[epiphany/mcatanzaro/#960] web-view: fix white flash when opening tabs in dark mode

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 87f2a382c020fc3a069a506e51ffb3fcaad05f06
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Thu Jan 30 04:46:03 2020 -0600

    web-view: fix white flash when opening tabs in dark mode
    
    It's OK to use a custom background color when opening new tabs, but we
    have to be careful to reset it back to white when loading anything
    that's not an internal Epiphany webpage.
    
    Fixes #960

 embed/ephy-web-view.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
---
diff --git a/embed/ephy-web-view.c b/embed/ephy-web-view.c
index a81a1711e..841baab17 100644
--- a/embed/ephy-web-view.c
+++ b/embed/ephy-web-view.c
@@ -1359,6 +1359,15 @@ update_ucm_ads_state (WebKitWebView *web_view,
   ephy_filters_manager_set_ucm_forbids_ads (ephy_embed_shell_get_filters_manager (shell), ucm, enable);
 }
 
+static void
+reset_background_color (WebKitWebView *web_view)
+{
+  GdkRGBA white = { 1.0, 1.0, 1.0, 1.0 };
+
+  /* https://bugs.webkit.org/show_bug.cgi?id=206953#c2 */
+  webkit_web_view_set_background_color (web_view, &white);
+}
+
 static void
 load_changed_cb (WebKitWebView   *web_view,
                  WebKitLoadEvent  load_event,
@@ -1447,6 +1456,12 @@ load_changed_cb (WebKitWebView   *web_view,
       if (!view->reader_active)
         g_clear_pointer (&view->reader_content, g_free);
 
+      /* We have to reset the background color here because we set a
+       * nonwhite background in constructed.
+       */
+      if (!g_str_has_prefix (uri, EPHY_ABOUT_SCHEME))
+        reset_background_color (web_view);
+
       break;
     }
     case WEBKIT_LOAD_FINISHED:
@@ -3488,6 +3503,8 @@ static void
 ephy_web_view_constructed (GObject *object)
 {
   EphyWebView *web_view = EPHY_WEB_VIEW (object);
+  GtkStyleContext *context;
+  GdkRGBA color;
 
   G_OBJECT_CLASS (ephy_web_view_parent_class)->constructed (object);
 
@@ -3497,6 +3514,14 @@ ephy_web_view_constructed (GObject *object)
                     G_CALLBACK (process_terminated_cb), NULL);
   g_signal_connect_swapped (webkit_web_view_get_back_forward_list (WEBKIT_WEB_VIEW (web_view)),
                             "changed", G_CALLBACK (update_navigation_flags), web_view);
+
+  /* Avoid flashing a white background when loading the overview in
+   * dark mode. Note that we have to later reset this to white before
+   * loading any non-Epiphany page.
+   */
+  context = gtk_widget_get_style_context (GTK_WIDGET (web_view));
+  if (gtk_style_context_lookup_color (context, "theme_base_color", &color))
+    webkit_web_view_set_background_color (WEBKIT_WEB_VIEW (web_view), &color);
 }
 
 static void