Simplify and tidy undo

src/complexitty/commands/main.py

@@ -26,6 +26,7 @@ class Undo(Command):
     """Undo the latest change"""
 
     BINDING_KEY = "backspace"
+    SHOW_IN_FOOTER = True
 
 
 ### main.py ends here

src/complexitty/providers/main.py

@@ -85,7 +85,7 @@ def commands(self) -> CommandHits:
         yield SetColourToShadesOfBlue()
         yield SetColourToShadesOfGreen()
         yield SetColourToShadesOfRed()
-        yield Undo()
+        yield from self.maybe(Undo)
         yield ZeroZero()
         yield ZoomIn()
         yield ZoomInFaster()

src/complexitty/screens/main.py

@@ -3,6 +3,7 @@
 ##############################################################################
 # Python imports.
 from argparse import Namespace
+from collections import deque
 from math import floor, log10
 from re import Pattern, compile
 from typing import Final, NamedTuple, TypeAlias
@@ -18,7 +19,6 @@
 from textual_enhanced.commands import ChangeTheme, Command, Help
 from textual_enhanced.dialogs import ModalInput
 from textual_enhanced.screen import EnhancedScreen
-from textual_enhanced.tools import History
 
 ##############################################################################
 # Local imports.
@@ -77,7 +77,7 @@ class Situation(NamedTuple):
 
 
 ##############################################################################
-PlotHistory: TypeAlias = History[Situation]
+PlotHistory: TypeAlias = deque[Situation]
 """Type of the plot history."""
 
 
@@ -96,25 +96,28 @@ class Main(EnhancedScreen[None]):
         # Keep these together as they're bound to function keys and destined
         # for the footer.
         Help,
-        ChangeTheme,
+        MoveLeft,
+        MoveRight,
+        MoveUp,
+        MoveDown,
+        ZoomIn,
+        ZoomOut,
+        IncreaseMaximumIteration,
+        DecreaseMaximumIteration,
+        Undo,
         Quit,
         # Everything else.
+        ChangeTheme,
         CopyCommandLineToClipboard,
-        DecreaseMaximumIteration,
         DecreaseMultibrot,
         GoMiddle,
         GoTo,
         GreatlyDecreaseMaximumIteration,
         GreatlyIncreaseMaximumIteration,
-        IncreaseMaximumIteration,
         IncreaseMultibrot,
-        MoveDown,
         MoveDownSlowly,
-        MoveLeft,
         MoveLeftSlowly,
-        MoveRight,
         MoveRightSlowly,
-        MoveUp,
         MoveUpSlowly,
         Reset,
         SetColourToBluesAndBrowns,
@@ -124,11 +127,8 @@ class Main(EnhancedScreen[None]):
         SetColourToShadesOfBlue,
         SetColourToShadesOfGreen,
         SetColourToShadesOfRed,
-        Undo,
         ZeroZero,
-        ZoomIn,
         ZoomInFaster,
-        ZoomOut,
         ZoomOutFaster,
     )
 
@@ -144,7 +144,7 @@ def __init__(self, arguments: Namespace) -> None:
         """
         self._arguments = arguments
         """The command line arguments passed to the application."""
-        self._history = PlotHistory()
+        self._history = PlotHistory(maxlen=128)
         """The plot situation history."""
         super().__init__()
 
@@ -166,7 +166,27 @@ def on_mount(self) -> None:
             if self._arguments.colour_map is None
             else get_colour_map(self._arguments.colour_map),
         )
-        self._remember()
+
+    def check_action(self, action: str, parameters: tuple[object, ...]) -> bool | None:
+        """Check if an action is possible to perform right now.
+
+        Args:
+            action: The action to perform.
+            parameters: The parameters of the action.
+
+        Returns:
+            `True` if it can perform, `False` or `None` if not.
+        """
+        if not self.is_mounted:
+            # Surprisingly it seems that Textual's "dynamic bindings" can
+            # cause this method to be called before the DOM is up and
+            # running. This breaks the rule of least astonishment, I'd say,
+            # but okay let's be defensive... (when I can come up with a nice
+            # little MRE I'll report it).
+            return True
+        if action == Undo.action_name():
+            return bool(self._history) or None
+        return True
 
     @on(Mandelbrot.Plotted)
     def _update_situation(self, message: Mandelbrot.Plotted) -> None:
@@ -198,7 +218,7 @@ def _update_situation(self, message: Mandelbrot.Plotted) -> None:
     def _remember(self) -> None:
         """Remember the current situation."""
         plot = self.query_one(Mandelbrot)
-        self._history.add(
+        self._history.append(
             Situation(
                 plot.x_position,
                 plot.y_position,
@@ -207,15 +227,16 @@ def _remember(self) -> None:
                 plot.multibrot,
             )
         )
+        self.refresh_bindings()
 
     def action_zoom(self, change: float) -> None:
         """Change the zoom value.
 
         Args:
             change: The amount to change the zoom by.
         """
-        self.query_one(Mandelbrot).zoom *= change
         self._remember()
+        self.query_one(Mandelbrot).zoom *= change
 
     def action_move(self, x: int, y: int) -> None:
         """Move the plot in the indicated direction.
@@ -224,17 +245,17 @@ def action_move(self, x: int, y: int) -> None:
             x: The number of pixels to move in the X direction.
             y: The number of pixels to move in the Y direction.
         """
-        self.query_one(Mandelbrot).move(x, y)
         self._remember()
+        self.query_one(Mandelbrot).move(x, y)
 
     def action_iterate(self, change: int) -> None:
         """Change the maximum iteration.
 
         Args:
             change: The change to make to the maximum iterations.
         """
-        self.query_one(Mandelbrot).max_iteration += change
         self._remember()
+        self.query_one(Mandelbrot).max_iteration += change
 
     def action_set_colour(self, colour_map: str) -> None:
         """Set the colour map for the plot.
@@ -250,8 +271,8 @@ def action_multibrot(self, change: int) -> None:
         Args:
             change: The change to make to the 'multibrot' value.
         """
-        self.query_one(Mandelbrot).multibrot += change
         self._remember()
+        self.query_one(Mandelbrot).multibrot += change
 
     def action_goto(self, x: int, y: int) -> None:
         """Go to a specific location.
@@ -265,8 +286,8 @@ def action_goto(self, x: int, y: int) -> None:
 
     def action_reset_command(self) -> None:
         """Reset the plot to its default values."""
-        self.query_one(Mandelbrot).reset()
         self._remember()
+        self.query_one(Mandelbrot).reset()
 
     _VALID_LOCATION: Final[Pattern[str]] = compile(
         r"(?P<x>[^, ]+) *[, ] *(?P<y>[^, ]+)"
@@ -318,17 +339,18 @@ def action_copy_command_line_to_clipboard_command(self) -> None:
 
     def action_undo_command(self) -> None:
         """Undo through the history."""
-        if (
-            self._history.backward()
-            and (situation := self._history.current_item) is not None
-        ):
-            self.query_one(Mandelbrot).set(
-                x_position=situation.x_position,
-                y_position=situation.y_position,
-                zoom=situation.zoom,
-                max_iteration=situation.max_iteration,
-                multibrot=situation.multibrot,
-            ).plot()
+        try:
+            situation = self._history.pop()
+        except IndexError:
+            return
+        self.refresh_bindings()
+        self.query_one(Mandelbrot).set(
+            x_position=situation.x_position,
+            y_position=situation.y_position,
+            zoom=situation.zoom,
+            max_iteration=situation.max_iteration,
+            multibrot=situation.multibrot,
+        ).plot()
 
 
 ### main.py ends here