From ce9983233737189b6ebc55345a97598bda6aea18 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 25 Jan 2014 16:52:28 +0530
Subject: [PATCH] Context menu actions to go to next/previous change

---
 src/calibre/gui2/tweak_book/diff.py | 38 ++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/calibre/gui2/tweak_book/diff.py b/src/calibre/gui2/tweak_book/diff.py
index 3f244460cf..2a08388a57 100644
--- a/src/calibre/gui2/tweak_book/diff.py
+++ b/src/calibre/gui2/tweak_book/diff.py
@@ -48,6 +48,7 @@ class TextBrowser(PlainTextEdit):  # {{{
 
     resized = pyqtSignal()
     wheel_event = pyqtSignal(object)
+    goto_change = pyqtSignal(object)
 
     def __init__(self, right=False, parent=None):
         PlainTextEdit.__init__(self, parent)
@@ -114,6 +115,30 @@ class TextBrowser(PlainTextEdit):  # {{{
         i = unicode(self.textCursor().selectedText())
         if i:
             a(QIcon(I('edit-copy.png')), _('Copy to clipboard'), self.copy)
+
+        if len(self.changes) > 0:
+            try:
+                b = self.cursorForPosition(pos).block().blockNumber()
+            except Exception:
+                b = -1
+            if b > -1:
+                pc = nc = None
+                for i, (top, bot, kind) in enumerate(self.changes):
+                    if top <= b and bot >= b:
+                        if len(self.changes) == 1:
+                            break
+                        pc = (i - 1) % len(self.changes)
+                        nc = (i + 1) % len(self.changes)
+                    if bot < b:
+                        pc = i
+                    if top > b:
+                        nc = i
+                        break
+                if pc is not None:
+                    a(QIcon(I('arrow-up.png')), _('Previous change'), partial(self.goto_change.emit, pc))
+                if nc is not None:
+                    a(QIcon(I('arrow-down.png')), _('Next change'), partial(self.goto_change.emit, nc))
+
         if len(m.actions()) > 0:
             m.exec_(self.mapToGlobal(pos))
 
@@ -755,6 +780,17 @@ class DiffView(QWidget):  # {{{
         self.view.left.resized.connect(self.resized)
         for v in self.view.left, self.view.right, self.view.handle(1):
             v.wheel_event.connect(self.scrollbar.wheelEvent)
+            if hasattr(v, 'goto_change'):
+                v.goto_change.connect(self.goto_change)
+
+    def goto_change(self, change):
+        for v in (self.view.left, self.view.right):
+            c = QTextCursor(v.document().findBlockByNumber(v.changes[change][0]))
+            v.setTextCursor(c)
+            v.centerCursor()
+        with self:
+            self.scroll_to(0, self.get_position_from_scrollbar(1))
+        self.view.handle(1).update()
 
     def resized(self):
         self.resize_timer.start(100)
@@ -805,7 +841,7 @@ class DiffView(QWidget):  # {{{
             val = start + offset
         bar.setValue(val - syncpos)
 
-    def scrolled(self, which):
+    def scrolled(self, which, *args):
         if self.syncing:
             return
         position = self.get_position_from_scrollbar(which)