Drop support for diagonal axline shapes

Author: robertoffmoura

CHANGELOG.md

@@ -5,7 +5,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## Unreleased
 
 ### Added
-- Add support for converting matplotlib reference lines (`axhline`, `axvline`, and `axline`) as well as axes-coordinate lines into Plotly layout shapes in `mpl_to_plotly`, including support for date axes [[#5719](https://github.com/plotly/plotly.py/pull/5719)], with thanks to @robertoffmoura for the contribution!
+- Add support for converting matplotlib reference lines (`axhline`, `axvline`, and horizontal/vertical `axline`) as well as axes-coordinate lines into Plotly layout shapes in `mpl_to_plotly`, including support for date axes [[#5719](https://github.com/plotly/plotly.py/pull/5719)], with thanks to @robertoffmoura for the contribution!
 
 ### Fixed
 - Fix `mpl_to_plotly` tick marker mirroring, axis positioning, and trace visibility for twinned and overlaid subplots (such as `twinx` and `twiny`) [[#5310](https://github.com/plotly/plotly.py/pull/5310)], with thanks to @robertoffmoura for the contribution!

plotly/matplotlylib/renderer.py

@@ -7,26 +7,22 @@
 
 """
 
-import datetime
 import math
 import warnings
 
 import matplotlib.patches as mpatches
-from matplotlib import dates as mdates
 from matplotlib import lines as mlines
 from matplotlib import transforms
 import plotly.graph_objs as go
 from plotly.matplotlylib.mplexporter import Renderer
 from plotly.matplotlylib import mpltools
+from plotly.matplotlylib.mpltools import _export_color
 
 # Artist class created by ``Axes.axline``: ``AxLine`` in matplotlib >= 3.8,
 # ``_AxLine`` in earlier versions.
 _AXLINE_CLASS = getattr(mlines, "AxLine", None) or getattr(mlines, "_AxLine", ())
 
 
-from plotly.matplotlylib.mpltools import _export_color
-
-
 def _per_path(values, i, default):
     """Return the style value for the i-th path of a path collection.
 
@@ -562,8 +558,8 @@ def draw_marked_line(self, **props):
         elif props["coordinates"] == "axes" and self._processing_legend:
             # dealing with legend graphical elements
             self.msg += "    Using native legend\n"
-        elif self._is_axes_reference_line(props):
-            self._draw_axes_line(props)
+        elif self._is_axes_reference_line(props) and self._draw_axes_line(props):
+            pass
         else:
             self.msg += "    Line didn't have 'data' coordinates, not drawing\n"
             warnings.warn(
@@ -574,8 +570,9 @@ def draw_marked_line(self, **props):
 
     def _is_axes_reference_line(self, props):
         """Check whether a line qualifies as an axes-coordinate reference line
-        (e.g. axhline, axvline, axline, or a 2-point segment drawn with
-        ``transform=ax.transAxes``) that can be drawn as a 2-point layout shape."""
+        (e.g. axhline, axvline, horizontal/vertical axline, or a 2-point
+        segment drawn with ``transform=ax.transAxes``) that can be drawn as a
+        2-point layout shape."""
         if not props.get("linestyle") or len(props.get("data", [])) != 2:
             return False
         if props["coordinates"] == "axes" and not self._processing_legend:
@@ -589,12 +586,12 @@ def _is_axes_reference_line(self, props):
     def _draw_axes_line(self, props):
         """Draw an axes-coordinate reference line as a layout shape.
 
