app/internal/window: don't second guess UI scale

Before this change, Gio tries hard to come up with a reasonable UI scale
factor on desktop OSes derived from the physical dimensions and
resolution of connected monitors. Gio also attempts to detect the user
specified system UI scale and apply it.

However, all that is complex and misguided:

- The UI scale should not depend on whatever monitor is connected at
program startup - For multiple monitors, it's unclear which one to base
the scale off.  - Applying both a monitor derived scale *and* the user
specified scale is wrong, because the user scale is relative to some
fixed scale, not Gio's derived scale.  - With an automatic scale, Gio
does not respect user preference and will not have a similar scale to
other programs on the desktop.

Get rid of the the automatic UI scale detection and rely only on the
user scale.

Updates gio#53

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/window/window.go

@@ -109,13 +109,4 @@ func newWindowRendezvous() *windowRendezvous {
 
 const (
 	inchPrDp = 1.0 / 160
-	mmPrDp   = 25.4 / 160
-	// monitorScale is the extra scale applied to
-	// monitor outputs to compensate for the extra
-	// viewing distance compared to phone and tables.
-	monitorScale = 1.20
-	// minDensity is the minimum pixels per dp to
-	// ensure font and ui legibility on low-dpi
-	// screens.
-	minDensity = 1.0
 )