Reputation: 1838
I'm trying to develop a way to select objects that are layered below and (totally) covered by other objects. One idea is to select the top object and then via doubleclick
walk downwards through the layers. This is what I got at the moment:
var canvas = new fabric.Canvas("c");
fabric.util.addListener(canvas.upperCanvasEl, "dblclick", function (e) {
var _canvas = canvas;
var _mouse = _canvas.getPointer(e);
var _active = _canvas.getActiveObject();
if (e.target) {
var _targets = _canvas.getObjects().filter(function (_obj) {
return _obj.containsPoint(_mouse);
});
//console.warn(_targets);
for (var _i=0, _max=_targets.length; _i<_max; _i+=1) {
//check if target is currently active
if (_targets[_i] == _active) {
//then select the one on the layer below
_targets[_i-1] && _canvas.setActiveObject(_targets[_i-1]);
break;
}
}
}
});
canvas
.add(new fabric.Rect({
top: 25,
left: 25,
width: 100,
height: 100,
fill: "red"
}))
.add(new fabric.Rect({
top: 50,
left: 50,
width: 100,
height: 100,
fill: "green"
}))
.add(new fabric.Rect({
top: 75,
left: 75,
width: 100,
height: 100,
fill: "blue"
}))
.renderAll();
canvas {
border: 1px solid;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.6.3/fabric.min.js"></script>
<canvas id="c" width="300" height="200"></canvas>
As you can see, trying to select the red
rectangle from within the blue
one is not working. I'm only able to select the green
or the blue
. I guess that after the first doubleclick
worked (green
is selected), clicking again just selects blue
so the following doubleclick is only able to get green
again.
Is there a way around this? Any other ideas?
Upvotes: 5
Views: 4999
Reputation: 3738
When fdirst creating the object, add an additional property:
perPixelTargetFind: true
Docs: http://fabricjs.com/docs/fabric.Object.html#perPixelTargetFind
When set to true
, objects are "found" on canvas on per-pixel basis rather than according to bounding box
Upvotes: 4
Reputation: 11
My task is a bit different - the mission is to pick the overlapping obj behind the current one:
The idea is, for each click-event, intercept the selected object and replace it with our desired object.
A Fabric mouse-down
event is like this:
target-obj
by the coordinates of mouse cursor and stores it in the instance-variable (canvas._target)mouse:down:before
target-obj
found from step(2) with current selected object, fire selection:cleared/update/create
events according to the results of comparison.mouse:down
We can use a customized event handler on mouse:down:before
to intercept the target-obj
found on Step(2) and replace it by our desired-object
fCanvas = new fabric.Canvas('my-canvas', {
backgroundColor: '#cbf1f1',
width: 800,
height: 600,
preserveObjectStacking: true
})
const r1 = new fabric.Rect({ width: 200, height: 200, stroke: null, top: 0, left: 0, fill:'red'})
const r2 = new fabric.Rect({ width: 200, height: 200, stroke: null, top: 50, left: 50, fill:'green'})
const r3 = new fabric.Rect({ width: 200, height: 200, stroke: null, top: 100, left: 100, fill:'yellow'})
fCanvas.add(r1, r2, r3)
fCanvas.requestRenderAll()
fCanvas.on('mouse:down:before', ev => {
if (!ev.e.metaKey) {
return
}
// Prevent conflicts with multi-selection
if (ev.e[fCanvas.altSelectionKey]) {
return
}
const currActiveObj = fCanvas.getActiveObject()
if (!currActiveObj) {
return
}
const pointer = fCanvas.getPointer(ev, true)
const hitObj = fCanvas._searchPossibleTargets([currActiveObj], pointer)
if (!hitObj) {
return
}
let excludeObjs = []
if (currActiveObj instanceof fabric.Group) {
currActiveObj._objects.forEach(x => { excludeObjs.push(x) })
} else {
// Target is single active object
excludeObjs.push(currActiveObj)
}
let remain = excludeObjs.length
let objsToSearch = []
let lastIdx = -1
const canvasObjs = fCanvas._objects
for (let i = canvasObjs.length-1; i >=0 ; i--) {
if (remain === 0) {
lastIdx = i
break
}
const obj = canvasObjs[i]
if (excludeObjs.includes(obj)) {
remain -= 1
} else {
objsToSearch.push(obj)
}
}
const headObjs = canvasObjs.slice(0, lastIdx+1)
objsToSearch = objsToSearch.reverse().concat(headObjs)
const found = fCanvas._searchPossibleTargets(objsToSearch, pointer)
if (found) {
fCanvas._target = found
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/4.3.1/fabric.min.js"></script>
<html>
<h4>Left-click + Cmd-key on overlapping area to pick the obj which is behind current one</h4>
<canvas id="my-canvas"></canvas>
</html>
Upvotes: 1
Reputation: 1838
After some time I finally was able to solve that by myself. Clicking on an object brings it to the top. On double-clicking I try to get the object one layer behind the current object. On another dblclick I get the one behind and so on. Works great for me and also allows for the selection of fully covered objects without the need to move others.
var canvas = new fabric.Canvas("c");
canvas.on("object:selected", function (e) {
if (e.target) {
e.target.bringToFront();
this.renderAll();
}
});
var _prevActive = 0;
var _layer = 0;
//
fabric.util.addListener(canvas.upperCanvasEl, "dblclick", function (e) {
var _canvas = canvas;
//current mouse position
var _mouse = _canvas.getPointer(e);
//active object (that has been selected on click)
var _active = _canvas.getActiveObject();
//possible dblclick targets (objects that share mousepointer)
var _targets = _canvas.getObjects().filter(function (_obj) {
return _obj.containsPoint(_mouse) && !_canvas.isTargetTransparent(_obj, _mouse.x, _mouse.y);
});
_canvas.deactivateAll();
//new top layer target
if (_prevActive !== _active) {
//try to go one layer below current target
_layer = Math.max(_targets.length-2, 0);
}
//top layer target is same as before
else {
//try to go one more layer down
_layer = --_layer < 0 ? Math.max(_targets.length-2, 0) : _layer;
}
//get obj on current layer
var _obj = _targets[_layer];
if (_obj) {
_prevActive = _obj;
_obj.bringToFront();
_canvas.setActiveObject(_obj).renderAll();
}
});
//create something to play with
canvas
//fully covered rect is selectable with dblclicks
.add(new fabric.Rect({
top: 75,
left: 75,
width: 50,
height: 50,
fill: "black",
stroke: "black",
globalCompositeOperation: "xor",
perPixelTargetFind: true
}))
.add(new fabric.Circle({
top: 25,
left: 25,
radius: 50,
fill: "rgba(255,0,0,.5)",
stroke: "black",
perPixelTargetFind: true
}))
.add(new fabric.Circle({
top: 50,
left: 50,
radius: 50,
fill: "rgba(0,255,0,.5)",
stroke: "black",
perPixelTargetFind: true
}))
.add(new fabric.Circle({
top: 75,
left: 75,
radius: 50,
fill: "rgba(0,0,255,.5)",
stroke: "black",
perPixelTargetFind: true
}))
.renderAll();
canvas {
border: 1px solid;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.6.4/fabric.min.js"></script>
<canvas id="c" width="300" height="200"></canvas>
Upvotes: 5