Do not make space for invisible items in menus
- In Menu.qml: Do not consider invisible menu items when evaluating whether to make space for icons or checkboxes.
- In MenuSeparator.qml: Only add space for menu separators if they are visible, otherwise set the height to 0.
| Before | After |
|---|---|
 |
 |
| The list view makes space for a separator and checkbox that are hidden | The list view only makes space for what's visible |
| This is a followup to !135 (merged) |