图形编辑器（Java）关于如何在顶点之间绘制边的技巧

Question

For a school assignment we have to make a graph editor like the next one (given example):

Most of the assignment goes well, we're stuck on one point: drawing the edges between vertices. In the given example, the lines are nicely drawn from points relatively close to the connecting vertex. For example the top one has two lines on its bottom edge, one more to the left and one more to the right.

We are not sure on how to let the drawing of the lines keep the positions of the connecting vertex in account and how to adjust the positions of the beginning and end points on that (what calculations to make). Can someone help out?

Answer 1

In fact, that's rather simple: Draw the lines first , from the position of each vertex to the position of the respective other vertex (the "position" here refers to the center of the rectangle). Afterwards, draw the rectangles for the vertices. They will be painted over the edges, and the result will look exactly like the screenshot.

Answer 2

If you extend the connector lines, you can see they are drawn from the geometric center of the graph node rectangles:

Since you already seem to have a good positioning algorithm for your nodes, all you need to do is draw the connector lines first. Then draw the node rectangles on top of them.