Add polyline edge layout for the tree series #7090

[deqingli]

• add edgeLayout in the TreeSeries.js.
• draw the polyline edge in the TreeView.js.

Fix #7090.

[pissang]

I think edgeShape is better. edgeLayout is more like the position of edge

[deqingli]

yeah, good suggestion!

[pissang]

Top and bottom horizontal lines are better to be connected with the vertical line.

ctx.moveTo(); // top line end point
ctx.lineTo(); // top line connect point
ctx.lineTo(); // bottom line connect point
ctx.lineTo(); // bottom line end point

It will have a nicer corner than current if the line is thicker.

[100pah]

Wrong indent

[100pah]

The indent is not good. The back brace should better align with the start of the sentence function,
and the rest of the code in the function should reduce 4 space.

[100pah]

The name location is not good.

[100pah]

I think ptMin ptMax and the switch case of 'TB' 'BT' 'LR' 'RL' and computeMidPoints are not needed.
The code can be simplified if you wish. And some critical case need to be considered. For example:

buildPath: function (ctx, shape) {
    var childPoints = shape.childPoints;
    var parentPoint = shape.parentPoint;
    var childLen = childPoints.length;
    var firstChildPos = childPoints[1];
    var lastChildPos = childPoints[childLen - 1];

    if (!childLen || !parentPoint) {
        return;
    }

    if (childLen === 1) {
        ctx.moveTo(firstChildPos[0], firstChildPos[1]);
        ctx.lineTo(parentPoint[0], parentPoint[1]);
        return;
    }

    var forkDim = (orient === 'TB' || orient === 'BT') ? 1 : 0;
    var otherDim = 1 - forkDim;
    var forkPosition = parsePercent(shape.forkPosition, 1);
    var tmpPt = [];

    ctx.moveTo(parentPoint[0], parentPoint[1]);
    tmpPt[forkDim] = parentPoint[forkDim] + (firstChildPos[forkDim] - parentPoint[forkDim]) * forkPosition;
    tmpPt[otherDim] = parentPoint[otherDim];
    ctx.lineTo(tmpPt[0], tmpPt[1]);

    ctx.moveTo(firstChildPos[0], firstChildPos[1]);
    tmpPt[otherDim] = firstChildPos[otherDim];
    ctx.lineTo(tmpPt[0], tmpPt[1]);
    tmpPt[otherDim] = lastChildPos[otherDim];
    ctx.lineTo(tmpPt[0], tmpPt[1]);
    ctx.lineTo(lastChildPos[0], lastChildPos[1]);

    for (var i = 1; i < childLen - 1; i++) {
        var childPos = childPoints[i];
        ctx.moveTo(childPos[0], childPos[1]);
        tmpPt[otherDim] = childPos[otherDim];
        ctx.lineTo(tmpPt[0], tmpPt[1]);
    }
}