gengrid: Added elm_gengrid_wheel_disabled_set/get() APIs.

Summary:
The basic idea is from Abhinandan Aryadipta and I implemented this in
upstream.
Special thanks to JackDanielZ for eolian madness.

@feature

Reviewers: JackDanielZ

Differential Revision: https://phab.enlightenment.org/D803

legacy/elementary/src/bin/test_gengrid.c

@@ -297,6 +297,12 @@ multi_select_cb(void *data, Evas_Object *obj, void *event_info EINA_UNUSED)
    elm_gengrid_multi_select_set(data, elm_check_state_get(obj));
 }
 
+static void
+wheel_disable_cb(void *data, Evas_Object *obj, void *event_info EINA_UNUSED)
+{
+   elm_gengrid_wheel_disabled_set(data, elm_check_state_get(obj));
+}
+
 static void
 clear_bt_clicked(void *data, Evas_Object *obj EINA_UNUSED, void *event_info EINA_UNUSED)
 {
@@ -541,6 +547,15 @@ test_gengrid(void *data EINA_UNUSED, Evas_Object *obj EINA_UNUSED, void *event_i
    elm_box_pack_end(bx, ck);
    evas_object_show(ck);
 
+   ck = elm_check_add(win);
+   evas_object_size_hint_weight_set(ck, EVAS_HINT_EXPAND, 0.0);
+   evas_object_size_hint_align_set(ck, EVAS_HINT_FILL, EVAS_HINT_FILL);
+   elm_object_text_set(ck, "Wheel Disable");
+   evas_object_smart_callback_add(ck, "changed", wheel_disable_cb,
+                                  api->grid);
+   elm_box_pack_end(bx, ck);
+   evas_object_show(ck);
+
    /* Gengrid Options 2 */
    bx = elm_box_add(win);
    elm_box_horizontal_set(bx, EINA_TRUE);

legacy/elementary/src/lib/elm_gengrid.c

@@ -4340,6 +4340,23 @@ _elm_gengrid_elm_widget_focused_item_get(Eo *obj EINA_UNUSED, Elm_Gengrid_Data *
    return sd->focused_item;
 }
 
+EOLIAN static void
+_elm_gengrid_wheel_disabled_set(Eo *obj, Elm_Gengrid_Data *sd, Eina_Bool disabled)
+{
+   disabled = !!disabled;
+   if (sd->wheel_disabled != disabled)
+     eo_do(obj,
+           elm_interface_scrollable_wheel_disabled_set(disabled));
+
+   sd->wheel_disabled = disabled;
+}
+
+EOLIAN static Eina_Bool
+_elm_gengrid_wheel_disabled_get(Eo *obj EINA_UNUSED, Elm_Gengrid_Data *sd)
+{
+   return sd->wheel_disabled;
+}
+
 EOLIAN static void
 _elm_gengrid_class_constructor(Eo_Class *klass)
 {

legacy/elementary/src/lib/elm_gengrid.eo

@@ -429,6 +429,37 @@ class Elm_Gengrid (Elm_Layout, Elm_Interface_Scrollable, Evas_Clickable_Interfac
             return Elm_Object_Item *;
          }
       }
+      wheel_disabled {
+         set {
+            /*@
+            Enable or disable mouse wheel to be used to scroll the gengrid.
+
+            Mouse wheel can be used for the user to scroll up and down the gengrid.
+
+            It's enabled by default.
+
+            @see elm_gengrid_wheel_disabled_get()
+
+            @ingroup Gengrid */
+         }
+         get {
+            /*@
+            Get a value whether mouse wheel is enabled or not.
+
+            @return @c EINA_TRUE means gengrid wheel is disabled. @c EINA_FALSE indicates
+            it is enabled.
+
+            Mouse wheel can be used for the user to scroll up and down the gengrid.
+
+            @see elm_gengrid_wheel_disabled_set()
+
+            @ingroup Gengrid */
+         }
+         values {
+            Eina_Bool disabled; /*@ Use @c EINA_TRUE to disable mouse wheel or @c EINA_FALSE
+            to enable it. */
+         }
+      }
    }
    methods {
       item_insert_before {

legacy/elementary/src/lib/elm_widget_gengrid.h

@@ -119,6 +119,7 @@ struct _Elm_Gengrid_Data
    Eina_Bool                             show_region : 1;
    Eina_Bool                             bring_in : 1;
    Eina_Bool                             mouse_down : 1; /**< a flag that mouse is down on the list at the moment. this flag is set to true on mouse and reset to false on mouse up */
+   Eina_Bool                             wheel_disabled : 1; /**< a flag that shows mouse wheel is disabled or not. */
 };
 
 struct Elm_Gen_Item_Type