I am creating a mapping application in d3 and want to tie some text to the top right corner of my view port. Additionally, I want the text to remain in the top right corner while I zoom and pan across the application.I think I can solve my problem by figuring out how to get the coordinates of the top right corner of my view. Knowing this information would allow me to then set the coordinates of my text element. I've tried manually setting the dimensions of the containing svg element and then moving the text to that location but interestingly this didn't work. I was hoping to be able to find the coordinates programatically rather than setting coordinates manually. How can I do this in d3/javascript?
EDIT: My code is a modification of this code by Andy Barefoot: https://codepen.io/nb123456/pen/zLdqvM
My own zooming and panning code has essentially remained the same as the above example:
function zoomed() {
t = d3
.event
.transform
;
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")")
;
}
I'm trying to append the text at the very bottom of the code:
countriesGroup.append("text")
.attr("transform", "translate(" How do I get top right coordinates? ")")
.style("fill", "#ff0000")
.attr("font-size", "50px")
.text("This is a test");
My idea is to be able to get the top right coordinates of the view port through the code rather than setting it manually and then have the coordinates of the text update as the user zooms or pans.
To keep something in place while zooming and panning you could invert the zoom:
point == invertZoom(applyZoom(point))
This isn't particularly efficient, as we are using two operations to get to the original number. The zoom is applied here:
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")");
While the inversion would need to look something like:
text.attr("x", d3.zoom.transform.invert(point)[0])
.attr("y", d3.zoom.transform.invert(point)[1])
.attr("font-size", baseFontSize / d3.zoom.transform.k);
Where point and base font size are the original anchor point and font size. This means storing that data somewhere. In the example below I assign it as a datum to the text element:
var width = 500;
var height = 200;
var data = d3.range(100).map(function() {
return {x:Math.random()*width,y:Math.random()*height}
})
var zoom = d3.zoom()
.on("zoom",zoomed);
var svg = d3.select("body")
.append("svg")
.attr("width",width)
.attr("height",height)
.call(zoom);
var g = svg.append("g")
var circles = g.selectAll()
.data(data)
.enter()
.append("circle")
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; })
.attr("r", 5)
.attr("fill","steelblue")
var text = g.append("text")
.datum({x: width-10, y: 20, fontSize: 12})
.attr("x", function(d) { return d.x; })
.attr("y", function(d) { return d.y; })
.style("text-anchor","end")
.attr("font-size",function(d) { return d.fontSize; })
.text("This is a test");
function zoomed() {
g.attr("transform", d3.event.transform);
var d = text.datum();
var p = d3.event.transform.invert([d.x,d.y]);
var x1 = p[0];
var y1 = p[1];
text.attr("x",x1)
.attr("y",y1)
.attr("font-size", d.fontSize / d3.event.transform.k)
}<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>Better Solution
The above is the solution to the approach you seem to be looking for. But the end result is best achieved by a different method. As I mention in my comment, the above approach goes through extra steps that can be avoided. There can also be some size/clarity changes in the text when zooming (quickly) using the above method
As noted above, you are applying the zoom here:
countriesGroup
.attr("transform","translate(" + [t.x, t.y] + ")scale(" + t.k + ")")
The zoom transform is applied only to countriesGroup, if your label happens to be in a different g (and not a child of countriesGroup), it won't be scaled or panned.
We wouldn't need to apply and invert the zoom, and we wouldn't need to update the position or font size of the text at all.
var width = 500;
var height = 200;
var data = d3.range(100).map(function() {
return {x:Math.random()*width,y:Math.random()*height}
})
var zoom = d3.zoom()
.on("zoom",zoomed);
var svg = d3.select("body")
.append("svg")
.attr("width",width)
.attr("height",height)
.call(zoom);
var g = svg.append("g");
var g2 = svg.append("g"); // order does matter in layering
var circles = g.selectAll()
.data(data)
.enter()
.append("circle")
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; })
.attr("r", 5)
.attr("fill","steelblue")
// position once and leave it alone:
var text = g2.append("text")
.attr("x", width - 10)
.attr("y", 20 )
.style("text-anchor","end")
.attr("font-size", 12)
.text("This is a test");
function zoomed() {
// apply the zoom to the g that has zoomable content:
g.attr("transform", d3.event.transform);
}<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>Collected from the Internet
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