matplotlib · lucaznch · May 5, 2026 · May 16, 2026 · May 16, 2026 · May 26, 2026
diff --git a/doc/api/widgets_api.rst b/doc/api/widgets_api.rst
@@ -35,11 +35,13 @@ Widget classes
    RangeSlider
    TextBox
    _SelectorWidget
+   _PolygonalSelector
    RectangleSelector
    EllipseSelector
    Lasso
    LassoSelector
    PolygonSelector
+   PolylineSelector
    SpanSelector
    SubplotTool
 

diff --git a/doc/release/next_whats_new/open_polygonal_chain.rst b/doc/release/next_whats_new/open_polygonal_chain.rst
@@ -0,0 +1,51 @@
+Introduce open polygonal chains in ``matplotlib.widgets``
+---------------------------------------------------------
+
+The widget class `.widgets.PolygonSelector` is used to select a
+polygon region of an Axes. More precisely, it enables the selection
+of a closed polygonal chain, a sequence of vertices connected by
+line segments where the first and last vertices are connected.
+
+.. plot::
+    :include-source: true
+    :alt: Closed polygonal chains using PolygonSelector.
+
+    import matplotlib.pyplot as plt
+    from matplotlib.widgets import PolygonSelector
+
+    _, ax = plt.subplots()
+    selector = PolygonSelector(ax)
+    selector.verts = [(0.1, 0.4), (0.5, 0.9), (0.3, 0.2)]
+
+    plt.show()
+
+Support for open polygonal chains has been added through the new
+`.widgets.PolylineSelector` class. A polyline is a sequence of
+vertices connected by line segments, where the first and
+last vertices are not connected, i.e., an open polygonal chain.
+
+.. plot::
+    :include-source: true
+    :alt: Open polygonal chains using PolylineSelector.
+
+    import matplotlib.pyplot as plt
+    from matplotlib.widgets import PolylineSelector
+
+    _, ax = plt.subplots()
+    selector = PolylineSelector(ax)
+    selector.verts = [(0.1, 0.4), (0.5, 0.9), (0.3, 0.2)]
+
+    plt.show()
+
+Both selectors share the same interactive editing capabilities,
+including vertex repositioning and removal, as well as the ability
+to define polygonal chains both programmatically and interactively.
+
+The interactive selection of an open polygonal chain is completed by
+pressing the *Enter* key after placing the final vertex.
+
+Internally, the common functionality of polygonal chain selector
+widgets has been extracted into the new private base class
+`.widgets._PolygonalSelector`. `~.widgets.PolygonSelector` now
+inherits from `~.widgets._PolygonalSelector` while preserving
+its existing API and behavior.
diff --git a/galleries/examples/widgets/polyline_selector_demo.py b/galleries/examples/widgets/polyline_selector_demo.py
@@ -0,0 +1,105 @@
+"""
+=========================================================
+Select four control points to define a cubic Bézier curve
+=========================================================
+
+Shows how one can use `.widgets.PolylineSelector` to create an interactive
+cubic Bézier curve visualizer. Select four control points to define the curve.
+"""
+
+import matplotlib.patches as patches
+from matplotlib.path import Path
+from matplotlib.widgets import PolylineSelector
+
+EMPTY_PATH = Path([(0, 0)], [Path.MOVETO])
+
+
+class CubicBezierCurveVisualizer:
+    """
+    Interactive cubic Bézier curve visualizer.
+
+    This tool allows you to define a cubic Bézier curve by selecting
+    four control points using `PolylineSelector`. The resulting curve
+    is displayed using `PathPatch` and updates as the selection changes,
+    provided that a valid set of control points is selected. Press the
+    'enter' key to complete the curve after selecting four control points.
+    Pressing 'esc' clears the current curve so a new one can be created.
+
+    Parameters
+    ----------
+    ax : `~matplotlib.axes.Axes`
+        Axes to interact with.
+    props : dict, optional
+        Properties with which the polyline selector lines will be drawn.
+    handle_props : dict, optional
+        Properties for the control point handles.
