Add redo, undo×10, brush preview, hide/show mask; drop Reload Saved

mask_canvas.py:
- Redo stack: new strokes clear it, undo pushes onto it, redo pops from it.
- undo10(): undoes up to 10 steps in one call with a single redraw.
- Brush circle preview: white Circle patch tracks mouse position and shows
  current brush radius; hidden when cursor leaves the axes.
- toggle_mask() / btn_mask: hides or shows the green mask overlay without
  affecting the underlying mask data.

annotator.py:
- Removed Reload Saved button and reload_saved() — clip already loads its
  saved state on navigation, making the button redundant.
- Added Undo×10 and Redo buttons wired to mc.undo10 / mc.redo.
- Added Hide Mask button (mc.btn_mask) to the toolbar row.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/river_annotation_tool/annotator.py

@@ -111,14 +111,22 @@ class Annotator(QMainWindow):
         btn_skip = QPushButton("Skip")
         btn_clear = QPushButton("Clear")
         btn_undo = QPushButton("Undo")
-        btn_reload = QPushButton("Reload Saved")
+        btn_undo10 = QPushButton("Undo×10")
+        btn_redo = QPushButton("Redo")
 
         row1 = QHBoxLayout()
         for b in [self.btn_prev, btn_next, btn_skip]:
             row1.addWidget(b)
 
         row2 = QHBoxLayout()
-        for b in [btn_clear, self.mc.btn_erase, btn_undo, btn_reload]:
+        for b in [
+            btn_clear,
+            self.mc.btn_erase,
+            btn_undo,
+            btn_undo10,
+            btn_redo,
+            self.mc.btn_mask,
+        ]:
             row2.addWidget(b)
         row2.addWidget(QLabel("Brush"))
         row2.addWidget(self.mc.brush_slider)
@@ -146,7 +154,8 @@ class Annotator(QMainWindow):
         btn_skip.clicked.connect(self.skip_clip)
         btn_clear.clicked.connect(self.mc.clear)
         btn_undo.clicked.connect(self.mc.undo)
-        btn_reload.clicked.connect(self.reload_saved)
+        btn_undo10.clicked.connect(self.mc.undo10)
+        btn_redo.clicked.connect(self.mc.redo)
 
         if self._pending_answers:
             self._set_answers(self._pending_answers)
@@ -258,15 +267,6 @@ class Annotator(QMainWindow):
 
         print("Saved:", out)
 
-    def reload_saved(self):
-        mask = self._read_saved_mask()
-        if mask is None:
-            return
-        self.mc.reset(mask)
-        answers = self._read_saved_answers()
-        if answers:
-            self._set_answers(answers)
-
     def _switch_ui_to_clip(self):
         self.frame_i = 0
         self.mc.load_clip(

src/river_annotation_tool/mask_canvas.py

@@ -1,12 +1,13 @@
 import numpy as np
 from matplotlib.backends.backend_qtagg import FigureCanvasQTAgg as FigureCanvas
 from matplotlib.figure import Figure
+from matplotlib.patches import Circle
 from PySide6.QtCore import Qt
 from PySide6.QtWidgets import QPushButton, QSlider
 
 
 class MaskCanvas:
-    """Matplotlib canvas with brush-based mask drawing, undo, and erase."""
+    """Matplotlib canvas with brush-based mask drawing, undo/redo, and erase."""
 
     def __init__(self, frames, dh: int, dw: int):
         self.dh = dh
@@ -14,8 +15,10 @@ class MaskCanvas:
 
         self.mask = np.zeros((dh, dw), dtype=np.uint8)
         self.history: list[np.ndarray] = []
+        self.redo_stack: list[np.ndarray] = []
         self.erase_mode = False
         self.drawing = False
+        self.mask_visible = True
 
         self._build_figure(frames)
         self._build_controls()
@@ -29,9 +32,14 @@ class MaskCanvas:
         self.img_artist = self.ax.imshow(frames[0])
         self.mask_artist = self.ax.imshow(np.zeros((self.dh, self.dw, 4)))
         self.title_text = self.ax.set_title("", fontsize=10, pad=4)
+        self.brush_circle = Circle(
+            (0, 0), radius=5, fill=False, color="white", linewidth=1.5, visible=False
+        )
+        self.ax.add_patch(self.brush_circle)
 
     def _build_controls(self):
         self.btn_erase = QPushButton("Eraser")
+        self.btn_mask = QPushButton("Hide Mask")
         self.brush_slider = QSlider(Qt.Horizontal)
         self.brush_slider.setRange(2, 50)
         self.brush_slider.setValue(5)
@@ -40,7 +48,9 @@ class MaskCanvas:
         self.canvas.mpl_connect("button_press_event", self._on_press)
         self.canvas.mpl_connect("motion_notify_event", self._on_move)
         self.canvas.mpl_connect("button_release_event", self._on_release)
+        self.canvas.mpl_connect("axes_leave_event", self._on_axes_leave)
         self.btn_erase.clicked.connect(self.toggle_erase)
+        self.btn_mask.clicked.connect(self.toggle_mask)
 
