terryjreedy · Jun 17, 2019 · May 30, 2019 · Jun 4, 2019 · Jun 4, 2019 · Jun 4, 2019
diff --git a/Lib/idlelib/zoomheight.py b/Lib/idlelib/zoomheight.py
@@ -2,42 +2,121 @@
 
 import re
 import sys
+import tkinter
 
-from idlelib import macosx
+
+class WmInfoGatheringError(Exception):
+    pass
 
 
 class ZoomHeight:
 
     def __init__(self, editwin):
         self.editwin = editwin
 
+        # Cached values for maximized window dimensions, one for each set
+        # of screen dimensions.
+        self._max_height_and_y_coords = {}
+
+    @property
+    def top(self):
+        return self.editwin.top
+
     def zoom_height_event(self, event=None):
-        top = self.editwin.top
-        zoomed = zoom_height(top)
-        menu_status = 'Restore' if zoomed else 'Zoom'
-        self.editwin.update_menu_label(menu='options', index='* Height',
-                                       label=f'{menu_status} Height')
+        zoomed = self.zoom_height()
+
+        if zoomed is not None:
+            menu_status = 'Restore' if zoomed else 'Zoom'
+            self.editwin.update_menu_label(menu='options', index='* Height',
+                                           label=f'{menu_status} Height')
+
         return "break"
 
+    def zoom_height(self):
+        width, height, x, y = get_window_geometry(self.top)
+
+        if self.top.wm_state() != 'normal':
+            # Can't zoom/restore window height for windows not in the 'normal'
+            # state, e.g. maximized and full-screen windows.
+            return None
+
+        try:
+            maxheight, maxy = self.get_max_height_and_y_coord()
+        except WmInfoGatheringError:
+            return None
+
+        if height != maxheight:
+            # Maximize the window's height.
+            set_window_geometry(self.top, (width, maxheight, x, maxy))
+            return True
+        else:
+            # Restore the window's height.
+            #
+            # .wm_geometry('') makes the window revert to the size requested
+            # by the widgets it contains.
+            self.top.wm_geometry('')
+            return False
+
+    def get_max_height_and_y_coord(self):
+        screen_dimensions = (self.top.winfo_screenwidth(),
+                             self.top.winfo_screenheight())
+        if screen_dimensions not in self._max_height_and_y_coords:
+            orig_state = self.top.wm_state()
 
-def zoom_height(top):
+            # Get window geometry info for maximized windows.
+            try:
+                self.top.wm_state('zoomed')
+            except tkinter.TclError:
+                # The 'zoomed' state is not supported by some esoteric WMs,
+                # such as Xvfb.
+                raise WmInfoGatheringError(
+                    'Failed getting geometry of maximized windows, because ' +
+                    'the "zoomed" window state is unavailable.')
+            self.top.update()
+            maxwidth, maxheight, maxx, maxy = get_window_geometry(self.top)
+            if sys.platform == 'win32':
+                # On Windows, the returned Y coordinate is the one before
+                # maximizing, so we use 0 which is correct unless a user puts
+                # their dock on the top of the screen (very rare).
+                maxy = 0
+            maxrooty = self.top.winfo_rooty()
+
+            # Get the "root y" coordinate for non-maximized windows with their
+            # y coordinate set to that of maximized windows.  This is needed
+            # to properly handle different title bar heights for non-maximized
+            # vs. maximized windows, as seen e.g. in Windows 10.
+            self.top.wm_state('normal')
+            self.top.update()
+            orig_geom = get_window_geometry(self.top)
+            max_y_geom = orig_geom[:3] + (maxy,)
+            set_window_geometry(self.top, max_y_geom)
+            self.top.update()
+            max_y_geom_rooty = self.top.winfo_rooty()
+
+            # Adjust the maximum window height to account for the different
+            # title bar heights of non-maximized vs. maximized windows.
+            maxheight += maxrooty - max_y_geom_rooty
+
+            self._max_height_and_y_coords[screen_dimensions] = maxheight, maxy
+
+            set_window_geometry(self.top, orig_geom)
+            self.top.wm_state(orig_state)
+
+        return self._max_height_and_y_coords[screen_dimensions]
+
+
+def get_window_geometry(top):
     geom = top.wm_geometry()
     m = re.match(r"(\d+)x(\d+)\+(-?\d+)\+(-?\d+)", geom)
     if not m:
         top.bell()
         return
     width, height, x, y = map(int, m.groups())
-    newheight = top.winfo_screenheight()
-
-    # The constants below for Windows and Mac Aqua are visually determined
-    # to avoid taskbar or menubar and app icons.
-    newy, bot_y = ((0, 72) if sys.platform == 'win32' else
-                   (22, 88) if macosx.isAquaTk() else
-                   (0, 88) ) # Guess for anything else.
-    newheight = newheight - newy - bot_y
-    newgeom = '' if height >= newheight else f"{width}x{newheight}+{x}+{newy}"
-    top.wm_geometry(newgeom)
-    return newgeom != ""
+    return width, height, x, y
+
+
+def set_window_geometry(top, geometry):
+    top.wm_geometry("{:d}x{:d}{:+d}{:+d}".format(*geometry))
 
 
 if __name__ == "__main__":

diff --git a/Misc/NEWS.d/next/IDLE/2019-06-04-23-27-33.bpo-37039.FN_fBf.rst b/Misc/NEWS.d/next/IDLE/2019-06-04-23-27-33.bpo-37039.FN_fBf.rst
@@ -0,0 +1 @@
+Fix incorrect behavior of IDLE's "Zoom Height" command across platforms.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix incorrect behavior of IDLE's "Zoom Height" command across platforms.