2. the idea is to linked the columns of two tables. Using RTArrowedLine, it is not beautiful (see DB_Schema_with-arrows) since the attach points are only on South and North Border of the shape whereas we would like to have them also on left and right.3. Usually, in DB schema, the links between tables are orthogonal multi lines. But in Roassal, the attach point are once again only on top or in bottom of the shape (see DB_Schema_with_Multines).
Mondrian (and I think shapes also) by default use RTVerticalAttachPoint (so only top and bottom), however we have more. Look at RTAttachPoint subclasses. Most relevant to you are probably RTShorterDistance(WithOffset)AttachPoint which uses all four sides (right, bottom, left, top), and RTRectangleAttachPoint which will slide along the sides (so the distance is the shortest).
How are you creating the visualization? I'm interested in edge creation and layouting — because the attach point has to be specified there.
4. Normally in database representations, the multi lines have arrows but since, in Roassal, the direction of the arrow is computed from the start and end points of the line, it looks ugly in case of multi line edge (see multiline arrows).
This shouldn't be hard to fix for the Roassal's multiline, I'll look into it.
5. When a column in a table references another column of the same table, the edge is in the middle of the table but we would like to have a recursive dependency represented as a loop. Is it possible to do that with Roassal (recursive_dependency figure)?
Something like this:
or this?
That's not currently not easily possible. You could specify by hand the control points of a multiline to get something like the bottom one, but there is nothing available in Roassal to do it for you.
Is there someone working on a real graph representation such as in graphviz where lines do not cross or at minima and so the entities are grouped?
I am... but I need to move from research to actually writing the code (right now I am writing edge labels layouting, classes/elements layouting will come next).
But since you would benefit from something, I'll try to have a prototype soon.
Can we easily add attached point? or define by default at least 4 attach points to box or ellipse?
See my answer earlier. Creating attach points is rather easy.
Is it possible to get multi lines with arrows but where the head of the arrow is computed with the perpendicular of the last segment of the multi line edges?
See my answer earlier, I'll look into this.
Two more question that are not visible in these figures:6. It seems that currently, it is not possible to play with the label font (size, italic, bold…).
You specify font size with "RTLabel>>#height:"
As for italic/bold/... I've recently added "RTStyledLabel". Look at it's class comment or RTGeneralExample>>styledLabel
But I think it needs to be also introduced to Mondrian... Alex?
7. Is it possible to put a label near an extremity of an edge (such as a role in UML class diagram)? And is it possible to put a label also in the middle of an edge to indicate the name of an association?
Yes, but only for straight lines.
[[[
TRConstraint
stick: label
between: edge from trachelShape
and: edge to trachelShape
offset: offsetOnEdge. "Float between 0 and 1. 1 is the start, 0 the end, 0.5 the middle, etc."
]]]
As for multilines, Roassal itself doesn't support it.
Finally, I have my own multiline that would solve some of your problems, but in the current state it would not play nicely with Mondrian, so I will have to think about how can I move it to Roassal...
Peter