E-book viewer: Fix clicking links going to slightly incorrect locations in some books. Fixes #1132641 (Private bug)

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

@@ -81,6 +81,11 @@ class BookIndexing
             if elem == null
                 pos = [body.scrollWidth+1000, body.scrollHeight+1000]
             else
+                # Because of a bug in WebKit's getBoundingClientRect() in
+                # column mode, this position can be inaccurate,
+                # see https://bugs.launchpad.net/calibre/+bug/1132641 for a
+                # test case. The usual symptom of the inaccuracy is br.top is
+                # highly negative.
                 br = elem.getBoundingClientRect()
                 pos = viewport_to_document(br.left, br.top, elem.ownerDocument)
 

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

@@ -410,7 +410,7 @@ class PagedDisplay
         elem.scrollIntoView()
         if this.in_paged_mode
             # Ensure we are scrolled to the column containing elem
-            this.scroll_to_xpos(calibre_utils.absleft(elem) + 5)
+            this.scroll_to_xpos(calibre_utils.viewport_to_document(elem.scrollLeft+this.margin_side, elem.scrollTop, elem.ownerDocument)[0])
 
     snap_to_selection: () ->
         # Ensure that the viewport is positioned at the start of the column

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

@@ -86,7 +86,9 @@ class CalibreUtils
     absleft: (elem) -> # {{{
         # The left edge of elem in document co-ords. Works in all
         # circumstances, including column layout. Note that this will cause
-        # a relayout if the render tree is dirty.
+        # a relayout if the render tree is dirty. Also, because of a bug in the
+        # version of WebKit bundled with Qt 4.8, this does not always work, see
+        # https://bugs.launchpad.net/bugs/1132641 for a test case.
         r = elem.getBoundingClientRect()
         return this.viewport_to_document(r.left, 0, elem.ownerDocument)[0]
     # }}}