Decouple mouse cursor and mouse wheel in accelerated mode (#6685)

* Decouples mouse cursor and mouse wheel movements in accelerated mode.

* Fixed comment indentation.

* Updated docs

Co-authored-by: Francis LAN <francislan@google.com>

tmk_core/common/mousekey.c

@@ -39,6 +39,9 @@ static uint16_t       last_timer      = 0;
 
 #ifndef MK_3_SPEED
 
+static uint16_t last_timer_c = 0;
+static uint16_t last_timer_w = 0;
+
 /*
  * Mouse keys  acceleration algorithm
  *  http://en.wikipedia.org/wiki/Mouse_keys
@@ -56,6 +59,10 @@ uint8_t mk_time_to_max = MOUSEKEY_TIME_TO_MAX;
 /* ramp used to reach maximum pointer speed (NOT SUPPORTED) */
 // int8_t mk_curve = 0;
 /* wheel params */
+/* milliseconds between the initial key press and first repeated motion event (0-2550) */
+uint8_t mk_wheel_delay = MOUSEKEY_WHEEL_DELAY / 10;
+/* milliseconds between repeated motion events (0-255) */
+uint8_t mk_wheel_interval    = MOUSEKEY_WHEEL_INTERVAL;
 uint8_t mk_wheel_max_speed   = MOUSEKEY_WHEEL_MAX_SPEED;
 uint8_t mk_wheel_time_to_max = MOUSEKEY_WHEEL_TIME_TO_MAX;
 
@@ -96,13 +103,12 @@ static uint8_t wheel_unit(void) {
 }
 
 void mousekey_task(void) {
-    if (timer_elapsed(last_timer) < (mousekey_repeat ? mk_interval : mk_delay * 10)) {
+    // report cursor and scroll movement independently
-        return;
+    report_mouse_t const tmpmr = mouse_report;
-    }
+    if ((mouse_report.x || mouse_report.y) && timer_elapsed(last_timer_c) > (mousekey_repeat ? mk_interval : mk_delay * 10)) {
-    if (mouse_report.x == 0 && mouse_report.y == 0 && mouse_report.v == 0 && mouse_report.h == 0) {
-        return;
-    }
         if (mousekey_repeat != UINT8_MAX) mousekey_repeat++;
+        mouse_report.v = 0;
+        mouse_report.h = 0;
         if (mouse_report.x > 0) mouse_report.x = move_unit();
         if (mouse_report.x < 0) mouse_report.x = move_unit() * -1;
         if (mouse_report.y > 0) mouse_report.y = move_unit();
@@ -118,11 +124,33 @@ void mousekey_task(void) {
                 mouse_report.y = 1;
             }
         }
+        mousekey_send();
+        last_timer_c = last_timer;
+        mouse_report = tmpmr;
+    }
+    if ((mouse_report.v || mouse_report.h) && timer_elapsed(last_timer_w) > (mousekey_repeat ? mk_wheel_interval : mk_wheel_delay * 10)) {
+        if (mousekey_repeat != UINT8_MAX) mousekey_repeat++;
+        mouse_report.x = 0;
+        mouse_report.y = 0;
         if (mouse_report.v > 0) mouse_report.v = wheel_unit();
         if (mouse_report.v < 0) mouse_report.v = wheel_unit() * -1;
         if (mouse_report.h > 0) mouse_report.h = wheel_unit();
         if (mouse_report.h < 0) mouse_report.h = wheel_unit() * -1;
+        /* diagonal move [1/sqrt(2)] */
+        if (mouse_report.v && mouse_report.h) {
+            mouse_report.v = times_inv_sqrt2(mouse_report.v);
+            if (mouse_report.v == 0) {
+                mouse_report.v = 1;
+            }
+            mouse_report.h = times_inv_sqrt2(mouse_report.h);
+            if (mouse_report.h == 0) {
+                mouse_report.h = 1;
+            }
+        }
         mousekey_send();
+        last_timer_w = last_timer;
+        mouse_report = tmpmr;
+    }
 }
 
 void mousekey_on(uint8_t code) {

tmk_core/common/mousekey.h

@@ -55,6 +55,12 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #    ifndef MOUSEKEY_TIME_TO_MAX
 #        define MOUSEKEY_TIME_TO_MAX 20
 #    endif
+#    ifndef MOUSEKEY_WHEEL_DELAY
+#        define MOUSEKEY_WHEEL_DELAY 300
+#    endif
+#    ifndef MOUSEKEY_WHEEL_INTERVAL
+#        define MOUSEKEY_WHEEL_INTERVAL 100
+#    endif
 #    ifndef MOUSEKEY_WHEEL_MAX_SPEED
 #        define MOUSEKEY_WHEEL_MAX_SPEED 8
 #    endif