Add auto-scroll with keyboard shortcut

src/pyj/read_book/flow_mode.pyj

@@ -63,8 +63,11 @@ last_change_spine_item_request = {}
 def _check_for_scroll_end(func, obj, args, report):
     before = window.pageYOffset
     func.apply(obj, args)
+
+    now = performance.now()
+    scroll_animator.sync(now)
+
     if window.pageYOffset is before:
-        now = Date.now()
         csi = current_spine_item()
         if last_change_spine_item_request.name is csi.name and now - last_change_spine_item_request.at < 2000:
             return False
@@ -128,10 +131,10 @@ def scroll_by_page(direction):
 
 def handle_shortcut(sc_name, evt):
     if sc_name is 'down':
-        scroll_animator.start(DIRECTION.Down)
+        scroll_animator.start(DIRECTION.Down, False)
         return True
     if sc_name is 'up':
-        scroll_animator.start(DIRECTION.Up)
+        scroll_animator.start(DIRECTION.Up, False)
         return True
     if sc_name is 'start_of_file':
         goto_boundary(-1)
@@ -157,13 +160,29 @@ def handle_shortcut(sc_name, evt):
     if sc_name is 'pagedown':
         scroll_by_page(1)
         return True
+    if sc_name is 'toggle_autoscroll':
+        if scroll_animator.auto and scroll_animator.is_running():
+            cancel_scroll()
+        else:
+            scroll_animator.start(DIRECTION.Down, True)
+        return True
+
+    if sc_name.startsWith('scrollspeed_'):
+        scroll_animator.sync()
+
     return False
 
 
 def layout(is_single_page):
+    cancel_scroll()
     set_css(document.body, margin='0', border_width='0', padding='0')
     line_height.doc_style = window.getComputedStyle(document.body)
 
+def cancel_scroll():
+    scroll_animator.stop()
+
+def is_scroll_end(pos):
+    return !(0 <= pos <= document_height() - window.innerHeight)
 
 DIRECTION = {'Up': -1, 'Down': 1}
 class ScrollAnimator:
@@ -171,17 +190,23 @@ class ScrollAnimator:
 
     def __init__(self):
         self.animation_id = None
+        self.auto = False
 
-    def start(self, direction):
+    def is_running(self):
+        return self.animation_id != None
+
+    def start(self, direction, auto):
         now = performance.now()
         self.end_time = now + self.DURATION
 
-        if self.animation_id is None or direction != self.direction:
+        if !self.is_running() or direction != self.direction or auto != self.auto:
+            self.paused = self.direction if self.auto and not auto else False
             self.stop()
+            self.auto = auto
             self.direction = direction
             self.start_time = now
             self.start_offset = window.pageYOffset
-            self.animation_id = window.requestAnimationFrame(self.smooth_scroll)
+            self.animation_id = window.requestAnimationFrame(self.auto_scroll if auto else self.smooth_scroll)
 
     def smooth_scroll(self, ts):
         duration = (self.end_time - self.start_time)
@@ -194,14 +219,40 @@ class ScrollAnimator:
         if progress < 1:
             self.animation_id = window.requestAnimationFrame(self.smooth_scroll)
         else:
-            self.animation_id = None
             amt = window.pageYOffset - self.start_offset
-            if abs(amt) < 3 and duration is self.DURATION and !(0 <= scroll_target <= document_height() - window.innerHeight):
+            if abs(amt) < 3 and duration is self.DURATION and is_scroll_end(scroll_target):
                 get_boss().send_message('next_spine_item', previous=self.direction is DIRECTION.Up)
+            elif self.paused:
+                self.start(self.paused, True)
             else:
+                self.animation_id = None
                 report_human_scroll(amt)
 
+    def auto_scroll(self, ts):
+        elapsed = max(0, ts - self.start_time) # max to account for jitter
+        scroll_target = self.start_offset
+        scroll_target += Math.trunc(self.direction * elapsed * line_height() * opts.lines_per_sec_auto) / 1000
+
+        window.scrollTo(0, scroll_target)
+        scroll_finished = is_scroll_end(scroll_target)
+
+        # report every second
+        if elapsed >= 1000:
+            self.sync(ts)
+
+        if scroll_finished:
+            self.stop()
+        else:
+            self.animation_id = window.requestAnimationFrame(self.auto_scroll)
+
+    def sync(self, ts):
+        if self.auto:
+            report_human_scroll(window.pageYOffset - self.start_offset)
+            self.start_time = ts or performance.now()
+            self.start_offset = window.pageYOffset
+
     def stop(self):
+        self.auto = False
         if self.animation_id is not None:
             window.cancelAnimationFrame(self.animation_id)
             self.animation_id = None

