improve performance of preview

Fixes: https://launchpad.net/bugs/856296

openlp/core/lib/renderer.py

@@ -201,7 +201,8 @@ class Renderer(object):
         if not self.force_page:
             self.display.buildHtml(serviceItem)
             raw_html = serviceItem.get_rendered_frame(0)
-            preview = self.display.text(raw_html)
+            self.display.text(raw_html)
+            preview = self.display.preview()
             # Reset the real screen size for subsequent render requests
             self._calculate_default()
             return preview

openlp/core/ui/maindisplay.py

@@ -194,7 +194,6 @@ class MainDisplay(QtGui.QGraphicsView):
         self.setGeometry(self.screen[u'size'])
         self.frame.evaluateJavaScript(u'show_text("%s")' %
             slide.replace(u'\\', u'\\\\').replace(u'\"', u'\\\"'))
-        return self.preview()
 
     def alert(self, text):
         """
@@ -256,7 +255,6 @@ class MainDisplay(QtGui.QGraphicsView):
         image = self.imageManager.get_image_bytes(name)
         self.resetVideo()
         self.displayImage(image)
-        return self.preview()
 
     def displayImage(self, image):
         """
@@ -387,7 +385,6 @@ class MainDisplay(QtGui.QGraphicsView):
         # Update the preview frame.
         if self.isLive:
             Receiver.send_message(u'maindisplay_active')
-        return self.preview()
 
     def videoState(self, newState, oldState):
         """
@@ -455,9 +452,8 @@ class MainDisplay(QtGui.QGraphicsView):
                         self.setVisible(True)
                 else:
                     self.setVisible(True)
-        preview = QtGui.QImage(self.screen[u'size'].width(),
-            self.screen[u'size'].height(),
-            QtGui.QImage.Format_ARGB32_Premultiplied)
+        preview = QtGui.QPixmap(self.screen[u'size'].width(),
+            self.screen[u'size'].height())
         painter = QtGui.QPainter(preview)
         painter.setRenderHint(QtGui.QPainter.Antialiasing)
         self.frame.render(painter)

openlp/core/ui/slidecontroller.py

@@ -940,16 +940,15 @@ class SlideController(QtGui.QWidget):
             else:
                 toDisplay = self.serviceItem.get_rendered_frame(row)
                 if self.serviceItem.is_text():
-                    frame = self.display.text(toDisplay)
+                    self.display.text(toDisplay)
                 else:
                     if start:
                         self.display.buildHtml(self.serviceItem, toDisplay)
-                        frame = self.display.preview()
                     else:
-                        frame = self.display.image(toDisplay)
+                        self.display.image(toDisplay)
                     # reset the store used to display first image
                     self.serviceItem.bg_image_bytes = None
-                self.slidePreview.setPixmap(QtGui.QPixmap.fromImage(frame))
+                self.slidePreview.setPixmap(self.display.preview())
             self.selectedRow = row
             self.__checkUpdateSelectedSlide(row)
         Receiver.send_message(u'slidecontroller_%s_changed' % self.typePrefix,
@@ -977,8 +976,7 @@ class SlideController(QtGui.QWidget):
             QtCore.QTimer.singleShot(0.5, self.grabMainDisplay)
             QtCore.QTimer.singleShot(2.5, self.grabMainDisplay)
         else:
-            self.slidePreview.setPixmap(
-                QtGui.QPixmap.fromImage(self.display.preview()))
+            self.slidePreview.setPixmap(self.display.preview())
 
     def grabMainDisplay(self):
         """

openlp/core/ui/themeform.py

@@ -232,7 +232,7 @@ class ThemeForm(QtGui.QWizard, Ui_ThemeWizard):
         if self.page(pageId) == self.previewPage:
             self.updateTheme()
             frame = self.thememanager.generateImage(self.theme)
-            self.previewBoxLabel.setPixmap(QtGui.QPixmap.fromImage(frame))
+            self.previewBoxLabel.setPixmap(frame)
             self.displayAspectRatio = float(frame.width()) / frame.height()
             self.resizeEvent()