Re: Gdiplus [1/3] Improve accuracy in calculating height

[Huw Davies]

On Fri, Jun 27, 2008 at 10:16:41AM -0400, Adam Petaccia wrote:
> The previous patch I sent incorrectly calculated font-height. Now its
> correctly calculated using points_per_inch and the user's DPI setting.
> diff --git a/dlls/gdiplus/font.c b/dlls/gdiplus/font.c
> index 86a3223..85df905 100644
> --- a/dlls/gdiplus/font.c
> +++ b/dlls/gdiplus/font.c
> @@ -34,6 +34,7 @@ WINE_DEFAULT_DEBUG_CHANNEL (gdiplus);
>  #include "gdiplus_private.h"
>
> static const REAL mm_per_pixel = 25.4;
> +static const REAL points_per_inch = 1/72;

I know there are several definitions of a point, but none are this big!

points_per_inch should be around 72.
> @@ -50,7 +51,7 @@ static inline REAL get_dpi (void)
>
> static inline REAL point_to_pixel (REAL point)
>  {
> - return point * 1.5;
> - return point * (get_dpi() * points_per_inch);

And this then becomes points * get_dpi() / points_per_inch;

[Hint check the units:
 pixels (aka dots) = points * (dots / inch) / (points / inch)
]

Huw.

Gdiplus [1/3] Improve accuracy in calculating height

[Huw Davies]

On Fri, Jun 27, 2008 at 03:27:44PM +0100, Huw Davies wrote:
> On Fri, Jun 27, 2008 at 10:16:41AM -0400, Adam Petaccia wrote:
> > --- a/dlls/gdiplus/font.c
> > +++ b/dlls/gdiplus/font.c
> > @@ -34,6 +34,7 @@ WINE_DEFAULT_DEBUG_CHANNEL (gdiplus);
> >  #include "gdiplus_private.h"
> >
> > static const REAL mm_per_pixel = 25.4;

Ah and I missed this one.  Please rename to mm_per_inch !

Huw.

Gdiplus [1/3] Improve accuracy in calculating height

[Michael Karcher]

Am Freitag, den 27.06.2008, 15:27 +0100 schrieb Huw Davies:
> > static const REAL mm_per_pixel = 25.4;
> > +static const REAL points_per_inch = 1/72;
>
> I know there are several definitions of a point, but none are this big!
>
> points_per_inch should be around 72.

And if this is code is compiled by a C compiler, you get
points_per_pixel=0, as 1 and 72 are integers, so 1/72 is an integer
division that yields zero. This zero *then* gets converted to REAL. You
probably mean points_per_inch = 72 or inches_per_point = 1./72 (note the
decimal dot!)

Regards,
  Michael Karcher

Gdiplus [1/3] Improve accuracy in calculating height

[Adam Petaccia]

On Fri, 2008-06-27 at 16:46 +0200, Michael Karcher wrote:
> Am Freitag, den 27.06.2008, 15:27 +0100 schrieb Huw Davies:
> > > static const REAL mm_per_pixel = 25.4;
> > > +static const REAL points_per_inch = 1/72;
> >
> > I know there are several definitions of a point, but none are this big!
> >
> > points_per_inch should be around 72.
>
> And if this is code is compiled by a C compiler, you get
> points_per_pixel=0, as 1 and 72 are integers, so 1/72 is an integer
> division that yields zero. This zero *then* gets converted to REAL. You
> probably mean points_per_inch = 72 or inches_per_point = 1./72 (note the
> decimal dot!)

Face, meet palm. Thank you. I think this went uncaught because 0
indicates a default value.

I'll resend this as well as some other function which got negatively
affected by a cleanup patch -- and after lots of valgrinding (making
sure that 3rd time is in fact a charm).
> Regards,
>   Michael Karcher