+    """
+    def __init__(self, ax, props=None, handle_props=None):
+        self.ax = ax
+        self.canvas = ax.figure.canvas
+        self.curve = patches.PathPatch(EMPTY_PATH, facecolor='none', lw=2)
+        self.ax.add_patch(self.curve)
+
+        if props is None:
+            props = dict(ls='--', c='gray')
+        if handle_props is None:
+            handle_props = dict(marker='o', ms=8, mfc='gray', mec='black')
+
+        self.selector = PolylineSelector(ax, self.onselect,
+                                         props=props, handle_props=handle_props)
+
+        self.cid = self.canvas.mpl_connect('key_press_event', self.on_key_press)
+
+    def onselect(self, verts):
+        if len(verts) != 4:
+            print("Select exactly 4 points for a cubic Bézier curve.")
+            self.clear()
+            return
+        path = Path(verts, [Path.MOVETO, Path.CURVE4, Path.CURVE4, Path.CURVE4])
+        self.curve.set_path(path)
+        self.canvas.draw_idle()
+
+    def clear(self):
+        self.curve.set_path(EMPTY_PATH)
+        self.canvas.draw_idle()
+
+    def on_key_press(self, event):
+        if event.key == 'escape':
+            self.clear()
+
+    def disconnect(self):
+        self.selector.disconnect_events()
+        self.canvas.mpl_disconnect(self.cid)
+
+
+if __name__ == '__main__':
+    import matplotlib.pyplot as plt
+
+    fig, ax = plt.subplots()
+
+    ax.set(xlim=(0, 1), ylim=(0, 1))
+    ax.grid(alpha=0.5)
+
+    bezier_visualizer = CubicBezierCurveVisualizer(ax)
+
+    print("Select exactly 4 control points to define a cubic Bézier curve.")
+    print("Press the 'enter' key to complete the selection.")
+    print("Hold 'ctrl' to reposition a single point while polyline is incomplete.")
+    print("Hold 'shift' to move all control points.")
+    print("Left click and drag a point to reposition it.")
+    print("Press the 'esc' key to start a new curve.")
+
+    plt.show()
+
+    bezier_visualizer.disconnect()
+
+# %%
+#
+# .. admonition:: References
+#
+#    The use of the following functions, methods, classes and modules is shown
+#    in this example:
+#
+#    - `matplotlib.widgets.PolylineSelector`
+#    - `matplotlib.path.Path`
+#    - `matplotlib.patches.PathPatch`
diff --git a/galleries/examples/widgets/polyline_selector_simple.py b/galleries/examples/widgets/polyline_selector_simple.py
@@ -0,0 +1,59 @@
+"""
+=================
+Polyline Selector
+=================
+
+Shows how to create a polyline programmatically or interactively
+"""
+
+import matplotlib.pyplot as plt
+
+from matplotlib.widgets import PolylineSelector
+
+# %%
+#
+# To create the polyline programmatically
+fig, ax = plt.subplots()
+fig.show()
+
+selector = PolylineSelector(ax, lambda *args: None)
+
+# Add three vertices
+selector.verts = [(0.1, 0.4), (0.5, 0.9), (0.3, 0.2)]
+
+
+# %%
+#
+# To create the polyline interactively
+
+fig2, ax2 = plt.subplots()
+fig2.show()
+
+selector2 = PolylineSelector(ax2, lambda *args: None)
+
+print("Click to add vertices sequentially.")
+print("Press the 'enter' key to complete the polyline.")
+print("Hold 'ctrl' to reposition a single vertex while polyline is incomplete.")
+print("Hold 'shift' to move all vertices.")
+print("Left click and drag a vertex to reposition it.")
+print("Right click to remove a vertex.")
+print("Press the 'esc' key to start a new polyline.")
+
+
+# %%
+# .. tags::
+#
+#    component: axes,
+#    styling: position,
+#    plot-type: line,
+#    level: intermediate,
+#    domain: cartography,
+#    domain: geometry,
+#    domain: statistics,
+#
+# .. admonition:: References
+#
+#    The use of the following functions, methods, classes and modules is shown
+#    in this example:
+#
+#    - `matplotlib.widgets.PolylineSelector`