fix(plot_marker): draw the legend icon symbol into a QRectF

QwtPlotMarker.legendIcon raised an AssertionError (QSize icon size) or a
TypeError (QSizeF icon size) for markers with a symbol, so that such a
marker could not be shown in a legend.

The Qwt C++ code passes a QRect to QwtSymbol::drawSymbol, which is
implicitly converted to a QRectF. The Python port passed the QRect as is,
which QwtSymbol.drawSymbol rejects, and QRect(0, 0, width, height) also
fails when the size is a QSizeF.

- Build a QRectF, like QwtPlotCurve.legendIcon already does.
- Regression tests: legend icon with QSize and QSizeF sizes, marker with a
  symbol shown in a QwtLegend.
- Changelog entry.

Refs #115

Assisted-by: Claude Opus 5.5

Author: PierreRaybaut

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Fixed [Issue #113](https://github.com/PlotPyStack/PythonQwt/issues/113): after replacing the scale draw of an axis (`QwtPlot.setAxisScaleDraw`), the axis ticks could be misaligned with the grid lines and plot items, until the next scale division change (e.g. after panning or zooming): a replot did not fix it. The new scale draw was laid out before getting the position and length of the previous one, so that the axis reserved space for its end labels that the canvas did not take into account. The new scale draw now takes the geometry of the previous one, and the axis stays aligned with the canvas
 - Fixed `QwtGraphic.toPixmap(size)`, `QwtGraphic.toImage()` and `QwtGraphic.toImage(size)`, which raised a `TypeError` (possibly aborting the process, as the painter was still active on the destroyed pixmap or image) instead of rendering the graphic: they now render it like `QwtGraphic.toPixmap()` ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
+- Fixed `QwtPlotMarker.legendIcon` for markers with a symbol, which raised an `AssertionError` or a `TypeError`: such markers can now be shown in a legend ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
 
 ## Version 0.16.3
 

qwt/plot_marker.py

@@ -13,7 +13,7 @@
    :members:
 """
 
-from qtpy.QtCore import QLineF, QObject, QPointF, QRect, QRectF, QSizeF, Qt
+from qtpy.QtCore import QLineF, QObject, QPointF, QRectF, QSizeF, Qt
 from qtpy.QtGui import QPainter, QPen
 
 from qwt.graphic import QwtGraphic
@@ -628,6 +628,6 @@ def legendIcon(self, index, size):
                 x = 0.5 * size.width()
                 painter.drawLine(QLineF(x, 0.0, x, size.height()))
         if self.__data.symbol:
-            r = QRect(0, 0, size.width(), size.height())
+            r = QRectF(0.0, 0.0, size.width(), size.height())
             self.__data.symbol.drawSymbol(painter, r)
         return icon

qwt/tests/test_issue115_porting_bugs.py

@@ -15,6 +15,7 @@
 from qtpy import QtGui as QG
 from qtpy import QtWidgets as QW
 
+from qwt import QwtLegend, QwtPlot, QwtPlotItem, QwtPlotMarker, QwtSymbol
 from qwt.graphic import QwtGraphic
 
 RED = QG.QColor(QC.Qt.red)
@@ -97,9 +98,54 @@ def test_graphic_conversion_keep_aspect_ratio(method):
     del app
 
 
+# ---------------------------------------------------------------------------
+# QwtPlotMarker.legendIcon
+# ---------------------------------------------------------------------------
+
+
+def _make_symbol():
+    return QwtSymbol(
+        QwtSymbol.Rect, QG.QBrush(RED), QG.QPen(QC.Qt.NoPen), QC.QSize(8, 8)
+    )
+
+
+@pytest.mark.parametrize(
+    "size", (QC.QSize(8, 8), QC.QSizeF(8.0, 8.0)), ids=("QSize", "QSizeF")
+)
+def test_marker_legend_icon_with_symbol(size):
+    """The legend icon of a marker with a symbol shows the symbol"""
+    app = _ensure_app()  # keep a reference alive for the duration of the test
+    marker = QwtPlotMarker.make(xvalue=0.0, yvalue=0.0, symbol=_make_symbol())
+    icon = marker.legendIcon(0, size)
+    assert not icon.isNull()
+    assert _is_red(icon.toImage(), 4, 4)
+    del app
+
+
+def test_marker_with_symbol_in_legend():
+    """A marker with a symbol can be shown in a legend"""
+    app = _ensure_app()  # keep a reference alive for the duration of the test
+    plot = QwtPlot()
+    legend = QwtLegend()
+    plot.insertLegend(legend)
+    marker = QwtPlotMarker.make(
+        xvalue=1.0, yvalue=1.0, title="Marker", symbol=_make_symbol(), plot=plot
+    )
+    marker.setItemAttribute(QwtPlotItem.Legend, True)
+    plot.updateLegend(marker)
+    label = legend.legendWidget(marker)
+    assert label is not None
+    assert not label.icon().isNull()
+    plot.close()
+    del app
+
+
 if __name__ == "__main__":
     for name in ("toPixmap", "toImage"):
         test_graphic_conversion_default_size(name)
         test_graphic_conversion_given_size(name)
         test_graphic_conversion_keep_aspect_ratio(name)
+    for size in (QC.QSize(8, 8), QC.QSizeF(8.0, 8.0)):
+        test_marker_legend_icon_with_symbol(size)
+    test_marker_with_symbol_in_legend()
     print("OK")