Comments (2)
d3.drag uses the coordinate system of whatever element you apply it to.
For SVG elements, the coordinate system is obtained using element.getScreenCTM; for other elements, the coordinate system is defined by event.clientX and event.clientY, offset by the subject element’s bounds. See d3-selection’s point.js for the implementation.
Unless you’ve applied an SVG transform, the default coordinate system has [0, 0] in the top-left corner, with +x going right and +y going down. So, one option would be to change the coordinate system of your SVG using the transform attribute.
But, really the problem here is that you are relying on the default drag.subject:
function subject(d) {
return d == null ? {x: d3.event.x, y: d3.event.y} : d;
}
Thus, d3.drag is using your bound datum as the drag subject, and using d.x and d.y as the starting position of the thing being dragged. Except d3.drag operates in SVG coordinates, and your data is in a different coordinate system. So, the right thing to do is to implement drag.subject and tell the drag behavior the actual starting position of your circle in SVG coordinates:
d3.drag()
.subject(function(d) { return {x: fromCartesianX(d.x), y: fromCartesianY(d.y)}; })
.on("drag", dragged)
Then on drag, you set the new position of the circle in SVG coordinates (event.x and event.y), and update the data in data coordinates:
function dragged(d) {
d.x = toCartesianX(d3.event.x);
d.y = toCartesianY(d3.event.y);
d3.select(this).attr("cx", d3.event.x).attr("cy", d3.event.y);
}
Live example:
https://bl.ocks.org/mbostock/519d494035dd642e19eee4e242570114
from d3-drag.
Looking into the code, I noticed the event object also exposes dx and dy. So I modified my example to do d.x += d3.event.dx
and dy += d3.event.dy
.
from d3-drag.
Related Issues (20)
- Possible typo in README HOT 2
- What are the perposes of functions yesdrag and nodrag?
- Drag event on Chrome 72 HOT 3
- d3 mouseup event not firing HOT 1
- Drag Event Issue on Windows Chrome 74, related to solution for #47 HOT 1
- The default filter should return false if event.ctrlKey. HOT 5
- drag start event is don't send when Ctrl-key is press HOT 1
- drag.on("init") ? HOT 7
- Click event not firing if drag enables with simulation HOT 1
- Non-cancelable event HOT 3
- remove drag.container? HOT 1
- Use native events (*element*.dispatchEvent) instead of d3-dispatch? HOT 1
- remove dragEvent.on?
- d3.event is not available in version 6.1.1 HOT 1
- DragEvent missing event.currentTarget for arrow function node selection HOT 1
- Make event listeners non-passive. HOT 2
- d3.drag() causes error in testing mousedown event via jsdom HOT 4
- d3.pointer() could use event.touches[0] HOT 2
- Add event.currentTarget
- Support d3.drag in testing environments
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from d3-drag.