[evolution-data-server/gnome-3-38] EBufferTagger: Derive link color from the theme

[Milan Crha <mcrha src gnome org>]

commit 69e8d0d829af1031b2ad379552802e1b1163b5e7
Author: Milan Crha <mcrha redhat com>
Date:   Fri Nov 13 12:15:19 2020 +0100

    EBufferTagger: Derive link color from the theme
    
    There had been used the 'blue' color, which doesn't look correctly
    in dark themes and can be totally wrong for any theme.
    
    Related to https://gitlab.gnome.org/GNOME/gtk/-/issues/3344

 src/libedataserverui/e-buffer-tagger.c | 45 ++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
---
diff --git a/src/libedataserverui/e-buffer-tagger.c b/src/libedataserverui/e-buffer-tagger.c
index c52dc78dd..7110139fb 100644
--- a/src/libedataserverui/e-buffer-tagger.c
+++ b/src/libedataserverui/e-buffer-tagger.c
@@ -467,6 +467,47 @@ update_mouse_cursor (GtkTextView *text_view,
        }
 }
 
+static void
+textview_style_updated_cb (GtkWidget *textview,
+                          gpointer user_data)
+{
+       GtkStyleContext *context;
+       GtkStateFlags state;
+       GtkTextBuffer *buffer;
+       GtkTextTagTable *tag_table;
+       GtkTextTag *tag;
+       GdkRGBA rgba;
+
+       g_return_if_fail (GTK_IS_WIDGET (textview));
+
+       buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (textview));
+       tag_table = gtk_text_buffer_get_tag_table (buffer);
+       tag = gtk_text_tag_table_lookup (tag_table, E_BUFFER_TAGGER_LINK_TAG);
+
+       if (!tag)
+               return;
+
+       context = gtk_widget_get_style_context (textview);
+
+       rgba.red = 0;
+       rgba.green = 0;
+       rgba.blue = 1;
+       rgba.alpha = 1;
+
+       state = gtk_style_context_get_state (context);
+       state = state & (~(GTK_STATE_FLAG_VISITED | GTK_STATE_FLAG_LINK));
+       state = state | GTK_STATE_FLAG_LINK;
+
+       gtk_style_context_save (context);
+       /* Remove the 'view' style, because it can "confuse" some themes */
+       gtk_style_context_remove_class (context, GTK_STYLE_CLASS_VIEW);
+       gtk_style_context_set_state (context, state);
+       gtk_style_context_get_color (context, state, &rgba);
+       gtk_style_context_restore (context);
+
+       g_object_set (G_OBJECT (tag), "foreground-rgba", &rgba, NULL);
+}
+
 static gboolean
 textview_query_tooltip (GtkTextView *text_view,
                         gint x,
@@ -715,6 +756,9 @@ e_buffer_tagger_connect (GtkTextView *textview)
 
        gtk_widget_set_has_tooltip (GTK_WIDGET (textview), TRUE);
 
+       g_signal_connect (
+               textview, "style-updated",
+               G_CALLBACK (textview_style_updated_cb), NULL);
        g_signal_connect (
                textview, "query-tooltip",
                G_CALLBACK (textview_query_tooltip), NULL);
@@ -759,6 +803,7 @@ e_buffer_tagger_disconnect (GtkTextView *textview)
 
        gtk_widget_set_has_tooltip (GTK_WIDGET (textview), FALSE);
 
+       g_signal_handlers_disconnect_by_func (textview, G_CALLBACK (textview_style_updated_cb), NULL);
        g_signal_handlers_disconnect_by_func (textview, G_CALLBACK (textview_query_tooltip), NULL);
        g_signal_handlers_disconnect_by_func (textview, G_CALLBACK (textview_key_press_event), NULL);
        g_signal_handlers_disconnect_by_func (textview, G_CALLBACK (textview_event_after), NULL);