Support interactive graphics in python scripts

bindings/pyroot/pythonizations/CMakeLists.txt

@@ -114,6 +114,7 @@ set(py_sources
   ROOT/_pythonization/_tfile.py
   ROOT/_pythonization/_tfilemerger.py
   ROOT/_pythonization/_tformula.py
+  ROOT/_pythonization/_tcanvas.py
   ROOT/_pythonization/_tgraph.py
   ROOT/_pythonization/_tgraph2d.py
   ROOT/_pythonization/_th1.py

bindings/pyroot/pythonizations/python/ROOT/__init__.py

@@ -173,15 +173,3 @@ def find_spec(self, fullname: str, path, target=None) -> ModuleSpec:
         import JupyROOT
         from . import JsMVA
 
-# Register cleanup
-import atexit
-
-
-def cleanup():
-    # If spawned, stop thread which processes ROOT events
-    facade = sys.modules[__name__]
-    if "app" in facade.__dict__ and hasattr(facade.__dict__["app"], "process_root_events"):
-        facade.__dict__["app"].keep_polling = False
-        facade.__dict__["app"].process_root_events.join()
-
-atexit.register(cleanup)

bindings/pyroot/pythonizations/python/ROOT/_application.py

@@ -78,28 +78,18 @@ def init_graphics(self):
         if self._is_ipython and 'IPython' in sys.modules and sys.modules['IPython'].version_info[0] >= 5:
             # ipython and notebooks, register our event processing with their hooks
             self._ipython_config()
-        elif sys.flags.interactive == 1 or not hasattr(__main__, '__file__') or gSystem.InheritsFrom('TMacOSXSystem'):
+        elif (sys.flags.interactive == 1 or not hasattr(__main__, '__file__')) and not gSystem.InheritsFrom('TWinNTSystem'):
             # Python in interactive mode, use the PyOS_InputHook to call our event processing
             # - sys.flags.interactive checks for the -i flags passed to python
             # - __main__ does not have the attribute __file__ if the Python prompt is started directly
-            # - MacOS does not allow to run a second thread to process events, fall back to the input hook
+            # - does not work properly on Windows
             self._inputhook_config()
+            gEnv.SetValue("WebGui.ExternalProcessEvents", "yes")
         else:
-            # Python in script mode, start a separate thread for the event processing
+            # Python in script mode, instead of separate thread methods like canvas.Update should run events
 
             # indicate that ProcessEvents called in different thread, let ignore thread id checks in RWebWindow
             gEnv.SetValue("WebGui.ExternalProcessEvents", "yes")
 
-            def _process_root_events(self):
-                while self.keep_polling:
-                    gSystem.ProcessEvents()
-                    time.sleep(0.01)
-            import threading
-            self.keep_polling = True # Used to shut down the thread safely at teardown time
-            update_thread = threading.Thread(None, _process_root_events, None, (self,))
-            self.process_root_events = update_thread # The thread is joined at teardown time
-            update_thread.daemon = True
-            update_thread.start()
-
         self._set_display_hook()
 

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_tcanvas.py

@@ -0,0 +1,96 @@
+# Author: Sergey Linev GSI  01/2025
+
+################################################################################
+# Copyright (C) 1995-2025, Rene Brun and Fons Rademakers.                      #
+# All rights reserved.                                                         #
+#                                                                              #
+# For the licensing terms see $ROOTSYS/LICENSE.                                #
+# For the list of contributors see $ROOTSYS/README/CREDITS.                    #
+################################################################################
+
+from . import pythonization
+
+def wait_press_windows():
+   from ROOT import gSystem
+   import msvcrt
+   import time
+
+   while not gSystem.ProcessEvents():
+      if msvcrt.kbhit():
+         k = msvcrt.getch()
+         if k[0] == 32:
+            break
+      else:
+         time.sleep(0.01)
+
+
+def wait_press_posix():
+   from ROOT import gSystem
+   import sys
+   import select
+   import tty
+   import termios
+   import time
+
+   old_settings = termios.tcgetattr(sys.stdin)
+
+   tty.setcbreak(sys.stdin.fileno())
+
+   try:
+
+      while not gSystem.ProcessEvents():
+         c = ''
+         if select.select([sys.stdin], [], [], 0) == ([sys.stdin], [], []):
+            c = sys.stdin.read(1)
+         if (c == '\x20'):
+            break
+         time.sleep(0.01)
+
+   finally:
+      termios.tcsetattr(sys.stdin, termios.TCSADRAIN, old_settings)
+
+
+def _TCanvas_Update(self, block = False):
+   """
+   Updates the canvas.
+   Also blocks script execution and runs the ROOT graphics event loop until the <space> keyword is pressed,
+   but only if the following conditions are met:
+   * The `block` optional argument is set to `True`.
+   * ROOT graphics are enabled, i.e. `ROOT.gROOT.IsBatch() == False`.
+   * The script is running not in ipython notebooks.
+   """
+
+   from ROOT import gROOT
+   import os
+   import sys
+
+   self._Update()
+
+   # blocking flag is not set
+   if not block:
+      return
+
+   # no special handling in batch mode
+   if gROOT.IsBatch():
+      return
+
+   # no special handling in case of notebooks
+   if 'IPython' in sys.modules and sys.modules['IPython'].version_info[0] >= 5:
+      return
+
+   print("Press <space> key to continue")
+
+   if os.name == 'nt':
+      wait_press_windows()
+   else:
+      wait_press_posix()
+
+
+@pythonization('TCanvas')
+def pythonize_tcanvas(klass):
+    # Parameters:
+    # klass: class to be pythonized
+
+    klass._Update = klass.Update
+    klass.Update = _TCanvas_Update
+