A SplitPane is used to divide two Widgets. These widgets can be resized by clicking the splitter widget and moving the slider. The orientation property states if the widgets should be aligned horizontally or vertically.
The most important class (and the class you will use mainly) inside the qx.ui.splitpane package is the Pane. One can add two widgets (of any type) to it. Besides these two widgets a Pane also contains a Splitter between them. By clicking on it (and holding down the mouse button), a Slider will appear and follow the mouse to indicate where the Splitter``s will be placed when the mouse button is released. Once the mouse button is released the available space inside the ``Pane is redivided to both widgets according to the Splitter's new position.
Here are some links that demonstrate the usage of the widget: