Fix/segment fault

CHANGELOG.md

@@ -1,5 +1,13 @@
 # PythonQwt Releases
 
+## Version 0.16.1
+
+### Bug fixes
+
+- Fixed [Issue #107](https://github.com/PlotPyStack/PythonQwt/issues/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
+
+
 ## Version 0.16.0
 
 ### Performance

qwt/__init__.py

@@ -63,7 +63,7 @@
 from qwt.text import QwtText  # noqa: F401
 from qwt.toqimage import array_to_qimage as toQImage  # noqa: F401
 
-__version__ = "0.16.0"
+__version__ = "0.16.1"
 QWT_VERSION_STR = "6.1.5"
 
 

qwt/scale_draw.py

@@ -24,6 +24,7 @@
 
 from qtpy.QtCore import (
     QLineF,
+    QObject,
     QPoint,
     QPointF,
     QRect,
@@ -50,22 +51,11 @@
 _ALIGN_BOTTOM = int(Qt.AlignBottom)
 
 
-class QwtAbstractScaleDraw_PrivateData(object):
-    # See QwtText_PrivateData: ``QObject`` inheritance is unused and the
-    # base class' ``__init__`` is a measurable cost in tick-heavy renders.
-    __slots__ = (
-        "spacing",
-        "penWidth",
-        "minExtent",
-        "components",
-        "tick_length",
-        "tick_lighter_factor",
-        "map",
-        "scaleDiv",
-        "labelCache",
-    )
+class QwtAbstractScaleDraw_PrivateData(QObject):
+    # QObject base class restored for Qt parent/child ownership semantics.
 
     def __init__(self):
+        QObject.__init__(self)
         self.spacing = 4
         self.penWidth = 0
         self.minExtent = 0.0
@@ -492,20 +482,11 @@ def invalidateCache(self):
         self.__data.labelCache.clear()
 
 
-class QwtScaleDraw_PrivateData(object):
-    # See QwtText_PrivateData: ``QObject`` inheritance is unused and the
-    # base class' ``__init__`` is a measurable cost in tick-heavy renders.
-    __slots__ = (
-        "len",
-        "alignment",
-        "orientation",
-        "labelAlignment",
-        "labelRotation",
-        "labelAutoSize",
-        "pos",
-    )
+class QwtScaleDraw_PrivateData(QObject):
+    # QObject base class restored for Qt parent/child ownership semantics.
 
     def __init__(self):
+        QObject.__init__(self)
         self.len = 0
         self.alignment = QwtScaleDraw.BottomScale
         # Cached orientation - kept in sync by ``QwtScaleDraw.setAlignment``

qwt/text.py

@@ -234,6 +234,7 @@ def draw(self, painter, rect, flags, text):
 _FONT_TUPLE_CACHE: dict = {}  # tuple_key -> tuple_key (interning, also acts
 #                              as the "have we seen this logical font" set)
 _FONT_KEY_CACHE_LIMIT = 1024
+_FM_CACHE_LIMIT = 256  # max QFontMetrics/QFontMetricsF entries per engine
 
 
 def _font_tuple_key(font):
@@ -317,13 +318,17 @@ def fontmetrics(self, font):
         try:
             return self._fm_cache[fid]
         except KeyError:
+            if len(self._fm_cache) >= _FM_CACHE_LIMIT:
+                self._fm_cache.clear()
             return self._fm_cache.setdefault(fid, QFontMetrics(font))
 
     def fontmetrics_f(self, font):
         fid = font_key_cached(font)
         try:
             return self._fm_cache_f[fid]
         except KeyError:
+            if len(self._fm_cache_f) >= _FM_CACHE_LIMIT:
+                self._fm_cache_f.clear()
             return self._fm_cache_f.setdefault(fid, QFontMetricsF(font))
 
     def heightForWidth(self, font, flags, text, width):
@@ -359,6 +364,8 @@ def effectiveAscent(self, font):
         ascent = ASCENTCACHE.get(fontKey)
         if ascent is not None:
             return ascent
+        if len(ASCENTCACHE) >= _FM_CACHE_LIMIT:
+            ASCENTCACHE.clear()
         return ASCENTCACHE.setdefault(fontKey, self.findAscent(font))
 
     def findAscent(self, font):
@@ -411,6 +418,8 @@ def textMargins(self, font):
         if cached is None:
             fm = self.fontmetrics(font)
             cached = (0, 0, fm.ascent() - self.effectiveAscent(font), fm.descent())
+            if len(self._margins_cache) >= _FM_CACHE_LIMIT:
+                self._margins_cache.clear()
             self._margins_cache[fkey] = cached
         self._margins_last_id = font_id
         self._margins_last_value = cached
@@ -557,26 +566,11 @@ def textMargins(self, font):
         return 0, 0, 0, 0
 
 
-class QwtText_PrivateData(object):
-    # ``QObject`` was previously used as the base class but no Qt signals
-    # or events are ever emitted from ``_PrivateData`` containers and the
-    # ``QObject.__init__`` call dominates ``QwtText.__init__`` (it is the
-    # single most expensive line for tick-label-heavy renders, see
-    # https://github.com/PlotPyStack/PythonQwt/issues/93).
-    __slots__ = (
-        "renderFlags",
-        "borderRadius",
-        "borderPen",
-        "backgroundBrush",
-        "paintAttributes",
-        "layoutAttributes",
-        "textEngine",
-        "text",
-        "font",
-        "color",
-    )
+class QwtText_PrivateData(QObject):
+    # QObject base class restored for Qt parent/child ownership semantics.
 
     def __init__(self):
+        QObject.__init__(self)
         self.renderFlags = Qt.AlignCenter
         self.borderRadius = 0
         self.borderPen = Qt.NoPen