command: add generic "multiply" command

Essentially works like "add".

DOCS/man/en/input.rst

@@ -112,6 +112,9 @@ List of Input Commands
     overflow, set the property back to the minimum, on underflow set it to the
     maximum. If ``up`` or ``down`` is omitted, assume ``up``.
 
+``multiply <property> <factor>``
+    Multiplies the value of a property with the numeric factor.
+
 ``speed_mult <value>``
     Multiply the ``speed`` property by the given value.
 

mpvcore/input/input.c

@@ -216,6 +216,7 @@ static const mp_cmd_t mp_cmds[] = {
         .optional = true,
         .v.d = 1 },
   }},
+  { MP_CMD_MULTIPLY, "multiply", { ARG_STRING, ARG_DOUBLE } },
 
   { MP_CMD_ENABLE_INPUT_SECTION,  "enable_section",  {
       ARG_STRING,

mpvcore/input/input.h

@@ -66,6 +66,7 @@ enum mp_command_type {
     MP_CMD_RADIO_SET_FREQ,
     MP_CMD_ADD,
     MP_CMD_CYCLE,
+    MP_CMD_MULTIPLY,
     MP_CMD_RADIO_STEP_FREQ,
     MP_CMD_TV_STEP_FREQ,
     MP_CMD_TV_START_SCAN,

mpvcore/m_option.c

@@ -346,6 +346,25 @@ static void add_int(const m_option_t *opt, void *val, double add, bool wrap)
     *(int *)val = tmp;
 }
 
+static void multiply_int64(const m_option_t *opt, void *val, double f)
+{
+    double v = *(int64_t *)val * f;
+    int64_t iv = v;
+    if (v < INT64_MIN)
+        iv = INT64_MIN;
+    if (v > INT64_MAX)
+        iv = INT64_MAX;
+    *(int64_t *)val = iv;
+    clamp_int64(opt, val);
+}
+
+static void multiply_int(const m_option_t *opt, void *val, double f)
+{
+    int64_t tmp = *(int *)val;
+    multiply_int64(opt, &tmp, f);
+    *(int *)val = MPCLAMP(tmp, INT_MIN, INT_MAX);
+}
+
 const m_option_type_t m_option_type_int = {
     .name  = "Integer",
     .size  = sizeof(int),
@@ -353,6 +372,7 @@ const m_option_type_t m_option_type_int = {
     .print = print_int,
     .copy  = copy_opt,
     .add = add_int,
+    .multiply = multiply_int,
     .clamp = clamp_int,
 };
 
@@ -363,6 +383,7 @@ const m_option_type_t m_option_type_int64 = {
     .print = print_int,
     .copy  = copy_opt,
     .add = add_int64,
+    .multiply = multiply_int64,
     .clamp = clamp_int64,
 };
 
@@ -644,6 +665,12 @@ static void add_double(const m_option_t *opt, void *val, double add, bool wrap)
     VAL(val) = v;
 }
 
+static void multiply_double(const m_option_t *opt, void *val, double f)
+{
+    *(double *)val *= f;
+    clamp_double(opt, val);
+}
+
 const m_option_type_t m_option_type_double = {
     // double precision float or ratio (numerator[:/]denominator)
     .name  = "Double",
@@ -654,6 +681,7 @@ const m_option_type_t m_option_type_double = {
     .copy  = copy_opt,
     .clamp = clamp_double,
     .add = add_double,
+    .multiply = multiply_double,
 };
 
 #undef VAL
@@ -694,6 +722,13 @@ static void add_float(const m_option_t *opt, void *val, double add, bool wrap)
     VAL(val) = tmp;
 }
 
+static void multiply_float(const m_option_t *opt, void *val, double f)
+{
+    double tmp = VAL(val);
+    multiply_double(opt, &tmp, f);
+    VAL(val) = tmp;
+}
+
 const m_option_type_t m_option_type_float = {
     // floating point number or ratio (numerator[:/]denominator)
     .name  = "Float",
@@ -703,6 +738,7 @@ const m_option_type_t m_option_type_float = {
     .pretty_print = print_float_f3,
     .copy  = copy_opt,
     .add = add_float,
+    .multiply = multiply_float,
     .clamp = clamp_float,
 };
 

mpvcore/m_option.h

@@ -273,6 +273,10 @@ struct m_option_type {
     // the value is clipped, or wraps around to the opposite max/min.
     void (*add)(const m_option_t *opt, void *val, double add, bool wrap);
 
+    // Multiply the value with the factor f. The callback must clip the result
+    // to the valid value range of the option.
+    void (*multiply)(const m_option_t *opt, void *val, double f);
+
     // Clamp the value in val to the option's valid value range.
     // Return values:
     //  M_OPT_OUT_OF_RANGE: val was invalid, and modified (clamped) to be valid

mpvcore/player/command.c

@@ -2379,6 +2379,29 @@ static void overlay_uninit(struct MPContext *mpctx){}
 
 #endif
 
+static int mp_property_multiply(char *property, double f, struct MPContext *mpctx)
+{
+    union m_option_value val = {0};
+    struct m_option opt = {0};
+    int r;
+
+    r = mp_property_do(property, M_PROPERTY_GET_TYPE, &opt, mpctx);
+    if (r != M_PROPERTY_OK)
+        return r;
+    assert(opt.type);
+
+    if (!opt.type->multiply)
+        return M_PROPERTY_NOT_IMPLEMENTED;
+
+    r = mp_property_do(property, M_PROPERTY_GET, &val, mpctx);
+    if (r != M_PROPERTY_OK)
+        return r;
+    opt.type->multiply(&opt, &val, f);
+    r = mp_property_do(property, M_PROPERTY_SET, &val, mpctx);
+    m_option_free(&opt, &val);
+    return r;
+}
+
 // Whether this property should react to key events generated by auto-repeat.
 static bool check_property_autorepeat(char *property,  struct MPContext *mpctx)
 {
@@ -2484,6 +2507,23 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
         break;
     }
 
+    case MP_CMD_MULTIPLY: {
+        char *property = cmd->args[0].v.s;
+        double f = cmd->args[1].v.d;
+        int r = mp_property_multiply(property, f, mpctx);
+
+        if (r == M_PROPERTY_OK || r == M_PROPERTY_UNAVAILABLE) {
+            show_property_osd(mpctx, property, cmd->on_osd);
+        } else if (r == M_PROPERTY_UNKNOWN) {
+            set_osd_msg(mpctx, OSD_MSG_TEXT, osdl, osd_duration,
+                        "Unknown property: '%s'", property);
+        } else if (r <= 0) {
+            set_osd_msg(mpctx, OSD_MSG_TEXT, osdl, osd_duration,
+                        "Failed to multiply property '%s' by %g", property, f);
+        }
+        break;
+    }
+
     case MP_CMD_GET_PROPERTY: {
         char *tmp;
         int r = mp_property_do(cmd->args[0].v.s, M_PROPERTY_GET_STRING,