Merge pull request #111 from luhuaei/master

            self.scroll_offset = new_offset

            self.update()

    def get_event_link(self, event):

        start_page_index = self.get_start_page_index()

        last_page_index = self.get_last_page_index()

        translate_y = (start_page_index * self.scale * self.page_height) - self.scroll_offset

        ex = event.globalX()

        ey = event.globalY()

        for index in list(range(start_page_index, last_page_index)):

            if index < self.page_total_number:

                page = self.document[index]

                for link in page.getLinks():

                    rect = link["from"]

                    link_x_start = int(rect.x0 * self.scale)

                    link_x_end = int(rect.x1 * self.scale)

                    link_y_start = int(rect.y0 * self.scale + translate_y)

                    link_y_end = int(rect.y1 * self.scale + translate_y)

                    if ex >= link_x_start and ex <= link_x_end and ey >= link_y_start and ey <= link_y_end:

                        if link["page"]:

                            return link

        return None

    def get_double_click_word(self, event):

    def get_event_absolute_position(self, event):

        start_page_index = self.get_start_page_index()

        last_page_index = self.get_last_page_index()

        pos = event.pos()

                x = int((pos.x() - render_x) * 1.0 / self.scale)

                if pos.y() + self.scroll_offset < (start_page_index + 1) * self.scale * self.page_height:

                    page_offset = self.scroll_offset - start_page_index * self.scale * self.page_height

                    page = self.document[index]

                    page_index = index

                else:

                    # if display two pages, pos.y() will add page_padding

                    page_offset = self.scroll_offset - (start_page_index + 1) * self.scale * self.page_height - self.page_padding

                    page = self.document[index + 1]

                    page_index = index + 1

                y = int((pos.y() + page_offset) * 1.0 / self.scale)

                return x, y, page_index

        return None, None, None

    def get_event_link(self, event):

        ex, ey, page_index = self.get_event_absolute_position(event)

        if page_index is None:

            return None

        page = self.document[page_index]

        for link in page.getLinks():

            rect = link["from"]

            if ex >= rect.x0 and ex <= rect.x1 and ey >= rect.y0 and ey <= rect.y1:

                if link["page"]:

                    return link

        return None

    def get_double_click_word(self, event):

        ex, ey, page_index = self.get_event_absolute_position(event)

        if page_index is None:

            return None

        page = self.document[page_index]

        word_offset = 10 # 10 pixel is enough for word intersect operation

                draw_rect = fitz.Rect(x, y, x + word_offset, y + word_offset)

        draw_rect = fitz.Rect(ex, ey, ex + word_offset, ey + word_offset)

        page.setCropBox(page.rect)

        page_words = page.getTextWords()

        if rect_words:

            return rect_words[0][4]

        return None

    def enterEvent(self, event):

        pass

    def eventFilter(self, obj, event):

        if event.type() == QEvent.MouseButtonPress: