Proper CFI calculation for paged mode

src/calibre/ebooks/oeb/display/cfi.coffee

@@ -572,6 +572,44 @@ class CanonicalFragmentIdentifier
         null
     # }}}
 
+    at_point: (ox, oy) ->
+        # The CFI at the specified point. Different to at() in that this method
+        # returns null if there is an error, and also calculates a point from
+        # the CFI and returns null if the calculated point is far from the
+        # original point.
+
+        dist = (p1, p2) ->
+            Math.sqrt(Math.pow(p1[0]-p2[0], 2), Math.pow(p1[1]-p2[1], 2))
+
+        try
+            cfi = window.cfi.at(ox, oy)
+            point = window.cfi.point(cfi)
+        catch err
+            cfi = null
+
+
+        if cfi
+            if point.range != null
+                r = point.range
+                rect = r.getClientRects()[0]
+
+                x = (point.a*rect.left + (1-point.a)*rect.right)
+                y = (rect.top + rect.bottom)/2
+                [x, y] = viewport_to_document(x, y, r.startContainer.ownerDocument)
+            else
+                node = point.node
+                r = node.getBoundingClientRect()
+                [x, y] = viewport_to_document(r.left, r.top, node.ownerDocument)
+                if typeof(point.x) == 'number' and node.offsetWidth
+                    x += (point.x*node.offsetWidth)/100
+                if typeof(point.y) == 'number' and node.offsetHeight
+                    y += (point.y*node.offsetHeight)/100
+
+            if dist(viewport_to_document(ox, oy), [x, y]) > 50
+                cfi = null
+
+        return cfi
+
     at_current: () -> # {{{
         [winx, winy] = window_scroll_pos()
         [winw, winh] = [window.innerWidth, window.innerHeight]
@@ -585,44 +623,12 @@ class CanonicalFragmentIdentifier
         minx = max(-winx, -winw)
         maxx = winw
 
-        dist = (p1, p2) ->
+        x_loop = (cury) =>
-            Math.sqrt(Math.pow(p1[0]-p2[0], 2), Math.pow(p1[1]-p2[1], 2))
-
-        get_cfi = (ox, oy) ->
-            try
-                cfi = window.cfi.at(ox, oy)
-                point = window.cfi.point(cfi)
-            catch err
-                cfi = null
-
-            if cfi
-                if point.range != null
-                    r = point.range
-                    rect = r.getClientRects()[0]
-
-                    x = (point.a*rect.left + (1-point.a)*rect.right)
-                    y = (rect.top + rect.bottom)/2
-                    [x, y] = viewport_to_document(x, y, r.startContainer.ownerDocument)
-                else
-                    node = point.node
-                    r = node.getBoundingClientRect()
-                    [x, y] = viewport_to_document(r.left, r.top, node.ownerDocument)
-                    if typeof(point.x) == 'number' and node.offsetWidth
-                        x += (point.x*node.offsetWidth)/100
-                    if typeof(point.y) == 'number' and node.offsetHeight
-                        y += (point.y*node.offsetHeight)/100
-
-                if dist(viewport_to_document(ox, oy), [x, y]) > 50
-                    cfi = null
-
-            return cfi
-
-        x_loop = (cury) ->
             for direction in [-1, 1]
                 delta = deltax * direction
                 curx = 0
                 until (direction < 0 and curx < minx) or (direction > 0 and curx > maxx)
-                    cfi = get_cfi(curx, cury)
+                    cfi = this.at_point(curx, cury)
                     if cfi
                         return cfi
                     curx += delta

src/calibre/ebooks/oeb/display/paged.coffee

@@ -67,6 +67,8 @@ class PagedDisplay
     ###
 
     constructor: () ->
+        if not this instanceof arguments.callee
+            throw new Error('PagedDisplay constructor called as function')
         this.set_geometry()
         this.page_width = 0
         this.screen_width = 0
@@ -213,11 +215,11 @@ class PagedDisplay
         # most column in the viewport is the column containing the start of the
         # element and that the scroll position is at the start of the column.
         elem = document.getElementById(name)
-        if !elem
+        if not elem
             elems = document.getElementsByName(name)
             if elems
                 elem = elems[0]
-        if !elem
+        if not elem
             return
         elem.scrollIntoView()
         if this.in_paged_mode
@@ -249,12 +251,48 @@ class PagedDisplay
                 window.scrollTo(0, y)
         )
 
+    current_cfi: () ->
+        # The Conformal Fragment Identifier at the current position, returns
+        # null if it could not be calculated. Requires the cfi.coffee library.
+        ans = null
+        if not window.cfi?
+            return ans
+        if this.in_paged_mode
+            c = this.current_column_location()
+            for x in [c, c-this.page_width, c+this.page_width]
+                # Try the current column, the previous column and the next
+                # column. Each column is tried from top to bottom.
+                [left, right] = [x, x + this.page_width]
+                if left < 0 or right > document.body.scrollWidth
+                    continue
+                deltax = Math.floor(this.page_width/25)
+                deltay = Math.floor(window.innerHeight/25)
+                cury = this.margin_top
+                until cury >= (window.innerHeight - this.margin_bottom)
+                    curx = left + this.current_margin_side
+                    until curx >= (right - this.current_margin_side)
+                        cfi = window.cfi.at_point(curx-window.pageXOffset, cury-window.pageYOffset)
+                        if cfi
+                            log('Viewport cfi:', cfi)
+                            return cfi
+                        curx += deltax
+                    cury += deltay
+        else
+            try
+                ans = window.cfi.at_current()
+                if not ans
+                    ans = null
+            catch err
+                log(err)
+        if ans
+            log('Viewport cfi:', ans)
+        return ans
+
 if window?
     window.paged_display = new PagedDisplay()
 
 # TODO:
 # css pagebreak rules
-# CFI and bookmarks
 # Go to reference positions
 # Indexing
 # Resizing of images

src/calibre/gui2/viewer/position.py

@@ -19,13 +19,10 @@ class PagePosition(object):
         ans = None
         res = self.document.mainFrame().evaluateJavaScript('''
             ans = 'undefined';
-            try {
+            if (window.paged_display) {
-                ans = window.cfi.at_current();
+                ans = window.paged_display.current_cfi();
                 if (!ans) ans = 'undefined';
-            } catch (err) {
-                window.console.log(err);
             }
-            window.console.log("Viewport cfi: " + ans);
             ans;
         ''')
         if res.isValid() and not res.isNull() and res.type() == res.String: