acid-drop

- Hacking the planet from a LilyGo T-Deck using custom firmware
git clone git://git.acid.vegas/acid-drop.git
lv_example_scroll_6.c (2639B)
      1 #include "../lv_examples.h"
      2 #if LV_BUILD_EXAMPLES && LV_USE_FLEX
      3 
      4 static void scroll_event_cb(lv_event_t * e)
      5 {
      6     lv_obj_t * cont = lv_event_get_target(e);
      7 
      8     lv_area_t cont_a;
      9     lv_obj_get_coords(cont, &cont_a);
     10     lv_coord_t cont_y_center = cont_a.y1 + lv_area_get_height(&cont_a) / 2;
     11 
     12     lv_coord_t r = lv_obj_get_height(cont) * 7 / 10;
     13     uint32_t i;
     14     uint32_t child_cnt = lv_obj_get_child_cnt(cont);
     15     for(i = 0; i < child_cnt; i++) {
     16         lv_obj_t * child = lv_obj_get_child(cont, i);
     17         lv_area_t child_a;
     18         lv_obj_get_coords(child, &child_a);
     19 
     20         lv_coord_t child_y_center = child_a.y1 + lv_area_get_height(&child_a) / 2;
     21 
     22         lv_coord_t diff_y = child_y_center - cont_y_center;
     23         diff_y = LV_ABS(diff_y);
     24 
     25         /*Get the x of diff_y on a circle.*/
     26         lv_coord_t x;
     27         /*If diff_y is out of the circle use the last point of the circle (the radius)*/
     28         if(diff_y >= r) {
     29             x = r;
     30         }
     31         else {
     32             /*Use Pythagoras theorem to get x from radius and y*/
     33             uint32_t x_sqr = r * r - diff_y * diff_y;
     34             lv_sqrt_res_t res;
     35             lv_sqrt(x_sqr, &res, 0x8000);   /*Use lvgl's built in sqrt root function*/
     36             x = r - res.i;
     37         }
     38 
     39         /*Translate the item by the calculated X coordinate*/
     40         lv_obj_set_style_translate_x(child, x, 0);
     41 
     42         /*Use some opacity with larger translations*/
     43         lv_opa_t opa = lv_map(x, 0, r, LV_OPA_TRANSP, LV_OPA_COVER);
     44         lv_obj_set_style_opa(child, LV_OPA_COVER - opa, 0);
     45     }
     46 }
     47 
     48 /**
     49  * Translate the object as they scroll
     50  */
     51 void lv_example_scroll_6(void)
     52 {
     53     lv_obj_t * cont = lv_obj_create(lv_scr_act());
     54     lv_obj_set_size(cont, 200, 200);
     55     lv_obj_center(cont);
     56     lv_obj_set_flex_flow(cont, LV_FLEX_FLOW_COLUMN);
     57     lv_obj_add_event_cb(cont, scroll_event_cb, LV_EVENT_SCROLL, NULL);
     58     lv_obj_set_style_radius(cont, LV_RADIUS_CIRCLE, 0);
     59     lv_obj_set_style_clip_corner(cont, true, 0);
     60     lv_obj_set_scroll_dir(cont, LV_DIR_VER);
     61     lv_obj_set_scroll_snap_y(cont, LV_SCROLL_SNAP_CENTER);
     62     lv_obj_set_scrollbar_mode(cont, LV_SCROLLBAR_MODE_OFF);
     63 
     64     uint32_t i;
     65     for(i = 0; i < 20; i++) {
     66         lv_obj_t * btn = lv_btn_create(cont);
     67         lv_obj_set_width(btn, lv_pct(100));
     68 
     69         lv_obj_t * label = lv_label_create(btn);
     70         lv_label_set_text_fmt(label, "Button %"LV_PRIu32, i);
     71     }
     72 
     73     /*Update the buttons position manually for first*/
     74     lv_event_send(cont, LV_EVENT_SCROLL, NULL);
     75 
     76     /*Be sure the fist button is in the middle*/
     77     lv_obj_scroll_to_view(lv_obj_get_child(cont, 0), LV_ANIM_OFF);
     78 }
     79 
     80 #endif