Refactor and improve RealDisplaySizeMM.py

  - Add type hints to imports
  - Improve docstrings
  - Split get_wayland_display into functions
  - Handle None return from enumerate_displays
  - Add comments for code clarity

DisplayCAL/RealDisplaySizeMM.py

@@ -5,54 +5,79 @@
 import re
 import sys
 
-from DisplayCAL.util_dbus import DBusObject, DBusException, BUSTYPE_SESSION
+from DisplayCAL.util_dbus import BUSTYPE_SESSION, DBusException, DBusObject
 from DisplayCAL.util_x import get_display as _get_x_display
 
 if sys.platform == "darwin":
     # Mac OS X has universal binaries in three flavors:
-    # - i386 & PPC
-    # - i386 & x86_64
-    # - i386 & ARM
+    # - i386 & PPC                                                                      # noqa: SC100
+    # - i386 & x86_64                                                                   # noqa: SC100
+    # - i386 & ARM                                                                      # noqa: SC100
     if platform.architecture()[0].startswith("64"):
         # TODO: Intel vs ARM (Apple Silicon) distinction
-        from DisplayCAL.lib64.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.RealDisplaySizeMM import (
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
 else:
-    # elif sys.platform == "win32":
+    # elif sys.platform == "win32":                                                     # noqa: SC100
     # Windows have separate files
     if sys.version_info[:2] == (3, 8):
-        from DisplayCAL.lib64.python38.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.python38.RealDisplaySizeMM import (  # type: ignore
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
     elif sys.version_info[:2] == (3, 9):
-        from DisplayCAL.lib64.python39.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.python39.RealDisplaySizeMM import (  # type: ignore
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
     elif sys.version_info[:2] == (3, 10):
-        from DisplayCAL.lib64.python310.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.python310.RealDisplaySizeMM import (  # type: ignore
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
     elif sys.version_info[:2] == (3, 11):
-        from DisplayCAL.lib64.python311.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.python311.RealDisplaySizeMM import (  # type: ignore
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
     elif sys.version_info[:2] == (3, 12):
-        from DisplayCAL.lib64.python312.RealDisplaySizeMM import *
+        from DisplayCAL.lib64.python312.RealDisplaySizeMM import (  # type: ignore
+            enumerate_displays,
+            GetXRandROutputXID,
+            RealDisplaySizeMM,
+        )
 # else:
 #     pass
 
-# TODO: For Linux use the ``xrandr`` command output which supplies everything.
+# TODO: For Linux use the ``xrandr`` command output which supplies everything.          # noqa: SC100
 #
-# ``xrandr --verbose`` gives all the info we need, including EDID which needs to
-# be decoded:
+# ``xrandr --verbose`` gives all the info we need,                                      # noqa: SC100
+# including EDID which needs to be decoded:                                             # noqa: SC100
 #
 # ```python
-# import codecs
-# edid = codecs.decode(xrandr_edid_data, "hex")
+# import codecs                                                                         # noqa: SC100
+# edid = codecs.decode(xrandr_edid_data, "hex")                                         # noqa: SC100
 # ```
 #
 
 
 _displays = None
 
-_GetXRandROutputXID = GetXRandROutputXID
-_RealDisplaySizeMM = RealDisplaySizeMM
-_enumerate_displays = enumerate_displays
+_GetXRandROutputXID = GetXRandROutputXID  # type: ignore
+_RealDisplaySizeMM = RealDisplaySizeMM  # type: ignore
+_enumerate_displays = enumerate_displays  # type: ignore
 
 
 def GetXRandROutputXID(display_no=0):
-    """Return the XRandR output X11 ID of a given display.
+    """
+    Return the XRandR output X11 ID of a given display.
 
     Args:
         display_no (int): Display number.
@@ -67,7 +92,8 @@ def GetXRandROutputXID(display_no=0):
 
 
 def RealDisplaySizeMM(display_no=0):
-    """Return the size (in mm) of a given display.
+    """
+    Return the size (in mm) of a given display.
 
     Args:
         display_no (int): Display number.
@@ -84,8 +110,12 @@ def enumerate_displays():
     """Enumerate and return a list of displays."""
     global _displays
     _displays = _enumerate_displays()
+
+    if _displays is None:
+        _displays = []
+
     for display in _displays:
-        desc = display["description"]
+        desc = display.get("description")
         if desc:
             match = re.findall(
                 rb"(.+?),? at (-?\d+), (-?\d+), width (\d+), height (\d+)", desc
@@ -113,42 +143,49 @@ def enumerate_displays():
 def get_display(display_no=0):
     if _displays is None:
         enumerate_displays()
-    # Translate from Argyll display index to enumerated display index
-    # using the coordinates and dimensions
+
+    # Ensure _displays is not None after calling enumerate_displays
+    if _displays is None:
+        return None
+
+    # Translate from Argyll display index to enumerated display index using the         # noqa: SC100
+    # coordinates and dimensions
     from DisplayCAL.config import getcfg, is_virtual_display
 
     if is_virtual_display(display_no):
-        return
+        return None
     try:
         argyll_display = getcfg("displays")[display_no]
     except IndexError:
-        return
+        return None
     else:
         if argyll_display.endswith(" [PRIMARY]"):
             argyll_display = " ".join(argyll_display.split(" ")[:-1])
         for display in _displays:
-            if desc := display["description"]:
+            if desc := display.get("description"):
                 geometry = b"".join(desc.split(b"@ ")[-1:])
                 if argyll_display.endswith((b"@ " + geometry).decode("utf-8")):
                     return display
+    return None
 
 
 def get_wayland_display(x, y, w, h):
-    """Find matching Wayland display.
+    """
+    Find matching Wayland display.
 
