I would greatly appreciated if you could share your ideas about writing the program as described in its specification below.
I just like to have some keys word, concepts that point me to the direction. I was puzzling me is how to move the object around.
These are some of my initial ideas:
1) Draw object
2) When mouse click down , notify the location
3) if the location match the location of the drawing object
then, if mouse release, update the new location.
4) Draw the object at the new location and erase the old location.
Thank very much for your attention.
The aim is to build a system which allows the user to draw, and edit a graph
(such as a flowchart). A graph consists of nodes and edges. Each edge joins
Assume that edges are straight lines, and that the same two nodes cannot have
more than one edge joining them. The basic operations are adding and deleting
adding and deleting edges, and moving nodes around.
Extras for nodes. The user should have a choice of shape to represent a node:
e.g. a little circle, little square etc. It should be possible to change the
shapes of existing
nodes. Also each node can have a small text-label displayed underneath. In
addition, it should be possible to attach a longer text comment to a node:
this will be too
small for direct display, but the user should have an option to display this
in a separate window or pop-up box.
Extras for edges. Similar features as for nodes: small label displayed
half-way along the edge, longer text comment displayable on request. Also
there should be a
choice of style for edges: plain line, line with arrow-head at one end, or at
both ends; of course it should be possible to change styles later.
Moving. It should be possible to move a node around: if there are any edges
which have one end at that node, they should "follow" the node as it moves
other ends remain fixed).
Multi-selections and regions. It should be possible to move several nodes at
once. The nodes to be moved can be selected in two ways (aim to provide both
The first way is by multi-selection: select nodes by clicking (perhaps with
the shift-key down, to distinguish this from selecting single nodes); the
selected nodes should be
highlighted somehow; clicking on a selected node (still with shift down)
should unselect it. The second way is by regions: use the mouse to drag out a
nodes within this area are selected. Whichever selection method has been
used, a subsequent move operation will apply to all the selected nodes. Also,
should be applicable to selections: e.g. delete all selected nodes, or change
shape of all selected nodes to small square.
Modes. This applies to the node-shapes and edge-shapes: the current mode
determines the shapes of nodes and edges which get created. There should be a
Shrink/grow. Drag out a rectangular area. Now drag out a second such area.
The first area gets "resized" to fit the second. This means that all nodes in
the first area
get moved: this will, for example, bring them closer together if the second
area is smaller than the first.
Initial, minimal system. The first stage can be produced jointly by the
group. Extensions are to be added to it separately by individual group
members. The first stage
should allow just creating nodes, and creating edges between nodes. The other
features can be worked on separately:
load/save work from/to file
modes for current node/edge shape
small labels for nodes/edges
large text comments for nodes/edges
moving a multi-selection or region
other operations on multi-selection or region