[Qt-interest] QGraphicsView and vertical/horizontal lines which do not display

[Cecilia Castillo]

Hi -

I am new to Qt (and gui programming).

I am writing an application which displays points and lines 
connecting these points.  The user can grab points and move them 
around causing the lines to adjust.

I am using QGraphicsView to implement this.

When I display my initial set of points and lines, if the lines are 
exactly vertical or horizontal, they sometimes do not display.  If I 
move a point which causes the line to be off vertical or horizontal, 
the line appears.  If I move the point back and the line goes 
vertical/horizontal...the line disappears.

This only happens on some vertical/horizontal lines.  I have one case 
where the points make a box and only the bottom line of the box does 
not appear.  The vertical lines appear and the top horizontal line 
appears.

Any advice would be welcome.

Thanks,
  Cecilia