Created attachment 343245 [details]
long text

With the Adobe Source Sans Font the line wrapping sometimes produces sporadic results. The wrapping seems to be dependent on the following text, so that a short text doesn't "fit" on a line, but does if it is followed by more text. This phenomen can be observed with pango-view:

pango-view --text='W1D1,W1D7,W2D14,W3D21,W4D28' --width 158 --wrap=word-char --font='Source Sans Pro 14'
(long text; look at the first line)

pango-view --text='W1D1,W1D7,W2D14,W3D21,' --width 158 --wrap=word-char --font='Source Sans Pro 14'
(short text; only the first line of the previous example, but now wrapped to two lines)

I see this with pango 1.40.3 on OpenBSD and pango 1.38.1 on Ubuntu 16.04.1.
I was not able to reproduce this issue with other fonts.