[gtksourceview] view: premix current line background colors

[Christian Hergert <chergert src gnome org>]

commit 96567beb2eb73d1c4ad5b0df779542148e2a3e8c
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jul 20 15:44:54 2021 -0700

    view: premix current line background colors
    
    This will give us a chance at rendering the background without any sort
    of alpha compositing.

 gtksourceview/gtksourceview.c | 68 +++++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 16 deletions(-)
---
diff --git a/gtksourceview/gtksourceview.c b/gtksourceview/gtksourceview.c
index a525223f..617e1035 100644
--- a/gtksourceview/gtksourceview.c
+++ b/gtksourceview/gtksourceview.c
@@ -188,6 +188,7 @@ typedef struct
 
        GdkRGBA background_pattern_color;
        GdkRGBA current_line_color;
+       GdkRGBA current_line_number_color;
        GdkRGBA right_margin_line_color;
        GdkRGBA right_margin_overlay_color;
 
@@ -208,6 +209,7 @@ typedef struct
 
        guint background_pattern_color_set : 1;
        guint current_line_color_set : 1;
+       guint current_line_number_color_set : 1;
        guint right_margin_line_color_set : 1;
        guint right_margin_overlay_color_set : 1;
        guint tabs_set : 1;
@@ -4621,22 +4623,6 @@ update_background_pattern_color (GtkSourceView *view)
                                                                       &priv->background_pattern_color);
 }
 
-static void
-update_current_line_color (GtkSourceView *view)
-{
-       GtkSourceViewPrivate *priv = gtk_source_view_get_instance_private (view);
-
-       if (priv->style_scheme == NULL)
-       {
-               priv->current_line_color_set = FALSE;
-               return;
-       }
-
-       priv->current_line_color_set =
-               _gtk_source_style_scheme_get_current_line_color (priv->style_scheme,
-                                                                &priv->current_line_color);
-}
-
 static inline void
 premix_colors (GdkRGBA       *dest,
                const GdkRGBA *fg,
@@ -4663,6 +4649,56 @@ premix_colors (GdkRGBA       *dest,
        }
 }
 
+static void
+update_current_line_color (GtkSourceView *view)
+{
+       GtkSourceViewPrivate *priv = gtk_source_view_get_instance_private (view);
+
+       if (priv->style_scheme != NULL)
+       {
+               priv->current_line_color_set =
+                       _gtk_source_style_scheme_get_current_line_color (priv->style_scheme,
+                                                                        &priv->current_line_color);
+               priv->current_line_number_color_set =
+                       _gtk_source_style_scheme_get_current_line_number_color (priv->style_scheme,
+                                                                               
&priv->current_line_number_color);
+       }
+
+       /* If we failed to get a highlight-current-line color, then premix the foreground
+        * and the background to give something relatively useful (and avoid alpha-composite
+        * if we can w/ premix).
+        */
+       if (!priv->current_line_color_set)
+       {
+               GtkStyleContext *style_context = gtk_widget_get_style_context (GTK_WIDGET (view));
+               gboolean has_bg = FALSE;
+               GdkRGBA fg, bg;
+
+               if (priv->style_scheme != NULL)
+                       has_bg = _gtk_source_style_scheme_get_background_color (priv->style_scheme, &bg);
+
+               gtk_style_context_get_color (style_context, &fg);
+
+               premix_colors (&priv->current_line_color, &fg, &bg, has_bg, 0.05);
+               priv->current_line_color_set = TRUE;
+       }
+
+       if (!priv->current_line_number_color_set)
+       {
+               GtkStyleContext *style_context = gtk_widget_get_style_context (GTK_WIDGET (view));
+               gboolean has_bg = FALSE;
+               GdkRGBA fg, bg;
+
+               if (priv->style_scheme != NULL)
+                       has_bg = _gtk_source_style_scheme_get_background_color (priv->style_scheme, &bg);
+
+               gtk_style_context_get_color (style_context, &fg);
+
+               premix_colors (&priv->current_line_number_color, &fg, &bg, has_bg, 0.05);
+               priv->current_line_number_color_set = TRUE;
+       }
+}
+
 static void
 update_right_margin_colors (GtkSourceView *view)
 {