select/unit: Add internal angle-to-degrees converter

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

2 files changed, 24 insertions, 0 deletions

diff --git a/src/select/unit.c b/src/select/unit.c
index 3294db3..5f0f179 100644
--- a/src/select/unit.c
+++ b/src/select/unit.c
@@ -511,3 +511,16 @@ css_error css_unit_compute_absolute_font_size(
 
 	return CSS_OK;
 }
+
+/* Exported function, documented in utils/unit.h. */
+css_fixed css_unit_angle2deg(const css_unit unit, const css_fixed angle)
+{
+	if (unit == CSS_UNIT_GRAD) {
+		return FMUL(angle, FLTTOFIX(0.9));
+	} else if (unit == CSS_UNIT_RAD) {
+		return FDIV(FMUL(angle, INTTOFIX(180)), F_PI);
+	} else {
+		/* Must be degrees as DEG/RAD/GRAD are all angle kinds */
+		return angle;
+	}
+}
diff --git a/src/select/unit.h b/src/select/unit.h
index 6a677b6..8b5d905 100644
--- a/src/select/unit.h
+++ b/src/select/unit.h
@@ -39,4 +39,15 @@ css_error css_unit_compute_absolute_font_size(
 		css_fixed font_size_default,
 		css_hint *size);
 
+/**
+ * Convert any angle to degrees.
+ *
+ * It is invalid to call this with a unit which isn't of \ref UNIT_ANGLE
+ *
+ * \param[in] unit The unit the angle is in
+ * \param[in] angle The angle to convert
+ * \return the angle in degrees
+ */
+css_fixed css_unit_angle2deg(const css_unit unit, const css_fixed angle);
+
 #endif