Fix bad loss of precision when manually editing values in numbuttons.

While drawing nice 'rounded' values is OK also for 'low precision'
editing like dragging and such, it's quite an issue when you type in a
precise value, validate, edit again the value, and find a rounded
version of it instead of what you typed in!

So now, *only when entering textedit of num buttons*, we always get the highest
reasonable precision for floats (and use exponential notation when
values are too low or too high, to avoid tremendous amounts of zero's).

1 files changed, 24 insertions, 4 deletions

diff --git a/source/blender/editors/interface/interface.c b/source/blender/editors/interface/interface.c
index bcb1e3e648a..2bf10c1c932 100644
--- a/source/blender/editors/interface/interface.c
+++ b/source/blender/editors/interface/interface.c
@@ -2146,9 +2146,14 @@ static float ui_get_but_step_unit(uiBut *but, float step_default)
 
 /**
  * \param float_precision  For number buttons the precision to use or -1 to fallback to the button default.
+ * \param use_exp_float  Use exponent representation of floats when out of reasonable range (outside of 1e3/1e-3).
  */
-void ui_but_string_get_ex(uiBut *but, char *str, const size_t maxlen, const int float_precision)
+void ui_but_string_get_ex(uiBut *but, char *str, const size_t maxlen, const int float_precision, const bool use_exp_float, bool *r_use_exp_float)
 {
+	if (r_use_exp_float) {
+		*r_use_exp_float = false;
+	}
+
 	if (but->rnaprop && ELEM(but->type, UI_BTYPE_TEXT, UI_BTYPE_SEARCH_MENU)) {
 		PropertyType type;
 		const char *buf = NULL;
@@ -2217,16 +2222,31 @@ void ui_but_string_get_ex(uiBut *but, char *str, const size_t maxlen, const int
 			}
 			else {
 				const int prec = (float_precision == -1) ? ui_but_calc_float_precision(but, value) : float_precision;
-				BLI_snprintf(str, maxlen, "%.*f", prec, value);
+				if (use_exp_float) {
+					const int l10 = (int)log10(fabs(value));
+					if (l10 < -6 || l10 > 12) {
+						BLI_snprintf(str, maxlen, "%.*g", prec, value);
+						if (r_use_exp_float) {
+							*r_use_exp_float = true;
+						}
+					}
+					else {
+						BLI_snprintf(str, maxlen, "%.*f", prec - l10 + (int)(l10 < 0), value);
+					}
+				}
+				else {
+					BLI_snprintf(str, maxlen, "%.*f", prec, value);
+				}
 			}
 		}
-		else
+		else {
 			BLI_snprintf(str, maxlen, "%d", (int)value);
+		}
 	}
 }
 void ui_but_string_get(uiBut *but, char *str, const size_t maxlen)
 {
-	ui_but_string_get_ex(but, str, maxlen, -1);
+	ui_but_string_get_ex(but, str, maxlen, -1, false, NULL);
 }
 
 /**