Sorry for the delayed answer - had to do some "real work" yesterday. ;-) vroonhof(a)math.ethz.ch wrote: You had the right feeling ...! After loading a file larger than the visible buffer and pressing the PgDown key, it stops at the breakpoint in the "else" branch (line 4107) and fheight has indeed a value of 0. But where does the 0 come from? Good question. I must admit that single stepping through default_face_height_and_width didn't make this clear to me. In other words: If I set a second breakpoint at the next line, i.e. if (Dynarr_length (dla) >= 1) modeline = Dynarr_atp (dla, 0)->modeline; dl = Dynarr_atp (dla, modeline); then fheight already has a value of 14 (which is my current default font size and thus correct), so it seems like default_face_height_and_width returns the correct value after its first pass. But pressing PgDown a second time still does not scroll, although one should think that fheight is non-zero now. In fact, my debugger shows a value of +804392872 when stopping again at the first breakpoint (overflow?). Continue to the 2nd breakpoint and fheight == 14 again. Don't know if this is of great help; let me know what I can do to provide any further information. Looks like that ... Markus