     # ── clip transition ────────────────────────────────────────────
     def load_clip(self, frames, dh: int, dw: int, mask=None, title: str = ""):
@@ -48,6 +58,7 @@ class MaskCanvas:
         self.dw = dw
         self.mask = mask if mask is not None else np.zeros((dh, dw), dtype=np.uint8)
         self.history = []
+        self.redo_stack = []
         self.img_artist.set_data(frames[0])
         self.set_title(title)
         self.redraw()
@@ -62,14 +73,20 @@ class MaskCanvas:
 
     # ── mask ops ───────────────────────────────────────────────────
     def reset(self, mask=None):
-        self.mask = mask if mask is not None else np.zeros((self.dh, self.dw), dtype=np.uint8)
+        self.mask = (
+            mask if mask is not None else np.zeros((self.dh, self.dw), dtype=np.uint8)
+        )
         self.history = []
+        self.redo_stack = []
         self.redraw()
 
     def redraw(self):
-        rgba = np.zeros((self.dh, self.dw, 4))
+        if self.mask_visible:
-        rgba[..., 1] = self.mask * 0.7
+            rgba = np.zeros((self.dh, self.dw, 4))
-        rgba[..., 3] = self.mask * 0.4
+            rgba[..., 1] = self.mask * 0.7
+            rgba[..., 3] = self.mask * 0.4
+        else:
+            rgba = np.zeros((self.dh, self.dw, 4))
         self.mask_artist.set_data(rgba)
         self.canvas.draw_idle()
 
@@ -79,17 +96,38 @@ class MaskCanvas:
 
     def undo(self):
         if self.history:
+            self.redo_stack.append(self.mask.copy())
             self.mask = self.history.pop()
             self.redraw()
 
+    def undo10(self):
+        for _ in range(10):
+            if not self.history:
+                break
+            self.redo_stack.append(self.mask.copy())
+            self.mask = self.history.pop()
+        self.redraw()
+
+    def redo(self):
+        if self.redo_stack:
+            self.history.append(self.mask.copy())
+            self.mask = self.redo_stack.pop()
+            self.redraw()
+
     def toggle_erase(self):
         self.erase_mode = not self.erase_mode
         self.btn_erase.setText("Eraser ON" if self.erase_mode else "Eraser")
 
+    def toggle_mask(self):
+        self.mask_visible = not self.mask_visible
+        self.btn_mask.setText("Show Mask" if not self.mask_visible else "Hide Mask")
+        self.redraw()
+
     def stamp(self, x, y):
         if x is None or y is None:
             return
         self.history.append(self.mask.copy())
+        self.redo_stack.clear()
         r = self.brush_slider.value()
         ix, iy = int(x), int(y)
         y0, y1 = max(0, iy - r), min(self.dh, iy + r + 1)
@@ -99,6 +137,20 @@ class MaskCanvas:
         self.mask[y0:y1, x0:x1][circle] = 0 if self.erase_mode else 1
         self.redraw()
 
+    # ── brush preview ──────────────────────────────────────────────
+    def _update_brush_preview(self, e):
+        if e.inaxes == self.ax and e.xdata is not None:
+            self.brush_circle.center = (e.xdata, e.ydata)
+            self.brush_circle.set_radius(self.brush_slider.value())
+            self.brush_circle.set_visible(True)
+        else:
+            self.brush_circle.set_visible(False)
+        self.canvas.draw_idle()
+
+    def _on_axes_leave(self, _):
+        self.brush_circle.set_visible(False)
+        self.canvas.draw_idle()
+
     # ── mouse events ───────────────────────────────────────────────
     def _on_press(self, e):
         if e.xdata is None:
@@ -107,6 +159,7 @@ class MaskCanvas:
         self.stamp(e.xdata, e.ydata)
 
     def _on_move(self, e):
+        self._update_brush_preview(e)
         if self.drawing:
             self.stamp(e.xdata, e.ydata)