[meld] windowstate: Avoid spurious dconf writes on allocate events (#247)

[Kai Willadsen <kaiw src gnome org>]

commit 01c65285709ab06d66769c4e27a83b4faacfcd87
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Thu Nov 22 06:53:54 2018 +1000

    windowstate: Avoid spurious dconf writes on allocate events (#247)
    
    Currently we write the window state a *lot*, because we constantly get
    spammed with `size-allocate` signals when nothing has changed (e.g.,
    we've scrolled a comparison). The window size is typically unchanged,
    so here we add the simplest possible check before assigning to our
    bound properties. In my testing, this completely eliminates the spurious
    writes.
    
    There's also the dconf part of this where it's constantly re-writing
    values that haven't actually changed; see GNOME/dconf#40 for the
    discussion about that.

 meld/windowstate.py | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)
---
diff --git a/meld/windowstate.py b/meld/windowstate.py
index 09c883c9..e11efbc5 100644
--- a/meld/windowstate.py
+++ b/meld/windowstate.py
@@ -61,10 +61,18 @@ class SavedWindowState(GObject.GObject):
     def on_size_allocate(self, window, allocation):
         if not (self.props.is_maximized or self.props.is_fullscreen):
             width, height = window.get_size()
-            self.props.width = width
-            self.props.height = height
+            if width != self.props.width:
+                self.props.width = width
+            if height != self.props.height:
+                self.props.height = height
 
     def on_window_state_event(self, window, event):
         state = event.window.get_state()
-        self.props.is_maximized = state & Gdk.WindowState.MAXIMIZED
-        self.props.is_fullscreen = state & Gdk.WindowState.FULLSCREEN
+
+        is_maximized = state & Gdk.WindowState.MAXIMIZED
+        if is_maximized != self.props.is_maximized:
+            self.props.is_maximized = is_maximized
+
+        is_fullscreen = state & Gdk.WindowState.FULLSCREEN
+        if is_fullscreen != self.props.is_fullscreen:
+            self.props.is_fullscreen = is_fullscreen