options: alternative way to specify color options

Try to make it more intuitive by not requiring hex values. The new way
uses float values in the range 0.0-1.0, separated by '/' (':' was
suggested, but that wouldn't allow color options in sub-options).

Example: --osd-color=1.0/0.0/0.0/0.75

Using the range 0.0-1.0 has the advantage that it could be easily
extended to colors beyond 8 bit.

Details see manpage.

Suggestions for alternative syntax or value ranges are welcome, but be
quick with it.

DOCS/man/en/options.rst

@@ -1485,13 +1485,13 @@ OPTIONS
 ``--osd-bar-h=<0.1-50>``
     Height of the OSD bar, in percentage of the screen height (default: 3.125).
 
-``--osd-back-color=<#RRGGBB>``, ``--sub-text-back-color=<#RRGGBB>``
+``--osd-back-color=<color>``, ``--sub-text-back-color=<color>``
     See ``--osd-color``. Color used for OSD/sub text background.
 
 ``--osd-blur=<0..20.0>``, ``--sub-text-blur=<0..20.0>``
     Gaussian blur factor. 0 means no blur applied (default).
 
-``--osd-border-color=<#RRGGBB>``, ``--sub-text-border-color=<#RRGGBB>``
+``--osd-border-color=<color>``, ``--sub-text-border-color=<color>``
     See ``--osd-color``. Color used for the OSD/sub font border.
 
     .. note::
@@ -1506,16 +1506,28 @@ OPTIONS
 
     Default: 2.5.
 
-``--osd-color=<#RRGGBB|#AARRGGBB>``, ``--sub-text-color=<#RRGGBB|#AARRGGBB>``
+``--osd-color=<color>``, ``--sub-text-color=<color>``
     Specify the color used for OSD/unstyled text subtitles.
 
-    The color is specified as a RGB hex triplet, and each 2-digit group
-    expresses a color value in the range 0 (``00``) to 255 (``FF``).
-    For example, ``#FF0000`` is red. This is similar to web colors.
+    The color is specified in the form ``r/g/b``, where each color component
+    is specified as number in the range 0.0 to 1.0. It's also possible to
+    specify the transparency by using ``r/g/b/a``, where the alpha value 0
+    means fully transparent, and 1.0 means opaque. If the alpha component is
+    not given, the color is 100% opaque.
 
-    You can specify transparency by specifying an alpha value in the form
-    ``#AARRGGBB``. ``00`` is fully transparent, while ``FF`` is opaque (opaque
-    is default with the shorter color specification).
+    Passing a single number to the option sets the OSD to gray, and the form
+    ``gray/a`` lets you specify alpha additionally.
+
+    .. admonition:: Examples
+
+        - ``--osd-color=1.0/0.0/0.0`` set OSD to opaque red
+        - ``--osd-color=1.0/0.0/0.0/0.75`` set OSD to opaque red with 75% alpha
+        - ``--osd-color=0.5/0.75`` set OSD to 50% gray with 75% alpha
+
+    Alternatively, the color can be specified as a RGB hex triplet in the form
+    ``#RRGGBB``, where each 2-digit group expresses a color value in the
+    range 0 (``00``) to 255 (``FF``). For example, ``#FF0000`` is red.
+    This is similar to web colors.
 
     .. admonition:: Examples
 
@@ -1587,7 +1599,7 @@ OPTIONS
     are always in actual pixels. The effect is that changing the window size
     won't change the OSD font size.
 
-``--osd-shadow-color=<#RRGGBB>, --sub-text-shadow-color=<#RRGGBB>``
+``--osd-shadow-color=<color>, --sub-text-shadow-color=<color>``
     See ``--osd-color``. Color used for OSD/sub text shadow.
 
 ``--osd-shadow-offset=<size>, --sub-text-shadow-offset=<size>``

options/m_option.c

@@ -1410,6 +1410,28 @@ const m_option_type_t m_option_type_msglevels = {
 
 #undef VAL
 
+// Split the string on the given split character.
+// out_arr is at least max entries long.
+// Return number of out_arr entries filled.
+static int split_char(bstr str, unsigned char split, int max, bstr *out_arr)
+{
+    if (max < 1)
+        return 0;
+
+    int count = 0;
+    while (1) {
+        int next = bstrchr(str, split);
+        if (next >= 0 && max - count > 1) {
+            out_arr[count++] = bstr_splice(str, 0, next);
+            str = bstr_cut(str, next + 1);
+        } else {
+            out_arr[count++] = str;
+            break;
+        }
+    }
+    return count;
+}
+
 static int parse_color(struct mp_log *log, const m_option_t *opt,
                        struct bstr name, struct bstr param, void *dst)
 {
@@ -1434,7 +1456,24 @@ static int parse_color(struct mp_log *log, const m_option_t *opt,
             has_alpha ? (c >> 24) & 0xFF : 0xFF,
         };
     } else {
-        goto error;
+        bstr comp_str[5];
+        int num = split_char(param, '/', 5, comp_str);
+        if (num < 1 || num > 4)
+            goto error;
+        double comp[4] = {0, 0, 0, 1};
+        for (int n = 0; n < num; n++) {
+            bstr rest;
+            double d = bstrtod(comp_str[n], &rest);
+            if (rest.len || !comp_str[n].len || d < 0 || d > 1 || !isnormal(d))
+                goto error;
+            comp[n] = d;
+        }
+        if (num == 2)
+            comp[3] = comp[1];
+        if (num < 3)
+            comp[2] = comp[1] = comp[0];
+        color = (struct m_color) { comp[0] * 0xFF, comp[1] * 0xFF,
+                                   comp[2] * 0xFF, comp[3] * 0xFF };
     }
 
     if (dst)
@@ -1445,7 +1484,9 @@ static int parse_color(struct mp_log *log, const m_option_t *opt,
 error:
     mp_err(log, "Option %.*s: invalid color: '%.*s'\n",
            BSTR_P(name), BSTR_P(param));
-    mp_err(log, "Valid colors must be in the form #RRRGGBB or #AARRGGBB (in hex)\n");
+    mp_err(log, "Valid colors must be in the form #RRGGBB or #AARRGGBB (in hex)\n"
+                "Or in the form 'r/g/b/a', where each component is a value in the\n"
+                "range 0.0-1.0. (Also allowed: 'gray', 'gray/a', 'r/g/b'.\n");
     return M_OPT_INVALID;
 }