Enhance menuconfig UI to match lxdialog appearance

This refines color scheme, layout, and dialog rendering to closely match
Linux kernel's lxdialog implementation. Key improvements include blue
background for separators and help text, proper shadow windows for
dialogs, corrected window sizing and centering, and immediate background
fill using bkgd().

Author: jserv

menuconfig.py

@@ -286,12 +286,12 @@
     # Precisely matches lxdialog's set_bluetitle_theme() and set_classic_theme()
     "linux": """
     path=fg:white,bg:blue,bold
-    separator=fg:black,bg:white
+    separator=fg:white,bg:blue
     list=fg:black,bg:white
     selection=fg:white,bg:blue,bold
     inv-list=fg:red,bg:white
     inv-selection=fg:red,bg:blue,bold
-    help=fg:black,bg:white
+    help=fg:white,bg:blue
     show-help=fg:black,bg:white
     frame=fg:white,bg:blue,bold
     body=fg:black,bg:white
@@ -999,6 +999,10 @@ def _init():
 
     _init_styles()
 
+    # Set stdscr background to match main list style
+    # This ensures areas not covered by subwindows have correct background
+    _stdscr.bkgd(' ', _style.get("list", 0))
+
     # Hide the cursor
     _safe_curs_set(0)
 
@@ -1044,17 +1048,24 @@ def _resize_main():
 
     screen_height, screen_width = _stdscr.getmaxyx()
 
-    _path_win.resize(1, screen_width)
-    _top_sep_win.resize(1, screen_width)
-    _bot_sep_win.resize(1, screen_width)
-
     help_win_height = _SHOW_HELP_HEIGHT if _show_help else \
         len(_MAIN_HELP_LINES)
 
+    # Screen layout:
+    # Row 0: _path_win, Row 1: _top_sep_win, Row 2+: _menu_win
+    # Row (2+menu_win_height): _bot_sep_win
+    # Row (2+menu_win_height+1): _help_win
+    # Total: 1 + 1 + menu_win_height + 1 + help_win_height = screen_height
     menu_win_height = screen_height - help_win_height - 3
+    menu_win_width = screen_width
+
+    _path_win.resize(1, screen_width)
+    _top_sep_win.resize(1, menu_win_width)
 
     if menu_win_height >= 1:
-        _menu_win.resize(menu_win_height, screen_width)
+        _menu_win.resize(menu_win_height, menu_win_width)
+        _bot_sep_win.resize(1, menu_win_width)
+        # _help_win uses full screen width for blue background to extend to right edge
         _help_win.resize(help_win_height, screen_width)
 
         _top_sep_win.mvwin(1, 0)
@@ -1363,8 +1374,10 @@ def _draw_main():
         _safe_hline(_top_sep_win, 0, 4, curses.ACS_UARROW, _N_SCROLL_ARROWS)
 
     # Add the 'mainmenu' text as the title, centered at the top
+    # Use _top_sep_win width instead of term_width for correct centering
+    top_sep_width = _width(_top_sep_win)
     _safe_addstr(_top_sep_win,
-                 0, max((term_width - len(_kconf.mainmenu_text))//2, 0),
+                 0, max((top_sep_width - len(_kconf.mainmenu_text))//2, 0),
                  _kconf.mainmenu_text)
 
     _top_sep_win.noutrefresh()
@@ -1752,12 +1765,22 @@ def edit_width():
     # Horizontal scroll offset
     hscroll = max(i - edit_width() + 1, 0)
 
+    # Create shadow windows once
+    win_y, win_x = win.getbegyx()
+    win_height, win_width = win.getmaxyx()
+    bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
+
     while True:
         # Draw the "main" display with the menu, etc., so that resizing still
         # works properly. This is like a stack of windows, only hardcoded for
         # now.
         _draw_main()
+
         _draw_input_dialog(win, title, info_lines, s, i, hscroll)
+
+        # Refresh shadow windows after dialog window to ensure they're on top
+        _refresh_shadow_windows(bottom_shadow, right_shadow)
+
         curses.doupdate()
 
