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Add debounce of pan events

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Group pan events together if needed, in order to avoid lag if drawing of layers takes more time than it should.
This commit is contained in:
Christophe Avenel 2023-10-31 15:38:38 +01:00
parent 810987210c
commit e836ffcc61
2 changed files with 41 additions and 10 deletions
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4
src/openseadragon.js
View File

@ -141,6 +141,9 @@
* <strong>DEPRECATED</strong>. A relative path to load a DZI file from the server.
* Prefer the newer Options.tileSources.
*
* @property {Boolean} [debouncePanEvents=false]
* Group multiple move events into one event. This is useful for debouncing.
*
* @property {String} [prefixUrl='/images/']
* Prepends the prefixUrl to navImages paths, which is very useful
* since the default paths are rarely useful for production
@ -1370,6 +1373,7 @@ function OpenSeadragon( options ){
useCanvas: true, // Use canvas element for drawing if available
tileRetryMax: 0,
tileRetryDelay: 2500,
debouncePanEvents: false,
//INTERFACE RESOURCE SETTINGS
prefixUrl: "/images/",

47
src/viewer.js
View File

@ -3097,28 +3097,55 @@ function onCanvasDrag( event ) {
* @property {?Object} userData - Arbitrary subscriber-defined object.
*/
this.raiseEvent( 'canvas-drag', canvasDragEventArgs);
gestureSettings = this.gestureSettingsByDeviceType( event.pointerType );
if (this.debouncePanEvents) {
if (!this.dragEventCombined) {
this.dragEventCombined = canvasDragEventArgs;
this.dragEventCombined.timeStamp = canvasDragEventArgs.originalEvent.timeStamp;
}
else {
this.dragEventCombined.delta = this.dragEventCombined.delta.plus(canvasDragEventArgs.delta);
}
if (this.dragEventCombined.timeout) {
clearTimeout(this.dragEventCombined.timeout);
this.dragEventCombined.timeout = null;
}
if (canvasDragEventArgs.originalEvent.timeStamp - this.dragEventCombined.timeStamp > this.debouncePanEvents) {
canvasDragEventArgs = this.dragEventCombined;
this.dragEventCombined = null;
}
else {
this.dragEventCombined.timeout = setTimeout(function () {
// call onCanvasDrag with en event with delta.x and delat.y = 0
let newEvent = event;
newEvent.delta.x = 0;
newEvent.delta.y = 0;
this.dragEventCombined.timeStamp -= this.debouncePanEvents;
onCanvasDrag.call(this, newEvent);
}.bind(this), this.debouncePanEvents / 5);
return;
}
}
gestureSettings = this.gestureSettingsByDeviceType( canvasDragEventArgs.pointerType );
if(!canvasDragEventArgs.preventDefaultAction && this.viewport){
if (gestureSettings.dblClickDragToZoom && THIS[ this.hash ].draggingToZoom){
var factor = Math.pow( this.zoomPerDblClickDrag, event.delta.y / 50);
var factor = Math.pow( this.zoomPerDblClickDrag, canvasDragEventArgs.delta.y / 50);
this.viewport.zoomBy(factor);
}
else if (gestureSettings.dragToPan && !THIS[ this.hash ].draggingToZoom) {
if( !this.panHorizontal ){
event.delta.x = 0;
canvasDragEventArgs.delta.x = 0;
}
if( !this.panVertical ){
event.delta.y = 0;
canvasDragEventArgs.delta.y = 0;
}
if(this.viewport.flipped){
event.delta.x = -event.delta.x;
canvasDragEventArgs.delta.x = -canvasDragEventArgs.delta.x;
}
if( this.constrainDuringPan ){
var delta = this.viewport.deltaPointsFromPixels( event.delta.negate() );
var delta = this.viewport.deltaPointsFromPixels( canvasDragEventArgs.delta.negate() );
this.viewport.centerSpringX.target.value += delta.x;
this.viewport.centerSpringY.target.value += delta.y;
@ -3129,14 +3156,14 @@ function onCanvasDrag( event ) {
this.viewport.centerSpringY.target.value -= delta.y;
if (constrainedBounds.xConstrained) {
event.delta.x = 0;
canvasDragEventArgs.delta.x = 0;
}
if (constrainedBounds.yConstrained) {
event.delta.y = 0;
canvasDragEventArgs.delta.y = 0;
}
}
this.viewport.panBy( this.viewport.deltaPointsFromPixels( event.delta.negate() ), gestureSettings.flickEnabled && !this.constrainDuringPan);
this.viewport.panBy( this.viewport.deltaPointsFromPixels( canvasDragEventArgs.delta.negate() ), gestureSettings.flickEnabled && !this.constrainDuringPan);
}
}