Move function is_color_light to gnc-gtk-utils and rename

Move is_color_light and rename to gnc_is_dark_theme and update required
files where used.

gnucash/gnome-utils/gnc-dense-cal.c

@@ -25,6 +25,7 @@
 #include "gnc-dense-cal.h"
 #include "gnc-dense-cal-model.h"
 #include "gnc-engine.h"
+#include "gnc-gtk-utils.h"
 #include <glib.h>
 #include <glib/gi18n.h>
 #include <gtk/gtk.h>
@@ -923,21 +924,6 @@ gnc_style_context_get_border_color (GtkStyleContext *context,
     gdk_rgba_free (c);
 }
 
-static gboolean
-is_color_light (GdkRGBA *color)
-{
-    gboolean is_light = FALSE;
-
-    // Counting the perceptive luminance - human eye favors green color...
-    double a = (0.299 * color->red + 0.587 * color->green + 0.114 * color->blue);
-
-    if (a > 0.5)
-        is_light = TRUE;
-
-    return is_light;
-}
-
-static void
 gnc_dense_cal_draw_to_buffer(GncDenseCal *dcal)
 {
     GtkWidget *widget;
@@ -980,7 +966,7 @@ gnc_dense_cal_draw_to_buffer(GncDenseCal *dcal)
 
          gtk_style_context_get_color (stylectxt, GTK_STATE_FLAG_NORMAL, &color);
 
-          if (is_color_light (&color))
+          if (gnc_is_dark_theme (&color))
               class_extension = "-dark";
 
           primary_color_class = g_strconcat ("primary", class_extension, NULL);

gnucash/gnome-utils/gnc-gtk-utils.c

@@ -223,3 +223,22 @@ gnc_cbwe_require_list_item (GtkComboBox *cbwe)
 
     g_object_set_data(G_OBJECT(cbwe), CHANGED_ID, GINT_TO_POINTER(id));
 }
+
+/** Test to see if fg_color is a light one which should be a foreground
+ *  one and hence would be on a dark background
+ *
+ *  @param fg_color The foreground color to test.
+ */
+gboolean
+gnc_is_dark_theme (GdkRGBA *fg_color)
+{
+    gboolean is_dark = FALSE;
+
+    // Counting the perceptive luminance - human eye favors green color...
+    double lightness = (0.299 * fg_color->red + 0.587 * fg_color->green + 0.114 * fg_color->blue);
+
+    if (lightness > 0.5)
+        is_dark = TRUE;
+
+    return is_dark;
+}

gnucash/gnome-utils/gnc-gtk-utils.h

@@ -45,6 +45,7 @@ void gnc_cbwe_set_by_string(GtkComboBox *cbwe, const gchar *text);
 void gnc_cbwe_add_completion (GtkComboBox *cbwe);
 void gnc_cbwe_require_list_item (GtkComboBox *cbwe);
 
+gboolean gnc_is_dark_theme (GdkRGBA *fg_color);
 /** @} */
 
 #endif /* GNC_GTK_UTILS_H */

gnucash/import-export/import-main-matcher.c

@@ -43,6 +43,7 @@
 #include "gnc-ui.h"
 #include "gnc-ui-util.h"
 #include "gnc-engine.h"
+#include "gnc-gtk-utils.h"
 #include "import-settings.h"
 #include "import-match-picker.h"
 #include "import-backend.h"
@@ -511,19 +512,7 @@ gnc_gen_trans_init_view (GNCImportMainMatcher *info,
                      G_CALLBACK(gnc_gen_trans_row_changed_cb), info);
 }
 
-static gboolean
-is_color_light (GdkRGBA *color)
-{
-    gboolean is_light = FALSE;
 
-    // Counting the perceptive luminance - human eye favors green color...
-    double a = (0.299 * color->red + 0.587 * color->green + 0.114 * color->blue);
-
-    if (a > 0.5)
-        is_light = TRUE;
-
-    return is_light;
-}
 
 GNCImportMainMatcher *gnc_gen_trans_list_new (GtkWidget *parent,
         const gchar* heading,
@@ -547,7 +536,7 @@ GNCImportMainMatcher *gnc_gen_trans_list_new (GtkWidget *parent,
 
     stylectxt = gtk_widget_get_style_context (GTK_WIDGET(parent));
     gtk_style_context_get_color (stylectxt, GTK_STATE_FLAG_NORMAL, &color);
-    info->dark_theme = is_color_light (&color);
+    info->dark_theme = gnc_is_dark_theme (&color);
 
     /* Initialize the GtkDialog. */
     builder = gtk_builder_new();
@@ -616,7 +605,7 @@ GNCImportMainMatcher * gnc_gen_trans_assist_new (GtkWidget *parent,
 
     stylectxt = gtk_widget_get_style_context (GTK_WIDGET(parent));
     gtk_style_context_get_color (stylectxt, GTK_STATE_FLAG_NORMAL, &color);
-    info->dark_theme = is_color_light (&color);
+    info->dark_theme = gnc_is_dark_theme (&color);
 
     /* load the interface */
     builder = gtk_builder_new();