[gnome-shell/gbsneto/custom-icon-positions: 22/35] appDisplay: Nudge items on hover

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 3ba17dec06b246da86a2aecb5c04fa85f7426d7e
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon May 25 15:59:07 2020 -0300

    appDisplay: Nudge items on hover
    
    Nudge items when hovering over the grid, but doesn't actually
    do anything with it. Moving icons, storing and loading the grid
    layout, etc, will come next.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1284

 js/ui/appDisplay.js | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 0719f6a7ec..3afe11e41d 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -963,6 +963,7 @@ class AppDisplay extends BaseAppView {
 
         this._eventBlocker.visible = this._currentDialog !== null;
         this._resetOvershoot();
+        this.removeNudges();
     }
 
     _canAccept(source) {
@@ -976,7 +977,33 @@ class AppDisplay extends BaseAppView {
         return true;
     }
 
-    handleDragOver(source) {
+    _dropTargetIsValid(source, item, dropTarget) {
+        const [sourcePage, sourcePosition] =
+            this._grid.getItemPosition(source);
+        let [itemPage, itemPosition] = this._grid.getItemPosition(item);
+        const pageItems =
+            this._grid.getItemsAtPage(itemPage).filter(c => c.visible);
+
+        if (sourcePage === itemPage && itemPosition > sourcePosition)
+            itemPosition--;
+
+        if (source !== item && dropTarget === IconGrid.DragLocation.END_EDGE)
+            itemPosition++;
+
+        itemPosition = clamp(itemPosition, 0, pageItems.length - 1);
+        const realDropTarget = this._grid.getItemAt(itemPage, itemPosition);
+
+        return source !== realDropTarget;
+    }
+
+    handleDragOver(source, _actor, x, y) {
+        const [item, dropTarget] = this.getDropTarget(x, y);
+
+        if (item && this._dropTargetIsValid(source, item, dropTarget))
+            this.nudgeItem(item, dropTarget);
+        else
+            this.removeNudges();
+
         if (!this._canAccept(source))
             return DND.DragMotionResult.NO_DROP;