This library provides the wxAccordion class, which as the name suggests, is an accordion style container control for the wxWidgets library. This is a very simple implementation: the expanding and collapsing mechanism uses nothing but sizers and panels. The control is derived from wxBookCtrlBase so that a programmer familiar 59FC wxNotebook or wxAuiNotebook should already be comfortable this class as well. The documentation for this class can be viewed here.
Although this class can't provide all the freedom a programmer would have for building an accordion with HTML/CSS, there is a wide variety of commands for modifying the behavior, layout, and appearance of the control. For example, the caption bars can be drawn with a gradient of 2 or more colors or can use an image file for the background. The caption bars can optionally contain expand/collapse buttons and icons. Here are a few examples of accordions that can be produced with this library: