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graphstream / gs-ui-swing

GraphStream Swing user interface
http://graphstream-project.org/
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Allow more control over cubic-curve styled edges #22

Open barrybecker4 opened 4 months ago

barrybecker4 commented 4 months ago

Currently, when the edges of a graph are styled with shape: cubic-curve; they are curved in a seemingly arbitrary way and it rarely looks how I want. For example, here is a graph where the edges are styled with cubic-curve: image Note that there are discontinuities at the nodes because the Bezier control vectors are either horizontal or vertical and determined by the angle between the source and destination vertices.

What I propose is a simple backward compatible change that would allow optionally specifying a control point for an edge that would determine the quadratic Bezier to use for its curvature like this: image

If an edge has the "ui.control-point" attribute set, then the edge renderer will draw a quadratic Bezier curve using that control point. The implementation is simple, and will give a lot of extra control. I will make a PR.

After adding the control point, I can get the curved edges to look they way that I want. image

barrybecker4 commented 4 months ago

PR - https://github.com/graphstream/gs-ui-swing/pull/23

barrybecker4 commented 4 months ago

I found a workaround for doing what I want without needing to make any code change. I can use the existing "ui.points" attribute on a node in conjunction with the "cubic-curve" style. For my case, I just want to have the middle 2 (of the 4) points be the same value (my control point). It seems a little bit redundant to have to specify the first and last points in the list of 4 points because, as far as I know, they will always be the position of the source and target nodes of the edges, respectively.

My helper code to do what I want is 

    private void setEdgePoint(Edge edge, double x, double y) {
        Object[] src = edge.getSourceNode().getAttribute("xyz", Object[].class);
        Object[] dst = edge.getTargetNode().getAttribute("xyz", Object[].class);
        edge.setAttribute("ui.points",
                src[0], src[1], 0.0,
                x, y, 0,
                x, y, 0,
                dst[0], dst[1], 0
        );
    }