qt_dotgraph: setting a device dependend font size in pixel instead of…

… points results in correctly sized text in the graph

qt_dotgraph/src/qt_dotgraph/graph_item.py

@@ -29,7 +29,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 
 from python_qt_binding.QtGui import QColor, QFont
-from python_qt_binding.QtWidgets import QGraphicsItemGroup, QGraphicsSimpleTextItem
+from python_qt_binding.QtWidgets import QGraphicsItemGroup
 
 
 class GraphItem(QGraphicsItemGroup):
@@ -41,27 +41,10 @@ class GraphItem(QGraphicsItemGroup):
     _COLOR_RED = QColor(255, 0, 0)
     _COLOR_TEAL = QColor(0, 170, 170)
 
-    _FONT_SIZE = 12.0
-    _FONT_SIZE_IS_ADJUSTED = False
-    _FONT_SIZE_REFERENCE_TEXT = ''.join(map(chr, range(0x20, 0x7f)))
-    _FONT_SIZE_REFERENCE_WIDTH = 650
-
-    _LABEL_FONT = QFont('sans', pointSize=_FONT_SIZE, weight=QFont.Light)
+    _LABEL_FONT = QFont('sans', weight=QFont.Light)
 
     def __init__(self, highlight_level, parent=None):
         super(GraphItem, self).__init__(parent)
         self._highlight_level = highlight_level
-        if not GraphItem._FONT_SIZE_IS_ADJUSTED:
-            GraphItem._adjust_font_size()
-
-    @staticmethod
-    def _adjust_font_size():
-        GraphItem._FONT_SIZE_IS_ADJUSTED = True
-
-        text_item = QGraphicsSimpleTextItem(GraphItem._FONT_SIZE_REFERENCE_TEXT)
-        text_item.setFont(GraphItem._LABEL_FONT)
-        # reduce font size on high resolution displays until text_item in smaller than reference width
-        while text_item.sceneBoundingRect().width() > GraphItem._FONT_SIZE_REFERENCE_WIDTH:
-            GraphItem._FONT_SIZE *= 0.95
-            GraphItem._LABEL_FONT.setPointSizeF(GraphItem._FONT_SIZE)
-            text_item.setFont(GraphItem._LABEL_FONT)
+        # use device depended font size to produce
+        GraphItem._LABEL_FONT.setPixelSize(11)