Different output from QPainter for X11, raster and opengl backend.

I got 2 problems.
1) When using QGLWidget or option -graphicssystem opengl (same result for both) then lines or rectangles and probably all paint operations with zero X coordinate are not visible. With X11 or raster backend they are visible. It looks like with x11 but shifted by 1 pixel to left.

2) Co-ordination rounding for raster paint engine is different from X11 and opengl. Raster co-ordinations are rounded and in X11 and opengl are ceiled. This different output is visible from attached images or you can compile source code. The most left vertical line has zero coordination. Rectangles with size 50x50 start with zero X co-ordinate and every lower rectangle has X co-ordinate increased by 0.2.

Maybe i use painter badly but i think output should be same.