Fix and clean up bad platform checks

- If the DISPLAY environment variable is present, its value is
  now checked before assuming an X11 session is present.
- Windows platform checks no longer use startswith().

dragonfly/_platform_checks.py

@@ -0,0 +1,84 @@
+#
+# This file is part of Dragonfly.
+# (c) Copyright 2022 by Dane Finlay
+# Licensed under the LGPL.
+#
+#   Dragonfly is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU Lesser General Public License as published
+#   by the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   Dragonfly is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+#   Lesser General Public License for more details.
+#
+#   You should have received a copy of the GNU Lesser General Public
+#   License along with Dragonfly.  If not, see
+#   <http://www.gnu.org/licenses/>.
+#
+
+""" This module handles complex platform checks. """
+
+import os
+
+
+def is_x11():
+    """
+    Check for X11 by looking at the value of the *DISPLAY* environment
+    variable.
+
+    If the *DISPLAY* environment variable is present, and is in one of the
+    two forms below, this function returns true.  Otherwise, it returns
+    false.
+
+    Acceptable forms of the *DISPLAY* variable:
+
+        * [hostname]:displaynumber[.screennumber]
+
+        * [protocol/hostname]:displaynumber[.screennumber]
+
+    Note: Although this function parses *hostname* and *protocol/hostname*
+    segments, no attempt is made to validate them.  The *displaynumber* and
+    segments, however, must be a digit string, as does the *screennumber*,
+    if it is present.
+    """
+
+    # Parse segments and delimiters from the env. variable.
+    display = os.environ.get("DISPLAY", "")
+    segments = ["", "", ""]
+    delimiters = ["", ""]
+    index = 0; current = "";
+    for char in display:
+        if index == 0 and char == ":" or index == 1 and char == ".":
+            delimiters[index] = char
+            segments[index] = current
+            index += 1; current = "";
+        else:
+            current += char
+    segments[index] += current
+
+    # Validate each segment as necessary.
+    hostname, display_number, screen_number = segments
+    if not display_number.isdigit(): return False
+    if len(delimiters[1]) > 0 and len(screen_number) == 0: return False
+    if len(screen_number) > 0 and not screen_number.isdigit(): return False
+    return True
+
+
+#: Whether the value of the DISPLAY env. variable indicates an X11 session.
+IS_X11 = is_x11()
+
+
+if __name__ == '__main__':
+    # Test the _is_x11() function.
+    for string in ["unix/localhost:0", "localhost:0", "localhost:0.0",
+                   ":0.0", ":0"]:
+        #print(string)
+        os.environ["DISPLAY"] = string
+        assert is_x11()
+    for string in ["", "localhost", "localhost:", "localhost:0.", ":",
+                   "0.0", ":0:", ":0.", ":a", ":0.a", ":a.0", ":a.a"]:
+        #print(string)
+        os.environ["DISPLAY"] = string
+        assert not is_x11()

dragonfly/accessibility/__init__.py

@@ -12,7 +12,11 @@
 from .utils import (CursorPosition, TextQuery)
 
 # Import and set the controller class based on the current platform.
-if os.environ.get("DISPLAY"):
+# Note: dragonfly._platform_checks is not used here in an effort to keep the
+#  accessibility sub-package modular.
+#  Please see the module docstring of utils.py.
+#
+if ":" in os.environ.get("DISPLAY", ""):
     # Use the AT-SPI controller on X11.
     from . import atspi
     os_controller_class = atspi.Controller

dragonfly/actions/keyboard/__init__.py

@@ -25,10 +25,13 @@
 import os
 import sys
 
+from dragonfly._platform_checks import IS_X11
+
+
 # Import the keyboard classes for the current platform.
 # Note: X11 is checked first here because it is possible to use on the other
 #  supported platforms.
-if os.environ.get("DISPLAY"):
+if IS_X11:
     # Import classes for X11.  This is typically used on Unix-like systems.
     # The DISPLAY environment variable is normally set in an X11 session.
     #  If it is not, it may be set manually in ~/.profile or equivalent.
@@ -44,7 +47,7 @@
     #  used.
     # from ._x11_libxdo import LibxdoKeyboard as Keyboard
 
-elif sys.platform.startswith("win"):
+elif sys.platform == "win32":
     # Import Win32 classes.
     from ._win32 import (
         Win32Keyboard as Keyboard,

dragonfly/actions/mouse/__init__.py

@@ -25,6 +25,8 @@
 import os
 import sys
 
+from dragonfly._platform_checks import IS_X11
+
 # Import mouse events common to each platform.
 from ._base import (EventBase, PauseEvent, MoveEvent, MoveRelativeEvent,
                     MoveScreenEvent, MoveWindowEvent)
@@ -33,7 +35,7 @@
 # Import the mouse functions and classes for the current platform.
 # Note: X11 is checked first here because it is possible to use on the other
 #  supported platforms.
-if os.environ.get("DISPLAY"):
+if IS_X11:
     try:
         # Prefer pynput over xdotool since it supports horizontal scrolling
         #  and the extra mouse buttons.
@@ -47,7 +49,7 @@
             PLATFORM_BUTTON_FLAGS, PLATFORM_WHEEL_FLAGS
         )
 
