[pyroot] Allow toggling batch mode from True to False in middle of session

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

@@ -142,7 +142,10 @@ def displayhook(v):
     def init_graphics(self, gEnv, gSystem):
         """Configure ROOT graphics to be used interactively"""
 
-        # Note that we only end up in this function if gROOT.IsBatch() is false
+        if getattr(self, "_graphics_initialized", False):
+            return
+        self._graphics_initialized = True
+
         import __main__
 
         if self._is_ipython and "IPython" in sys.modules and sys.modules["IPython"].version_info[0] >= 5:

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

@@ -0,0 +1,36 @@
+# Author: PyROOT Team
+
+################################################################################
+# Copyright (C) 1995-2026, Rene Brun and Fons Rademakers.                      #
+# All rights reserved.                                                         #
+#                                                                              #
+# For the licensing terms see $ROOTSYS/LICENSE.                                #
+# For the list of contributors see $ROOTSYS/README/CREDITS.                    #
+################################################################################
+
+r"""
+\pythondoc TROOT
+
+Pythonizations for TROOT class, enabling dynamic batch mode toggling.
+"""
+
+from . import pythonization
+
+
+def _TROOT_SetBatch(self, batch=True):
+    """
+    Sets the batch mode on ROOT.
+    If batch mode is turned off in the middle of a session, ensure the
+    interactive graphics environment is initialized.
+    """
+    import ROOT
+
+    self._cpp_SetBatch(batch)
+    if not batch and hasattr(ROOT, "app") and ROOT.PyConfig.StartGUIThread:
+        ROOT.app.init_graphics(ROOT._cppyy.gbl.gEnv, ROOT._cppyy.gbl.gSystem)
+
+
+@pythonization("TROOT")
+def pythonize_troot(klass):
+    klass._cpp_SetBatch = klass.SetBatch
+    klass.SetBatch = _TROOT_SetBatch