implement page-down key

diff --git a/editor.coffee b/editor.coffee
index a02e278..c78151a 100644 (file)
--- a/editor.coffee
+++ b/editor.coffee
@@ -955,6 +955,7 @@ class PeachHTML5Editor
                                @on_page_up_key e
                                return false
                        when KEY_PAGE_DOWN
+                               @on_page_down_key e
                                return false
                        when KEY_TAB
                                return false
@@ -1076,47 +1077,69 @@ class PeachHTML5Editor
                                @kill_cursor()
                return
        on_page_up_key: (e) ->
+               if @cursor?
+                       screen_y = @cursor.y - @wrap2.scrollTop
                scroll_amount = @wrap2_height - breathing_room
-               # scroll up a page
                @wrap2.scrollTop = Math.max 0, @wrap2.scrollTop - scroll_amount
-               # note: if cursor innacuracy causes it no not be within new scroll,
-               # @move_cursor will adjust the scroll a bit.
                if @cursor?
-                       # move cursor up approximately scroll_amount
-                       was = @cursor
-                       y_target = @cursor.y - scroll_amount
-                       y_min = Math.min y_target, @wrap2.scrollTop
-                       y_max = Math.min y_target, @wrap2.scrollTop - scroll_amount
-                       y_target = Math.min y_target, y_max
-                       y_target = Math.max y_target, y_min
-                       loop
-                               cur = find_up_cursor_position @tree, was, @cursor_ideal_x
-                               break unless cur?
-                               break if cur.y <= y_target
-                               was = cur
-                       if was is @cursor
-                               if cur?
-                                       new_cursor = cur
-                               else
-                                       # should this move the cursor to the beginning of the line?
-                                       new_cursor = null
+                       @move_cursor_into_view screen_y + @wrap2.scrollTop
+       on_page_down_key: (e) ->
+               if @cursor?
+                       screen_y = @cursor.y - @wrap2.scrollTop
+               scroll_amount = @wrap2_height - breathing_room
+               lowest_scrollpos = @wrap2.scrollHeight - @wrap2_height
+               @wrap2.scrollTop = Math.min lowest_scrollpos, @wrap2.scrollTop + scroll_amount
+               if @cursor?
+                       @move_cursor_into_view screen_y + @wrap2.scrollTop
+               return
+       move_cursor_into_view: (y_target) ->
+               return if y_target is @cursor.y
+               was = @cursor
+               y_min = @wrap2.scrollTop + breathing_room
+               y_max = @wrap2.scrollTop + @wrap2_height - 2 * breathing_room
+               y_target = Math.min y_target, y_max
+               y_target = Math.max y_target, y_min
+               if y_target < @cursor.y
+                       finder = find_up_cursor_position
+                       far_enough = (a, b) ->
+                               return a <= b
+               else
+                       finder = find_down_cursor_position
+                       far_enough = (a, b) ->
+                               return a >= b
+               loop
+                       cur = finder @tree, was, @cursor_ideal_x
+                       break unless cur?
+                       break if far_enough cur.y, y_target
+                       was = cur
+               if was is @cursor
+                       was = null
+               if was?
+                       if was.y > y_max
+                               was = null
+                       else if was.y < y_min
+                               was = null
+               if cur?
+                       if cur.y > y_max
+                               cur = null
+                       else if cur.y < y_min
+                               cur = null
+               if cur? and was?
+                       # both valid, pick best
+                       if cur.y < y_min
+                               new_cursor = was
+                       else if was.y > y_max
+                               new_cursor = cur
+                       else if cur.y - y_target < y_target - was.y
+                               new_cursor = cur
                        else
-                               if cur?
-                                       # both valid, pick best
-                                       if cur.y < y_min
-                                               new_cursor = was
-                                       else if was.y > y_max
-                                               new_cursor = cur
-                                       else if cur.y - y_target < y_target - was.y
-                                               new_cursor = cur
-                                       else
-                                               new_cursor = was
-                               else
-                                       new_cursor = was
-                       if new_cursor?
-                               saved_ideal_x = @cursor_ideal_x
-                               @move_cursor new_cursor
-                               @cursor_ideal_x = saved_ideal_x
+                               new_cursor = was
+               else
+                       new_cursor = was ? cur
+               if new_cursor?
+                       saved_ideal_x = @cursor_ideal_x
+                       @move_cursor new_cursor
+                       @cursor_ideal_x = saved_ideal_x
                return
        clear_dom: -> # remove all the editable content (and cursor, overlays, etc)
                while @idoc.body.childNodes.length