touchscreen: Kinetic scrolling v3

commit 0e0982cb293ec6238cbd99f6ff2055b23c5decd1
Author: Aidan MacDonald <[email protected]>
Date:   Sun Nov 27 01:48:10 2022 +0000

    touchscreen: Kinetic scrolling v3
    
    Tune accel/decel/press coefficients and add a braking force which
    kicks in when swiping in the opposite direction of scrolling. This
    is instead of the usual acceleration force.
    
    Change-Id: I2b220c98674933a6957d6982020406342cd019bd

diff --git a/apps/gui/bitmap/list.c b/apps/gui/bitmap/list.c
index 3d77afc929..ba155c0a16 100644
--- a/apps/gui/bitmap/list.c
+++ b/apps/gui/bitmap/list.c
@@ -561,22 +561,31 @@ struct kinetic {
 static struct kinetic kinetic;
 static struct gesture_vel list_gvel;
 
+/*
+ * NOTE: defaults were chosen for the Shanling Q1, and may need
+ *       tuning for other devices
+ */
+
 const struct list_kinetic_scroll_settings list_kinetic_scroll_accel_default = {
-    .a0 = 1000 << LIST_KINETIC_FRACBITS,
-    .a1 = 1 << (LIST_KINETIC_FRACBITS - 1),
-    /* delay is ignored for this one */
+    .a0 = 200 << LIST_KINETIC_FRACBITS,         /* 200.0 */
+    .a1 = (6 << LIST_KINETIC_FRACBITS) / 5,     /* 1.2 */
+};
+
+const struct list_kinetic_scroll_settings list_kinetic_scroll_brake_default = {
+    .a0 = 200 << LIST_KINETIC_FRACBITS,         /* 200.0 */
+    .a1 = (1 << LIST_KINETIC_FRACBITS) / 2,     /* 0.5 */
 };
 
 const struct list_kinetic_scroll_settings list_kinetic_scroll_decel_default = {
-    .a0 = 3000 << LIST_KINETIC_FRACBITS,
-    .a1 = 1 << (LIST_KINETIC_FRACBITS - 1),
-    .delay = 125 * HZ / 1000,
+    .a0 = 2000 << LIST_KINETIC_FRACBITS,        /* 2000.0 */
+    .a1 = (1 << LIST_KINETIC_FRACBITS) / 2,     /* 0.5 */
+    .delay = 125 * HZ / 1000,                   /* 125 ms */
 };
 
 const struct list_kinetic_scroll_settings list_kinetic_scroll_press_default = {
-    .a0 = 35000 << LIST_KINETIC_FRACBITS,
-    .a1 = 4 << LIST_KINETIC_FRACBITS,
-    .delay = 250 * HZ / 1000,
+    .a0 = 35000 << LIST_KINETIC_FRACBITS,       /* 35000.0 */
+    .a1 = 4 << LIST_KINETIC_FRACBITS,           /* 4.0 */
+    .delay = 250 * HZ / 1000,                   /* 250 ms */
 };
 
 static void kinetic_stop_scrolling(struct kinetic *k, struct gui_synclist *list)
@@ -683,22 +692,26 @@ static bool kinetic_start_scrolling(struct kinetic *k, struct gui_synclist *list
         return false;
 
     long yvel_fp = yvel << LIST_KINETIC_FRACBITS;
+    int vel_sgn = SIGN(k->cb_data.velocity);
+
     if (list->scroll_mode == SCROLL_KINETIC)
     {
-        long accel = kinetic_calc_accel(k->cb_data.velocity, LONG_MAX,
-                                        &global_settings.kinetic_scroll_accel);
-        accel = fp_mul(accel, RELOAD_INTERVAL_FP, LIST_KINETIC_FRACBITS);
-
-        /* the acceleration is in the direction of the swipe */
-        if (SIGN(accel) != SIGN(yvel_fp))
-            accel = -accel;
+        long accel;
+        if (SIGN(yvel) == vel_sgn)
+            accel = kinetic_calc_accel(k->cb_data.velocity, LONG_MAX,
+                                       &global_settings.kinetic_scroll_accel);
+        else
+            accel = -kinetic_calc_accel(k->cb_data.velocity, LONG_MAX,
+                                        &global_settings.kinetic_scroll_brake);
 
