[meld] ui.findbar: Update styling on failed find (#290)

[Kai Willadsen <kaiw src gnome org>]

commit 70a16af3a9f7e71aa601beb57d73242d7e00b401
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Mar 2 07:58:02 2019 +1000

    ui.findbar: Update styling on failed find (#290)

 data/meld.css      |  6 ------
 meld/ui/findbar.py | 25 ++++++++++++++++++++-----
 2 files changed, 20 insertions(+), 11 deletions(-)
---
diff --git a/data/meld.css b/data/meld.css
index 86d40ec3..ddc0c948 100644
--- a/data/meld.css
+++ b/data/meld.css
@@ -30,9 +30,3 @@ link-map {
     border-style: solid;
     border-color: @borders;
 }
-
-.not-found {
-    color: white;
-    background-image: none;
-    background-color: rgb(237, 54, 54);
-}
diff --git a/meld/ui/findbar.py b/meld/ui/findbar.py
index ed9ad63c..2f0dd1a2 100644
--- a/meld/ui/findbar.py
+++ b/meld/ui/findbar.py
@@ -42,6 +42,9 @@ class FindBar(Gtk.Grid):
         super().__init__()
         self.init_template()
 
+        self.search_context = None
+        self.notify_id = None
+
         self.set_text_view(None)
         self.arrow_left.show()
         self.arrow_right.show()
@@ -67,13 +70,30 @@ class FindBar(Gtk.Grid):
         self.wrap_box.set_visible(False)
         Gtk.Widget.hide(self)
 
+    def update_match_state(self, *args):
+        # Note that -1 here implies that the search is still running
+        no_matches = (
+            self.search_context.props.occurrences_count == 0 and
+            self.search_settings.props.search_text
+        )
+        style_context = self.find_entry.get_style_context()
+        if no_matches:
+            style_context.add_class(Gtk.STYLE_CLASS_ERROR)
+        else:
+            style_context.remove_class(Gtk.STYLE_CLASS_ERROR)
+
     def set_text_view(self, textview):
         self.textview = textview
         if textview is not None:
             self.search_context = GtkSource.SearchContext.new(
                 textview.get_buffer(), self.search_settings)
             self.search_context.set_highlight(True)
+            self.notify_id = self.search_context.connect(
+                'notify::occurrences-count', self.update_match_state)
         else:
+            if self.notify_id:
+                self.search_context.disconnect(self.notify_id)
+                self.notify_id = None
             self.search_context = None
 
     def start_find(self, textview, text=None):
@@ -81,7 +101,6 @@ class FindBar(Gtk.Grid):
         self.replace_label.hide()
         self.replace_entry.hide()
         self.hbuttonbox2.hide()
-        self.find_entry.get_style_context().remove_class("not-found")
         if text:
             self.find_entry.set_text(text)
         self.set_row_spacing(0)
@@ -104,7 +123,6 @@ class FindBar(Gtk.Grid):
 
     def start_replace(self, textview, text=None):
         self.set_text_view(textview)
-        self.find_entry.get_style_context().remove_class("not-found")
         if text:
             self.find_entry.set_text(text)
         self.set_row_spacing(6)
@@ -146,7 +164,6 @@ class FindBar(Gtk.Grid):
 
     @Template.Callback()
     def on_find_entry_changed(self, entry):
-        self.find_entry.get_style_context().remove_class("not-found")
         self._find_text(0)
 
     @Template.Callback()
@@ -175,9 +192,7 @@ class FindBar(Gtk.Grid):
             buf.move_mark(buf.get_selection_bound(), end_iter)
             self.textview.scroll_to_mark(
                 buf.get_insert(), 0.25, True, 0.5, 0.5)
-            self.find_entry.get_style_context().remove_class("not-found")
             return True
         else:
             buf.place_cursor(buf.get_iter_at_mark(buf.get_insert()))
-            self.find_entry.get_style_context().add_class("not-found")
             self.wrap_box.set_visible(False)