[Lazarus] Controlling DPI

David W Noon david.w.noon at ntlworld.com
Sat Mar 28 21:00:57 CET 2009


On Sat, 2009-03-28 at 19:17 +0100, Hans-Peter Diettrich wrote:

> David W Noon schrieb:
> 
> >> I prefer the latter, but the zoon factor can also do the trick.
> > 
> > The DPI is controlled by the hardware driver for the video card.
> 
> That's a matter of definition of "DPI".

There is only one definition of DPI for any given device. Moreover, what
you have written below isn't it -- for any device.

> Windows allows to change the font size (DPI) at any time, and most other 
> systems have similar capabilities. Since Delphi has its roots in 
> Windows, this definition also should apply to FPC/Lazarus.

The *point size* of the font has nothing whatsoever to do with the DPI
of the screen or printer, other than the rendering engine querying the
DPI of the device in order to render the text to the appropriate size in
pica points. There are approximately 72 pica points to an inch,
regardless of the DPI of the device on which the text is being rendered.

See:
http://en.wikipedia.org/wiki/Pica_(unit_of_measure)

[The pica has also been "Americanized" to be exactly 1/72nd of an inch
within the computer industry, but the classic definition if picas/didots
and ciceros does not fit easily in Imperial Measures.]

-- 
Regards,

Dave  [RLU #314465]
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david.w.noon at ntlworld.com (David W Noon)
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