TCanvas / printerdriver problems

I'm developing a component to render text (like rich-text but with more
control and features) and I'm having the following two problems:

1. Because Windows uses pixels for measuring (why, oh why, not use
1000th of mm or something?) the resulting output looks different on
various printers and on a preview screen.

2. Output differs between various printers. Some printers leave out
pieces of output, while for example my HP Deskjet 870Cxi in 600dpi
monochrome mode does not allow transparent text.

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