Added optional props argument to Lasso Widget __init__ to customize Lasso line (matplotlib#26594)

* Added the ability for Lasso color, style, and lw to be set in the init function

* Added props option to Lasso widget

updated Lasso documentation with props

updated Lasso documentation with props

* wrote a test for the lasso tool

Lasso test passes

* fixed whitespace issues

* fixed whitespace on test, added some test code to make sure defaults worked as intended

* fixed whitespace in widget.py

* updated with suggestions from oscargus

* corrected over indented docstring

* ...fixed indentions

* docstrings

* doc-string corrections

* Update lib/matplotlib/widgets.py

---------

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

Author: kbturk

lib/matplotlib/tests/test_widgets.py

@@ -1020,6 +1020,27 @@ def test_lasso_selector_set_props(ax):
     assert artist.get_alpha() == 0.3
 
 
+def test_lasso_set_props(ax):
+    onselect = mock.Mock(spec=noop, return_value=None)
+    tool = widgets.Lasso(ax, (100, 100), onselect)
+    line = tool.line
+    assert mcolors.same_color(line.get_color(), 'black')
+    assert line.get_linestyle() == '-'
+    assert line.get_lw() == 2
+    tool = widgets.Lasso(ax, (100, 100), onselect, props=dict(
+        linestyle='-', color='darkblue', alpha=0.2, lw=1))
+
+    line = tool.line
+    assert mcolors.same_color(line.get_color(), 'darkblue')
+    assert line.get_alpha() == 0.2
+    assert line.get_lw() == 1
+    assert line.get_linestyle() == '-'
+    line.set_color('r')
+    line.set_alpha(0.3)
+    assert mcolors.same_color(line.get_color(), 'r')
+    assert line.get_alpha() == 0.3
+
+
 def test_CheckButtons(ax):
     labels = ('a', 'b', 'c')
     check = widgets.CheckButtons(ax, labels, (True, False, True))

lib/matplotlib/widgets.py

@@ -4142,18 +4142,29 @@ class Lasso(AxesWidget):
         Whether to use blitting for faster drawing (if supported by the
         backend). See the tutorial :ref:`blitting`
         for details.
-    """
+    props: dict, optional
+        Lasso line properties. See `.Line2D` for valid properties.
+        Default *props* are::
+
+            {'linestyle' : '-', 'color' : 'black', 'lw' : 2}
 
-    def __init__(self, ax, xy, callback, *, useblit=True):
+        .. versionadded:: 3.9
+    """
+    def __init__(self, ax, xy, callback, *, useblit=True, props=None):
         super().__init__(ax)
 
         self.useblit = useblit and self.canvas.supports_blit
         if self.useblit:
             self.background = self.canvas.copy_from_bbox(self.ax.bbox)
 
+        style = {'linestyle': '-', 'color': 'black', 'lw': 2}
+
+        if props is not None:
+            style.update(props)
+
         x, y = xy
         self.verts = [(x, y)]
-        self.line = Line2D([x], [y], linestyle='-', color='black', lw=2)
+        self.line = Line2D([x], [y], **style)
         self.ax.add_line(self.line)
         self.callback = callback
         self.connect_event('button_release_event', self.onrelease)

lib/matplotlib/widgets.pyi

@@ -478,6 +478,7 @@ class Lasso(AxesWidget):
         callback: Callable[[list[tuple[float, float]]], Any],
         *,
         useblit: bool = ...,
+        props: dict[str, Any] | None = ...,
     ) -> None: ...
     def onrelease(self, event: Event) -> None: ...
     def onmove(self, event: Event) -> None: ...