Use the default digit values to calculate the width for float widget

Closes #14153

sao/src/view/form.js

@@ -2205,14 +2205,14 @@ function eval_pyson(value){
             }
         },
         get width() {
-            var digits = this.digits;
-            if (digits && digits.every(d => d !== null)) {
-                return digits.reduce(function(acc, cur) {
-                    return acc + cur;
-                });
-            } else {
-                return this.attributes.width || 18;
-            }
+            let default_ = [16, 2];
+            let digits = this.digits || [null, null];
+            return digits.reduce((acc, cur, i) => {
+                if (cur === null) {
+                    cur = default_[i];
+                }
+                return acc + cur;
+            }, 0);
         },
         display: function() {
             var record = this.record;

tryton/tryton/gui/window/view_form/view/form_gtk/float.py

@@ -13,11 +13,8 @@ class Float(Integer):
 
     @property
     def width(self):
-        digits = self.digits
-        if digits and all(d is not None for d in digits):
-            return sum(digits)
-        else:
-            return self.attrs.get('width', 18)
+        digits = self.digits or [None, None]
+        return sum(v if v is not None else d for v, d in zip(digits, [16, 2]))
 
     def display(self):
         self.entry.digits = self.digits