[gimp] app: add configurable nonlinear mapping (gamma) to spinscale widget

[Michael Natterer <mitch src gnome org>]

commit 553b7c7c035f427009a48632847f2a186a1243a0
Author: Ãyvind KolÃs <pippin gimp org>
Date:   Fri Mar 30 21:34:59 2012 +0100

    app: add configurable nonlinear mapping (gamma) to spinscale widget
    
    The default value is 1.0 which is linear and the old behavior, values above
    1.0 gives finer control in the lower portions of the range, the lower half of
    the widget behaves like before doing small relative adjustments.

 app/widgets/gimpspinscale.c |   34 ++++++++++++++++++++++++++++++++--
 app/widgets/gimpspinscale.h |    4 ++++
 2 files changed, 36 insertions(+), 2 deletions(-)
---
diff --git a/app/widgets/gimpspinscale.c b/app/widgets/gimpspinscale.c
index 5c2aded..807b3d1 100644
--- a/app/widgets/gimpspinscale.c
+++ b/app/widgets/gimpspinscale.c
@@ -23,6 +23,7 @@
 #include <gtk/gtk.h>
 
 #include "libgimpwidgets/gimpwidgets.h"
+#include "libgimpmath/gimpmath.h"
 
 #include "widgets-types.h"
 
@@ -54,6 +55,7 @@ struct _GimpSpinScalePrivate
   gboolean     scale_limits_set;
   gdouble      scale_lower;
   gdouble      scale_upper;
+  gdouble      gamma;
 
   PangoLayout *layout;
   gboolean     changing_value;
@@ -459,6 +461,7 @@ gimp_spin_scale_change_value (GtkWidget *widget,
       gdouble fraction;
 
       fraction = x / (gdouble) width;
+      fraction = pow (fraction, private->gamma);
 
       value = fraction * (upper - lower) + lower;
     }
@@ -582,6 +585,7 @@ static void
 gimp_spin_scale_value_changed (GtkSpinButton *spin_button)
 {
   GtkAdjustment *adjustment = gtk_spin_button_get_adjustment (spin_button);
+  GimpSpinScalePrivate *private = GET_PRIVATE (spin_button);
   gdouble        lower;
   gdouble        upper;
   gdouble        value;
@@ -590,8 +594,9 @@ gimp_spin_scale_value_changed (GtkSpinButton *spin_button)
 
   value = CLAMP (gtk_adjustment_get_value (adjustment), lower, upper);
 
+
   gtk_entry_set_progress_fraction (GTK_ENTRY (spin_button),
-                                   (value - lower) / (upper - lower));
+                  pow((value - lower) / (upper - lower), 1.0/private->gamma));
 }
 
 
@@ -632,11 +637,37 @@ gimp_spin_scale_set_scale_limits (GimpSpinScale *scale,
   private->scale_limits_set = TRUE;
   private->scale_lower      = lower;
   private->scale_upper      = upper;
+  private->gamma            = 1.0;
 
   gimp_spin_scale_value_changed (spin_button);
 }
 
 void
+gimp_spin_scale_set_gamma (GimpSpinScale *scale,
+                           gdouble        gamma)
+{
+  GimpSpinScalePrivate *private;
+
+  g_return_if_fail (GIMP_IS_SPIN_SCALE (scale));
+
+  private = GET_PRIVATE (scale);
+
+  private->gamma = gamma;
+}
+
+gdouble
+gimp_spin_scale_get_gamma (GimpSpinScale *scale)
+{
+  GimpSpinScalePrivate *private;
+
+  g_return_if_fail (GIMP_IS_SPIN_SCALE (scale));
+
+  private = GET_PRIVATE (scale);
+
+  return private->gamma;
+}
+
+void
 gimp_spin_scale_unset_scale_limits (GimpSpinScale *scale)
 {
   GimpSpinScalePrivate *private;
@@ -671,4 +702,3 @@ gimp_spin_scale_get_scale_limits (GimpSpinScale *scale,
 
   return private->scale_limits_set;
 }
-
diff --git a/app/widgets/gimpspinscale.h b/app/widgets/gimpspinscale.h
index d896845..2ab3090 100644
--- a/app/widgets/gimpspinscale.h
+++ b/app/widgets/gimpspinscale.h
@@ -58,5 +58,9 @@ gboolean    gimp_spin_scale_get_scale_limits   (GimpSpinScale *scale,
                                                 gdouble       *lower,
                                                 gdouble       *upper);
 
+void        gimp_spin_scale_set_gamma          (GimpSpinScale *scale,
+                                                gdouble        gamma);
+
+gdouble     gimp_spin_scale_get_gamma          (GimpSpinScale *scale);
 
 #endif  /*  __GIMP_SPIN_SCALE_H__  */