patch [#23758] Better handling of UTF chars in UNITS fields (lengths, angles, etc.)

from Lorenzo Tozzi (oni_niubbo) with minor edits.

--- from the tracker
The present situation is this: due to bug#22274, during editing, UTF chars are stripped from buttons with a unit associated
(length, angles, etc.).
Example: if the button displays '90°' and you click on it with LMB, the editing string will become '90'.

The problem arises if you use microns: '34µm' becomes '34' that blender interprets as 34 meters. So clicking on a button
and hitting enter won't confirm the previous value, but will change it (very badly also).

Of course nobody is using microns in blender, but the problem will arise when we will implement areas and option 'Separate
Units' will be enabled. The value '2m² 3cm²' will become '2m' during editing.

This patch solves the problem rewriting the string in a smarter way than just stripping the UTF chars: the unit is translated
from unit->name_short ('µm') to unit->name_alt ('um'). So clicking on '34µm' the editing string will become
'34um'.
--- end

note: rather then allowing empty strings in name_alt field I made it so if the unit system was the default one a NULL name_alt will just strip the string, since its the default its not needed.

source/blender/blenkernel/BKE_unit.h

@@ -36,6 +36,9 @@ void	bUnit_AsString(char *str, int len_max, double value, int prec, int system,
 /* replace units with values, used before python button evaluation */
 int		bUnit_ReplaceString(char *str, int len_max, char *str_prev, double scale_pref, int system, int type);
 
+/* make string keyboard-friendly: 10µm --> 10um */
+void bUnit_ToUnitAltName(char *str, int len_max, char *orig_str, int system, int type);
+
 /* the size of the unit used for this value (used for calculating the ckickstep) */
 double bUnit_ClosestScalar(double value, int system, int type);
 

source/blender/blenkernel/intern/unit.c

@@ -44,7 +44,8 @@ typedef struct bUnitDef {
 	char *name;
 	char *name_plural;	/* abused a bit for the display name */
 	char *name_short;	/* this is used for display*/
-	char *name_alt;		/* can be NULL */
+	char *name_alt;		/* keyboard-friendly ASCII-only version of name_short, can be NULL */
+						/* if name_short has non-ASCII chars, name_alt should be present */
 	
 	char *name_display;		/* can be NULL */
 
@@ -76,7 +77,7 @@ static struct bUnitCollection buDummyCollecton = {buDummyDef, 0, 0, sizeof(buDum
 static struct bUnitDef buMetricLenDef[] = {
 	{"kilometer", "kilometers",		"km", NULL,	"Kilometers", 1000.0, 0.0,		B_UNIT_DEF_NONE},
 	{"hectometer", "hectometers",	"hm", NULL,	"100 Meters", 100.0, 0.0,			B_UNIT_DEF_SUPPRESS},
-	{"dekameter", "dekameters",		"dkm",NULL,	"10 Meters", 10.0, 0.0,			B_UNIT_DEF_SUPPRESS},
+	{"dekameter", "dekameters",		"dam",NULL,	"10 Meters", 10.0, 0.0,			B_UNIT_DEF_SUPPRESS},
 	{"meter", "meters",				"m",  NULL,	"Meters", 1.0, 0.0, 			B_UNIT_DEF_NONE}, /* base unit */
 	{"decimetre", "decimetres",		"dm", NULL,	"10 Centimeters", 0.1, 0.0,			B_UNIT_DEF_SUPPRESS},
 	{"centimeter", "centimeters",	"cm", NULL,	"Centimeters", 0.01, 0.0,			B_UNIT_DEF_NONE},
@@ -543,6 +544,49 @@ int bUnit_ReplaceString(char *str, int len_max, char *str_prev, double scale_pre
 	return change;
 }
 
+/* 45µm --> 45um */
+void bUnit_ToUnitAltName(char *str, int len_max, char *orig_str, int system, int type)
+{
+	bUnitCollection *usys = unit_get_system(system, type);
+
+	bUnitDef *unit;
+	bUnitDef *unit_def= unit_default(usys);
+
+	/* find and substitute all units */
+	for(unit= usys->units; unit->name; unit++) {
+		if(len_max > 0 && (unit->name_alt || unit == unit_def))
+		{
+			char *found= NULL;
+
+			found= unit_find_str(orig_str, unit->name_short);
+			if(found) {
+				int offset= found - orig_str;
+				int len_name= 0;
+
+				/* copy everything before the unit */
+				offset= (offset<len_max? offset: len_max);
+				strncpy(str, orig_str, offset);
+
+				str+= offset;
+				orig_str+= offset + strlen(unit->name_short);
+				len_max-= offset;
+
+				/* print the alt_name */
+				if(unit->name_alt)
+					len_name= snprintf(str, len_max, "%s", unit->name_alt);
+				else
+					len_name= 0;
+
+				len_name= (len_name<len_max? len_name: len_max);
+				str+= len_name;
+				len_max-= len_name;
+			}
+		}
+	}
+
+	/* finally copy the rest of the string */
+	strncpy(str, orig_str, len_max);
+}
 
 double bUnit_ClosestScalar(double value, int system, int type)
 {

source/blender/editors/interface/interface.c

@@ -1443,6 +1443,23 @@ static double ui_get_but_scale_unit(uiBut *but, double value)
 	}
 }
 
+/* str will be overwritten */
+void ui_convert_to_unit_alt_name(uiBut *but, char *str, int maxlen)
+{
+	if(ui_is_but_unit(but)) {
+		int unit_type= RNA_SUBTYPE_UNIT_VALUE(RNA_property_subtype(but->rnaprop));
+		char *orig_str;
+		Scene *scene= CTX_data_scene((bContext *)but->block->evil_C);
+		
+		orig_str= MEM_callocN(sizeof(char)*maxlen + 1, "textedit sub str");
+		memcpy(orig_str, str, maxlen);
+		
+		bUnit_ToUnitAltName(str, maxlen, orig_str, scene->unit.system, unit_type);
+		
+		MEM_freeN(orig_str);
+	}
+}
+
 static void ui_get_but_string_unit(uiBut *but, char *str, int len_max, double value, int pad)
 {
 	Scene *scene= CTX_data_scene((bContext *)but->block->evil_C);

source/blender/editors/interface/interface_handlers.c

@@ -1555,7 +1555,8 @@ static void ui_textedit_begin(bContext *C, uiBut *but, uiHandleButtonData *data)
 		int i;
 		for(i=0; data->str[i]; i++) {
 			if(!isascii(data->str[i])) {
-				data->str[i]= '\0';
+				/* no stripping actually: just convert to alt name */
+				ui_convert_to_unit_alt_name(but, data->str, data->maxlen);
 				break;
 			}
 		}

source/blender/editors/interface/interface_intern.h

@@ -356,6 +356,7 @@ extern void ui_set_but_vectorf(uiBut *but, float *vec);
 extern void ui_hsvcircle_vals_from_pos(float *valrad, float *valdist, rcti *rect, float mx, float my);
 
 extern void ui_get_but_string(uiBut *but, char *str, int maxlen);
+extern void ui_convert_to_unit_alt_name(uiBut *but, char *str, int maxlen);
 extern int ui_set_but_string(struct bContext *C, uiBut *but, const char *str);
 extern int ui_get_but_string_max_length(uiBut *but);