Fix some loss of precision in BKE's unit code.

When converting text to value, units' "value" had only 6 digits of precision,
leading to annoying loss of precision esp. when mixing big and small units
(like e.g. miles and inches).

source/blender/blenkernel/BKE_unit.h

@@ -61,17 +61,19 @@ const char *bUnit_GetNameDisplay(void *usys_pt, int index);
 double      bUnit_GetScaler(void *usys_pt, int index);
 
 /* aligned with PropertyUnit */
-#define     B_UNIT_NONE 0
-#define     B_UNIT_LENGTH 1
-#define     B_UNIT_AREA 2
-#define     B_UNIT_VOLUME 3
-#define     B_UNIT_MASS 4
-#define     B_UNIT_ROTATION 5
-#define     B_UNIT_TIME 6
-#define     B_UNIT_VELOCITY 7
-#define     B_UNIT_ACCELERATION 8
-#define     B_UNIT_CAMERA 9
-#define     B_UNIT_TYPE_TOT 10
+enum {
+	B_UNIT_NONE             = 0,
+	B_UNIT_LENGTH           = 1,
+	B_UNIT_AREA             = 2,
+	B_UNIT_VOLUME           = 3,
+	B_UNIT_MASS             = 4,
+	B_UNIT_ROTATION         = 5,
+	B_UNIT_TIME             = 6,
+	B_UNIT_VELOCITY         = 7,
+	B_UNIT_ACCELERATION     = 8,
+	B_UNIT_CAMERA           = 9,
+	B_UNIT_TYPE_TOT         = 10,
+};
 
 #ifdef __cplusplus
 }

source/blender/blenkernel/intern/unit.c

@@ -536,7 +536,7 @@ static int unit_scale_str(char *str, int len_max, char *str_tmp, double scale_pr
 
 		len_name = strlen(replace_str);
 		len_move = (len - (found_ofs + len_name)) + 1; /* 1+ to copy the string terminator */
-		len_num = BLI_snprintf(str_tmp, TEMP_STR_SIZE, "*%g"SEP_STR, unit->scalar / scale_pref); /* # removed later */
+		len_num = BLI_snprintf(str_tmp, TEMP_STR_SIZE, "*%.9g"SEP_STR, unit->scalar / scale_pref); /* # removed later */
 
 		if (len_num > len_max)
 			len_num = len_max;
@@ -598,7 +598,7 @@ static int unit_find(const char *str, bUnitDef *unit)
  * ...will be resolved by python.
  *
  * values will be split by a comma's
- * 5'2" -> 5'0.0254, 2*0.3048
+ * 5'2" -> 5*0.3048, 2*0.0254
  *
  * str_prev is optional, when valid it is used to get a base unit when none is set.
  *