From 0c5959f2983cd863ee87dd956b4881c1ba077003 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 18 Jul 2013 10:03:30 +0530
Subject: [PATCH] PDF Output: Fix anchors sometimes located incorrectly

PDF Output: Workaround bug in WebKit's getBoundingClientRect() method
that could cause links to occasionally point to incorrect locations.
Fixes #1202390 [Private bug](https://bugs.launchpad.net/calibre/+bug/1202390)
---
 resources/compiled_coffeescript.zip         | Bin 71983 -> 72211 bytes
 src/calibre/ebooks/oeb/display/paged.coffee |  16 ++++++++++++++--
 src/calibre/ebooks/pdf/render/from_html.py  |   1 +
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/resources/compiled_coffeescript.zip b/resources/compiled_coffeescript.zip
index 3c5f0e80c6f57fd0b309fa8ea039fcfcd3f1e310..ddf0db08e77d28f55c7eb8344a7899e938a18244 100644
GIT binary patch
delta 260
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zuk7S*Al|R0!=IXynyXiwT$G=a<CB_JGI^h$>SSJZ^~onK1zF>ZQqv44_v`CVw#}3V
zit=(AMjOQHD3s(EOpbXVy}8f&j~w$#*H4>!qkin>L$!DMWHCl-kmU4>VvN#EDbbTR
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h(;Fp#@|C|QZ~P@c{S1g5!!iAb1fwBatT-dk%K$LVTLJ(8

delta 224
zcmbQdg=PIF7Ks3FW)=|!5LmwUqtihXQ5W|p1_t-2$-S+T)8~mZa%{9*Z#DV7mEq)r
zYFd+JZ44(%sY`7xviT#&{A$g|&4tlFcJra?oL(-@XsrO0bXrvtbDKqsfdPc&z;?ih
zhN#ICTScco7iTnOI#2*+8%r=+Fiouju_v#p=9=Ck!KlSFu?5JNoqiR>c9=AsQIgS}
psdXk;eY_;20n^l9(<e$YdNNnAGfsA#EIj>#B%>@_r5Gd79stY?N45X}

diff --git a/src/calibre/ebooks/oeb/display/paged.coffee b/src/calibre/ebooks/oeb/display/paged.coffee
index f97f1b3cf8..39c4b12fe9 100644
--- a/src/calibre/ebooks/oeb/display/paged.coffee
+++ b/src/calibre/ebooks/oeb/display/paged.coffee
@@ -294,9 +294,21 @@ class PagedDisplay
         return Math.floor(xpos/this.page_width)
 
     column_location: (elem) ->
-        # Return the location of elem relative to its containing column
+        # Return the location of elem relative to its containing column.
+        # WARNING: This method may cause the viewport to scroll (to workaround
+        # a bug in WebKit).
         br = elem.getBoundingClientRect()
-        [left, top] = calibre_utils.viewport_to_document(br.left, br.top, elem.ownerDocument)
+        # Because of a bug in WebKit's getBoundingClientRect() in column
+        # mode, this position can be inaccurate, see
+        # https://bugs.launchpad.net/calibre/+bug/1202390 for a test case.
+        # The usual symptom of the inaccuracy is br.top is highly negative.
+        if br.top < -100
+            # We have to actually scroll the element into view to get its
+            # position
+            elem.scrollIntoView()
+            [left, top] = calibre_utils.viewport_to_document(elem.scrollLeft, elem.scrollTop, elem.ownerDocument)
+        else
+            [left, top] = calibre_utils.viewport_to_document(br.left, br.top, elem.ownerDocument)
         c = this.column_at(left)
         width = Math.min(br.right, (c+1)*this.page_width) - br.left
         if br.bottom < br.top
diff --git a/src/calibre/ebooks/pdf/render/from_html.py b/src/calibre/ebooks/pdf/render/from_html.py
index 8ea1d8203e..771cc33ede 100644
--- a/src/calibre/ebooks/pdf/render/from_html.py
+++ b/src/calibre/ebooks/pdf/render/from_html.py
@@ -353,6 +353,7 @@ class PDFWriter(QObject):
         paged_display.layout();
         paged_display.fit_images();
         py_bridge.value = book_indexing.all_links_and_anchors();
+        window.scrollTo(0, 0); // This is needed as getting anchor positions could have caused the viewport to scroll
         '''%(self.margin_top, 0, self.margin_bottom))
 
         amap = self.bridge_value