-        axhline/axvline span their axes-fraction extent along one axis and sit
-        at a data value on the other. Segments in axes coordinates keep their
-        exact endpoints in axes domain coordinates. axline is extended in data
-        coordinates."""
+        axhline/axvline and horizontal/vertical axline span the axes domain
+        along one axis and sit at a data value on the other. Segments in axes
+        coordinates keep their exact endpoints in axes domain coordinates.
+        Returns True when a shape is drawn."""
         if not props.get("linestyle") or len(props.get("data", [])) != 2:
-            return
+            return False
         ax = self.current_mpl_ax
         line = props["mplobj"]
         trans = line.get_transform()
@@ -635,7 +632,7 @@ def _draw_axes_line(self, props):
             xref = x_domain
             yref = y_domain
         else:
-            # general reference line (e.g. axline)
+            # general reference line (e.g. horizontal or vertical axline)
             if props["coordinates"] == "display":
                 px_points = props["data"]
             elif props["coordinates"] == "axes":
@@ -664,38 +661,7 @@ def _draw_axes_line(self, props):
                 xref = x_axis
                 yref = y_domain
             else:
-                # Diagonal line: extend endpoints in data coordinates so it spans
-                # across zoom levels while staying locked to data coordinates on pan/zoom
-                extension_factor = 100.0
-                x0_ext = x0 - extension_factor * dx
-                y0_ext = y0 - extension_factor * dy
-                x1_ext = x1 + extension_factor * dx
-                y1_ext = y1 + extension_factor * dy
-
-                if self.x_is_mpl_date:
-                    min_date_num = float(mdates.date2num(datetime.datetime(1, 1, 1)))
-                    max_date_num = float(
-                        mdates.date2num(datetime.datetime(9999, 12, 31))
-                    )
-                    slope = dy / dx
-                    if x0_ext < min_date_num:
-                        y0_ext = y0 + slope * (min_date_num - x0)
-                        x0_ext = min_date_num
-                    elif x0_ext > max_date_num:
-                        y0_ext = y0 + slope * (max_date_num - x0)
-                        x0_ext = max_date_num
-                    if x1_ext > max_date_num:
-                        y1_ext = y1 + slope * (max_date_num - x1)
-                        x1_ext = max_date_num
-                    elif x1_ext < min_date_num:
-                        y1_ext = y1 + slope * (min_date_num - x1)
-                        x1_ext = min_date_num
-                    x0, x1 = self._convert_x_dates([x0_ext, x1_ext])
-                else:
-                    x0, x1 = float(x0_ext), float(x1_ext)
-                y0, y1 = float(y0_ext), float(y1_ext)
-                xref = x_axis
-                yref = y_axis
+                return False
 
         color = _export_color(props["linestyle"]["color"], props["linestyle"]["alpha"])
         shape = go.layout.Shape(
@@ -715,6 +681,7 @@ def _draw_axes_line(self, props):
         )
         self.plotly_fig["layout"]["shapes"] += (shape,)
         self.msg += "    Heck yeah, I drew that reference line\n"
+        return True
 
     def draw_image(self, **props):
         """Draw image.

plotly/matplotlylib/tests/test_renderer.py

@@ -876,123 +876,8 @@ def test_axvline_converts():
     assert shape.yref == "y domain"
 
 
-def test_axline_converts():
-    """axline converts to a layout shape extended in data coordinates."""
-    fig, ax = plt.subplots()
-    ax.axline((0.5, 0.5), slope=1)
-
-    plotly_fig = tls.mpl_to_plotly(fig)
-
-    assert len(plotly_fig.data) == 0
-    assert len(plotly_fig.layout.shapes) == 1
-    shape = plotly_fig.layout.shapes[0]
-    assert shape.type == "line"
-    assert shape.xref == "x"
-    assert shape.yref == "y"
-    x_min, x_max = ax.get_xlim()
-    assert shape.x0 < x_min
-    assert shape.x1 > x_max
-    slope = (shape.y1 - shape.y0) / (shape.x1 - shape.x0)
-    assert abs(slope - 1.0) < 1e-9
-    # Passes through (0.5, 0.5)
-    y_at_05 = shape.y0 + slope * (0.5 - shape.x0)
-    assert abs(y_at_05 - 0.5) < 1e-9
-
-
-def test_axline_arbitrary_slope_and_limits():
-    """axline with non-trivial slopes and limits extends in data coordinates."""
-    fig, ax = plt.subplots()
-    ax.scatter([1, 2, 4, 7, 9], [2, 5, 4, 8, 10])
-    ax.axline((0, 1), slope=1.0)
-    ax.axline((1, 8), (8, 2))
-    ax.set_xlim(0, 10)
-    ax.set_ylim(0, 12)
-
-    plotly_fig = tls.mpl_to_plotly(fig)
-    shapes = plotly_fig.layout.shapes
-    assert len(shapes) == 2
-
-    # Line 1: (0, 1), slope 1, xlim [0, 10], ylim [0, 12]
-    assert shapes[0].xref == "x"
-    assert shapes[0].yref == "y"
-    assert shapes[0].x0 < -500
-    assert shapes[0].x1 > 500
-    slope1 = (shapes[0].y1 - shapes[0].y0) / (shapes[0].x1 - shapes[0].x0)
-    assert abs(slope1 - 1.0) < 1e-9
-    y_at_0 = shapes[0].y0 + slope1 * (0.0 - shapes[0].x0)
-    assert abs(y_at_0 - 1.0) < 1e-9
-
-    # Line 2: (1, 8) to (8, 2) with slope -6/7
-    assert shapes[1].xref == "x"
-    assert shapes[1].yref == "y"
-    assert shapes[1].x0 < -500
-    assert shapes[1].x1 > 500
-    slope2 = (shapes[1].y1 - shapes[1].y0) / (shapes[1].x1 - shapes[1].x0)
-    assert abs(slope2 - (-6.0 / 7.0)) < 1e-9
-    y_at_1 = shapes[1].y0 + slope2 * (1.0 - shapes[1].x0)
-    assert abs(y_at_1 - 8.0) < 1e-9
-
-
-def _shape_x_datenums(shape):
-    """Return a shape's date-string x endpoints as matplotlib date numbers."""
-    return [
-        matplotlib.dates.date2num(datetime.datetime.fromisoformat(x))
-        for x in (shape.x0, shape.x1)
-    ]
-
-
-def test_axline_on_pre_1970_date_axis():
-    """axline on a date axis before the matplotlib epoch (1970) extends on both
-    sides of the data and stays on the original line."""
-    dates = [datetime.datetime(1950, 1, i) for i in range(1, 10)]
-    fig, ax = plt.subplots()
-    ax.plot(dates, range(len(dates)))
-    x_ref = matplotlib.dates.date2num(dates[0])
-    ax.axline((x_ref, 0), slope=1)
-
-    plotly_fig = tls.mpl_to_plotly(fig)
-    shapes = plotly_fig.layout.shapes
-    assert len(shapes) == 1
-    shape = shapes[0]
-    assert shape.xref == "x"
-    assert shape.yref == "y"
-
-    n0, n1 = _shape_x_datenums(shape)
-    x_min, x_max = ax.get_xlim()
-    assert n0 < x_min
-    assert n1 > x_max
-    slope = (shape.y1 - shape.y0) / (n1 - n0)
-    assert abs(slope - 1.0) < 1e-6
-    assert abs(shape.y0 + slope * (x_ref - n0)) < 1e-6
-
-
-def test_axline_on_date_axis_clamps_to_matplotlib_date_range():
-    """When extending a diagonal axline would leave matplotlib's supported date
-    range (years 0001-9999), its endpoints stop at the range limits while
-    staying on the original line."""
-    dates = [datetime.datetime(1900, 1, 1), datetime.datetime(2000, 1, 1)]
-    fig, ax = plt.subplots()
-    ax.plot(dates, [0, 1])
-    # Nearly flat line crossing the whole century, so the 100x extension of the
-    # visible segment reaches past both year 0001 and year 9999
-    x_ref = matplotlib.dates.date2num(dates[0])
-    ax.axline((x_ref, 0.5), slope=1e-6)
-
-    plotly_fig = tls.mpl_to_plotly(fig)
-    shape = plotly_fig.layout.shapes[0]
-    assert isinstance(shape.x0, str)
-    assert isinstance(shape.x1, str)
-    assert shape.x0.startswith("0001-01-01")
-    assert shape.x1.startswith("9999-12-31")
-
-    n0, n1 = _shape_x_datenums(shape)
-    slope = (shape.y1 - shape.y0) / (n1 - n0)
-    assert abs(slope - 1e-6) < 1e-12
-    assert abs(shape.y0 + slope * (x_ref - n0) - 0.5) < 1e-6
-
-
 def test_axline_horizontal_and_vertical():
-    """Horizontal and vertical axline use domain coordinates appropriately."""
+    """Horizontal and vertical axline use domain coordinates on the spanned axis."""
     fig, ax = plt.subplots()
     ax.axline((0, 5), slope=0)
     ax.axline((3, 0), (3, 10))
@@ -1018,9 +903,21 @@ def test_axline_horizontal_and_vertical():
     assert abs(shapes[1].y1 - 1.0) < 1e-9
 
 
+def test_diagonal_axline_warns_and_is_skipped():
+    """Diagonal axline emits a UserWarning for non-data Line2D coordinates."""
+    fig, ax = plt.subplots()
+    ax.axline((0.5, 0.5), slope=1)
+
+    with pytest.warns(UserWarning, match="Line2D objects from matplotlib"):
+        plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert len(plotly_fig.data) == 0
+    assert len(plotly_fig.layout.shapes) == 0
+
+
 def test_axes_coordinate_segments_keep_their_endpoints():
-    """Two-point lines in axes coordinates (not axline) convert to shapes in
-    axes domain coordinates with their exact endpoints, without extension."""
+    """Two-point lines in axes coordinates convert to shapes in axes domain
+    coordinates with their exact endpoints."""
     fig, ax = plt.subplots()
     ax.set_xlim(0, 10)
     ax.set_ylim(0, 10)