src/pyj/read_book/iframe.pyj

@@ -12,7 +12,7 @@ from read_book.extract import get_elements
 from read_book.flow_mode import (
     anchor_funcs as flow_anchor_funcs, flow_onwheel, flow_to_scroll_fraction,
     handle_gesture as flow_handle_gesture, handle_shortcut as flow_handle_shortcut,
-    layout as flow_layout, scroll_by_page as flow_scroll_by_page
+    layout as flow_layout, scroll_by_page as flow_scroll_by_page, cancel_scroll
 )
 from read_book.footnotes import is_footnote_link
 from read_book.globals import (
@@ -108,6 +108,7 @@ class IframeBoss:
             'set_reference_mode': self.set_reference_mode,
             'wheel_from_margin': self.wheel_from_margin,
             'window_size': self.received_window_size,
+            'overlay_shown': cancel_scroll,
         }
         self.comm = IframeClient(handlers)
         self.last_window_ypos = 0
@@ -245,8 +246,8 @@ class IframeBoss:
             apply_font_size()
 
     def change_scroll_speed(self, data):
-        if data.lines_per_sec_smooth?:
-            opts.lines_per_sec_smooth = data.lines_per_sec_smooth
+        if data.lines_per_sec_auto?:
+            opts.lines_per_sec_auto = data.lines_per_sec_auto
 
     def change_stylesheet(self, data):
         opts.user_stylesheet = data.sheet or ''

src/pyj/read_book/prefs/scrolling.pyj

@@ -12,7 +12,7 @@ from session import defaults
 
 CONTAINER = unique_id('standalone-scrolling-settings')
 MIN_SCROLL_SPEED = 0.5
-MAX_SCROLL_SPEED = 50
+MAX_SCROLL_SPEED = 5
 
 
 def restore_defaults():

src/pyj/read_book/settings.pyj

@@ -17,6 +17,7 @@ def update_settings(settings):
     opts.cover_preserve_aspect_ratio = v'!!settings.cover_preserve_aspect_ratio'
     opts.hide_tooltips = settings.hide_tooltips
     opts.is_dark_theme = v'!!settings.is_dark_theme'
+    opts.lines_per_sec_auto = settings.lines_per_sec_auto
     opts.lines_per_sec_smooth = settings.lines_per_sec_smooth
     opts.margin_left = max(0, settings.margin_left)
     opts.margin_right = max(0, settings.margin_right)

src/pyj/read_book/shortcuts.pyj

@@ -270,16 +270,22 @@ def shortcuts_definition():
         _('Go to a specified book location or position'),
     ),
 
+    'toggle_autoscroll': desc(
+        "Ctrl+ ",
+        'scroll',
+        _('Toggle auto-scroll'),
+    ),
+
     'scrollspeed_increase': desc(
         "Alt+ArrowUp",
         'scroll',
-        _('Smooth scroll faster'),
+        _('Auto scroll faster'),
     ),
 
     'scrollspeed_decrease': desc(
         "Alt+ArrowDown",
         'scroll',
-        _('Smooth scroll slower'),
+        _('Auto scroll slower'),
     ),
 
     }

src/pyj/read_book/view.pyj

@@ -339,6 +339,8 @@ class View:
 
     def overlay_visibility_changed(self, visible):
         if self.iframe_wrapper.send_message:
+            if visible:
+                self.iframe_wrapper.send_message('overlay_shown')
             self.iframe_wrapper.send_message('set_forward_keypresses', forward=v'!!visible')
         if ui_operations.overlay_visibility_changed:
             ui_operations.overlay_visibility_changed(visible)
@@ -708,6 +710,7 @@ class View:
             'hide_tooltips': sd.get('hide_tooltips'),
             'cover_preserve_aspect_ratio': sd.get('cover_preserve_aspect_ratio'),
             'paged_wheel_scrolls_by_screen': sd.get('paged_wheel_scrolls_by_screen'),
+            'lines_per_sec_auto': sd.get('lines_per_sec_auto'),
             'lines_per_sec_smooth': sd.get('lines_per_sec_smooth'),
         }
 
@@ -1000,7 +1003,7 @@ class View:
         self.iframe_wrapper.send_message('change_font_size', base_font_size=get_session_data().get('base_font_size'))
 
     def update_scroll_speed(self, amt):
-        self.iframe_wrapper.send_message('change_scroll_speed', lines_per_sec_smooth=change_scroll_speed(amt))
+        self.iframe_wrapper.send_message('change_scroll_speed', lines_per_sec_auto=change_scroll_speed(amt))
 
     def update_color_scheme(self):
         cs = self.get_color_scheme(True)

src/pyj/session.pyj

@@ -37,6 +37,7 @@ defaults = {
     'header': {},
     'hide_tooltips': False,
     'keyboard_shortcuts': {},
+    'lines_per_sec_auto': 1,
     'lines_per_sec_smooth': 30,
     'margin_bottom': 20,
     'margin_left': 20,
@@ -64,6 +65,7 @@ is_local_setting = {
     'columns_per_screen': True,
     'controls_help_shown_count': True,
     'current_color_scheme': True,
+    'lines_per_sec_auto': True,
     'lines_per_sec_smooth': True,
     'margin_bottom': True,
     'margin_left': True,