After loading stackoverflow.com and zooming (via ewk_view_scale_set) there are following errors:
1) First zoom out (nominally 0.9) lowers the elements at around 0.78, the second zoom out (nominally 0.8) - decrease ~ 0.63, third (nominally 0.67) - decreasing ~ 0.44.
2) ewk_view_scale_set function, in addition to the scale factor, has the other two arguments corresponding to the position of the mouse. However, regardless of the position of the mouse function places the reduced page image always near the top left corner, leaving wide right margin.
3) Reducing the width of the window in the situation described above causes first two-sided reduction in margins. When the left margin disappears, further reducing the width of the window causes at some point truncation content from the right side, although the right margin is at this point about 1/3 the width of the window.
*** This bug has been marked as a duplicate of bug 130962 ***