[gnumeric] GUI: Handle having a non-white auto-expression background.

[Morten Welinder <mortenw src gnome org>]

commit 0ecc82456d20ab251b4a7dc9a288611f5227ea09
Author: Morten Welinder <terra gnome org>
Date:   Thu Jan 16 20:20:11 2014 -0500

    GUI: Handle having a non-white auto-expression background.

 ChangeLog     |    6 +++++
 NEWS          |    1 +
 src/wbc-gtk.c |   71 +++++++++++++++++++++++++++++++++++++++++++++------------
 3 files changed, 63 insertions(+), 15 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index ddfea90..0c784fc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2014-01-16  Morten Welinder  <terra gnome org>
+
+       * src/wbc-gtk.c (cb_adjust_foreground_attributes): Renamed from
+       cb_darken_foreground_attributes and change to take non-white
+       background into account.
+
 2014-01-12  Morten Welinder  <terra gnome org>
 
        * src/mathfunc.c (expmx2h): Split out from dnorm.
diff --git a/NEWS b/NEWS
index da03491..69136ad 100644
--- a/NEWS
+++ b/NEWS
@@ -26,6 +26,7 @@ Morten:
        * Improve accuracy of R.QCAUCHY.
        * Improve accuracy of R.DHYPER, R.DBINOM, R.DNBINOM, R.DPOIS,
          RAYLEIGH.
+       * Minor theming improvement.  [#722074]
 
 --------------------------------------------------------------------------
 Gnumeric 1.12.9
diff --git a/src/wbc-gtk.c b/src/wbc-gtk.c
index b78f20b..6c23a18 100644
--- a/src/wbc-gtk.c
+++ b/src/wbc-gtk.c
@@ -1328,18 +1328,49 @@ wbcg_sheet_remove_all (WorkbookControl *wbc)
        }
 }
 
+static double
+color_diff (const GdkRGBA *a, const GdkRGBA *b)
+{
+       /* Ignoring alpha.  */
+       return ((a->red - b->red) * (a->red - b->red) +
+               (a->green - b->green) * (a->green - b->green) +
+               (a->blue - b->blue) * (a->blue - b->blue));
+}
+
+
 static gboolean
-cb_darken_foreground_attributes (PangoAttribute *attribute,
-                                G_GNUC_UNUSED gpointer data)
+cb_adjust_foreground_attributes (PangoAttribute *attribute,
+                                gpointer data)
 {
+       const GdkRGBA *back = data;
+
        if (attribute->klass->type == PANGO_ATTR_FOREGROUND) {
-               PangoAttrColor *cat = (PangoAttrColor *) attribute;
-               guint total = (guint)cat->color.red + (guint)cat->color.green + (guint)cat->color.blue;
-               if (total > 98302) {
-                       float adj = 98302.5/total;
-                       cat->color.red = cat->color.red * adj;
-                       cat->color.green = cat->color.green * adj;
-                       cat->color.blue = cat->color.blue * adj;
+               PangoColor *pfore = &((PangoAttrColor *)attribute)->color;
+               GdkRGBA fore;
+               const double threshold = 0.01;
+
+               fore.red = pfore->red / 65535.0;
+               fore.green = pfore->green / 65535.0;
+               fore.blue = pfore->blue / 65535.0;
+
+               if (color_diff (&fore, back) < threshold) {
+                       static const GdkRGBA black = { 0, 0, 0, 1 };
+                       static const GdkRGBA white = { 1, 1, 1, 1 };
+                       double back_norm = color_diff (back, &black);
+                       double fore_norm = color_diff (back, &black);
+                       double f = 0.2;
+                       const GdkRGBA *ref =
+                               back_norm > 0.75 ? &black : &white;
+
+#define DO_CHANNEL(channel)                                            \
+do {                                                                   \
+       double val = fore.channel * (1 - f) + ref->channel * f;         \
+       pfore->channel = CLAMP (val, 0, 1) * 65535;                     \
+} while (0)                    
+                       DO_CHANNEL(red);
+                       DO_CHANNEL(green);
+                       DO_CHANNEL(blue);
+#undef DO_CHANNEL
                }
        }
        return FALSE;
@@ -1349,13 +1380,22 @@ cb_darken_foreground_attributes (PangoAttribute *attribute,
    colors are to the themed background and push the colors that are
    too close away (along the light axis, presumably).  */
 static void
-darken_foreground_attributes (PangoAttrList *attrs)
+adjust_foreground_attributes (PangoAttrList *attrs, GtkWidget *w)
 {
+       GdkRGBA c;
+       GtkStyleContext *ctxt = gtk_widget_get_style_context (w);
+
+       gtk_style_context_get_background_color (ctxt, GTK_STATE_FLAG_NORMAL,
+                                               &c);
+
+       if (0)
+               g_printerr ("back=%s\n", gdk_rgba_to_string (&c));
+
        pango_attr_list_unref
                (pango_attr_list_filter
                 (attrs,
-                 cb_darken_foreground_attributes,
-                 NULL));
+                 cb_adjust_foreground_attributes,
+                 &c));
 }
 
 
@@ -1397,9 +1437,10 @@ wbcg_auto_expr_value_changed (WorkbookView *wbv,
                                                (attrs, atl, old_len,
                                                 str->len - old_len);
                                        pango_attr_list_unref (atl);
-                                       /* The field background is white so we need to ensure that no */
-                                       /* foreground colour is set to white (or close to white)      */
-                                       darken_foreground_attributes (attrs);
+                                       /* Adjust colours to make text visible. */
+                                       adjust_foreground_attributes
+                                               (attrs,
+                                                gtk_widget_get_parent (GTK_WIDGET (lbl)));
                                }
                                break;
                        }