x11: pseudo HiDPI scaling

Scale the window by the assumed DPI scaling factor, using 96 DPI as
base. For example, a screen that reports 192 DPI is assumed to have a
DPI scale factor 2. The window will then be created with twice the size.

For robustness reasons, we accept only integer DPI scales between 1 and
9. We also error out if the X and Y scales are very different, as this
most likely indicates a multiscreen system with botched size reporting.

I'm not sure if reading the X server's DPI is such a good idea - maybe
the Xrdb "Xft.dpi" value should be used instead. The current method
follows what xdpyinfo does.

This can be disabled with --hidpi-window-scale=no.

1 files changed, 1 insertions, 0 deletions

diff --git a/video/out/x11_common.h b/video/out/x11_common.h
index 6c92fdb480..e69640cc64 100644
--- a/video/out/x11_common.h
+++ b/video/out/x11_common.h
@@ -54,6 +54,7 @@ struct vo_x11_state {
     int display_is_local;
     int ws_width;
     int ws_height;
+    int dpi_scale;
     struct mp_rect screenrc;
     char *window_title;