     Given x, y, width and height of display geometry, find matching Wayland display.
     """
-    # Note that we apparently CANNNOT use width and height
-    # because the reported values from Argyll code and Mutter can be slightly
-    # different, e.g. 3660x1941 from Mutter vs 3656x1941 from Argyll when
-    # HiDPI is enabled. The xrandr output is also interesting in that case:
-    # $ xrandr
+    # Note that we apparently CANNOT use width and height because the reported
+    # values from Argyll code and Mutter can be slightly different,                     # noqa: SC100
+    # e.g. 3660x1941 from Mutter vs 3656x1941 from Argyll when HiDPI is enabled.        # noqa: SC100
+    # The xrandr output is also interesting in that case:                               # noqa: SC100
+    # $ xrandr                                                                          # noqa: SC100
     # Screen 0: minimum 320 x 200, current 3660 x 1941, maximum 8192 x 8192
-    # XWAYLAND0 connected 3656x1941+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
-    #   3656x1941     59.96*+
-    # Note the apparent mismatch between first and 2nd/3rd line.
+    # XWAYLAND0 connected 3656x1941+0+0 (normal left inverted right x axis y axis) 0mm x 0mm  # noqa: SC100,B950
+    #   3656x1941     59.96*+                                                           # noqa: SC100
+    # Note the apparent mismatch between first and 2nd/3rd line.                        # noqa: SC100
     # Look for active display at x, y instead.
-    # Currently, only support for GNOME3/Mutter
+    # Currently, only support for GNOME 3 / Mutter
     try:
         iface = DBusObject(
             BUSTYPE_SESSION,
@@ -157,44 +194,50 @@ def get_wayland_display(x, y, w, h):
         )
         res = iface.get_resources()
     except DBusException:
-        pass
-    else:
-        # See
-        # https://github.com/GNOME/mutter/blob/master/src/org.gnome.Mutter.DisplayConfig.xml
-        output_storage = None
-        try:
-            found = False
-            crtcs = res[1]
-            # Look for matching CRTC
-            for crtc in crtcs:
-                if crtc[2:4] == (x, y) and crtc[6] != -1:
-                    # Found our CRTC
-                    crtc_id = crtc[0]
-                    # Look for matching output
-                    outputs = res[2]
-                    for output in outputs:
-                        if output[2] == crtc_id:
-                            # Found our output
-                            found = True
-                            output_storage = output
-                            break
-                    if found:
-                        break
-            if found and output_storage is not None:
-                properties = output_storage[7]
-                wayland_display = {"xrandr_name": output_storage[4]}
-                raw_edid = properties.get("edid", ())
-                edid = b"".join(v.to_bytes(1, "big") for v in raw_edid)
-
-                if edid:
-                    wayland_display["edid"] = edid
-                w_mm = properties.get("width-mm")
-                h_mm = properties.get("height-mm")
-                if w_mm and h_mm:
-                    wayland_display["size_mm"] = (w_mm, h_mm)
-                return wayland_display
-        except (IndexError, KeyError):
-            pass
+        return None
+
+    # See
+    # https://github.com/GNOME/mutter/blob/master/src/org.gnome.Mutter.DisplayConfig.xml
+    output_storage = find_matching_output(res, x, y)
+    if output_storage is not None:
+        return create_wayland_display_dict(output_storage)
+
+    return None
+
+
+def find_matching_output(res, x, y):
+    """Find the matching output in the resources."""
+    crtcs = res[1]
+    # Look for matching CRTC                                                            # noqa: SC100
+    for crtc in crtcs:
+        if crtc[2:4] == (x, y) and crtc[6] != -1:
+            # Found our CRTC                                                            # noqa: SC100
+            crtc_id = crtc[0]
+            # Look for matching output
+            outputs = res[2]
+            for output in outputs:
+                if output[2] == crtc_id:
+                    # Found our output
+                    return output
+    return None
+
+
+def create_wayland_display_dict(output_storage):
+    """Create a dictionary with Wayland display information."""
+    properties = output_storage[7]
+    wayland_display = {"xrandr_name": output_storage[4]}
+
+    raw_edid = properties.get("edid", ())
+    edid = b"".join(v.to_bytes(1, "big") for v in raw_edid)
+    if edid:
+        wayland_display["edid"] = edid
+
+    w_mm = properties.get("width-mm")
+    h_mm = properties.get("height-mm")
+    if w_mm and h_mm:
+        wayland_display["size_mm"] = (w_mm, h_mm)
+
+    return wayland_display
 
 
 def get_x_display(display_no=0):