On 2014.09.22 18:12, Allan wrote:
On 22/09/14 22:25, Jack wrote:
On 2014.09.22 15:17, Allan wrote:
On 22/09/14 19:04, Jack wrote:
On 2014.09.22 13:08, Allan wrote:
[snip....]
I don't think it really matters what font the system is using, as
long as that font is available. I'm using DejaVu Sans at the
moment, but I understand that if that is not available, the system
will substitute a similar one.
I'm not sure you understand my question. If the system is displaying
a font other than the one you specify but doing the size calculation
based on the font you specified, then the calculation may not match
the display. I'm just trying to be sure the size calculations are
being done with whatever font is actually being displayed.
As I specify the same font for both, wouldn't that avoid the situation
you foresee?
Not necessarily. You specify font X for display, but the system uses
font Y. You specify font X for doing font matrix calculations, and my
question is whether you know for sure that it is doing those
calculations on font X or on font Y. Since those calculations are not
necessarily tied to the active display, I can imagine the system not
doing the font substitution.
My non-expert view is that, if I specify font X, but the system
substitutes font Y, then the system would only have cause to do that
if font X was not available. So, I don't see how, some nano-seconds
later, font X has suddenly become available and now gets used. I hope
I don't need to keep checking?
I'm no more an expert than you, but I take a slightly paranoid approach
here. First, I don't know that non-availability is the only reason for
a system to use a font other than the one requested. I can imagine a
use case where user preference takes precedence, for example. (Think
css.) I can also imagine that when asked for font metrics for a
non-available font, the system might use some defaults, and not
necessarily those for the font it substituted in a particular instance.
So far, all looks well on both systems now. The column widths are
identical, and the only difference is in the overall width of the
tableWidget. That, I believe, comes from the margins, which do
differ, but I have already taken that into account. The aspect ratios
of the two screens are different, too.
Again, taking the paranoid view, I'm not sure "both systems" is a
sufficient sample. I take Cristian's view here that it is generally not
a good idea to override the user's choice of system default font. Think
of a vision impaired user who has chosen a particularly large font, or a
font chosen specifically for readability. If you can query what font
was actually used, and then use that to request the metric calculations,
shouldn't that give equivalent results?
Are the fonts identical?
I take it you mean between my two systems? Again, my non-expert view
is that if the two fonts have the same name, then the are identical.
Otherwise, they would not be the same font.
I accept that - but if those two systems are both using the font you
requested, then what happens when a system does not have that font
available?
If not, then why should the column widths be identical?
If the columns contain the same data and use the same font, then that
gives me the information needed to calculate/obtain the pixel width,
and therefore I use that to set the column width.
Again, the question is whether you can be sure that is the font that
will always be used? New train of thought - what about non-Roman
character sets? Greek? Cyrillic? Arabic? It may be that the
procedure you use will set up appropriate column widths, but if that is
the case, then what have you actually gained from specifying a font?
I assume the point is for the column to display the text in it
without clipping and without wasting space. To me, different fonts
are likely to need different column widths.
Yes, that was exactly the problem I had, which led me to specify the
actual font to use for both calculations and display, within the
plugin, to avoid the idiosyncrasies of different distros. It seems to
be working.
While my argument is certainly more academic than practical, the
minimalist in me asks why you would specify more than you need to. My
paranoid self asks whether your font specification has really done what
you expect, or if it simply happens to achieve the expected results in
the cases you have tested. (Just for context, I have several friends
that would call this exchange a "violent agreement.")
Jack
