Created attachment 29953 [details] sample ppt demonstrating the problem The current TextPainter class handles linespacing attributes for absolute values (represented by a negative linespacing number) incorrectly. It adds the value of linespacing to both the ascent and descent of the TextElement, which results in rendering twice as much space as it should when drawing slides. Sample PPT demonstrates the problem if you try to render the slide.
Created attachment 29954 [details] Proposed patch
PPTX2PNG renders this now ok ... nothing to change/apply anymore