Drag and Drop Commands
API Drag and Drop Commands
For background information about the commands described on this page,
refer to the
information about the drag and drop mode
in the corresponding section of the API reference.
On this page, API commands of the drag and drop category are described.
This category covers all commands to implement user interaction with
drag and drop available for an application.
The commands of this category are enclosed by keyword "drag_and_drop(...)".
Click here to get an
overview of all API commands.
drag_and_drop(dragging_on)
To enable the
drag and drop mode
for accessing functions of the application by using direct manipulation
interactions in a uDraw(Graph) graph visualization.
Afterwards the
2-D scrolling
that can usually be accessed with the middle mouse button is no
longer available.
After sending this command, the application has to be prepared for
the following API answers used to inform about drag and drop operations:
drag_and_drop(dragging_off)
To disable the
drag and drop mode,
so
2-D scrolling
is available again.
drag_and_drop(new_node_at_coord(node_update))
This command is the recommended action after receiving the API answer
create_node(...),
see
information about the drag and drop mode.
When the API has sent this answer, the coordinates where the mouse
button was released are stored internally and used as the preferred
position of the next node that will be inserted with this command.
Therefore only a single node can be used in the parameter.
uDraw(Graph) tries to insert the new node at the stored coordinate, but
this may not be (completely) possible due to layout restrictions, see
graph layout concepts.
Without a previous
create_node(...),
create_node_and_edge(...)
or
drop_node(...)
answer, no coordinate is available and the command behaves like an
usual graph update with command
graph(update(...)).
This command is the recommended action after receiving the API answer
create_node_and_edge(...),
see
information about the drag and drop mode.
All information about parameter "node_update" in command
drag_and_drop(new_node_at_coord(...))
is applicable here, too.
The additional "edge_update" has to be used to insert a new edge
where the parent is the start node of the drag and drop operation
(reported to the application by answer
create_node_and_edge(...))
and the child is the new node created here in parameter "node_update".
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