I am using Openseadragon library with fabricjs overlay. I have a case where I want to drag the canvas but instead of mouse primary button, I want to drag it with middle mouse button press. Could anyone please help me get the desired behavior?
How to drag an Openseadragon canvas with mouse middle wheel button
1.1k Views Asked by Fateh At
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Expanding on @iangilman 's answer...
To improve the user experience when the middle button is released outside the MouseTracker's element while dragging, causing the nonPrimaryReleaseHandler to never get called, the pointer can be captured...something like this:
var trackerElement = viewer.container;
var drag;
function capturePointer(event) {
if (OpenSeadragon.MouseTracker.havePointerCapture) {
if (OpenSeadragon.MouseTracker.havePointerEvents) {
// Can throw InvalidPointerId
try {
trackerElement.setPointerCapture(event.originalEvent.pointerId);
} catch () {
//
}
} else {
trackerElement.setCapture(true);
}
}
}
function releasePointer(event) {
if (OpenSeadragon.MouseTracker.havePointerCapture) {
if (OpenSeadragon.MouseTracker.havePointerEvents) {
// Can throw InvalidPointerId
try {
trackerElement.releasePointerCapture(event.originalEvent.pointerId);
} catch () {
//
}
} else {
trackerElement.releaseCapture();
}
}
}
var mouseTracker = new OpenSeadragon.MouseTracker({
element: trackerElement,
nonPrimaryPressHandler: function(event) {
if (event.button === 1) { // Middle
capturePointer(event);
drag = {
lastPos: event.position.clone()
};
}
},
moveHandler: function(event) {
if (drag) {
var deltaPixels = drag.lastPos.minus(event.position);
var deltaPoints = viewer.viewport.deltaPointsFromPixels(deltaPixels);
viewer.viewport.panBy(deltaPoints);
drag.lastPos = event.position.clone();
}
},
nonPrimaryReleaseHandler: function(event) {
if (event.button === 1) {
releasePointer(event);
drag = null;
}
}
});
OpenSeadragon doesn't have a flag for that, but you can easily build it using the MouseTracker. Here's an example (coded from memory and not tested, but it should give you the idea).
EDIT: I had a bug in the example code above; fixed.