[loaders] improve fixed-width saver saulpw#2255

Don't add so many spaces between columns.
Use the max width of the data, rather than the max width of the window.

visidata/column.py

@@ -473,6 +473,20 @@ def getMaxWidth(self, rows):
         w = min(w, self.sheet.windowWidth)
         return w
 
+    def getMaxDataWidth(self, rows):  #2255  need real max width for fixed width saver
+        '''Return the maximum length of any cell in column or its header,
+        even if wider than window. (Slow for large cells!)'''
+
+        w = 0
+        nlen = dispwidth(self.name)
+        if len(rows) > 0:
+            w_max = 0
+            for r in rows:
+                row_w = dispwidth(self.getDisplayValue(r))
+                if w_max < row_w:
+                    w_max = row_w
+            w = w_max
+        return max(w, nlen)
 
 
 # ---- basic Columns

visidata/loaders/fixed_width.py

@@ -84,7 +84,7 @@ def save_fixed(vd, p, *vsheets):
             widths = {}  # Column -> width:int
             # headers
             for col in Progress(sheet.visibleCols, gerund='sizing'):
-                widths[col] = col.getMaxWidth(sheet.rows)  #1849
+                widths[col] = col.getMaxDataWidth(sheet.rows)  #1849 #2255
                 fp.write(('{0:%s} ' % widths[col]).format(col.name))
             fp.write('\n')