-elif sys.platform.startswith("win"):
+elif sys.platform == "win32":
     from ._win32 import (
         ButtonEvent, get_cursor_position, set_cursor_position,
         PLATFORM_BUTTON_FLAGS, PLATFORM_WHEEL_FLAGS

dragonfly/test/suites.py

@@ -24,8 +24,9 @@
 
 import pytest
 
-from dragonfly.log import setup_log
-from dragonfly import get_engine
+from dragonfly                   import get_engine
+from dragonfly.log               import setup_log
+from dragonfly._platform_checks  import IS_X11
 
 # Setup logging.
 _log = logging.getLogger("dfly.test")
@@ -51,16 +52,8 @@
     "documentation/test_recobs_doctest.txt",
 ]
 
-# Include clipboard tests if on a desktop system.
-desktop = (
-    # Windows
-    os.name == "nt" or
-    # X11
-    os.environ.get("DISPLAY") or
-    # macOS
-    sys.platform == "darwin"
-)
-if desktop:
+# Include clipboard tests if on a desktop system: Windows/X11/macOS.
+if os.name == "nt" or IS_X11 or sys.platform == "darwin":
     common_names.insert(2, "test_clipboard")
 
 # Include accessibility tests if dragonfly.accessibility is available.

dragonfly/windows/clipboard.py

@@ -25,24 +25,25 @@
 import os
 import sys
 
+from dragonfly._platform_checks                 import IS_X11
 from dragonfly.windows.base_clipboard           import BaseClipboard
 
 
 # Import the clipboard classes and functions for the current platform.
 # Note: X11 is checked first here because it is possible to use on the other
 #  supported platforms.
-if os.environ.get("DISPLAY"):
-    from dragonfly.windows.x11_clipboard        import (XselClipboard as
-                                                        Clipboard)
-
-elif sys.platform.startswith("win"):
-    from dragonfly.windows.win32_clipboard      import (Win32Clipboard as
-                                                        Clipboard,
-                                                        win32_clipboard_ctx)
+if IS_X11:
+    from dragonfly.windows.x11_clipboard        import \
+        XselClipboard as Clipboard
+
+elif sys.platform == "win32":
+    from dragonfly.windows.win32_clipboard      import \
+        Win32Clipboard as Clipboard, win32_clipboard_ctx
+
 elif sys.platform == "darwin":
     from dragonfly.windows.pyperclip_clipboard  import \
         PyperclipClipboard as Clipboard
 
 else:
-    from dragonfly.windows.base_clipboard       import (BaseClipboard as
-                                                        Clipboard)
+    from dragonfly.windows.base_clipboard       import \
+        BaseClipboard as Clipboard

dragonfly/windows/monitor.py

@@ -25,14 +25,16 @@
 import os
 import sys
 
+from dragonfly._platform_checks import IS_X11
+
 
 # Import the Monitor class for the current platform.
 # Note: X11 is checked first here because it is possible to use on the other
 #  supported platforms.
-if os.environ.get("DISPLAY"):
+if IS_X11:
     from dragonfly.windows.x11_monitor     import X11Monitor as Monitor
 
-elif sys.platform.startswith("win"):
+elif sys.platform == "win32":
     from dragonfly.windows.win32_monitor   import Win32Monitor as Monitor
 
 elif sys.platform == "darwin":

dragonfly/windows/pyperclip_clipboard.py

@@ -28,10 +28,11 @@
 
 import os
 
-from six                              import integer_types
+from six                               import integer_types
 import pyperclip
 
-from dragonfly.windows.base_clipboard import BaseClipboard
+from dragonfly._platform_checks        import IS_X11
+from dragonfly.windows.base_clipboard  import BaseClipboard
 
 
 class PyperclipClipboard(BaseClipboard):
@@ -79,8 +80,7 @@ def copy_from_system(self, formats=None, clear=False):
         # Determine the supported formats.  Copied file paths may be
         #  available to us on X11.
         supported_formats = [self.format_text, self.format_unicode]
-        if os.environ.get("DISPLAY"):
-            supported_formats.append(self.format_hdrop)
+        if IS_X11: supported_formats.append(self.format_hdrop)
 
         # Determine which formats to retrieve.
         caller_specified_formats = bool(formats)

dragonfly/windows/window.py

@@ -26,14 +26,16 @@
 import os
 import sys
 
+from dragonfly._platform_checks import IS_X11
+
 
 # Import the Window class for the current platform.
 # Note: X11 is checked first here because it is possible to use on the other
 #  supported platforms.
-if os.environ.get("DISPLAY"):
+if IS_X11:
     from dragonfly.windows.x11_window    import X11Window as Window
 
-elif sys.platform.startswith("win"):
+elif sys.platform == "win32":
     from dragonfly.windows.win32_window  import Win32Window as Window
 
 elif sys.platform == "darwin":