[REG] GLWidget renderText() fails to render on Mac and Windows

renderText() worked in Qt4.8.2 but fails to draw the text in Qt5. The problem is clearly demonstrated by a simple modification of the hellogl example (see attachment). The relevant changes to the example are in ::paintGL() where a simple triangle is drawn with single digit text drawn at each vertex. When compiled against Qt4 the text is rendered as expected. When compiled against Qt5 the text is not visible. Note that it is possible to make the text visible in Qt5 by adding glDisable(GL_DEPTH_TEST) but that leads to errors in depth ordering of drawn objects.