To piggyback on RhinoBull's comments. Tabs are not necessarily the same from control to control or on the printer. A tab in a listbox may not be the same tab in a textbox and may not be same as a tab in a picturebox, etc, etc. Tabs are almost always related to font type/size; though some may be hard-set pixel offsets.

In addition, many controls allow users to explicitly set tabs to custom offsets so a tab in the same types of controls may not match. I wouldn't make the blanket assumption that a tab is always a fixed amount of "spaces" every time a tab character is encountered; tabs can be fixed or dynamically spaced