Implement LastItemHolder for managing last selected items in CurveStatsTool and ImageStatsTool

Author: PierreRaybaut

plotpy/tools/base.py

@@ -22,6 +22,8 @@
 
     from qtpy.QtCore import QPointF
 
+    from plotpy.interfaces import ICurveItemType, IImageItemType
+    from plotpy.items import BaseImageItem, CurveItem
     from plotpy.plot import BasePlot, PlotManager
 
 
@@ -644,3 +646,40 @@ def end_rect(
         if self.switch_to_default_tool:
             shape = self.get_last_final_shape()
             plot.set_active_item(shape)
+
+
+class LastItemHolder:
+    """Class to hold a weak reference to the last item"""
+
+    def __init__(self, item_type: IImageItemType | ICurveItemType) -> None:
+        self._item_type = item_type
+        self._last_item: weakref.ReferenceType[CurveItem | BaseImageItem] | None = None
+
+    def set(self, item: CurveItem | BaseImageItem) -> None:
+        """Set the last item
+
+        Args:
+            item: BaseImageItem instance
+        """
+        self._last_item = weakref.ref(item)
+
+    def get(self) -> CurveItem | BaseImageItem | None:
+        """Get the last item
+
+        Returns:
+            BaseImageItem instance or None
+        """
+        if self._last_item is not None:
+            return self._last_item()
+        return None
+
+    def update_from_selection(self, plot: BasePlot) -> CurveItem | BaseImageItem | None:
+        """Update the last item from the selected items of the plot, and return it.
+
+        Args:
+            plot: BasePlot instance
+        """
+        items = plot.get_selected_items(item_type=self._item_type)
+        if len(items) == 1:
+            self.set(items[0])
+        return self.get()

plotpy/tools/curve.py

@@ -3,7 +3,6 @@
 
 from __future__ import annotations
 
-import weakref
 from typing import TYPE_CHECKING, Any, Callable
 
 import numpy as np
@@ -28,7 +27,12 @@
 from plotpy.interfaces import ICurveItemType
 from plotpy.items import Marker, XRangeSelection
 from plotpy.items.curve.base import CurveItem
-from plotpy.tools.base import DefaultToolbarID, InteractiveTool, ToggleTool
+from plotpy.tools.base import (
+    DefaultToolbarID,
+    InteractiveTool,
+    LastItemHolder,
+    ToggleTool,
+)
 from plotpy.tools.cursor import BaseCursorTool
 
 if TYPE_CHECKING:
@@ -66,7 +70,7 @@ def __init__(
         tip: str | None = None,
     ) -> None:
         super().__init__(manager, toolbar_id, title=title, icon=icon, tip=tip)
-        self._last_item: weakref.ReferenceType[CurveItem] | None = None
+        self.last_item_holder = LastItemHolder(ICurveItemType)
         self.label: DataInfoLabel | None = None
         if labelfuncs is None:
             labelfuncs: tuple[tuple[str, Callable[..., Any]], ...] = (
@@ -102,12 +106,6 @@ def set_labelfuncs(
         """
         self.labelfuncs = labelfuncs
 
-    def get_last_item(self) -> CurveItem | None:
-        """Get last item on which the tool was used"""
-        if self._last_item is not None:
-            return self._last_item()
-        return None
-
     def create_shape(self) -> XRangeSelection:
         """Create shape associated with the tool"""
         return XRangeSelection(0, 0)
@@ -119,7 +117,7 @@ def create_label(self) -> DataInfoLabel:
         from plotpy.builder import make
 
         plot = self.manager.get_plot()
-        curve = self.get_associated_item(plot)
+        curve = self.last_item_holder.update_from_selection(plot)
         specs = [(curve, label, func) for label, func in self.labelfuncs]
         title: QwtText = curve.title()
         label = make.computations(self.shape, "TL", specs, title.text())
@@ -151,27 +149,13 @@ def end_move(self, filter: StatefulEventFilter, event: QG.QMouseEvent) -> None:
             filter.plot.add_item_with_z_offset(self.label, SHAPE_Z_OFFSET)
             self.label = None
 
-    def get_associated_item(self, plot: BasePlot) -> CurveItem | None:
-        """Get associated item
-
-        Args:
-            plot: BasePlot instance
-
-        Returns:
-            curve item or None
-        """
-        items = plot.get_selected_items(item_type=ICurveItemType)
-        if len(items) == 1:
-            self._last_item = weakref.ref(items[0])
-        return self.get_last_item()
-
     def update_status(self, plot: BasePlot) -> None:
         """Update tool status
 
         Args:
             plot: BasePlot instance
         """
-        item = self.get_associated_item(plot)
+        item = self.last_item_holder.update_from_selection(plot)
         self.action.setEnabled(item is not None)
 
 

plotpy/tools/image.py

@@ -3,7 +3,6 @@
 
 from __future__ import annotations
 
-import weakref
 from typing import TYPE_CHECKING, Any, Callable, Literal
 
 from guidata.configtools import get_icon
@@ -39,6 +38,7 @@
     DefaultToolbarID,
     GuiTool,
     InteractiveTool,
+    LastItemHolder,
     PanelTool,
     ToggleTool,
 )
@@ -243,7 +243,7 @@ def __init__(
             icon,
             tip,
         )
-        self._last_item = None
+        self.last_item_holder = LastItemHolder(IImageItemType)
         self.stats_func = stats_func
         self.replace_stats = replace
 
@@ -263,16 +263,6 @@ def set_stats_func(
         self.stats_func = stats_func
         self.replace_stats = replace
 
-    def get_last_item(self) -> BaseImageItem | None:
-        """Last image item getter
-
-        Returns:
-            Returns last image item or None
-        """
-        if self._last_item is not None:
-            return self._last_item()
-        return None
-
     def create_shape(self) -> tuple[ImageStatsRectangle, Literal[0], Literal[2]]:
         """Returns a new ImageStatsRectangle instance and the index of handles to
         display.
@@ -311,7 +301,7 @@ def register_shape(self, shape: ImageStatsRectangle, final=False) -> None:
             final: unused argument. Defaults to False.
         """
         plot = shape.plot()
-        image = self.get_last_item()
+        image = self.last_item_holder.get()
         if plot is not None and image is not None:
             plot.unselect_all()
             plot.set_active_item(shape)
@@ -326,28 +316,14 @@ def handle_final_shape(self, shape: ImageStatsRectangle) -> None:
         super().handle_final_shape(shape)
         self.register_shape(shape, final=True)
 
-    def get_associated_item(self, plot: BasePlot) -> BaseImageItem | None:
-        """Return a reference to the last image item associated with the tool
-
-        Args:
-            plot: Plot instance
-
-        Returns:
-            Reference to the last image item associated with the tool
-        """
-        items = plot.get_selected_items(item_type=IImageItemType)
-        if len(items) == 1:
-            self._last_item = weakref.ref(items[0])
-        return self.get_last_item()
-
     def update_status(self, plot: BasePlot) -> None:
         """Update tool status if the plot type is not PlotType.CURVE.
 
         Args:
             plot: Plot instance
         """
         if update_image_tool_status(self, plot):
-            item = self.get_associated_item(plot)
+            item = self.last_item_holder.update_from_selection(plot)
             self.action.setEnabled(item is not None)