m_property: add `>` for fixed precision floating-point expansion

This enhancement makes it easier to create constant width property
expansions, useful for the `--term-status-msg`. Additionally, it changes
to `%f` printing with manual zero trimming, which is easier to control
than `%g`. With this method, we can directly specify precision, not just
significant numbers. This approach also avoids overly high precision for
values less than 1, which is not necessary for a generic floating-point
print function.

A new print helper function is added, which can be used with adjusted
precision for specific cases where a different default is needed. This
also unifies the code slightly.

2 files changed, 25 insertions, 0 deletions

diff --git a/common/common.c b/common/common.c
index 9f8230fbff..7089a6674b 100644
--- a/common/common.c
+++ b/common/common.c
@@ -94,6 +94,25 @@ char *mp_format_time(double time, bool fractions)
     return mp_format_time_fmt(fractions ? "%H:%M:%S.%T" : "%H:%M:%S", time);
 }
 
+char *mp_format_double(void *talloc_ctx, double val, int precision,
+                       bool plus_sign, bool percent_sign, bool trim)
+{
+    bstr str = {0};
+    const char *fmt = plus_sign ? "%+.*f" : "%.*f";
+    bstr_xappend_asprintf(talloc_ctx, &str, fmt, precision, val);
+    size_t pos = str.len;
+    if (trim) {
+        while (--pos && str.start[pos] == '0')
+            str.len--;
+        if (str.start[pos] == '.')
+            str.len--;
+    }
+    if (percent_sign)
+        bstr_xappend(talloc_ctx, &str, bstr0("%"));
+    str.start[str.len] = '\0';
+    return str.start;
+}
+
 // Set rc to the union of rc and rc2
 void mp_rect_union(struct mp_rect *rc, const struct mp_rect *rc2)
 {
diff --git a/common/common.h b/common/common.h
index ccdd94bba9..cd9bea93c2 100644
--- a/common/common.h
+++ b/common/common.h
@@ -99,6 +99,12 @@ extern const char mpv_copyright[];
 char *mp_format_time(double time, bool fractions);
 char *mp_format_time_fmt(const char *fmt, double time);
 
+// Formats a double value to a string with the specified precision.
+// Trailing zeros (and the dot) can be trimmed.
+// Optionally, a plus sign and a percent sign can be added.
+char *mp_format_double(void *talloc_ctx, double val, int precision,
+                       bool plus_sign, bool percent_sign, bool trim);
+
 struct mp_rect {
     int x0, y0;
     int x1, y1;