GUI

TRootCanvas/TCanvas

Implement tooltip displaying information about the primitive below the mouse pointer in a canvas.
It is possible to enable/disable this optional feature with the "Tooltip Info" menu entry from the "View" menu of the canvas.
To change the default behaviour (off by default), a new option has been added in system.rootrc:
Canvas.ShowToolTips: false

TBrowser

Automatically switch to the tab containing the current canvas (if any) when e.g. drawing a histogram by double-clicking on its list tree item in a root file.
Automatically switch to (and update) the list of files in the file browser (left panel) when opening a ROOT file from the "Open File" menu

TGListView

Keyboard navigation is now fully working in the list view.

TGMainFrame

Allow to save a snapshot of the GUI in a picture file. The supported formats are gif, jpg, png, tiff, and xpm.

TGFileDialog

Allow to change directory by typing its name in the text entry field of the dialog

TProofProgressDialog

Added a speedometer widget (TGSpeedo) to display the processing rate
Added a check button to enable/disable smooth update of the speedometer (enabled by default). This could be useful in the case of slow displays (e.g. when using it via ssh)
Several layout improvements

TRecorder

Improvements and consolidation of the cross-platform interoperability, allowing to record and replay sessions between different platforms with less side effects. NB: Using different OS/WM (Window Managers) and using different ROOT GUI settings (via e.g. system.rootrc) between recording and replaying may still produce a wrong behavior of the recorder.
New tutorial guitest_playback.C replaying a recorded session showing and validating the GUI (using guitest.C)

GUI Builder

New features, new user interface

Several important features have been added to the builder, and its user interface has been redesigned. Editing modes are now clearly distinguished with enabled and disabled layout mode. Possibility to enable automatic layout fasten the interface development, as the positioning doesn't have to be done manually anymore
Major changes in the user interface:

Added a list tree displaying the complete structure of the GUI
The name of every element of the GUI is now editable
New, more intuitive interface for padding and layout hints
Color settings option was added to the widget editor
Extended commands in the top menu (open project, save project...)
Added important warning dialogs, such as "Save project" dialog when closing the window
Added several tool tips