Turbo Pascal 5.x and onwards were implemented using Turbo Vision, a really good, object-oriented UI framework [1]. Every view could render a sub-rectangle of it

Turbo Pascal 5.x and onwards were implemented using Turbo Vision, a really good, object-oriented UI framework [1]. Every view could render a sub-rectangle of itself on command into a buffer, which is how the UI was able to render drop shadows. The C++ version was open-sourced in 1997 and ported to a bunch of platforms including Linux [2]. [1] http://www.sigala.it/sergio/tvision/html/index.html http://www.sigala.it/sergio/tvision/html/index.html [2] http://tvision.sourceforge.net/ http://tvision.sourceforge.net/