stats.lua: calculate sizes like --osd-*-size options

Currently --script-opt=stats-font_size=n is much bigger than
--osd-font-size=n, which can confuse users, so calculate sizes the same
way.

The \fs value to replicate --osd-font-size is
${osd-font-size} * 288 / 720 with --osd-scale-by-window, and
\fs${osd-font-size} * 288 / ${osd-height}
with --osd-scale-by-window=no. This is because
sub/osd_libass.c:update_playres() sets
track->PlayResY = ass->res_y ? ass->res_y : MP_ASS_FONT_PLAYRESY,
where MP_ASS_FONT_PLAYRESY is 288.

This also works with persistent_overlay=yes.

{\fscx100}{\fscy100} would also replicate --osd-font-size with show-text
and with osd-verlay + --osd-scale-by-window, but not with osd-overlay +
--osd-scale-by-window=no.

The default sizes are multiplied by 720/288 = 2.5 to keep them the same
as before.

DOCS/interface-changes/stats-sizes.rst

@@ -0,0 +1 @@
+`stats-font_size`, `stats-border_size`, `stats-shadow_x_offset`, `stats-shadow_y_offset` and `stats-plot_bg_border_width` script-opt values result in 2.5 times smaller sizes in order to have the same sizes as the values of equivalent OSD options like `--osd-font-size`. If you customized these sizes, multiply them by 2.5 to get the previous sizes.

DOCS/man/stats.rst

@@ -155,7 +155,7 @@ Configurable Options
     text. Currently, monospaced digits are sufficient.
 
 ``font_size``
-    Default: 8
+    Default: 20
 
     Font size used to render text.
 
@@ -165,7 +165,7 @@ Configurable Options
     Color of the text.
 
 ``border_size``
-    Default: 0.8
+    Default: 2
 
     Size of border drawn around the font.
 
@@ -202,7 +202,7 @@ Configurable Options
     Border color used for drawing graphs.
 
 ``plot_bg_border_width``
-    Default: 0.5
+    Default: 1.25
 
     Border width used for drawing graphs.