E-book viewer: Improve scrolling behavior when extending the selection using keyboard shortcuts

src/pyj/read_book/flow_mode.pyj

@@ -626,6 +626,27 @@ def ensure_selection_visible():
         unwrap(wrapper)
 
 
+def ensure_selection_boundary_visible(use_end):
+    sel = window.getSelection()
+    rr = sel.getRangeAt(0)
+    if rr:
+        r = rr.getBoundingClientRect()
+        if r:
+            node = sel.focusNode if use_end else sel.anchorNode
+            x = scroll_viewport.rect_inline_end(r) if use_end else scroll_viewport.rect_inline_start(r)
+            if x < 0 or x >= window.innerWidth:
+                x = scroll_viewport.viewport_to_document_inline(x, doc=node.ownerDocument)
+                if use_end:
+                    x -= line_height()
+                scroll_viewport.scroll_to_in_inline_direction(x, True)
+            y = scroll_viewport.rect_block_end(r) if use_end else scroll_viewport.rect_block_start(r)
+            if y < 0 or y >= window.innerHeight:
+                y = scroll_viewport.viewport_to_document_block(y, doc=node.ownerDocument)
+                if use_end:
+                    y -= line_height()
+                scroll_viewport.scroll_to_in_block_direction(y, True)
+
+
 def jump_to_cfi(cfi):
     # Jump to the position indicated by the specified conformal fragment
     # indicator.

src/pyj/read_book/iframe.pyj

@@ -7,11 +7,9 @@ from fs_images import fix_fullscreen_svg_images
 from gettext import gettext as _
 from iframe_comm import IframeClient
 from range_utils import (
-    highlight_associated_with_selection,
+    highlight_associated_with_selection, last_span_for_crw, reset_highlight_counter,
-    last_span_for_crw, reset_highlight_counter, select_crw, unwrap_all_crw,
+    select_crw, unwrap_all_crw, unwrap_crw, wrap_text_in_range
-    unwrap_crw, wrap_text_in_range
 )
-from read_book.hints import hint_visible_links, unhint_links, apply_prefix_to_hints
 from read_book.cfi import cfi_for_selection, range_from_cfi
 from read_book.extract import get_elements
 from read_book.find import (
@@ -19,10 +17,12 @@ from read_book.find import (
 )
 from read_book.flow_mode import (
     anchor_funcs as flow_anchor_funcs, auto_scroll_action as flow_auto_scroll_action,
-    cancel_drag_scroll as cancel_drag_scroll_flow, ensure_selection_visible,
+    cancel_drag_scroll as cancel_drag_scroll_flow,
-    flow_onwheel, flow_to_scroll_fraction, handle_gesture as flow_handle_gesture,
+    ensure_selection_boundary_visible as ensure_selection_boundary_visible_flow,
-    handle_shortcut as flow_handle_shortcut, jump_to_cfi as flow_jump_to_cfi,
+    ensure_selection_visible, flow_onwheel, flow_to_scroll_fraction,
-    layout as flow_layout, scroll_by_page as flow_scroll_by_page,
+    handle_gesture as flow_handle_gesture, handle_shortcut as flow_handle_shortcut,
+    jump_to_cfi as flow_jump_to_cfi, layout as flow_layout,
+    scroll_by_page as flow_scroll_by_page,
     scroll_to_extend_annotation as flow_annotation_scroll,
     start_drag_scroll as start_drag_scroll_flow
 )
@@ -33,11 +33,13 @@ from read_book.globals import (
     set_toc_anchor_map
 )
 from read_book.highlights import highlight_style_as_css
+from read_book.hints import apply_prefix_to_hints, hint_visible_links, unhint_links
 from read_book.mathjax import apply_mathjax
 from read_book.paged_mode import (
     anchor_funcs as paged_anchor_funcs,
     auto_scroll_action as paged_auto_scroll_action, calc_columns_per_screen,
     cancel_drag_scroll as cancel_drag_scroll_paged, current_cfi,
+    ensure_selection_boundary_visible as ensure_selection_boundary_visible_paged,
     get_columns_per_screen_data, handle_gesture as paged_handle_gesture,
     handle_shortcut as paged_handle_shortcut, jump_to_cfi as paged_jump_to_cfi,
     layout as paged_layout, onwheel as paged_onwheel, page_counts,
@@ -65,7 +67,7 @@ from read_book.touch import (
 )
 from read_book.viewport import scroll_viewport
 from select import (
-    move_end_of_selection, selection_extents, word_at_point, first_visible_word
+    first_visible_word, move_end_of_selection, selection_extents, word_at_point
 )
 from utils import debounce, is_ios
 
@@ -185,18 +187,20 @@ class IframeBoss:
 
     def modify_selection(self, data):
         sel = window.getSelection()
+        use_end = False
         if data.granularity is 'all':
             r = document.createRange()
             r.selectNode(document.body)
             sel.removeAllRanges()
             sel.addRange(r)
         else:
+            use_end = data.direction is 'forward' or data.direction is 'right'
             try:
                 sel.modify('extend', data.direction, data.granularity)
             except:
                 if data.granularity is 'paragraph':
                     sel.modify('extend', data.direction, 'line')
-        self.ensure_selection_visible()
+        self.ensure_selection_boundary_visible(use_end)
 
     def initialize(self, data):
         scroll_viewport.update_window_size(data.width, data.height)
@@ -271,6 +275,7 @@ class IframeBoss:
             self.auto_scroll_action = flow_auto_scroll_action
             self.scroll_to_extend_annotation = flow_annotation_scroll
             self.ensure_selection_visible = ensure_selection_visible
+            self.ensure_selection_boundary_visible = ensure_selection_boundary_visible_flow
             self.start_drag_scroll = start_drag_scroll_flow
             paged_auto_scroll_action('stop')
         else:
@@ -284,6 +289,7 @@ class IframeBoss:
             self.auto_scroll_action = paged_auto_scroll_action
             self.scroll_to_extend_annotation = paged_annotation_scroll
             self.ensure_selection_visible = snap_to_selection
+            self.ensure_selection_boundary_visible = ensure_selection_boundary_visible_paged
             self.start_drag_scroll = start_drag_scroll_paged
             flow_auto_scroll_action('stop')
         update_settings(data.settings)

src/pyj/read_book/paged_mode.pyj

@@ -566,6 +566,23 @@ def snap_to_selection():
         # selection
         scroll_to_pos(pos+5)
 
+
+def ensure_selection_boundary_visible(use_end):
+    sel = window.getSelection()
+    rr = sel.getRangeAt(0)
+    if rr:
+        r = rr.getBoundingClientRect()
+        if r:
+            cnum = column_at_current_scroll_offset()
+            scroll_to_column(cnum)
+            node = sel.focusNode if use_end else sel.anchorNode
+            # Columns are in the inline direction, so get the beginning of the element in the inline
+            x = scroll_viewport.rect_inline_end(r) if use_end else scroll_viewport.rect_inline_start(r)
+            if x < 0 or x >= scroll_viewport.inline_size():
+                pos = scroll_viewport.viewport_to_document_inline(x, doc=node.ownerDocument)
+                scroll_to_pos(pos+5)
+
+
 def jump_to_cfi(cfi):
     # Jump to the position indicated by the specified conformal fragment
     # indicator.

src/pyj/read_book/viewport.pyj

@@ -75,20 +75,20 @@ class ScrollViewport:
         else:
             window.scrollTo(x, y)
 
-    def scroll_to_in_inline_direction(self, pos):
+    def scroll_to_in_inline_direction(self, pos, preserve_other):
         # Lines flow vertically, so inline is vertical.
         if self.vertical_writing_mode:
-            self.scroll_to(0, pos)
+            self.scroll_to(self.x() if preserve_other else 0, pos)
         else:
-            self.scroll_to(pos, 0)
+            self.scroll_to(pos, self.y() if preserve_other else 0)
 
-    def scroll_to_in_block_direction(self, pos):
+    def scroll_to_in_block_direction(self, pos, preserve_other):
         # In horizontal modes, the block direction is vertical.
         if self.horizontal_writing_mode:
-            self.scroll_to(0, pos)
+            self.scroll_to(self.x() if preserve_other else 0, pos)
         # In vertical modes, the block direction is horizontal.
         else:
-            self.scroll_to(pos, 0)
+            self.scroll_to(pos, self.y() if preserve_other else 0)
 
     def flow_scroll_into_view(self, elem):
         elem.scrollIntoView()