Wiresheet: grey margin strip, saved-state tint on and off the sheet

- The top/left margin no box may enter is grey and ungridded, so the white
  sheet starts where boxes can actually be placed.
- Saving/unsaved state no longer resets the canvas to white: the sheet goes
  white/pink and the area around it grey/greyish pink.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.174"
+VERSION = "0.0.0.175"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True
@@ -41,6 +41,9 @@ status_label = None      # the window's bottom status bar
 # colour wherever the change was made.
 DIRTY_TINT = "#ffe6e6"
 CLEAN_TINT = "white"
+# The wiresheet canvas around the sheet itself, clean and with unsaved changes.
+OFF_SHEET_TINT = "#f3f3f3"
+OFF_SHEET_DIRTY_TINT = "#f0dcdc"
 
 # The file name on the tree's root row turns this colour while anything is unwritten,
 # which is the one place a file name appears on screen -- a Tk window title cannot be
@@ -239,8 +242,7 @@ def mark_dirty():
     global is_dirty
     if not is_dirty:
         is_dirty = True
-        if canvas is not None:
-            canvas.config(bg=DIRTY_TINT)
+        paint_sheet_tint()
     refresh_dirty_display()
 
 
@@ -248,11 +250,26 @@ def mark_clean():
     """Clears the unsaved-state marker after a successful save or a fresh load."""
     global is_dirty
     is_dirty = False
-    if canvas is not None:
-        canvas.config(bg=CLEAN_TINT)
+    paint_sheet_tint()
     refresh_dirty_display()
 
 
+def sheet_tints():
+    """(sheet, off-sheet) colours for the wiresheet in the current saved/unsaved state."""
+    if is_dirty:
+        return DIRTY_TINT, OFF_SHEET_DIRTY_TINT
+    return CLEAN_TINT, OFF_SHEET_TINT
+
+
+def paint_sheet_tint():
+    """Recolours the sheet (the "sheet_bg" rectangle) and the canvas around it."""
+    if canvas is None:
+        return
+    sheet, off_sheet = sheet_tints()
+    canvas.config(bg=off_sheet)
+    canvas.itemconfig("sheet_bg", fill=sheet)
+
+
 # ── Live device connection state ────────────────────────────────
 live_mode = False
 device_session = None       # device_session.DeviceSession instance

main.py

@@ -3743,7 +3743,7 @@ canvas_hscroll.pack(side=tk.BOTTOM, fill=tk.X)
 
 canvas = tk.Canvas(
     frame_editor,
-    bg=wiresheet.OFF_SHEET_COLOUR,
+    bg=app_state.OFF_SHEET_TINT,
     highlightthickness=0,
     xscrollcommand=canvas_hscroll.set,
     yscrollcommand=canvas_vscroll.set,

wiresheet.py

@@ -123,7 +123,6 @@ FIT_PADDING = 20
 # as a grey wash rather than a grid, so the grid is left off instead.
 MIN_GRID_STEP = 3
 SHEET_MARGIN_GRIDS = 3  # grid squares of grey kept past anything that overflows the sheet
-OFF_SHEET_COLOUR = "#f3f3f3"  # canvas outside the area a box's origin can be stored in
 
 
 def snap_up(value, grid_size):
@@ -240,16 +239,18 @@ def measure_box(comp, fonts, linked_slot_index):
 
 
 def draw_grid():
-    """Paints the sheet white and grids it; the canvas around it stays OFF_SHEET_COLOUR.
+    """Paints the sheet and grids it; the canvas around it is the off-sheet tint.
 
     Drawn at the sheet's zoom, so a box still lands on a line at every scale.
     """
     canvas = app_state.canvas
     canvas.delete("grid")
 
-    x1, y1 = 0, 0
+    # The sheet starts past the margin strip no box may enter, which stays grey too.
+    x1 = y1 = layout_margin(app_state.meta_scale) * app_state.zoom
     x2, y2 = (coord * app_state.zoom for coord in sheet_extent())
-    canvas.create_rectangle(x1, y1, x2, y2, fill="white", outline="#c8c8c8", tags="grid")
+    canvas.create_rectangle(x1, y1, x2, y2, outline="#c8c8c8", tags=("grid", "sheet_bg"))
+    app_state.paint_sheet_tint()   # white or pink by saved state, grey or pink around it
 
     step = app_state.GRID_SIZE * app_state.zoom
     if step >= MIN_GRID_STEP: