Make smooth scroll speed configurable

Includes keyboard shortcuts, will add menu options next

src/pyj/read_book/flow_mode.pyj

@@ -6,6 +6,7 @@ from select import word_at_point
 
 from dom import set_css
 from read_book.globals import current_spine_item, get_boss
+from read_book.settings import opts
 from read_book.viewport import scroll_viewport
 from utils import document_height, viewport_to_document
 
@@ -167,7 +168,6 @@ def layout(is_single_page):
 DIRECTION = {'Up': -1, 'Down': 1}
 class ScrollAnimator:
     DURATION = 100 # milliseconds
-    SCROLL_SPEED = 30 # lines/sec TODO: This will be configurable
 
     def __init__(self):
         self.animation_id = None
@@ -187,7 +187,7 @@ class ScrollAnimator:
         duration = (self.end_time - self.start_time)
         progress = max(0, min(1, (ts - self.start_time) / duration)) # max/min to account for jitter
         scroll_target = self.start_offset
-        scroll_target += Math.trunc(self.direction * progress * duration * line_height() * self.SCROLL_SPEED) / 1000
+        scroll_target += Math.trunc(self.direction * progress * duration * line_height() * opts.lines_per_sec_smooth) / 1000
 
         window.scrollTo(0, scroll_target)
 
@@ -196,7 +196,7 @@ class ScrollAnimator:
         else:
             self.animation_id = None
             amt = window.pageYOffset - self.start_offset
-            if abs(amt) < 3 and duration is self.DURATION:
+            if abs(amt) < 3 and duration is self.DURATION and !(0 <= scroll_target <= document_height() - window.innerHeight):
                 get_boss().send_message('next_spine_item', previous=self.direction is DIRECTION.Up)
             else:
                 report_human_scroll(amt)

src/pyj/read_book/iframe.pyj

@@ -93,6 +93,7 @@ class IframeBoss:
         handlers = {
             'change_color_scheme': self.change_color_scheme,
             'change_font_size': self.change_font_size,
+            'change_scroll_speed': self.change_scroll_speed,
             'display': self.display,
             'find': self.find,
             'gesture_from_margin': self.gesture_from_margin,
@@ -243,6 +244,10 @@ class IframeBoss:
             opts.base_font_size = data.base_font_size
             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
+
     def change_stylesheet(self, data):
         opts.user_stylesheet = data.sheet or ''
         apply_stylesheet()

src/pyj/read_book/prefs/scrolling.pyj

@@ -11,6 +11,8 @@ from read_book.prefs.utils import create_button_box
 from session import defaults
 
 CONTAINER = unique_id('standalone-scrolling-settings')
+MIN_SCROLL_SPEED = 0.5
+MAX_SCROLL_SPEED = 50
 
 
 def restore_defaults():
@@ -23,6 +25,15 @@ def get_container():
     return document.getElementById(CONTAINER)
 
 
+def change_scroll_speed(amt):
+    sd = get_session_data()
+    lps = sd.get('lines_per_sec_smooth')
+    nlps = max(MIN_SCROLL_SPEED, min(lps + amt, MAX_SCROLL_SPEED))
+    if nlps != lps:
+        sd.set('lines_per_sec_smooth', nlps)
+    return nlps
+
+
 def create_scrolling_panel(container, apply_func, cancel_func):
     container.appendChild(E.div(id=CONTAINER, style='margin: 1rem'))
     container = container.lastChild

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_smooth = settings.lines_per_sec_smooth
     opts.margin_left = max(0, settings.margin_left)
     opts.margin_right = max(0, settings.margin_right)
     opts.override_book_colors = settings.override_book_colors

src/pyj/read_book/shortcuts.pyj

@@ -270,6 +270,18 @@ def shortcuts_definition():
         _('Go to a specified book location or position'),
     ),
 
+    'scrollspeed_increase': desc(
+        "Alt+ArrowUp",
+        'scroll',
+        _('Smooth scroll faster'),
+    ),
+
+    'scrollspeed_decrease': desc(
+        "Alt+ArrowDown",
+        'scroll',
+        _('Smooth scroll slower'),
+    ),
+
     }
     return ans
 

src/pyj/read_book/view.pyj

@@ -23,6 +23,7 @@ from read_book.overlay import Overlay
 from read_book.prefs.colors import resolve_color_scheme
 from read_book.prefs.font_size import change_font_size_by
 from read_book.prefs.head_foot import render_head_foot
+from read_book.prefs.scrolling import change_scroll_speed, MIN_SCROLL_SPEED as SCROLL_SPEED_STEP
 from read_book.resources import load_resources
 from read_book.search import SearchOverlay, find_in_spine
 from read_book.shortcuts import create_shortcut_map
@@ -409,6 +410,10 @@ class View:
             self.iframe_wrapper.send_message('modify_selection', direction='backward', granularity='word')
         elif data.name is 'extend_selection_by_word':
             self.iframe_wrapper.send_message('modify_selection', direction='forward', granularity='word')
+        elif data.name is 'scrollspeed_increase':
+            self.update_scroll_speed(SCROLL_SPEED_STEP)
+        elif data.name is 'scrollspeed_decrease':
+            self.update_scroll_speed(-SCROLL_SPEED_STEP)
 
     def on_selection_change(self, data):
         self.currently_showing.selected_text = data.text
@@ -703,6 +708,7 @@ 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_smooth': sd.get('lines_per_sec_smooth'),
         }
 
     def show_name(self, name, initial_position=None):
@@ -993,6 +999,9 @@ class View:
     def update_font_size(self):
         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))
+
     def update_color_scheme(self):
         cs = self.get_color_scheme(True)
         self.iframe_wrapper.send_message('change_color_scheme', color_scheme=cs)

src/pyj/session.pyj

@@ -37,6 +37,7 @@ defaults = {
     'header': {},
     'hide_tooltips': False,
     'keyboard_shortcuts': {},
+    'lines_per_sec_smooth': 30,
     'margin_bottom': 20,
     'margin_left': 20,
     'margin_right': 20,
@@ -63,6 +64,7 @@ is_local_setting = {
     'columns_per_screen': True,
     'controls_help_shown_count': True,
     'current_color_scheme': True,
+    'lines_per_sec_smooth': True,
     'margin_bottom': True,
     'margin_left': True,
     'margin_right': True,