[gnome-sudoku] Display incorrect earmark as red

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 4cca1c55fcf26c319a02a2e681d6143762ea5e84
Author: Andrey Kutejko <andy128k gmail com>
Date:   Sat Aug 22 02:36:49 2020 +0200

    Display incorrect earmark as red

 src/sudoku-view.vala | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/src/sudoku-view.vala b/src/sudoku-view.vala
index 21909c8..df401f0 100644
--- a/src/sudoku-view.vala
+++ b/src/sudoku-view.vala
@@ -387,7 +387,6 @@ private class SudokuCellView : DrawingArea
         {
             double possibility_size = get_allocated_height () / size_ratio / 2;
             c.set_font_size (possibility_size);
-            c.set_source_rgb (0.0, 0.0, 0.0);
 
             double height = (double) get_allocated_height () / game.board.block_rows;
             double width = (double) get_allocated_width () / game.board.block_cols;
@@ -401,6 +400,11 @@ private class SudokuCellView : DrawingArea
 
                     if (marks[num - 1])
                     {
+                        if (_show_warnings && !game.board.is_possible (row, col, num))
+                            c.set_source_rgb (1.0, 0.0, 0.0);
+                        else
+                            c.set_source_rgb (0.0, 0.0, 0.0);
+
                         var text = "%d".printf (num);
 
                         c.save ();