Draggable widget: Add option to hide drag image

Thanks @ericshulman

Fixes #6027

core/modules/utils/dom/dragndrop.js

@@ -16,7 +16,7 @@ Browser data transfer utilities, used with the clipboard and drag and drop
 Options:
 
 domNode: dom node to make draggable
-dragImageType: "pill" or "dom"
+dragImageType: "pill", "blank" or "dom" (the default)
 dragTiddlerFn: optional function to retrieve the title of tiddler to drag
 dragFilterFn: optional function to retreive the filter defining a list of tiddlers to drag
 widget: widget to use as the contect for the filter
@@ -73,6 +73,9 @@ exports.makeDraggable = function(options) {
 				if(dataTransfer.setDragImage) {
 					if(dragImageType === "pill") {
 						dataTransfer.setDragImage(dragImage.firstChild,-16,-16);
+					} else if (dragImageType === "blank") {
+						dragImage.removeChild(dragImage.firstChild);
+						dataTransfer.setDragImage(dragImage,0,0);
 					} else {
 						var r = domNode.getBoundingClientRect();
 						dataTransfer.setDragImage(domNode,event.clientX-r.left,event.clientY-r.top);

core/modules/widgets/draggable.js

@@ -54,6 +54,7 @@ DraggableWidget.prototype.render = function(parent,nextSibling) {
 		dragFilterFn: function() {return self.getAttribute("filter");},
 		startActions: self.startActions,
 		endActions: self.endActions,
+		dragImageType: self.dragImageType,
 		widget: this
 	});
 	// Insert the link into the DOM and render any children
@@ -71,6 +72,7 @@ DraggableWidget.prototype.execute = function() {
 	this.draggableClasses = this.getAttribute("class");
 	this.startActions = this.getAttribute("startactions");
 	this.endActions = this.getAttribute("endactions");
+	this.dragImageType = this.getAttribute("dragimagetype"); 
 	// Make the child widgets
 	this.makeChildWidgets();
 };

editions/tw5.com/tiddlers/widgets/DraggableWidget.tid

@@ -1,6 +1,6 @@
 caption: draggable
 created: 20170406081938627
-modified: 20190118084621046
+modified: 20210912141544224
 tags: Widgets
 title: DraggableWidget
 type: text/vnd.tiddlywiki
@@ -20,6 +20,7 @@ See DragAndDropMechanism for an overview.
 |tag |Optional tag to override the default "div" element |
 |startactions |Optional action string that gets invoked when dragging ''starts'' |
 |endactions |Optional action string that gets invoked when dragging ''ends'' |
+|dragimagetype |<<.from-version "5.2.0">> Optional type of drag image: `dom` (the default) or `blank` to disable the drag image |
 
 Either or both of the ''tiddler'' and ''filter'' attributes must be specified in order for there to be a payload to drag.