Factor out function to get value with broadest digits

src/gfx.cpp

@@ -1528,6 +1528,24 @@ byte GetDigitWidth(FontSize size)
 	return width;
 }
 
+/**
+ * Return some number that is suitable for string size computations.
+ * @param count Number of digits which shall be displayable.
+ * @param size  Font of the number
+ * @return The number.
+ */
+uint64 GetBroadestDigitsValue(uint count, FontSize size)
+{
+	uint front = 0;
+	uint next = 0;
+	GetBroadestDigit(&front, &next, size);
+	uint64 val = count > 1 ? front : next;
+	for (; count > 1; count--) {
+		val = 10 * val + next;
+	}
+	return val;
+}
+
 /**
  * Determine the broadest digits for guessing the maximum width of a n-digit number.
  * @param[out] front Broadest digit, which is not 0. (Use this digit as first digit for numbers with more than one digit.)

src/gfx_func.h

@@ -220,6 +220,7 @@ bool ToggleFullScreen(bool fs);
 byte GetCharacterWidth(FontSize size, WChar key);
 byte GetDigitWidth(FontSize size = FS_NORMAL);
 void GetBroadestDigit(uint *front, uint *next, FontSize size = FS_NORMAL);
+uint64 GetBroadestDigitsValue(uint count, FontSize size = FS_NORMAL);
 
 extern int font_height_cache[FS_END];
 

src/strings.cpp

@@ -116,14 +116,7 @@ void SetDParamMaxValue(uint n, uint64 max_value, uint min_count, FontSize size)
  */
 void SetDParamMaxDigits(uint n, uint count, FontSize size)
 {
-	uint front = 0;
-	uint next = 0;
-	GetBroadestDigit(&front, &next, size);
-	uint64 val = count > 1 ? front : next;
-	for (; count > 1; count--) {
-		val = 10 * val + next;
-	}
-	SetDParam(n, val);
+	SetDParam(n, GetBroadestDigitsValue(count, size));
 }
 
 /**