global reviewer override, fix fading in previewer/clayout

you can use the debug console to define custom html/css/js to be added
to the bottom of the reviewer on all note types, so to increase the fade
time on the question you'd use

mw.col.conf["reviewExtra"]="<script>qFade=500;</script>"
mw.col.setMod()

also make sure the fading for question/answer is used correctly in
previewer, and use answer fading in clayout to speed it up

aqt/browser.py

@@ -1118,7 +1118,7 @@ where id in %s""" % ids2str(sf))
         jsinc = ["jquery.js","browsersel.js",
                  "mathjax/conf.js", "mathjax/MathJax.js",
                  "reviewer.js"]
-        self._previewWeb.stdHtml(self.mw.reviewer._revHtml,
+        self._previewWeb.stdHtml(self.mw.reviewer.revHtml(),
                                  css=["reviewer.css"],
                                  head=base, js=jsinc)
 
@@ -1146,6 +1146,7 @@ where id in %s""" % ids2str(sf))
             return
         c = self.card
         self._updatePreviewButtons()
+        func = "_showQuestion"
         if not c or not self.singleCard:
             txt = _("(please select 1 card)")
             bodyclass = ""
@@ -1155,6 +1156,7 @@ where id in %s""" % ids2str(sf))
             # need to force reload even if answer
             txt = c.q(reload=True)
             if self._previewState == "answer":
+                func = "_showAnswer"
                 txt = c.a()
             txt = re.sub("\[\[type:[^]]+\]\]", "", txt)
 
@@ -1167,7 +1169,7 @@ where id in %s""" % ids2str(sf))
             txt = mungeQA(self.col, txt)
 
         self._previewWeb.eval(
-            "_showQuestion(%s,'%s');" % (json.dumps(txt), bodyclass))
+            f"{func}({json.dumps(txt)},'{bodyclass}');")
 
     # Card deletion
     ######################################################################

aqt/clayout.py

@@ -174,10 +174,10 @@ class CardLayout(QDialog):
         jsinc = ["jquery.js","browsersel.js",
                  "mathjax/conf.js", "mathjax/MathJax.js",
                  "reviewer.js"]
-        pform.frontWeb.stdHtml(self.mw.reviewer._revHtml,
+        pform.frontWeb.stdHtml(self.mw.reviewer.revHtml(),
                                css=["reviewer.css"],
                                head=base, js=jsinc)
-        pform.backWeb.stdHtml(self.mw.reviewer._revHtml,
+        pform.backWeb.stdHtml(self.mw.reviewer.revHtml(),
                               css=["reviewer.css"],
                               head=base, js=jsinc)
 
@@ -290,7 +290,8 @@ Please create a new card type first."""))
         q = ti(mungeQA(self.mw.col, c.q(reload=True)))
         a = ti(mungeQA(self.mw.col, c.a()), type='a')
 
-        self.pform.frontWeb.eval("_showQuestion(%s,'%s');" % (json.dumps(q), bodyclass))
+        # use _showAnswer to avoid the longer delay
+        self.pform.frontWeb.eval("_showAnswer(%s,'%s');" % (json.dumps(q), bodyclass))
         self.pform.backWeb.eval("_showAnswer(%s, '%s');" % (json.dumps(a), bodyclass))
 
         clearAudioQueue()

aqt/reviewer.py

@@ -117,16 +117,19 @@ class Reviewer:
     # Initializing the webview
     ##########################################################################
 
-    _revHtml = """
+    def revHtml(self):
+        extra = self.mw.col.conf.get("reviewExtra", "")
+        return f"""
 <img src="qrc:/icons/rating.png" id=star class=marked>
 <div id=qa></div>
+{extra}
 """
 
     def _initWeb(self):
         self._reps = 0
         base = self.mw.baseHTML()
         # main window
-        self.web.stdHtml(self._revHtml,
+        self.web.stdHtml(self.revHtml(),
                          head=base,
                          css=["reviewer.css"],
                          js=["jquery.js",