ecore_evas: add API to offset drag position relative to cursor

The values are stored in the ee itself. And it is the responsibility of
the engine to use that value correctly.

src/lib/ecore_evas/Ecore_Evas.h

@@ -3816,6 +3816,19 @@ typedef void (*Ecore_Evas_Drag_Finished_Cb)(Ecore_Evas *ee, unsigned int seat, v
  */
 EAPI Eina_Bool ecore_evas_drag_start(Ecore_Evas *ee, unsigned int seat, Eina_Content *content, Ecore_Evas *drag_rep,
                                      const char* action, Ecore_Evas_Drag_Finished_Cb terminate_cb, void *data);
+/**
+ * @brief Set the offset of the dragged symbol. Only valid during a drag
+ *
+ * @param[in] ee The Ecore Evas the drag operation started on.
+ * @param[in] seat The seat to use
+ * @param[in] offset The offset to apply to the upper left corner ofthe dragged window
+ *
+ * This must be called on the ee where ecore_evas_drag_start is called on, NOT on the drag representation
+ *
+ * @since 1.24
+ */
+EAPI void ecore_evas_drag_offset_set(Ecore_Evas *ee, unsigned int seat, Eina_Size2D offset);
+
 
 /**
  * @brief Cancels an ongoing drag operation.

src/lib/ecore_evas/ecore_evas.c

@@ -5645,10 +5645,28 @@ ecore_evas_drag_start(Ecore_Evas *ee, unsigned int seat, Eina_Content *content,
    ee->drag.free = terminate_cb;
    ee->drag.data = data;
    ee->drag.accepted = EINA_FALSE;
+   ee->drag.offset = EINA_SIZE2D(INT_MAX, INT_MAX);
 
    return success;
 }
 
+EAPI void
+ecore_evas_drag_offset_set(Ecore_Evas *ee, unsigned int seat, Eina_Size2D offset) {
+   Ecore_Evas_Selection_Seat_Buffers *buffers;
+
+   EINA_SAFETY_ON_NULL_RETURN(ee);
+   buffers = _fetch_selection_buffers_of_seat(ee, seat, EINA_FALSE);
+   EINA_SAFETY_ON_NULL_RETURN(buffers);
+   EINA_SAFETY_ON_TRUE_RETURN(buffers->selection_buffer[ECORE_EVAS_SELECTION_BUFFER_DRAG_AND_DROP_BUFFER] == NULL);
+   if (offset.w == INT_MAX || offset.h == INT_MAX)
+     {
+        ERR("Offset is INT_MAX, this is a reserved value! Executing Fallback!");
+     }
+
+   INF("Set offset to %d %d", offset.w, offset.h);
+   ee->drag.offset = offset;
+}
+
 EAPI Eina_Bool
 ecore_evas_drag_cancel(Ecore_Evas *ee, unsigned int seat)
 {

src/lib/ecore_evas/ecore_evas_private.h

@@ -404,6 +404,7 @@ struct _Ecore_Evas
    struct
      {
         Ecore_Evas *rep;
+        Eina_Size2D offset;
         void *data;
         Ecore_Evas_Drag_Finished_Cb free;
         Eina_Bool accepted;

src/lib/elementary/efl_ui_dnd.c

@@ -64,6 +64,12 @@ _efl_ui_dnd_drag_start(Eo *obj, Efl_Ui_Dnd_Data *pd, Eina_Content *content, cons
    return drag_win;
 }
 
+EOLIAN static void
+_efl_ui_dnd_drag_offset_set(Eo *obj EINA_UNUSED, Efl_Ui_Dnd_Data *pd, unsigned int seat, Eina_Size2D size)
+{
+   ecore_evas_drag_offset_set(pd->ee, seat, size);
+}
+
 EOLIAN static void
 _efl_ui_dnd_drag_cancel(Eo *obj EINA_UNUSED, Efl_Ui_Dnd_Data *pd, unsigned int seat)
 {

src/lib/elementary/efl_ui_dnd.eo

@@ -53,6 +53,17 @@ mixin @beta Efl.Ui.Dnd requires Efl.Object {
                                  of the content being dragged (like a thumbnail, for example).
                                  Use @Efl.Content.content.set on it to do so.]]
       }
+      @property drag_offset {
+        [[Set the offset during a drag that was initiated through drag_start]]
+        keys {
+          seat: uint; [[Seat setting the offset on.]]
+        }
+        values {
+          offset : Eina.Size2D; [[The offset for which the window will be shifted. The upper left of the window is
+                                calculated by adding this offset to the cursor position]]
+        }
+        set {}
+      }
       drag_cancel {
          [[Cancels an on-going drag operation.]]
          params {

src/lib/elementary/elm_dnd.c

@@ -776,10 +776,11 @@ elm_drag_start(Evas_Object *obj, Elm_Sel_Format format,
    Eina_Array *mime_types;
    Eina_Content *content;
    Efl_Content *ui;
-   int x, y, w, h;
+   int x = 0, y = 0, w, h;
    Efl_Ui_Widget *widget;
    Elm_Drag_Data *dd;
    const char *str_action;
+   Eina_Position2D pointer;
 
    EINA_SAFETY_ON_NULL_RETURN_VAL(obj, EINA_FALSE);
 
@@ -803,6 +804,9 @@ elm_drag_start(Evas_Object *obj, Elm_Sel_Format format,
    content = eina_content_new((Eina_Slice) EINA_SLICE_STR_FULL(data), eina_array_data_get(mime_types, 0));
    ui = efl_ui_dnd_drag_start(obj, content, str_action, _default_seat(obj));
    widget = createicon(createdata, ui, &x, &y);
+
+   evas_pointer_canvas_xy_get(evas_object_evas_get(obj), &pointer.x, &pointer.y);
+   efl_ui_dnd_drag_offset_set(obj, _default_seat(obj), EINA_SIZE2D(x - pointer.x, y - pointer.y));
    evas_object_geometry_get(widget, NULL, NULL, &w, &h);
    evas_object_show(widget);
    efl_content_set(ui, widget);