E-book viewer: Try to preserve page position when the window is resized

src/calibre/gui2/viewer/documentview.py

@@ -8,7 +8,7 @@ import os, math, re, glob, sys, zipfile
 from base64 import b64encode
 from functools import partial
 
-from PyQt4.Qt import (QSize, QSizePolicy, QUrl, SIGNAL, Qt, QTimer,
+from PyQt4.Qt import (QSize, QSizePolicy, QUrl, SIGNAL, Qt,
                      QPainter, QPalette, QBrush, QFontDatabase, QDialog,
                      QColor, QPoint, QImage, QRegion, QVariant, QIcon,
                      QFont, pyqtSignature, QAction, QByteArray, QMenu,
@@ -184,12 +184,10 @@ class Document(QWebPage): # {{{
                 self.misc_config()
                 self.after_load()
 
-    def __init__(self, shortcuts, parent=None, resize_callback=lambda: None,
-            debug_javascript=False):
+    def __init__(self, shortcuts, parent=None, debug_javascript=False):
         QWebPage.__init__(self, parent)
         self.setObjectName("py_bridge")
         self.debug_javascript = debug_javascript
-        self.resize_callback = resize_callback
         self.current_language = None
         self.loaded_javascript = False
         self.js_loader = JavaScriptLoader(
@@ -259,12 +257,6 @@ class Document(QWebPage): # {{{
         if self.loaded_javascript:
             return
         self.loaded_javascript = True
-        self.javascript(
-            '''
-            window.onresize = function(event) {
-                window.py_bridge.window_resized();
-            }
-            ''')
         self.loaded_lang = self.js_loader(self.mainFrame().evaluateJavaScript,
                 self.current_language, self.hyphenate_default_lang)
 
@@ -310,10 +302,6 @@ class Document(QWebPage): # {{{
     def debug(self, msg):
         prints(msg)
 
-    @pyqtSignature('')
-    def window_resized(self):
-        self.resize_callback()
-
     def reference_mode(self, enable):
         self.javascript(('enter' if enable else 'leave')+'_reference_mode()')
 
@@ -444,7 +432,7 @@ class Document(QWebPage): # {{{
     def scroll_fraction(self):
         def fget(self):
             try:
-                return float(self.ypos)/(self.height-self.window_height)
+                return abs(float(self.ypos)/(self.height-self.window_height))
             except ZeroDivisionError:
                 return 0.
         def fset(self, val):
@@ -516,7 +504,6 @@ class DocumentView(QWebView): # {{{
         self.initial_pos = 0.0
         self.to_bottom = False
         self.document = Document(self.shortcuts, parent=self,
-                resize_callback=self.viewport_resized,
                 debug_javascript=debug_javascript)
         self.setPage(self.document)
         self.manager = None
@@ -1035,13 +1022,9 @@ class DocumentView(QWebView): # {{{
         return handled
 
     def resizeEvent(self, event):
-        ret = QWebView.resizeEvent(self, event)
-        QTimer.singleShot(10, self.initialize_scrollbar)
-        return ret
-
-    def viewport_resized(self):
         if self.manager is not None:
-            self.manager.viewport_resized(self.scroll_fraction)
+            self.manager.viewport_resize_started(event)
+        return QWebView.resizeEvent(self, event)
 
     def event(self, ev):
         if ev.type() == ev.Gesture:

src/calibre/gui2/viewer/main.py

@@ -224,6 +224,10 @@ class EbookViewer(MainWindow, Ui_EbookViewer):
         self.toc.setVisible(False)
         self.action_quit = QAction(self)
         self.addAction(self.action_quit)
+        self.view_resized_timer = QTimer(self)
+        self.view_resized_timer.timeout.connect(self.viewport_resize_finished)
+        self.view_resized_timer.setSingleShot(True)
+        self.resize_in_progress = False
         qs = [Qt.CTRL+Qt.Key_Q]
         if isosx:
             qs += [Qt.CTRL+Qt.Key_W]
@@ -301,8 +305,6 @@ class EbookViewer(MainWindow, Ui_EbookViewer):
                     _('Press Esc to quit')),
                     self)
         self.full_screen_label.setVisible(False)
-        self.window_mode_toggle_timer = QTimer(self)
-        self.window_mode_toggle_timer.timeout.connect(self.handle_window_mode_toggle)
         self.full_screen_label.setStyleSheet('''
         QLabel {
             text-align: center;
@@ -693,20 +695,28 @@ class EbookViewer(MainWindow, Ui_EbookViewer):
         self.open_progress_indicator(_('Laying out %s')%self.current_title)
         self.view.load_path(path, pos=pos)
 
-    def viewport_resized(self, frac):
+    def viewport_resize_started(self, event):
+        if not self.resize_in_progress:
+            # First resize, so save the current page position
+            self.resize_in_progress = True
+            if not self.window_mode_changed:
+                # The special handling for window mode changed will already
+                # have saved page position, so only save it if this is not a
+                # mode change
+                self.view.document.page_position.save()
+
+        if self.resize_in_progress:
+            self.view_resized_timer.start(75)
+
+    def viewport_resize_finished(self):
+        # There hasn't been a resize event for some time
+        # restore the current page position.
+        self.resize_in_progress = False
         if self.window_mode_changed:
-            # Soak up extra window resize events
-            self.window_mode_toggle_timer.start(15)
-            return
-        new_page = self.pos.value()
-        if self.current_page is not None:
-            try:
-                frac = float(new_page-self.current_page.start_page)/(self.current_page.pages-1)
-            except ZeroDivisionError:
-                frac = 0
-            self.view.scroll_to(frac, notify=False)
+            # This resize is part of a window mode change, special case it
+            self.handle_window_mode_toggle()
         else:
-            self.set_page_number(frac)
+            self.view.document.page_position.restore()
 
     def close_progress_indicator(self):
         self.pi.stop()