How to invert scrolling?

How-to
1

Hello,
I am using a Renesas RA6M3 microcontroller to drive the display I am using. It all works fine.

However, I am trying to flip the display via dedicated hardware, which visually speaking works well, but the touch inputs are read the wrong way around.

I have fixed this by simply inverting the read inputs in my input’s callback function:

void touch_read_cb(lv_indev_drv_t* drv, lv_indev_data_t* data)
{
    FSP_PARAMETER_NOT_USED(drv);

    if (xMessageBufferReceiveFromISR(g_touch_message_buffer, &touch_data, sizeof(touch_data_t), NULL))
    {
#if !FLIP_INPUT
        data->point.x = (lv_coord_t)touch_data.point[0].x;
        data->point.y = (lv_coord_t)touch_data.point[0].y;
#else
        data->point.x = (lv_coord_t)(DISP_HOR_RES - touch_data.point[0].x);
        data->point.y = (lv_coord_t)(DISP_VER_RES - touch_data.point[0].y);

#endif
        data->state = LV_INDEV_STATE_PRESSED;
    }
    else
    {
        data->state = LV_INDEV_STATE_RELEASED;
    }
}

This works fine for buttons and even sliders in the horizontal axis… but when I try to use scrollable objects in the vertical axis, the input is inverted. I understand WHY this happens, but is there an easy fix?

EDIT: Sorry to bother you, @kisvegabor but I really think you are the only person who might know this and I’m still pondering this issue. Inverting the display using LVGL also inverts touch, so it is definitely possible.

2

Hi,

Just to be sure, you don’t set disp_drv->rotated, right? So LVGL doesn’t want to do any flipping internally.

To better see what’s going on, please create a cursor like this:

  lv_obj_t * cursor_obj = lv_img_create(lv_scr_act()); /*Create an image object for the cursor */
  lv_img_set_src(cursor_obj, LV_SYMBOL_HOME);           /*Set the image source*/
  lv_indev_set_cursor(mouse_indev, cursor_obj);             /*Connect the image  object to the driver*/

and send a video about it.

1 Like
3

Hello,

First of all, thanks for responding and I am very sorry for the very late response.

Since asking this question I have moved on to LVGL V9, in which I am now able to rotate the display in hardware. Using the (new?) lv_display_set_rotation() function, touch is also inverted properly.
The trick now is to just NOT invert the coordinates yourself.

1 Like