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- def scroll_event_cb(e):
- cont = e.get_target()
- cont_a = lv.area_t()
- cont.get_coords(cont_a)
- cont_y_center = cont_a.y1 + cont_a.get_height() // 2
- r = cont.get_height() * 7 // 10
- child_cnt = cont.get_child_cnt()
- for i in range(child_cnt):
- child = cont.get_child(i)
- child_a = lv.area_t()
- child.get_coords(child_a)
- child_y_center = child_a.y1 + child_a.get_height() // 2
- diff_y = child_y_center - cont_y_center
- diff_y = abs(diff_y)
- # Get the x of diff_y on a circle.
- # If diff_y is out of the circle use the last point of the circle (the radius)
- if diff_y >= r:
- x = r
- else:
- # Use Pythagoras theorem to get x from radius and y
- x_sqr = r * r - diff_y * diff_y
- res = lv.sqrt_res_t()
- lv.sqrt(x_sqr, res, 0x8000) # Use lvgl's built in sqrt root function
- x = r - res.i
- # Translate the item by the calculated X coordinate
- child.set_style_translate_x(x, 0)
- # Use some opacity with larger translations
- opa = lv.map(x, 0, r, lv.OPA.TRANSP, lv.OPA.COVER)
- child.set_style_opa(lv.OPA.COVER - opa, 0)
- #
- # Translate the object as they scroll
- #
- cont = lv.obj(lv.scr_act())
- cont.set_size(200, 200)
- cont.center()
- cont.set_flex_flow(lv.FLEX_FLOW.COLUMN)
- cont.add_event_cb(scroll_event_cb, lv.EVENT.SCROLL, None)
- cont.set_style_radius(lv.RADIUS.CIRCLE, 0)
- cont.set_style_clip_corner(True, 0)
- cont.set_scroll_dir(lv.DIR.VER)
- cont.set_scroll_snap_y(lv.SCROLL_SNAP.CENTER)
- cont.set_scrollbar_mode(lv.SCROLLBAR_MODE.OFF)
- for i in range(20):
- btn = lv.btn(cont)
- btn.set_width(lv.pct(100))
- label = lv.label(btn)
- label.set_text("Button " + str(i))
- # Update the buttons position manually for first*
- lv.event_send(cont, lv.EVENT.SCROLL, None)
- # Be sure the fist button is in the middle
- #lv.obj.scroll_to_view(cont.get_child(0), lv.ANIM.OFF)
- cont.get_child(0).scroll_to_view(lv.ANIM.OFF)
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