diff --git a/base b/base
index 5d2ad62a0..d0bed73cd 160000
--- a/base
+++ b/base
@@ -1 +1 @@
-Subproject commit 5d2ad62a04701fb233b362551f0cbc44b0ee62f1
+Subproject commit d0bed73cd630aa7f304cd7447eea8abfd3500aec
diff --git a/frontend/apps/reader/modules/readerlink.lua b/frontend/apps/reader/modules/readerlink.lua
index 0345367b6..f8145ed00 100644
--- a/frontend/apps/reader/modules/readerlink.lua
+++ b/frontend/apps/reader/modules/readerlink.lua
@@ -59,7 +59,7 @@ local function is_follow_links_on()
 end
 
 local function swipe_to_go_back()
-    return G_reader_settings:readSetting("swipe_to_go_back") ~= false
+    return G_reader_settings:readSetting("swipe_to_go_back") == true
 end
 
 function ReaderLink:addToMainMenu(tab_item_table)
diff --git a/frontend/apps/reader/modules/readerwikipedia.lua b/frontend/apps/reader/modules/readerwikipedia.lua
index 214378675..87587e286 100644
--- a/frontend/apps/reader/modules/readerwikipedia.lua
+++ b/frontend/apps/reader/modules/readerwikipedia.lua
@@ -24,11 +24,7 @@ end
 function ReaderWikipedia:onLookupWikipedia(word, box)
     -- detect language of the text
     local ok, lang = pcall(Translator.detect, Translator, word)
-    -- prompt users to turn on Wifi if network is unreachable
-    if not ok and lang and lang:find("Network is unreachable") then
-        NetworkMgr:promptWifiOn()
-        return
-    end
+    if not ok then return end
     -- convert "zh-CN" and "zh-TW" to "zh"
     lang = lang:match("(.*)-") or lang
     -- strip punctuation characters around selected word
diff --git a/frontend/document/koptinterface.lua b/frontend/document/koptinterface.lua
index 316d08e4d..94bc73cdb 100644
--- a/frontend/document/koptinterface.lua
+++ b/frontend/document/koptinterface.lua
@@ -256,7 +256,10 @@ end
 get first page image
 --]]
 function KoptInterface:getCoverPageImage(doc)
-    local tile = self:renderPage(doc, 1, nil, 1, 0, 1, 0)
+    local native_size = Document.getNativePageDimensions(doc, 1)
+    local screen_size = Screen:getSize()
+    local zoom = math.min(screen_size.w / native_size.w, screen_size.h / native_size.h)
+    local tile = Document.renderPage(doc, 1, nil, zoom, 0, 1, 0)
     if tile then
         return tile.bb
     end
diff --git a/frontend/ui/geometry.lua b/frontend/ui/geometry.lua
index c7552296c..29231333c 100644
--- a/frontend/ui/geometry.lua
+++ b/frontend/ui/geometry.lua
@@ -1,3 +1,4 @@
+local Math = require("optmath")
 local DEBUG = require("dbg")
 
 --[[
@@ -62,8 +63,8 @@ scale rectangle (grow to bottom and to the right) or dimension
 if a single factor is given, it is applied to both width and height
 ]]--
 function Geom:scaleBy(zx, zy)
-    self.w = self.w * zx
-    self.h = self.h * (zy or zx)
+    self.w = Math.round(self.w * zx)
+    self.h = Math.round(self.h * (zy or zx))
     return self
 end
 
@@ -71,8 +72,8 @@ end
 this method also takes care of x and y
 ]]--
 function Geom:transformByScale(zx, zy)
-    self.x = self.x * zx
-    self.y = self.y * (zx or zy)
+    self.x = Math.round(self.x * zx)
+    self.y = Math.round(self.y * (zx or zy))
     self:scaleBy(zx, zy)
 end
 
@@ -327,8 +328,8 @@ return the midpoint of two geoms
 ]]--
 function Geom:midpoint(geom)
     return Geom:new{
-        x = (self.x + geom.x) / 2,
-        y = (self.y + geom.y) / 2,
+        x = Math.round((self.x + geom.x) / 2),
+        y = Math.round((self.y + geom.y) / 2),
         w = 0, h = 0,
     }
 end
@@ -338,8 +339,8 @@ return center point in this geom
 ]]--
 function Geom:center()
     return Geom:new{
-        x = self.x + self.w / 2,
-        y = self.y + self.h / 2,
+        x = self.x + Math.round(self.w / 2),
+        y = self.y + Math.round(self.h / 2),
         w = 0, h = 0,
     }
 end