 
@@ -1767,6 +1790,10 @@ def edit_width():
             # Resize the main display too. The dialog floats above it.
             _resize_main()
             _resize_input_dialog(win, title, info_lines)
+            # Recreate shadow windows with new dialog size
+            win_y, win_x = win.getbegyx()
+            win_height, win_width = win.getmaxyx()
+            bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
 
         elif c == "\n":
             _safe_curs_set(0)
@@ -1806,13 +1833,6 @@ def _resize_input_dialog(win, title, info_lines):
 def _draw_input_dialog(win, title, info_lines, s, i, hscroll):
     edit_width = _width(win) - 4
 
-    # Get window position and size for shadow
-    win_y, win_x = win.getbegyx()
-    win_height, win_width = win.getmaxyx()
-
-    # Draw shadow on stdscr first
-    _draw_shadow(_stdscr, win_y, win_x, win_height, win_width)
-
     win.erase()
 
     # Note: Perhaps having a separate window for the input field would be nicer
@@ -1968,10 +1988,20 @@ def _key_dialog(title, text, keys):
 
     _resize_key_dialog(win, text)
 
+    # Create shadow windows once
+    win_y, win_x = win.getbegyx()
+    win_height, win_width = win.getmaxyx()
+    bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
+
     while True:
         # See _input_dialog()
         _draw_main()
+
         _draw_key_dialog(win, title, text)
+
+        # Refresh shadow windows after dialog window to ensure they're on top
+        _refresh_shadow_windows(bottom_shadow, right_shadow)
+
         curses.doupdate()
 
 
@@ -1981,6 +2011,10 @@ def _key_dialog(title, text, keys):
             # Resize the main display too. The dialog floats above it.
             _resize_main()
             _resize_key_dialog(win, text)
+            # Recreate shadow windows with new dialog size
+            win_y, win_x = win.getbegyx()
+            win_height, win_width = win.getmaxyx()
+            bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
 
         elif c == "\x1B":  # \x1B = ESC
             return None
@@ -2007,13 +2041,6 @@ def _resize_key_dialog(win, text):
 
 
 def _draw_key_dialog(win, title, text):
-    # Get window position and size for shadow
-    win_y, win_x = win.getbegyx()
-    win_height, win_width = win.getmaxyx()
-
-    # Draw shadow on stdscr first
-    _draw_shadow(_stdscr, win_y, win_x, win_height, win_width)
-
     win.erase()
 
     # Draw the frame first
@@ -2060,16 +2087,15 @@ def _button_dialog(title, text, buttons, default_button=0):
     win.mvwin((_height(_stdscr) - win_height)//2,
               (_width(_stdscr) - win_width)//2)
 
+    # Create shadow windows once
+    win_y, win_x = win.getbegyx()
+    win_height, win_width = win.getmaxyx()
+    bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
+
     while True:
-        # Draw main display behind dialog
+        # Draw main display behind dialog (calls noutrefresh on all subwindows)
         _draw_main()
 
-        # Get window position and size
-        win_y, win_x = win.getbegyx()
-        win_height, win_width = win.getmaxyx()
-
-        # Don't draw shadow for now - TODO: Add shadow support later
-
         win.erase()
 
         # Draw box border with proper colors
@@ -2147,6 +2173,10 @@ def _button_dialog(title, text, buttons, default_button=0):
             _print_button(win, button_label, button_y, button_positions[i], i == selected_button)
 
         win.noutrefresh()
+
+        # Refresh shadow windows after dialog window to ensure they're on top
+        _refresh_shadow_windows(bottom_shadow, right_shadow)
+
         curses.doupdate()
 
         # Handle input
@@ -2158,6 +2188,10 @@ def _button_dialog(title, text, buttons, default_button=0):
             win.resize(win_height, win_width)
             win.mvwin((_height(_stdscr) - win_height)//2,
                       (_width(_stdscr) - win_width)//2)
+            # Recreate shadow windows with new dialog size
+            win_y, win_x = win.getbegyx()
+            win_height, win_width = win.getmaxyx()
+            bottom_shadow, right_shadow = _create_shadow_windows(win_y, win_x, win_height, win_width)
 
         elif c == "\x1B":  # ESC
             return None
@@ -2260,37 +2294,64 @@ def _draw_box(win, y, x, height, width, box_attr, border_attr):
                 pass  # Interior is handled by caller
 
