[fix] cre: fix position and page number after window resize (#4754)

frontend/apps/reader/modules/readerrolling.lua

@@ -665,21 +665,34 @@ function ReaderRolling:onRedrawCurrentView()
 end
 
 function ReaderRolling:onSetDimensions(dimen)
-    self.ui.document:setViewDimen(Screen:getSize())
+    if self.ui.postReaderCallback ~= nil then
+        -- ReaderUI:init() not yet done: just set document dimensions
+        self.ui.document:setViewDimen(Screen:getSize())
+        -- (what's done in the following else is done elsewhere by
+        -- the initialization code)
+    else
+        -- Initialization done: we are called on orientation change
+        -- or on window resize (SDL, Android possibly).
+        -- We need to temporarily re-enable internal history as crengine
+        -- uses it to reposition after resize
+        self.ui.document:enableInternalHistory(true)
+        -- Set document dimensions
+        self.ui.document:setViewDimen(Screen:getSize())
+        -- Re-setup previous position
+        self:onChangeViewMode()
+        self:onUpdatePos()
+        -- Re-disable internal history, with required redraw
+        self.ui.document:enableInternalHistory(false)
+        self:onRedrawCurrentView()
+    end
 end
 
 function ReaderRolling:onChangeScreenMode(mode, rotation)
-    -- We need to temporarily re-enable internal history as crengine
-    -- uses it to reposition after resize
-    self.ui.document:enableInternalHistory(true)
-    -- Flag it as interactive so we can properly swap to Inverted orientations (we usurp the second argument, which usually means rotation)
+    -- Flag it as interactive so we can properly swap to Inverted orientations
+    -- (we usurp the second argument, which usually means rotation)
     self.ui:handleEvent(Event:new("SetScreenMode", mode, rotation or true))
-    self.ui.document:setViewDimen(Screen:getSize())
-    self:onChangeViewMode()
-    self:onUpdatePos()
-    -- Re-disable internal history, with required redraw
-    self.ui.document:enableInternalHistory(false)
-    self:onRedrawCurrentView()
+    -- (This had the above ReaderRolling:onSetDimensions() called to resize
+    -- document dimensions and keep up with current position)
 end
 
 function ReaderRolling:onColorRenderingUpdate()