https://bugs.documentfoundation.org/show_bug.cgi?id=169948

--- Comment #9 from V Stuart Foote <[email protected]> ---
(In reply to wlmcderm from comment #4)

> However, I wonder if font substitution is the whole story. I'll also attach
> screenshots (Selection-1.jpg and Selection-2.jpg) showing that the affected
> line is imported as two different blocks of text. The horizontal placement
> of the two text blocks is causing the overlap in Screenshot1. If all the
> text in that line of the paragraph had been placed in the same block,
> presumably it would have been more legible even without manually
> substituting the font.

Manifestation of the Internal structure of published PDF. The text elements are
laid down with no syntactical detail nor "sense" of their relation to other
text elements--just their finished published presentation on the document page.
The text elements are laid down between /BT and /ET flags.  The text element
strings are positioned accurately between those tags with horizontal
positioning measures.

Glyphs of the font(s) used although subset are recorded into the PDF, and as
the poppler based filter can not read those glyphs they must be substituted. We
can explicitly substitute the font with the 'Replacement Table' as noted, or
simply trust to the poppler <--> cairo fallback and object creation, but not
use the embedded glyphs.

So the remaining overlap is bcz the /BT /ET text element metrics differ with
the glyphs from the replacement font. The ending text of the first extends over
the beginning text of the next. It can go the other direction, and you can end
up with gaps rather than overlaps between adjacent text elements.

The alternative to "Opening" the PDF and using the pdfium based Insert filter
always directly reads the internal layout of the PDF and the embedded subset
font. So if you need fidelity, break the PDF into its pages externally, and
then insert as image.  Image resolution can be controoled by setting a system
variable PDFIMPORT_RESOLUTION_DPI, default is 96. 300 or 450 works well for
full page rendering when placed onto an ODF document page. YMMV depending on
need. And there are enhancment requests to improve handling the insert process
(e.g. page range selection, resolution, rotation, etc.).

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