Various optimizations around QwtTextEngine and QwtText

Author: Pierre Raybaut

qwt/qwt_text.py

@@ -10,40 +10,6 @@
 import math
 
 
-class QwtTextEngineDict(object):
-    def __init__(self):
-        self.__map = {QwtText.PlainText: QwtPlainTextEngine(),
-                      QwtText.RichText:  QwtRichTextEngine()}
-    
-    def textEngine(self, *args):
-        if len(args) == 1:
-            format_ = args[0]
-            return self.__map.get(format_)
-        elif len(args) == 2:
-            text, format_ = args
-        
-            if format_ == QwtText.AutoText:
-                for key, engine in list(self.__map.iteritems()):
-                    if key != QwtText.PlainText:
-                        if engine and engine.mightRender(text):
-                            return engine
-            
-            engine = self.__map.get(format_)
-            if engine is not None:
-                return engine
-            
-            engine = self.__map[QwtText.PlainText]
-            return engine
-        else:
-            raise TypeError("%s().textEngine() takes 1 or 2 argument(s) (%s "\
-                            "given)" % (self.__class__.__name__, len(args)))
-        
-    def setTextEngine(self, format_, engine):
-        if format_ == QwtText.AutoText:
-            return
-        if format_ == QwtText.PlainText and engine is None:
-            return
-        self.__map.setdefault(format_, engine)
 
 
 class QwtText_PrivateData(object):
@@ -286,6 +252,43 @@ def setTextEngine(self, format_, engine):
         self._dict.setTextEngine(format_, engine)
 
 
+class QwtTextEngineDict(object):
+    # Optimization: a single text engine for all QwtText objects
+    # (this is not how it's implemented in Qwt6 C++ library)
+    __map = {QwtText.PlainText: QwtPlainTextEngine(),
+             QwtText.RichText:  QwtRichTextEngine()}
+    
+    def textEngine(self, *args):
+        if len(args) == 1:
+            format_ = args[0]
+            return self.__map.get(format_)
+        elif len(args) == 2:
+            text, format_ = args
+        
+            if format_ == QwtText.AutoText:
+                for key, engine in list(self.__map.iteritems()):
+                    if key != QwtText.PlainText:
+                        if engine and engine.mightRender(text):
+                            return engine
+            
+            engine = self.__map.get(format_)
+            if engine is not None:
+                return engine
+            
+            engine = self.__map[QwtText.PlainText]
+            return engine
+        else:
+            raise TypeError("%s().textEngine() takes 1 or 2 argument(s) (%s "\
+                            "given)" % (self.__class__.__name__, len(args)))
+        
+    def setTextEngine(self, format_, engine):
+        if format_ == QwtText.AutoText:
+            return
+        if format_ == QwtText.PlainText and engine is None:
+            return
+        self.__map.setdefault(format_, engine)
+
+
 class QwtTextLabel_PrivateData(object):
     def __init__(self):
         self.indent = 4

qwt/qwt_text_engine.py

@@ -50,10 +50,36 @@ def __init__(self, text, flags, font):
         self.adjustSize();
 
 
-ASCENTCACHE = {}
+class QwtTextEngine(object):
+    def __init__(self):
+        pass
+
 
-class QwtPlainTextEngine_PrivateData(object):
+ASCENTCACHE = {}
 
+class QwtPlainTextEngine(QwtTextEngine):
+    def __init__(self):
+        self.qrectf_max = QRectF(0, 0, QWIDGETSIZE_MAX, QWIDGETSIZE_MAX)
+        self._fm_cache = {}
+    
+    def fontmetrics(self, font):
+        fm = self._fm_cache.get(font)
+        if fm is None:
+            return self._fm_cache.setdefault(font, QFontMetricsF(font))
+        else:
+            return fm
+    
+    def heightForWidth(self, font, flags, text, width):
+        fm = self.fontmetrics(font)
+        rect = fm.boundingRect(QRectF(0, 0, width, QWIDGETSIZE_MAX),
+                               flags, text)
+        return rect.height()
+    
+    def textSize(self, font, flags, text):
+        fm = self.fontmetrics(font)
+        rect = fm.boundingRect(self.qrectf_max, flags, text)
+        return rect.size()
+    
     def effectiveAscent(self, font):
         global ASCENTCACHE
         fontKey = font.key()
@@ -66,7 +92,7 @@ def findAscent(self, font):
         dummy = "E"
         white = QColor(Qt.white)
 
-        fm = QFontMetrics(font)
+        fm = self.fontmetrics(font)
         pm = QPixmap(fm.width(dummy), fm.height())
         pm.fill(white)
 
@@ -87,32 +113,10 @@ def findAscent(self, font):
                     return fm.ascent()-row+1
         return fm.ascent()
 
-
-class QwtTextEngine(object):
-    def __init__(self):
-        pass
-
-
-class QwtPlainTextEngine(QwtTextEngine):
-    def __init__(self):
-        self.__data = QwtPlainTextEngine_PrivateData()
-    
-    def heightForWidth(self, font, flags, text, width):
-        fm = QFontMetricsF(font)
-        rect = fm.boundingRect(QRectF(0, 0, width, QWIDGETSIZE_MAX),
-                               flags, text)
-        return rect.height()
-    
-    def textSize(self, font, flags, text):
-        fm = QFontMetricsF(font)
-        rect = fm.boundingRect(QRectF(0, 0, QWIDGETSIZE_MAX, QWIDGETSIZE_MAX),
-                               flags, text)
-        return rect.size()
-    
     def textMargins(self, font):
         left = right = top = 0
-        fm = QFontMetricsF(font)
-        top = fm.ascent() - self.__data.effectiveAscent(font)
+        fm = self.fontmetrics(font)
+        top = fm.ascent() - self.effectiveAscent(font)
         bottom = fm.descent()
         return left, right, top, bottom