1 files changed, 71 insertions, 0 deletions
diff --git a/ptpython/eventloop.py b/ptpython/eventloop.py
new file mode 100644
index 0000000..c841972
--- /dev/null
+++ b/ptpython/eventloop.py
@@ -0,0 +1,71 @@
+"""
+Wrapper around the eventloop that gives some time to the Tkinter GUI to process
+events when it's loaded and while we are waiting for input at the REPL. This
+way we don't block the UI of for instance ``turtle`` and other Tk libraries.
+
+(Normally Tkinter registers it's callbacks in ``PyOS_InputHook`` to integrate
+in readline. ``prompt-toolkit`` doesn't understand that input hook, but this
+will fix it for Tk.)
+"""
+import sys
+import time
+
+__all__ = ["inputhook"]
+
+
+def _inputhook_tk(inputhook_context):
+    """
+    Inputhook for Tk.
+    Run the Tk eventloop until prompt-toolkit needs to process the next input.
+    """
+    # Get the current TK application.
+    import tkinter
+
+    import _tkinter  # Keep this imports inline!
+
+    root = tkinter._default_root
+
+    def wait_using_filehandler():
+        """
+        Run the TK eventloop until the file handler that we got from the
+        inputhook becomes readable.
+        """
+        # Add a handler that sets the stop flag when `prompt-toolkit` has input
+        # to process.
+        stop = [False]
+
+        def done(*a):
+            stop[0] = True
+
+        root.createfilehandler(inputhook_context.fileno(), _tkinter.READABLE, done)
+
+        # Run the TK event loop as long as we don't receive input.
+        while root.dooneevent(_tkinter.ALL_EVENTS):
+            if stop[0]:
+                break
+
+        root.deletefilehandler(inputhook_context.fileno())
+
+    def wait_using_polling():
+        """
+        Windows TK doesn't support 'createfilehandler'.
+        So, run the TK eventloop and poll until input is ready.
+        """
+        while not inputhook_context.input_is_ready():
+            while root.dooneevent(_tkinter.ALL_EVENTS | _tkinter.DONT_WAIT):
+                pass
+            # Sleep to make the CPU idle, but not too long, so that the UI
+            # stays responsive.
+            time.sleep(0.01)
+
+    if root is not None:
+        if hasattr(root, "createfilehandler"):
+            wait_using_filehandler()
+        else:
+            wait_using_polling()
+
+
+def inputhook(inputhook_context):
+    # Only call the real input hook when the 'Tkinter' library was loaded.
+    if "Tkinter" in sys.modules or "tkinter" in sys.modules:
+        _inputhook_tk(inputhook_context)