To Do

A MacOS X native driver using Carbon.
A wxWidgets driver? A Qt driver?
A tutorial section in the documentation. Add more complete samples.
To show a border for visual location of VBOX, HBOX and FILL. Can be a dialog attribute. Or most likely a function to display the layout.
Drag&Drop between controls or dialogs in the same application.
Buttons with image and text simultaneously.
IupLua executables in SunOS using the Sun WorkShop 6 C++ and in AIX using the C++ for AIX compilers do not include the IMLua binaries.
BUG: In Windows when using a callback to show a dialog during a key press in Multiline, if the key contains a character even with a Ctrl modifier, the key is inserted in the Multiline after the dialog is hidden.

Support for MDI.
Callback SHOW_CB is not called when the dialog is hidden because of PARENTDIALOG.
Sometimes the control initialization is incomplete and its size is miscalculated. To solve this call IupRefresh(dialog). This will fix the sizes.

Move iupMask to the mail library using attributes instead of functions.
A vertical IupGauge?
IupSbox can be resized above the maximum size so some controls go to outside the dialog area at right or bottom. In fact thi is part of the dynamic layout default reposition of controls inside the dialog. See the IupRefresh function. The IUP layout does not have a maximum limit only a minimum.

Fix column resize when line is moved outside the matrix canvas.
When removing a line, if it has the focus an invalid call to enteritem_cb/leave_item_cb will occur for the removed cell.
Lines and columns are not unmarked when clicking on the title.
Should allows to start the selection on cell 0:0.

Define minimum size based on tree nodes. New callback mode. Change internal list to real tree?
Images with variable sizes for nodes.