docs(indev): add description about gestures

lvgl · Jan 3, 2022 · 2719862 · 2719862
1 parent 5c19b8f
commit 2719862
Showing 1 changed file with 34 additions and 2 deletions.
diff --git a/docs/overview/indev.md b/docs/overview/indev.md
@@ -16,22 +16,54 @@ An input device usually means:
 
 ## Pointers
 
+### Cursor
+
 Pointer input devices (like a mouse) can have a cursor.
 
 ```c
 ...
 lv_indev_t * mouse_indev = lv_indev_drv_register(&indev_drv);
 
-LV_IMG_DECLARE(mouse_cursor_icon);                          /*Declare the image file.*/
+LV_IMG_DECLARE(mouse_cursor_icon);                          /*Declare the image source.*/
 lv_obj_t * cursor_obj =  lv_img_create(lv_scr_act());       /*Create an image object for the cursor */
 lv_img_set_src(cursor_obj, &mouse_cursor_icon);             /*Set the image source*/
 lv_indev_set_cursor(mouse_indev, cursor_obj);               /*Connect the image  object to the driver*/
-
 ```
 
 Note that the cursor object should have `lv_obj_clear_flag(cursor_obj, LV_OBJ_FLAG_CLICKABLE)`.
 For images, *clicking* is disabled by default.
 
+### Gestures
+Pointer input devives can detect basic gestures. By default, most of the widgets send the gestures to its parent, so finally the gestures can be detected on the screen object in a form of an `LV_EVENT_GESTURE` event. For example:
+
+```c
+void my_event(lv_event_t * e)
+{
+  lv_obj_t * screen = lv_event_get_current_target(e);
+  lv_dir_t dir = lv_indev_get_gesture_dir(lv_indev_act());
+  switch(dir) {
+    case LV_DIR_LEFT:
+      ...
+      break;
+    case LV_DIR_RIGHT:
+      ...
+      break;
+    case LV_DIR_TOP:
+      ...
+      break;
+    case LV_DIR_BOTTOM:
+      ...
+      break;
+  }
+}
+
+...
+
+lv_obj_add_event_cb(screen1, my_event, LV_EVENT_GESTURE, NULL);
+```
+
+To prevent passing the gesture event to the parent from an obejct use `lv_obj_clear_flag(obj, LV_OBJ_FLAG_GESTURE_BUBBLE)`.
+
 ## Keypad and encoder
 
 You can fully control the user interface without a touchpad or mouse by using a keypad or encoder(s). It works similar to the *TAB* key on the PC to select an element in an application or a web page.