console: use hidpi scale reporting

I decided to factor this into the user's scale option (instead of
somehow using it as default if the user has not specified it), because
it makes the option handling simpler, and won't break things like
per-screen DPI if the user only wants to scale the console font by a
factor.

DOCS/man/console.rst

@@ -89,7 +89,10 @@ Configurable Options
     Default: 1
 
     All drawing is scaled by this value, including the text borders and the
-    cursor. Change it if you have a high-DPI display.
+    cursor.
+
+    If the VO backend in use has HiDPI scale reporting implemented, the option
+    value is scaled with the reported HiDPI scale.
 
 ``font``
     Default: unset (picks a hardcoded font depending on detected platform)

player/lua/console.lua

@@ -143,9 +143,13 @@ end
 function update()
     pending_update = false
 
+    local dpi_scale = mp.get_property_native("display-hidpi-scale", 1.0)
+
+    dpi_scale = dpi_scale * opts.scale
+
     local screenx, screeny, aspect = mp.get_osd_size()
-    screenx = screenx / opts.scale
-    screeny = screeny / opts.scale
+    screenx = screenx / dpi_scale
+    screeny = screeny / dpi_scale
 
     -- Clear the OSD if the REPL is not active
     if not repl_active then
@@ -675,6 +679,7 @@ end)
 -- PlayRes of the OSD will need to be adjusted.
 mp.observe_property('osd-width', 'native', update)
 mp.observe_property('osd-height', 'native', update)
+mp.observe_property('display-hidpi-scale', 'native', update)
 
 -- Enable log messages. In silent mode, mpv will queue log messages in a buffer
 -- until enable_messages is called again without the silent: prefix.