Handling continuous scroll key input.

autoload/comfortable_motion.vim

@@ -37,6 +37,8 @@ let s:comfortable_motion_state = {
 \ 'impulse': 0.0,
 \ 'velocity': 0.0,
 \ 'delta': 0.0,
+\ 'air_drag' : 0.0,
+\ 'syntax' : ''
 \ }
 
 function! s:tick(timer_id)
@@ -50,26 +52,48 @@ function! s:tick(timer_id)
       \            ? 0
       \            : l:st.velocity / abs(l:st.velocity)
     let l:friction = -l:vel_sign * g:comfortable_motion_friction * 1  " The mass is 1
-    let l:air_drag = -l:st.velocity * g:comfortable_motion_air_drag
+    let l:air_drag = -l:st.velocity * l:st.air_drag
     let l:additional_force = l:friction + l:air_drag
 
     " Update the state
     let l:st.delta += l:st.velocity * l:dt
     let l:st.velocity += l:st.impulse + (abs(l:additional_force * l:dt) > abs(l:st.velocity) ? -l:st.velocity : l:additional_force * l:dt)
     let l:st.impulse = 0
 
+    " Current Position
+    let l:topline = line('w0')
+    let l:botline = line('w$')
+
     " Scroll
     let l:int_delta = float2nr(l:st.delta >= 0 ? floor(l:st.delta) : ceil(l:st.delta))
     let l:st.delta -= l:int_delta
     if l:int_delta > 0
-      execute "normal! " . string(abs(l:int_delta)) . g:comfortable_motion_scroll_down_key
+      if l:botline == line("$") " when can see bottom line, move cursor
+        execute "normal! " . string(abs(l:int_delta)) . "j"
+      else
+        execute "normal! " . string(abs(l:int_delta)) . g:comfortable_motion_scroll_down_key
+      endif
     elseif l:int_delta < 0
-      execute "normal! " . string(abs(l:int_delta)) . g:comfortable_motion_scroll_up_key
+      if l:topline == 1
+        execute "normal! " . string(abs(l:int_delta)) . "k"
+      else
+        execute "normal! " . string(abs(l:int_delta)) . g:comfortable_motion_scroll_up_key
+      endif
     else
       " Do nothing
     endif
     redraw
+
+    " stop at the top and bottom
+    let l:pos = getpos('.')
+    if ( l:pos[1] == 1 && l:st.velocity < 0 )
+      \ || ( l:pos[1] == line('$') && l:st.velocity > 0 )
+      let l:st.velocity = 0
+      let l:st.delta = 0
+    endif
   else
+    execute "setlocal syntax=".s:comfortable_motion_state.syntax
+    "let g:airline#extensions#wordcount#enabled = 1
     " Stop scrolling and the thread
     let l:st.velocity = 0
     let l:st.delta = 0
@@ -78,13 +102,46 @@ function! s:tick(timer_id)
   endif
 endfunction
 
-function! comfortable_motion#flick(impulse)
+function! comfortable_motion#flick_impl(impulse, air_drag)
+  let l:st = s:comfortable_motion_state  " This is just an alias for the global variable
+  let l:st.air_drag = a:air_drag
   if !exists('s:timer_id')
+    let s:comfortable_motion_state.syntax = &syntax
+    "let g:airline#extensions#wordcount#enabled = 0
     " There is no thread, start one
     let l:interval = float2nr(round(g:comfortable_motion_interval))
     let s:timer_id = timer_start(l:interval, function("s:tick"), {'repeat': -1})
+  else
+    if l:st.velocity > a:impulse * 3
+      execute "setlocal syntax="
+    endif
   endif
-  let s:comfortable_motion_state.impulse += a:impulse
+
+  " stop if velocity and impulse is not same direction
+  if ( l:st.velocity > 0 && a:impulse < 0 )
+    \ || ( l:st.velocity < 0 && a:impulse > 0 )
+    "let s:comfortable_motion_state.impulse -= l:st.velocity * 4 / 5
+    "let s:comfortable_motion_state.impulse = a:impulse
+    let s:comfortable_motion_state.impulse += a:impulse
+  else
+    let s:comfortable_motion_state.impulse += a:impulse - l:st.velocity * 0.6
+  endif
+endfunction
+
+function! comfortable_motion#flick(impulse, air_drag)
+  call comfortable_motion#flick_impl( a:impulse, g:comfortable_motion_air_drag )
+endfunction
+
+function! comfortable_motion#flickDist(dist)
+  let l:friction = g:comfortable_motion_friction
+  let l:dt = g:comfortable_motion_interval / 1000.0
+  let l:fdt = l:friction * l:dt
+  let l:fddt = l:fdt * l:dt
+  let l:dist_sign = a:dist == 0 ? 0 : a:dist / abs(a:dist)
+
+  let l:impulse = l:fdt * ( sqrt( 2.0 * abs(a:dist) / l:fddt + 1.0/4.0 ) - 1.0/2.0 )
+
+  call comfortable_motion#flick_impl( l:impulse * l:dist_sign, 0 )
 endfunction
 
 let &cpo = s:save_cpo