vo_gpu, options: don't return NaN through API

Internally, vo_gpu uses NaN for some options to indicate a default value
that is different depending on the context (e.g. different scalers).
There are 2 problems with this:

1. you couldn't reset the options to their defaults
2. NaN is a damn mess and shouldn't be part of the API

The option parser already rejected NaN explicitly, which is why 1.
didn't work. Regarding 2., JSON might be a good example, and actually
caused a bug report.

Fix this by mapping NaN to the special value "default". I think I'd
prefer other mechanisms (maybe just having every scaler expose separate
options?), but for now this will do. See you in a future commit, which
painfully deprecates this and replaces it with something else.

I refrained from using "no" (my favorite magic value for "unset" etc.)
because then I'd have e.g. make --no-scale-param1 work, which in
addition to a lot of effort looks dumb and nobody will use it.

Here's also an apology for the shitty added test script.

Fixes: #6691

1 files changed, 3 insertions, 0 deletions

diff --git a/options/m_option.h b/options/m_option.h
index a3d008a400..390919141e 100644
--- a/options/m_option.h
+++ b/options/m_option.h
@@ -424,6 +424,9 @@ char *format_file_size(int64_t size);
 #define UPDATE_OPTS_MASK \
     (((UPDATE_OPT_LAST << 1) - 1) & ~(unsigned)(UPDATE_OPT_FIRST - 1))
 
+// type_float/type_double: string "default" is parsed as NaN (and reverse)
+#define M_OPT_DEFAULT_NAN       (1 << 29)
+
 // Like M_OPT_TYPE_OPTIONAL_PARAM.
 #define M_OPT_OPTIONAL_PARAM    (1 << 30)