         yvel_fp += accel;
     }
 
     k->cb_data.list = list;
     k->cb_data.velocity += yvel_fp;
-    if (list->scroll_mode != SCROLL_KINETIC)
+    /* also reset distance & scroll duration after a direction change */
+    if (list->scroll_mode != SCROLL_KINETIC ||
+        vel_sgn != SIGN(k->cb_data.velocity))
     {
         k->cb_data.distance = 0;
         k->cb_data.scroll_duration = 0;
diff --git a/apps/gui/list.h b/apps/gui/list.h
index 534558c0bc..0e3a350ed7 100644
--- a/apps/gui/list.h
+++ b/apps/gui/list.h
@@ -203,20 +203,25 @@ struct list_kinetic_scroll_settings
     long delay;
 };
 
-/* Acceleration applied to the scroll velocity when a swipe occurs during
- * kinetic scrolling. This is needed to counteract the deceleration term
- * for high scrolling speeds, since the user can only input a low constant
- * acceleration from swiping alone. Delay is ignored. */
+/*
+ * accel: Extra impulse applied when swiping in the direction of scrolling,
+ *        proportional to the current velocity. This is what allows for high
+ *        scroll speeds. Delay is ignored.
+ *
+ * brake: Braking impulse applied when swiping in the opposite direction of
+ *        scrolling, which helps to change direction quickly even at high
+ *        speed. Delay is ignored.
+ *
+ * decel: Deceleration applied during scrolling. The delay is measured from
+ *        the start of scrolling or last change of direction.
+ *
+ * press: Deceleration applied while the screen is pressed (motion is not
+ *        needed to trigger). Additive with "decel". The delay is measured
+ *        from the start of the press.
+ */
 extern const struct list_kinetic_scroll_settings list_kinetic_scroll_accel_default;
-
-/* Deceleration applied to the scroll velocity during kinetic scrolling.
- * The delay occurs right at the beginning of scrolling, eg. a delay of
- * 1 second means deceleration starts 1 second after scrolling. */
+extern const struct list_kinetic_scroll_settings list_kinetic_scroll_brake_default;
 extern const struct list_kinetic_scroll_settings list_kinetic_scroll_decel_default;
-
-/* Deceleration applied during kinetic scrolling when the screen is
- * pressed for longer than the delay interval (motion is not required).
- * This is additive with list_kinetic_scroll_decel. */
 extern const struct list_kinetic_scroll_settings list_kinetic_scroll_press_default;
 #endif
 
diff --git a/apps/settings.h b/apps/settings.h
index 35af24c97d..f5d036f9da 100644
--- a/apps/settings.h
+++ b/apps/settings.h
@@ -801,6 +801,7 @@ struct user_settings
     int touch_mode;
     struct touchscreen_parameter ts_calibration_data;
     struct list_kinetic_scroll_settings kinetic_scroll_accel;
+    struct list_kinetic_scroll_settings kinetic_scroll_brake;
     struct list_kinetic_scroll_settings kinetic_scroll_decel;
     struct list_kinetic_scroll_settings kinetic_scroll_press;
 #endif
diff --git a/apps/settings_list.c b/apps/settings_list.c
index 958e61f07f..5d4e6e6cb7 100644
--- a/apps/settings_list.c
+++ b/apps/settings_list.c
@@ -2429,6 +2429,10 @@ const struct settings_list settings[] = {
                    &list_kinetic_scroll_accel_default, "kinetic scroll accel",
                    list_kinetic_load_from_cfg, list_kinetic_write_to_cfg,
                    list_kinetic_is_default, list_kinetic_set_default),
+    CUSTOM_SETTING(0, kinetic_scroll_brake, -1,
+                   &list_kinetic_scroll_brake_default, "kinetic scroll brake",
+                   list_kinetic_load_from_cfg, list_kinetic_write_to_cfg,
+                   list_kinetic_is_default, list_kinetic_set_default),
     CUSTOM_SETTING(0, kinetic_scroll_decel, -1,
                    &list_kinetic_scroll_decel_default, "kinetic scroll decel",
                    list_kinetic_load_from_cfg, list_kinetic_write_to_cfg,
-- 
rockbox-cvs mailing list
[email protected]
https://lists.haxx.se/mailman/listinfo/rockbox-cvs