The objective is simplify the semantics of the code so that we don't
need to check for "(iter != NULL && !g_sequence_iter_is_end (iter))"
in the callers.
The newly-added gtk_flow_box_child_is_selected() needed to return a
gboolean, so use g_return_val_if_fail() to return FALSE when an invalid
GtkFlowBoxChild* is passed in.
Make flowbox selection more orthodox. Control and Shift now
modify the selection behaviour pretty much in the same way
they do in a tree view, and clicking without modifiers will
clear the selection.
When dealing with touch devices, we treat modifier-less events
as modifying the selection.
This commit also adds a few other selection necessities, such
as catching Escape key presses to cancel rubberband selection,
and handling grab notify.
GtkFlowBox is a container that its children in a reflowing
grid, which can be oriented horizontally or vertically.
It is similar to GtkListBox in that the children can
be sorted and filtered, and by requiring a dedicated child
widget type, GtkFlowBoxChild. It is similar to GtkTreeView
in that is supports a full set of selection modes, including
rubberband selection.
This is the culmination of work that has happened in the
egg-list-box module, and earlier in libegg. The origins of
this code are the EggSpreadTable in libegg, which was written
by Tristan van Berkom. It was moved to egg-list-box and
renamed EggFlowBox by Jon McCann, and I gave it some finishing
touched in the flowbox-improvements branch of that module.
