Resolve all non-strict mode Pyright errors

src/textual_paint/paint.py

@@ -887,6 +887,9 @@ def is_inside_polygon(x: int, y: int, points: List[Offset]) -> bool:
         if y > min(p1y, p2y):
             if y <= max(p1y, p2y):
                 if x <= max(p1x, p2x):
+                    x_intersection = x  # Avoid "possibly unbound" type checker error
+                    # I don't know if this is right; should it flip `inside` in this case?
+                    # Is this an actual case that can occur, where p1y == p2y AND p1x != p2x?
                     if p1y != p2y:
                         x_intersection = (y - p1y) * (p2x - p1x) / (p2y - p1y) + p1x
                     if p1x == p2x or x <= x_intersection:
@@ -2588,6 +2591,7 @@ class PaintApp(App[None]):
     def cancel_preview(self) -> None:
         """Revert the currently previewed action."""
         if self.preview_action:
+            assert self.preview_action.region is not None, "region should have been initialized for preview_action"
             self.preview_action.undo(self.image)
             self.canvas.refresh_scaled_region(self.preview_action.region)
             self.preview_action = None

src/textual_paint/wallpaper.py

@@ -47,10 +47,11 @@ def get_desktop_environment() -> str:
                 return "razor-qt"
             elif desktop_session.startswith("wmaker"): # e.g. wmaker-common
                 return "windowmaker"
+        gnome_desktop_session_id = os.environ.get("GNOME_DESKTOP_SESSION_ID")
         if os.environ.get('KDE_FULL_SESSION') == 'true':
             return "kde"
-        elif os.environ.get('GNOME_DESKTOP_SESSION_ID'):
+        elif gnome_desktop_session_id:
-            if not "deprecated" in os.environ.get('GNOME_DESKTOP_SESSION_ID'):
+            if not "deprecated" in gnome_desktop_session_id:
                 return "gnome2"
         #From http://ubuntuforums.org/showthread.php?t=652320
         elif is_running("xfce-mcs-manage"):
@@ -61,13 +62,16 @@ def get_desktop_environment() -> str:
 
 def is_running(process: str) -> bool:
     """Returns whether a process with the given name is (likely) currently running.
-    Uses a basic text search, and so may have false positives."""
+
+    Uses a basic text search, and so may have false positives.
+    """
     #From http://www.bloggerpolis.com/2011/05/how-to-check-if-a-process-is-running-using-python/
     # and http://richarddingwall.name/2009/06/18/windows-equivalents-of-ps-and-kill-commands/
     try: #Linux/Unix
         s = subprocess.Popen(["ps", "axw"],stdout=subprocess.PIPE)
     except: #Windows
         s = subprocess.Popen(["tasklist", "/v"],stdout=subprocess.PIPE)
+    assert s.stdout is not None
     for x in s.stdout:
         # if re.search(process, x):
         if process in str(x):
@@ -183,10 +187,11 @@ def set_wallpaper(file_loc: str, first_run: bool = True):
         #From https://stackoverflow.com/questions/1977694/change-desktop-background
         import ctypes
         SPI_SETDESKWALLPAPER = 20
-        ctypes.windll.user32.SystemParametersInfoW(SPI_SETDESKWALLPAPER, 0, file_loc, 0)
+        ctypes.windll.user32.SystemParametersInfoW(SPI_SETDESKWALLPAPER, 0, file_loc, 0)  # type: ignore
     elif desktop_env=="mac": #Not tested since I do not have a mac
         #From https://stackoverflow.com/questions/431205/how-can-i-programatically-change-the-background-in-mac-os-x
         try:
+            assert os.name == "mac"  # avoid 'Import "appscript" could not be resolved' on other platforms
             from appscript import app, mactypes
             app('Finder').desktop_picture.set(mactypes.File(file_loc))
         except ImportError: