Use native legends when converting from matplotlib

Author: robertoffmoura

plotly/matplotlylib/renderer.py

@@ -60,6 +60,8 @@ def __init__(self):
         self.mpl_x_bounds = (0, 1)
         self.mpl_y_bounds = (0, 1)
         self.msg = "Initialized PlotlyRenderer\n"
+        self._processing_legend = False
+        self._legend_visible = False
 
     def open_figure(self, fig, props):
         """Creates a new figure by beginning to fill out layout dict.
@@ -108,7 +110,6 @@ def close_figure(self, fig):
         fig -- a matplotlib.figure.Figure object.
 
         """
-        self.plotly_fig["layout"]["showlegend"] = False
         self.msg += "Closing figure\n"
 
     def open_axes(self, ax, props):
@@ -198,6 +199,35 @@ def close_axes(self, ax):
         self.msg += "  Closing axes\n"
         self.x_is_mpl_date = False
 
+    def open_legend(self, legend, props):
+        """Enable Plotly's native legend when matplotlib legend is detected.
+
+        This method is called when a matplotlib legend is found. It enables
+        Plotly's showlegend only if the matplotlib legend is visible.
+
+        Positional arguments:
+        legend -- matplotlib.legend.Legend object
+        props -- legend properties dictionary
+        """
+        self.msg += "  Opening legend\n"
+        self._processing_legend = True
+        self._legend_visible = props.get("visible", True)
+        if self._legend_visible:
+            self.msg += "    Enabling native plotly legend (matplotlib legend is visible)\n"
+            self.plotly_fig["layout"]["showlegend"] = True
+        else:
+            self.msg += "    Not enabling legend (matplotlib legend is not visible)\n"
+
+    def close_legend(self, legend):
+        """Finalize legend processing.
+
+        Positional arguments:
+        legend -- matplotlib.legend.Legend object
+        """
+        self.msg += "  Closing legend\n"
+        self._processing_legend = False
+        self._legend_visible = False
+
     def draw_bars(self, bars):
 
         # sort bars according to bar containers
@@ -310,83 +340,6 @@ def draw_bar(self, coll):
                 "assuming data redundancy, not plotting."
             )
 
-    def draw_legend_shapes(self, mode, shape, **props):
-        """Create a shape that matches lines or markers in legends.
-
-        Main issue is that path for circles do not render, so we have to use 'circle'
-        instead of 'path'.
-        """
-        for single_mode in mode.split("+"):
-            x = props["data"][0][0]
-            y = props["data"][0][1]
-            if single_mode == "markers" and props.get("markerstyle"):
-                size = shape.pop("size", 6)
-                symbol = shape.pop("symbol")
-                # aligning to "center"
-                x0 = 0
-                y0 = 0
-                x1 = size
-                y1 = size
-                markerpath = props["markerstyle"].get("markerpath")
-                if markerpath is None and symbol != "circle":
-                    self.msg += (
-                        "not sure how to handle this marker without a valid path\n"
-                    )
-                    return
-                # marker path to SVG path conversion
-                path = " ".join(
-                    [f"{a} {t[0]},{t[1]}" for a, t in zip(markerpath[1], markerpath[0])]
-                )
-
-                if symbol == "circle":
-                    # symbols like . and o in matplotlib, use circle
-                    # plotly also maps many other markers to circle, such as 1,8 and p
-                    path = None
-                    shape_type = "circle"
-                    x0 = -size / 2
-                    y0 = size / 2
-                    x1 = size / 2
-                    y1 = size + size / 2
-                else:
-                    # triangles, star etc
-                    shape_type = "path"
-                legend_shape = go.layout.Shape(
-                    type=shape_type,
-                    xref="paper",
-                    yref="paper",
-                    x0=x0,
-                    y0=y0,
-                    x1=x1,
-                    y1=y1,
-                    xsizemode="pixel",
-                    ysizemode="pixel",
-                    xanchor=x,
-                    yanchor=y,
-                    path=path,
-                    **shape,
-                )
-
-            elif single_mode == "lines":
-                mode = "line"
-                x1 = props["data"][1][0]
-                y1 = props["data"][1][1]
-
-                legend_shape = go.layout.Shape(
-                    type=mode,
-                    xref="paper",
-                    yref="paper",
-                    x0=x,
-                    y0=y + 0.02,
-                    x1=x1,
-                    y1=y1 + 0.02,
-                    **shape,
-                )
-            else:
-                self.msg += "not sure how to handle this element\n"
-                return
-            self.plotly_fig.add_shape(legend_shape)
-            self.msg += "    Heck yeah, I drew that shape\n"
-
     def draw_marked_line(self, **props):
         """Create a data dict for a line obj.
 
@@ -502,7 +455,7 @@ def draw_marked_line(self, **props):
             self.msg += "    Heck yeah, I drew that line\n"
         elif props["coordinates"] == "axes":
             # dealing with legend graphical elements
-            self.draw_legend_shapes(mode=mode, shape=shape, **props)
+            self.msg += "    Using native legend\n"
         else:
             self.msg += "    Line didn't have 'data' coordinates, " "not drawing\n"
             warnings.warn(
@@ -668,6 +621,10 @@ def draw_text(self, **props):
             self.draw_title(**props)
         else:  # just a regular text annotation...
             self.msg += "      Text object is a normal annotation\n"
+            # Skip creating annotations for legend text when using native legend
+            if self._processing_legend and self._legend_visible and props["coordinates"] == "axes":
+                self.msg += "        Skipping legend text annotation (using native legend)\n"
+                return
             if props["coordinates"] != "data":
                 self.msg += (
                     "        Text object isn't linked to 'data' " "coordinates\n"

plotly/matplotlylib/tests/__init__.py

@@ -0,0 +1,4 @@
+import matplotlib
+
+matplotlib.use("Agg")
+import matplotlib.pyplot as plt

plotly/matplotlylib/tests/test_renderer.py

@@ -0,0 +1,81 @@
+import plotly.tools as tls
+
+from . import plt
+
+
+def test_native_legend_enabled_when_matplotlib_legend_present():
+    """Test that when matplotlib legend is present, Plotly uses native legend."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], label="Line 1")
+    ax.plot([0, 1], [1, 0], label="Line 2")
+    ax.legend()
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    # Should enable native legend
+    assert plotly_fig.layout.showlegend == True
+    # Should have 2 traces with names
+    assert len(plotly_fig.data) == 2
+    assert plotly_fig.data[0].name == "Line 1"
+    assert plotly_fig.data[1].name == "Line 2"
+
+
+def test_no_fake_legend_shapes_with_native_legend():
+    """Test that fake legend shapes are not created when using native legend."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], "o-", label="Data with markers")
+    ax.legend()
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    # Should use native legend
+    assert plotly_fig.layout.showlegend == True
+    # Should not create fake legend elements
+    assert len(plotly_fig.layout.shapes) == 0
+    assert len(plotly_fig.layout.annotations) == 0
+
+
+def test_legend_disabled_when_no_matplotlib_legend():
+    """Test that legend is not enabled when no matplotlib legend is present."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], label="Line 1")  # Has label but no legend() call
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    # Should not have showlegend explicitly set to True
+    # (Plotly's default behavior when no legend elements exist)
+    assert not hasattr(plotly_fig.layout, 'showlegend') or plotly_fig.layout.showlegend != True
+
+
+def test_legend_disabled_when_matplotlib_legend_not_visible():
+    """Test that legend is not enabled when no matplotlib legend is not visible."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], label="Line 1")
+    legend = ax.legend()
+    legend.set_visible(False)  # Hide the legend
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    # Should not enable legend when matplotlib legend is hidden
+    assert not hasattr(plotly_fig.layout, 'showlegend') or plotly_fig.layout.showlegend != True
+
+
+def test_multiple_traces_native_legend():
+    """Test native legend works with multiple traces of different types."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1, 2], [0, 1, 0], '-', label="Line")
+    ax.plot([0, 1, 2], [1, 0, 1], 'o', label="Markers")
+    ax.plot([0, 1, 2], [0.5, 0.5, 0.5], 's-', label="Line+Markers")
+    ax.legend()
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.showlegend == True
+    assert len(plotly_fig.data) == 3
+    assert plotly_fig.data[0].name == "Line"
+    assert plotly_fig.data[1].name == "Markers"
+    assert plotly_fig.data[2].name == "Line+Markers"
+    # Verify modes are correct
+    assert plotly_fig.data[0].mode == "lines"
+    assert plotly_fig.data[1].mode == "markers"
+    assert plotly_fig.data[2].mode == "lines+markers"