From 9c244a873b0f819fda54edea84a26e14f959a6c2 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 6 Sep 2014 21:14:21 +0530
Subject: [PATCH] E-book viewer: Try to detect when a chapter has a page break
 near the start resulting in a blank page and override the page break. Fixes
 #1366074 [Private bug](https://bugs.launchpad.net/calibre/+bug/1366074)

---
 resources/compiled_coffeescript.zip         | Bin 92292 -> 93276 bytes
 src/calibre/ebooks/oeb/display/paged.coffee |  40 +++++++++++++++++---
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/resources/compiled_coffeescript.zip b/resources/compiled_coffeescript.zip
index cdb6a36af848c58dcceb79f1613c7bbf98c09a11..8547c11ebe6666052303a33902e138f031a9fae4 100644
GIT binary patch
delta 1006
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z3&oP6=7F|J^L3{Jb#_@CmTegfxR`fPS-%s`&td2qV%+(tAV<LSc-2s=d1X^i%=*lo
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SCf)sL7cue3xOiPc-_UPm<vhXw

delta 414
zcmca}gSF)%>xKz4_!MHwUDmypTy2!Vz+jXx`QabQ$=hdiZjPNfiE*>|yd**X{G9mm
z%#@N09fjol(!7$%t?TzrmTTkK9JqmpRW~I+ximL5uS72?Kc!MHEwiY&#5p4~C&ije
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diff --git a/src/calibre/ebooks/oeb/display/paged.coffee b/src/calibre/ebooks/oeb/display/paged.coffee
index 8ed5ae0da1..6a922ac043 100644
--- a/src/calibre/ebooks/oeb/display/paged.coffee
+++ b/src/calibre/ebooks/oeb/display/paged.coffee
@@ -12,6 +12,26 @@ runscripts = (parent) ->
     for script in parent.getElementsByTagName('script')
         eval(script.text || script.textContent || script.innerHTML || '')
 
+first_child = (parent) ->
+    c = parent.firstChild
+    count = 0
+    while c?.nodeType != 1 and count < 20
+        c = c?.nextSibling
+        count += 1
+    if c?.nodeType == 1
+        return c
+    return null
+
+has_start_text = (elem) ->
+    # Returns true if elem has some non-whitespace text before its first child
+    # element
+    for c in elem.childNodes
+        if c.nodeType not in [Node.TEXT_NODE, Node.COMMENT_NODE, Node.PROCESSING_INSTRUCTION_NODE]
+            break
+        if c.nodeType == Node.TEXT_NODE and c.nodeValue != null and /\S/.test(c.nodeValue)
+            return true
+    return false
+
 class PagedDisplay
     # This class is a namespace to expose functions via the
     # window.paged_display object. The most important functions are:
@@ -144,13 +164,21 @@ class PagedDisplay
         # Otherwise, you could end up with an effective negative margin, I dont
         # understand exactly why, but see:
         # https://bugs.launchpad.net/calibre/+bug/1082640 for an example
-        c = document.body.firstChild
-        count = 0
-        while c?.nodeType != 1 and count < 20
-            c = c?.nextSibling
-            count += 1
-        if c?.nodeType == 1
+        c = first_child(document.body)
+        if c != null
             c.style.setProperty('-webkit-margin-before', '0')
+            # Remove page breaks on the first few elements to prevent blank pages
+            # at the start of a chapter
+            c.style.setProperty('-webkit-column-break-before', 'avoid')
+            if c.tagName?.toLowerCase() == 'div'
+                c2 = first_child(c)
+                if c2 != null and not has_start_text(c)
+                    # Common pattern of all content being enclosed in a wrapper
+                    # <div>, see for example: https://bugs.launchpad.net/bugs/1366074
+                    # In this case, we also modify the first child of the div
+                    # as long as there was no text before it.
+                    c2.style.setProperty('-webkit-column-break-before', 'avoid')
+
 
         this.effective_margin_top = this.margin_top
         this.effective_margin_bottom = this.margin_bottom