Fix wibox.layout.flex:fit() (FS#1126)

The flex:fit() function was calling the fit() function of the widgets it
contained with too large values, trying to hand out more space than it had
available. This resulted in more space being requested than was available and
some weird layout issues resulted.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/wibox/layout/flex.lua.in

@@ -85,8 +85,12 @@ function flex:fit(orig_width, orig_height)
             #self.widgets * self._max_widget_size)
     end
 
+    -- Figure out the maximum size we can give out to sub-widgets
+    local sub_height = self.dir == "x" and orig_height or floor(used_in_dir / #self.widgets)
+    local sub_width  = self.dir == "y" and orig_width  or floor(used_in_dir / #self.widgets)
+
     for k, v in pairs(self.widgets) do
-        local w, h = v:fit(orig_width, orig_height)
+        local w, h = v:fit(sub_width, sub_height)
         local max
         if self.dir == "y" then
             max = w