[gimp] app: use CAIRO_OPERATOR_SOURCE in gimp_display_shell_scroll()

[Michael Natterer <mitch src gnome org>]

commit c393eff089fedef284ceb5c236a31c3352cb24d0
Author: Michael Natterer <mitch gimp org>
Date:   Wed Jul 17 00:18:00 2019 +0200

    app: use CAIRO_OPERATOR_SOURCE in gimp_display_shell_scroll()
    
    to copy around the render cache when scrolling.

 app/display/gimpdisplayshell-scroll.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/app/display/gimpdisplayshell-scroll.c b/app/display/gimpdisplayshell-scroll.c
index d120f4c2ab..9ea742a4e4 100644
--- a/app/display/gimpdisplayshell-scroll.c
+++ b/app/display/gimpdisplayshell-scroll.c
@@ -107,11 +107,13 @@ gimp_display_shell_scroll (GimpDisplayShell *shell,
                                                 shell->disp_height);
 
           cr = cairo_create (surface);
+          cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
           cairo_set_source_surface (cr, shell->render_cache, 0, 0);
           cairo_paint (cr);
           cairo_destroy (cr);
 
           cr = cairo_create (shell->render_cache);
+          cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
           cairo_set_source_surface (cr, surface,
                                     -x_offset, -y_offset);
           cairo_paint (cr);