input: add a keybinding to toggle hardware decoding

We sure as hell won't enable hardware decoding by default, but we can
make it more accessible with a key binding.

DOCS/man/mpv.rst

@@ -180,6 +180,9 @@ d
 A
     Cycle aspect ratio override.
 
+Ctrl h
+    Toggle hardware video decoding on/off.
+
 (The following keys are valid only when using a video output that supports the
 corresponding adjustment, or the software equalizer (``--vf=eq``).)
 

etc/input.conf

@@ -143,6 +143,7 @@
 #L cycle-values loop-file "inf" "no"    # toggle infinite looping
 #ctrl+c quit 4
 #DEL script-binding osc/visibility      # cycle OSC display
+#ctrl+h cycle-values hwdec "auto" "no"  # cycle hardware decoding
 
 # Apple Remote section
 #AR_PLAY cycle pause

player/command.c

@@ -4321,6 +4321,7 @@ static const struct property_osd_display {
     {"ab-loop-a", "A-B loop start"},
     {"ab-loop-b", .msg = "A-B loop: ${ab-loop-a} - ${ab-loop-b}"},
     {"audio-device", "Audio device"},
+    {"hwdec", .msg = "Hardware decoding: ${hwdec-current}"},
     // By default, don't display the following properties on OSD
     {"pause", NULL},
     {"fullscreen", NULL},