Fix SelectTool: enable direct shape-to-shape selection (#29)

Users can now click directly between shapes without intermediate
deselection step. Preserves multi-selection and manipulation features.

Fixes #29

Author: PierreRaybaut

CHANGELOG.md

@@ -42,6 +42,10 @@
 
 * Fixed plot update after inserting a point using the `EditPointTool` on non-Windows platforms
 * [Issue #46](https://github.com/PlotPyStack/PlotPy/issues/46) - Contrast adjustment with 'Eliminate outliers' failed for float images with high dynamic range
+* [Issue #29](https://github.com/PlotPyStack/PlotPy/issues/29) - SelectTool: Selecting Another Shape Without Unselection
+  * Fixed direct selection between different shapes without requiring intermediate click on empty space
+  * Users can now click directly from one shape to another for immediate selection
+  * Maintains all existing functionality including multi-selection (Ctrl+click), moving, and resizing
 * Fixed `ErrorBarCurveItem` handling of all-NaN data:
   * Fixed `ValueError: zero-size array to reduction operation minimum which has no identity` when error bar curves contain only NaN values
   * Added proper checks in `boundingRect()` and `draw()` methods to handle empty arrays gracefully

plotpy/events.py

@@ -1497,9 +1497,25 @@ def start_tracking(self, filter: StatefulEventFilter, event: QC.QEvent) -> None:
                         self.inside = inside
                         break
                 else:
-                    self.__unselect_objects(filter)
-                    filter.set_state(self.start_state, event)
-                    return
+                    # Check if user clicked on a different selectable object
+                    if nearest is not None and nearest.can_select():
+                        # Direct selection of a different object
+                        plot.unselect_all()
+                        plot.select_item(nearest)
+                        plot.set_active_item(nearest)
+                        self.active = nearest
+                        self.handle = nearest_handle
+                        self.inside = nearest_inside
+                        # Clear unselection pending since we've switched to a new object
+                        self.unselection_pending = False
+                        # No need to process further - we've completed the selection
+                        plot.replot()
+                        return
+                    else:
+                        # Clicked on empty space - unselect everything
+                        self.__unselect_objects(filter)
+                        filter.set_state(self.start_state, event)
+                        return
         else:
             # No item is selected
             self.active = nearest