK_COLOR_SCALE_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass), GTK_TYPE_COLOR_SCALE, GtkColorScaleClass))
+#define GTK_IS_COLOR_SCALE(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GTK_TYPE_COLOR_SCALE))
+#define GTK_IS_COLOR_SCALE_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GTK_TYPE_COLOR_SCALE))
+#define GTK_COLOR_SCALE_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj), GTK_TYPE_COLOR_SCALE, GtkColorScaleClass))
+
+
+typedef struct _GtkColorScale         GtkColorScale;
+typedef struct _GtkColorScaleClass    GtkColorScaleClass;
+typedef struct _GtkColorScalePrivate  GtkColorScalePrivate;
+
+struct _GtkColorScale
+{
+  GtkScale parent_instance;
+
+  GtkColorScalePrivate *priv;
+};
+
+struct _GtkColorScaleClass
+{
+  GtkScaleClass parent_class;
+
+  /* Padding for future expansion */
+  void (*_gtk_reserved1) (void);
+  void (*_gtk_reserved2) (void);
+  void (*_gtk_reserved3) (void);
+  void (*_gtk_reserved4) (void);
+};
+
+typedef enum
+{
+  GTK_COLOR_SCALE_HUE,
+  GTK_COLOR_SCALE_ALPHA
+} GtkColorScaleType;
+
+GType       gtk_color_scale_get_type  (void) G_GNUC_CONST;
+
+GtkWidget * gtk_color_scale_new       (void);
+void        gtk_color_scale_set_type  (GtkColorScale     *scale,
+                                       GtkColorScaleType  type);
+void        gtk_color_scale_set_color (GtkColorScale     *scale,
+                                       const GdkRGBA     *color);
+
+G_END_DECLS
+
+#endif /* __GTK_COLOR_SCALE_H__ */