fix(graphic): record clipped paint operations

Painting into a QwtGraphic with clipping enabled raised "TypeError:
unsupported operand type(s) for &=: 'QRectF' and 'QRect'" on each paint
operation. As the exception is raised in a Qt virtual method (paint engine
drawPath, drawPixmap and drawImage), PyQt aborts the process with its
default exception hook.

QwtGraphic.updateBoundingRect intersects the bounding rectangle with the
bounding rectangle of the clip region, which is a QRect. The Qwt C++ code
converts it implicitly to a QRectF; the Python port did not.

- Convert the clip region bounding rectangle to a QRectF before mapping
  and intersecting it.
- Regression test: clipped path, pixmap and image recorded with a
  translated painter; control point rectangle not clipped, bounding
  rectangle clipped. Exceptions raised in Qt virtual methods are collected
  so that the test fails instead of aborting the process.
- Changelog entry.

Found while writing the tests for the painter command copy.

Refs #115

Assisted-by: Claude Opus 5.5

Author: PierreRaybaut

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Fixed `QwtPlotGrid.make`, which raised a `TypeError` when only some of the minor pen arguments (`mincolor`, `minwidth`, `minstyle`) were given: each of them is now honored, the missing ones taking their documented default value ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
 - Fixed `QwtPowerTransform`, which raised a `ValueError` when drawing a curve on an axis with a power scale (curve data are mapped as NumPy arrays), and an `AttributeError` with NumPy < 2.0 (`numpy.pow` does not exist there): it now transforms scalars (with unchanged results) as well as NumPy arrays, with any supported NumPy version ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
 - Fixed `QwtPlotDirectPainter.setAttribute`, which did not set or clear attributes as requested: enabling `AtomicPainter` twice disabled it, and `FullRepaint` or `CopyBackingStore` could not be disabled anymore once enabled ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
+- Fixed painting into a `QwtGraphic` with clipping enabled, which raised a `TypeError` on each paint operation (aborting the process with PyQt's default exception hook): clipped paint operations are now recorded, and the bounding rectangle of the graphic is clipped as in Qwt ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
 
 ## Version 0.16.3
 

qwt/graphic.py

@@ -757,7 +757,7 @@ def updateBoundingRect(self, rect):
         br = QRectF(rect)
         painter = self.paintEngine().painter()
         if painter and painter.hasClipping():
-            cr = painter.clipRegion().boundingRect()
+            cr = QRectF(painter.clipRegion().boundingRect())
             cr = painter.transform().mapRect(cr)
             br &= cr
         if self.__data.boundingRect.width() < 0:

qwt/tests/test_issue115_porting_bugs.py

@@ -10,7 +10,10 @@
 which made the API raise an exception or ignore some of its arguments.
 """
 
+import contextlib
 import math
+import sys
+import traceback
 
 import numpy as np
 import pytest
@@ -46,6 +49,26 @@ def _ensure_app():
     return QW.QApplication.instance() or QW.QApplication([])
 
 
+@contextlib.contextmanager
+def _qt_exceptions():
+    """Collect the exceptions raised in Qt virtual method overrides.
+
+    PyQt aborts the process on such exceptions when the default exception
+    hook is installed: collecting them makes the test fail instead.
+    """
+    errors = []
+    old_hook = sys.excepthook
+    sys.excepthook = lambda *exc_info: errors.append(exc_info)
+    try:
+        yield errors
+    finally:
+        sys.excepthook = old_hook
+
+
+def _format_exceptions(errors):
+    return "".join("".join(traceback.format_exception(*exc)) for exc in errors)
+
+
 # ---------------------------------------------------------------------------
 # QwtGraphic.toPixmap / QwtGraphic.toImage
 # ---------------------------------------------------------------------------
@@ -115,6 +138,35 @@ def test_graphic_conversion_keep_aspect_ratio(method):
     del app
 
 
+def test_graphic_clipped_recording():
+    """Clipped paint operations are recorded, with a clipped bounding rect"""
+    app = _ensure_app()  # keep a reference alive for the duration of the test
+    pixmap = QG.QPixmap(4, 4)
+    pixmap.fill(QC.Qt.blue)
+    image = QG.QImage(4, 4, QG.QImage.Format_ARGB32)
+    image.fill(QC.Qt.green)
+    path = QG.QPainterPath()
+    path.addRect(QC.QRectF(0.0, 0.0, 20.0, 20.0))
+    subrect = QC.QRectF(0.0, 0.0, 4.0, 4.0)
+    graphic = QwtGraphic()
+    with _qt_exceptions() as errors:
+        painter = QG.QPainter(graphic)
+        painter.translate(5.0, 5.0)
+        painter.setClipRect(QC.QRectF(0.0, 0.0, 10.0, 10.0))
+        painter.setPen(QC.Qt.NoPen)
+        painter.setBrush(RED)
+        painter.drawPath(path)
+        painter.drawPixmap(QC.QRectF(0.0, 0.0, 4.0, 4.0), pixmap, subrect)
+        painter.drawImage(QC.QRectF(8.0, 8.0, 4.0, 4.0), image, subrect)
+        painter.end()
+    assert not errors, _format_exceptions(errors)
+    assert len(graphic.commands()) > 3
+    # Control points are not clipped, the bounding rectangle is
+    assert graphic.controlPointRect() == QC.QRectF(5.0, 5.0, 20.0, 20.0)
+    assert graphic.boundingRect() == QC.QRectF(5.0, 5.0, 10.0, 10.0)
+    del app
+
+
 # ---------------------------------------------------------------------------
 # QwtPlotMarker.legendIcon
 # ---------------------------------------------------------------------------
@@ -373,6 +425,7 @@ def test_direct_painter_atomic_painter_reset():
         test_graphic_conversion_default_size(name)
         test_graphic_conversion_given_size(name)
         test_graphic_conversion_keep_aspect_ratio(name)
+    test_graphic_clipped_recording()
     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()