PDF Output: Fix a regression that caused the last page of a chapter t…

…o sometimes be dropped from the output

src/calibre/ebooks/pdf/render/engine.py

@@ -285,7 +285,8 @@ def drawTextItem(self, point, text_item):
             last_x, last_y = x, y
 
         if not self.content_written_to_current_page:
-            ypositions = [y for x, y in gi.positions]
+            painter_top = self.painter().clipPath().boundingRect().y()
+            ypositions = [y - painter_top for x, y in gi.positions]
             miny = min(ypositions or (0,))
             maxy = max(ypositions or (self.pixel_height,))
             page_top = self.header_height if self.has_headers else 0