v0.16.2

Version 0.16.2

Bug fixes

• Fixed a QFont/GDI handle leak that release 0.16.1 only masked: the font-key cache retained a strong reference to every distinct QFont it had seen (up to 1024 entries), each pinning its underlying font engine and, on Windows GDI builds, an HFONT handle, accumulating towards the per-process GDI limit. The cache is now a single-slot, leak-free memo and the remaining metrics caches use proper LRU eviction instead of a clear-on-overflow that periodically rebuilt QFontMetrics results
• Fixed delayed release of native GDI handles caused by Python reference cycles: QwtPlotItem and QwtPlotCanvas held strong back-references to their parent QwtPlot, so plots were only reclaimed by the cyclic garbage collector. These back-references are now weak, matching the C++ Qwt parent/child model, so a plot is freed by reference counting alone and could otherwise exhaust the ~10000 GDI-object limit on Windows under heavy create/destroy churn
• Fixed noisy "Unhandled exception" AttributeError tracebacks at teardown on Python 3.14 / Qt 6: during widget destruction Qt still delivers events and calls size-hint methods on QwtPlot objects whose Python __dict__ has already been cleared. Access to private instance data in QwtPlot.eventFilter and QwtPlot.minimumSizeHint is now guarded

Performance

• Restored most of the text-layout performance lost to the GDI-leak fix by reinstating a bounded, leak-free id(font) fast path in QwtText.textSize (the layout cache holds a strong reference to its single cached font, so the font id cannot be reused)

Other changes

• Added GDI-handle and font-cache telemetry/benchmark scripts under scripts/ (bench_gdi_loadtest.py, telemetry_fontcache.py) and a pytest stress test (qwt/tests/test_issue107_gdi_leak.py) to detect resource leaks under repeated plot create/render/destroy cycles

v0.16.1

Version 0.16.1

Bug fixes

• Fixed Issue #107: corrected a Windows crash/access violation that could occur in long-running sessions creating and rendering large amounts of data, due to GDI handle exhaustion caused by object lifetime and cache growth
• Preserved the rendering performance improvements introduced in 0.16.0 while restoring safer Qt object ownership for internal text/scale-draw private data and adding defensive limits to font-metrics caches

v0.16.0

Performance

• Major performance optimizations addressing Issue #93 (rendering performance degradation with Qt 6, also benefitting Qt 5):
  • QwtText: removed unnecessary QObject inheritance and added a font key cache to avoid expensive QFont hashing on every text rendering operation
  • QwtText: cached Qt alignment and text format flags as plain integers to bypass PyQt6 enum overhead in hot paths
  • QwtText: enabled font key caching fast path for Qt 6, kept disabled for Qt 5 to preserve consistent text rendering
  • QwtGraphic and QwtPainterCommand: cached Qt flags as integers to reduce per-command overhead, especially under PyQt6
  • QwtScaleDraw, QwtScaleEngine, QwtScaleMap and QwtScaleDiv: micro-optimizations on the tick computation and coordinate transform code paths
• Added benchmarking and visual regression scripts under scripts/ (bench_qt.ps1, bench_plotpy_loadtest.py, profile_loadtest.py, lineprofile_loadtest.py, capture_screenshots.py, diff_screenshots.py) to measure and validate rendering performance and correctness

Bug fixes

• Merged PR #105: fixed legend icon being rendered incorrectly - thanks to @Adrian-B-Moreira
• Fixed QPaintDevice warnings on DevicePixelRatio and DevicePixelRatioScaled metrics in QwtNullPaintDevice
• Fixed integer division in QwtScaleEngine so that medium ticks are actually produced (previously, the medium tick step was truncated to zero in some configurations)
• Fixed QwtScaleMap rectangle transform and degenerate scale handling (when source or destination interval has zero width)

Other changes

• Internal refactor: removed unnecessary QObject inheritance from QwtText (QwtText instances are no longer QObject subclasses; this is an internal change with no impact on the public plotting API, but downstream code relying on Qt signals/slots on QwtText instances should be adapted)
• Development workflow: replaced legacy .bat scripts with a unified scripts/run_with_env.py environment loader, refactored VS Code tasks, added coverage tasks and CI gating of PyPI deployment on the test suite passing
• Documentation: updated README, Sphinx documentation, dependencies and added AI coding agent instructions

v0.15.0

Version 0.15.0

• Added support for QwtDateTimeScaleDraw and QwtDateTimeScaleEngine for datetime axis support (see QwtDateTimeScaleDraw and QwtDateTimeScaleEngine classes in the qwt module)
• Improved font rendering for rotated text in QwtPlainTextEngine.draw method: disabled font hinting to avoid character misalignment in rotated text

v0.14.6

Version 0.14.6

• Fixed Issue #100 - TypeError in QwtSymbol.drawSymbol method due to outdated renderSymbols call
• Fixed Issue #101 - RuntimeWarning: overflow encountered in cast when plotting numpy.float32 curve data
• Merged PR #103: [FIX] wrong handling of border.rectList with PySide6 backend - thanks to @martinschwinzerl

v0.14.5

Version 0.14.5

• Merged PR #98: Fix legend still being visible after removed
• Merged PR #99: Fix QRectF to QRect cast in QwtPainterClass.drawBackground

v0.14.4

Version 0.14.4

• Fixed canvas rectangle type in drawItems method call in QwtPlot.drawCanvas (was causing a hard crash when printing to PDF a canvas with upstream PlotPy project)

v0.14.3

Version 0.14.3

• Fixed Issue #94 - Different logarithmic scale behavior when compared to Qwt
• Merged PR #91: Fix: legend now showing up when enabled later - thanks to @nicoddemus
• Removed QwtPlotItem.setIcon and QwtPlotItem.icon methods (introduced in 0.9.0 but not used in PythonQwt)

v0.14.2

Version 0.14.2

• Merged PR #89: fixed call to ScaleEngine.autoScale in QwtPlot.updateAxes (returned values were not used) - thanks to @nicoddemus
• Merged PR #90: updated QwtLinearScaleEngine.autoScale method implementation to the latest Qwt version - thanks to @nicoddemus

v0.14.1

Version 0.14.1

• Handled RuntimeError when running test_eventfilter.py on Ubuntu 22.04 (Python 3.12, PyQt5)
• Fixed ResourceWarning: unclosed file in test_cpudemo.py (purely test issue)
• Fixed segmentation fault in test_multidemo.py (purely test issue, related to test utility module qwt.tests.utils)
• Update GitHub actions to use the latest versions of actions/checkout, actions/setup-python, ...