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