fix(dyngrid_layout): compute the number of rows with integer division

QwtDynGridLayout.setGeometry and QwtDynGridLayout.stretchGrid computed the
number of rows with a true division (`/`) where the Qwt C++ code uses an
integer division: numRows() returned a float (e.g. 2.5 for 3 items on 2
columns), and laying out the items with vertical expansion
(setExpandingDirections(Qt.Vertical)) raised "TypeError: 'float' object
cannot be interpreted as an integer".

- Use an integer division (`//`) in both methods. The other row count
  computations already convert the quotient to an integer and are left
  unchanged.
- Regression tests: integer number of rows for several item and column
  counts, rows stretched to the layout height with vertical expansion.
- Changelog entry.

Refs #115

Assisted-by: Claude Opus 5.5

Author: PierreRaybaut

CHANGELOG.md

@@ -16,6 +16,7 @@
 - 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))
 - Fixed the `QwtPainterCommand` copy constructor (`QwtPainterCommand(other)`), which raised an `AttributeError` for state commands and a `TypeError` (Qt objects cannot be pickled) for pixmap and image commands: commands of every type can now be copied, the copy being independent of the original ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
+- Fixed `QwtDynGridLayout` (used by `QwtLegend`), whose `numRows()` returned a float (e.g. `2.5` for 3 items on 2 columns) and which raised a `TypeError` when laying out its items with vertical expansion (`setExpandingDirections(Qt.Vertical)`) ([Issue #115](https://github.com/PlotPyStack/PythonQwt/issues/115))
 
 ## Version 0.16.3
 

qwt/dyngrid_layout.py

@@ -159,7 +159,7 @@ def setGeometry(self, rect):
         if self.isEmpty():
             return
         self.__data.numColumns = self.columnsForWidth(rect.width())
-        self.__data.numRows = self.itemCount() / self.__data.numColumns
+        self.__data.numRows = self.itemCount() // self.__data.numColumns
         if self.itemCount() % self.__data.numColumns:
             self.__data.numRows += 1
         itemGeometries = self.layoutItems(rect, self.__data.numColumns)
@@ -314,7 +314,7 @@ def stretchGrid(self, rect, numColumns, rowHeight, colWidth):
                     colWidth[col] += space
                     xDelta -= space
         if expandV:
-            numRows = self.itemCount() / numColumns
+            numRows = self.itemCount() // numColumns
             if self.itemCount() % numColumns:
                 numRows += 1
             yDelta = rect.height() - hmargins - (numRows - 1) * self.spacing()

qwt/tests/test_issue115_porting_bugs.py

@@ -34,6 +34,7 @@
     QwtScaleMap,
     QwtSymbol,
 )
+from qwt.dyngrid_layout import QwtDynGridLayout
 from qwt.graphic import QwtGraphic
 from qwt.painter_command import QwtPainterCommand
 from qwt.plot_curve import series_to_polyline
@@ -521,6 +522,51 @@ def test_painter_command_copy_replay():
     del app
 
 
+# ---------------------------------------------------------------------------
+# QwtDynGridLayout
+# ---------------------------------------------------------------------------
+
+
+def _make_grid_layout(count, max_columns):
+    widget = QW.QWidget()
+    layout = QwtDynGridLayout(widget)
+    layout.setMaxColumns(max_columns)
+    for index in range(count):
+        layout.addWidget(QW.QLabel(f"Item {index}"))
+    return widget, layout
+
+
+@pytest.mark.parametrize(
+    "count, max_columns, rows",
+    ((1, 1, 1), (3, 2, 2), (4, 2, 2), (5, 3, 2), (6, 1, 6), (7, 3, 3)),
+)
+def test_dyngrid_layout_rows(count, max_columns, rows):
+    """The number of rows of the layout is an integer"""
+    app = _ensure_app()  # keep a reference alive for the duration of the test
+    widget, layout = _make_grid_layout(count, max_columns)
+    layout.setGeometry(QC.QRect(0, 0, 2000, 2000))
+    assert layout.numColumns() == max_columns
+    assert layout.numRows() == rows
+    assert isinstance(layout.numRows(), int)
+    widget.close()
+    del app
+
+
+def test_dyngrid_layout_vertical_expanding():
+    """Rows are stretched to fill the layout height with vertical expansion"""
+    app = _ensure_app()  # keep a reference alive for the duration of the test
+    widget, layout = _make_grid_layout(3, 2)
+    layout.setExpandingDirections(QC.Qt.Vertical)
+    layout.setGeometry(QC.QRect(0, 0, 400, 300))
+    geometries = [layout.itemAt(index).geometry() for index in range(3)]
+    assert geometries[0].top() == geometries[1].top()
+    assert geometries[2].top() > geometries[0].bottom()
+    margins = layout.contentsMargins()
+    assert geometries[2].bottom() + 1 + margins.bottom() == 300
+    widget.close()
+    del app
+
+
 if __name__ == "__main__":
     for name in ("toPixmap", "toImage"):
         test_graphic_conversion_default_size(name)
@@ -539,4 +585,5 @@ def test_painter_command_copy_replay():
     test_painter_command_copy()
     test_painter_command_copy_is_independent()
     test_painter_command_copy_replay()
+    test_dyngrid_layout_vertical_expanding()
     print("OK")