 
-def _draw_shadow(win, y, x, height, width):
-    # Draw shadows along the right and bottom edge to give a more 3D look,
-    # matching lxdialog's draw_shadow()
+def _create_shadow_windows(y, x, height, width, right_y_offset=1):
+    # Create shadow windows for bottom and right edges
+    # Returns tuple of (bottom_shadow_win, right_shadow_win)
+    #
+    # Based on lxdialog's draw_shadow():
+    # - Bottom: at y + height, from x + 2, width chars
+    # - Right: from y + right_y_offset to y + height (inclusive), at x + width, 2 chars wide
 
-    if curses.has_colors():
-        # Note: We need to define shadow color if not already defined
-        # For now, use a simple approach: draw with shadow style
-        try:
-            win.attrset(_style.get("shadow", 0))
-        except:
-            # Fallback: use dimmed/dark color
-            win.attrset(curses.A_DIM)
+    if not curses.has_colors():
+        return None, None
+
+    try:
+        shadow_attr = _style.get("shadow", 0)
 
-        # Bottom shadow (offset by 2 on x-axis)
-        for i in range(width):
+        # Bottom shadow window (1 line high, width wide, offset by 2 on x)
+        bottom_shadow = None
+        if y + height < _height(_stdscr) and x + 2 + width <= _width(_stdscr):
             try:
-                ch = win.inch(y + height, x + 2 + i)
-                _safe_addch(win, y + height, x + 2 + i, ch & curses.A_CHARTEXT)
+                bottom_shadow = curses.newwin(1, width, y + height, x + 2)
+                bottom_shadow.bkgd(' ', shadow_attr)
             except:
                 pass
 
-        # Right shadow (2 characters wide)
-        for i in range(1, height + 1):
+        # Right shadow window
+        # lxdialog: for (i = y + 1; i < y + height + 1; i++)
+        # Draw from y+right_y_offset to y+height (inclusive)
+        right_shadow = None
+        if x + width + 2 <= _width(_stdscr) and y + height <= _height(_stdscr):
             try:
-                ch1 = win.inch(y + i, x + width)
-                _safe_addch(win, y + i, x + width, ch1 & curses.A_CHARTEXT)
-                ch2 = win.inch(y + i, x + width + 1)
-                _safe_addch(win, y + i, x + width + 1, ch2 & curses.A_CHARTEXT)
+                # From (y + right_y_offset) to (y + height) inclusive
+                # Total rows = (y + height) - (y + right_y_offset) + 1 = height - right_y_offset + 1
+                shadow_height = height - right_y_offset + 1
+                if shadow_height > 0:
+                    right_shadow = curses.newwin(shadow_height, 2, y + right_y_offset, x + width)
+                    right_shadow.bkgd(' ', shadow_attr)
             except:
                 pass
 
+        return bottom_shadow, right_shadow
+    except:
+        return None, None
+
+
+def _refresh_shadow_windows(bottom_shadow, right_shadow):
+    # Refresh shadow windows, refilling them each time to ensure visibility
+    if bottom_shadow:
+        try:
+            bottom_shadow.erase()  # Clear and refill with background
+            bottom_shadow.noutrefresh()
+        except:
+            pass
+    if right_shadow:
+        try:
+            right_shadow.erase()  # Clear and refill with background
+            right_shadow.noutrefresh()
+        except:
+            pass
+
 
 def _draw_frame(win, title):
     # Draw a frame around the inner edges of 'win', with 'title' at the top
@@ -3147,8 +3208,9 @@ def _styled_win(style):
 
 def _set_style(win, style):
     # Changes the style of an existing window
+    # Use bkgd() to immediately fill window with background
 
-    win.bkgdset(" ", _style[style])
+    win.bkgd(" ", _style[style])
 
 
 def _max_scroll(lst, win):