Draft: fix number_length for imperial dimensions (#25369)

* The number_length function did not take imperial dimensions into account. For `9" + 7/8"` it would return 1.
* In ArchRoof reference number_length function from DraftGui.py to avoid duplicate code.

src/Mod/BIM/ArchRoof.py

@@ -1108,13 +1108,5 @@ if FreeCAD.GuiUp:
 
         def eventFilter(self, widget, event):
             if event.type() == QtCore.QEvent.FocusIn:
-                widget.setSelection(0, self.number_length(widget.text()))
+                widget.setSelection(0, FreeCADGui.draftToolBar.number_length(widget.text()))
             return super().eventFilter(widget, event)
-
-        def number_length(self, str):
-            # Code taken from DraftGui.py.
-            nl = 0
-            for char in str:
-                if char in "0123456789.,-":
-                    nl += 1
-            return nl

src/Mod/Draft/DraftGui.py

@@ -803,11 +803,12 @@ class DraftToolBar:
             self.xValue.setFocus()
             self.xValue.setSelection(0, self.number_length(self.xValue.text()))
 
-    def number_length(self, str):
-        nl = 0
-        for char in str:
-            if char in "0123456789.,-":
-                nl += 1
+    def number_length(self, st):
+        nl = len(st)
+        for char in st[::-1]:
+            if char in "0123456789.,-+/":
+                break
+            nl -= 1
         return nl
 
     def extraLineUi(self):