Fix Tab key causing entire screen to redraw

kitty/keys.py

@@ -3,7 +3,7 @@
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
 
-from PyQt5.QtCore import Qt
+from PyQt5.QtCore import Qt, QObject, QEvent
 
 CTRL_MASK = 0b10011111
 
@@ -20,3 +20,35 @@ def key_event_to_data(ev, mods):
         else:
             data.extend(t)
     return bytes(data)
+
+
+class KeyFilter(QObject):
+
+    def __init__(self, parent=None):
+        QObject.__init__(self, parent)
+        self.disabled = False
+
+    @property
+    def disable_filtering(self):
+        return self
+
+    def __enter__(self):
+        self.disabled = True
+
+    def __exit__(self, *args):
+        self.disabled = False
+
+    def eventFilter(self, watched, event):
+        if self.disabled:
+            return False
+        etype = event.type()
+        if etype == QEvent.KeyPress:
+            # We use a global event filter to prevent Qt from re-painting the
+            # entire terminal widget on a Tab key press
+            app = self.parent()
+            window, fw = app.activeWindow(), app.focusWidget()
+            if hasattr(window, 'boss') and fw is window.boss.term:
+                window.boss.term.keyPressEvent(event)
+                if event.isAccepted():
+                    return True
+        return False

kitty/main.py

@@ -17,6 +17,7 @@ from .config import load_config, validate_font
 from .constants import appname, str_version, config_dir
 from .boss import Boss
 from .utils import fork_child
+from .keys import KeyFilter
 
 
 class MainWindow(QMainWindow):
@@ -105,6 +106,8 @@ def main():
 
     QApplication.setAttribute(Qt.AA_DisableHighDpiScaling, True)
     app = QApplication([appname])
+    keyfilter = KeyFilter(app)
+    app.installEventFilter(keyfilter)
     app.setOrganizationName(args.cls)
     app.setApplicationName(args.name)
     try:
@@ -122,4 +125,6 @@ def main():
         pr.disable()
     else:
         ret = run_app()
-        return ret
+    app.installEventFilter(None)
+    del keyfilter
+    return ret

kitty/term.py

@@ -105,6 +105,7 @@ class TerminalWidget(QWidget):
 
     def update_screen(self, changes):
         self.cursor = changes['cursor'] or self.cursor
+
         if changes['screen']:
             self.pending_update += self.rect()
         else:
@@ -217,3 +218,5 @@ class TerminalWidget(QWidget):
         if data:
             self.send_data_to_child.emit(data)
             ev.accept()
+            return
+        return QWidget.keyPressEvent(self, ev)