Fix multi-units drawing re precision handling.

This is still far from prefect, but yet much better than what we had so
far (more consistent with inheritent precision available in floats).

Note that this fixes some (currently commented out) units unittests, and
requires adjusting some others, will be done in next commit.

1 files changed, 7 insertions, 3 deletions

diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index a013f75f9e8..7ab4e1d9c35 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -2228,20 +2228,24 @@ void ui_but_string_get_ex(uiBut *but, char *str, const size_t maxlen, const int
 			else {
 				int prec = (float_precision == -1) ? ui_but_calc_float_precision(but, value) : float_precision;
 				if (use_exp_float) {
-					const int l10 = (value == 0.0f) ? 0 : (int)log10(fabs(value));
-					if (l10 < -6 || l10 > 12) {
+					const int int_digits_num = integer_digits_f(value);
+					if (int_digits_num < -6 || int_digits_num > 12) {
 						BLI_snprintf(str, maxlen, "%.*g", prec, value);
 						if (r_use_exp_float) {
 							*r_use_exp_float = true;
 						}
 					}
 					else {
-						prec -= l10 + (int)(l10 < 0);
+						prec -= int_digits_num;
 						CLAMP(prec, 0, UI_PRECISION_FLOAT_MAX);
 						BLI_snprintf(str, maxlen, "%.*f", prec, value);
 					}
 				}
 				else {
+#if 0				/* TODO, but will likely break some stuff, so better after 2.79 release. */
+					prec -= int_digits_num;
+					CLAMP(prec, 0, UI_PRECISION_FLOAT_MAX);
+#endif
 					BLI_snprintf(str, maxlen, "%.*f", prec, value);
 				}
 			}