GtkMathView is a GTK widget for rendering MathML documents. It is meant to be a standalone, light-weight component and not a full browser. GTK applications can use the widget as a window for displaying mathematical formulas and doing simple interactions. Among other features, GtkMathView includes support for breaking long mathematical expressions, rendering of stretchy operators, and provides a customizable support for additional fonts.
GtkGLMaterialDialogis a GTK+ dialog that can be used to edit 3D-object material properties. It is based on the material properties of OpenGL with diffuse, ambient, specular, emissive colors (RGBA), and a specular coefficient (shininess). The material is previewed by rendering a lit OpenGL sphere in a gtkglarea widget.
GTKExtra is a useful set of widgets for creating GUIs for the X Window System using GTK+. It is written in C and includes the following widgets: GtkSheet, GtkPlot, GtkPlotCanvas, GtkItemEntry, GtkComboBox, GtkColorCombo, GtkBorderCombo, GtkFontCombo, GtkDirTree, GtkIconList, GtkFileList, GtkIconFileSelection, and GtkCheckItem.