CreDocument: fix document loading interferences (#4349)

When a main document is opened for displaying, some other
document openings (for getting metadata or cover image)
could affect the main document.
Split some code from CreDocument:init() into another new
method CreDocument:setupDefaultView(), that will only be
called by ReaderUI when opening the main document (and not
by these other openings like Book inforation, View cover...)

Also speed up some of these other openings (Search, Screensaver)
by using doc:loadDocument(false) to load only metadata and
avoid parsing the HTML.

Details in https://github.com/koreader/koreader/issues/4346#issuecomment-440036496

base

@@ -1 +1 @@
-Subproject commit 84299a585587f306230c448f80e4e4811f2f990d
+Subproject commit 461b750936897041c115f5de6c94eb9e0309a5ee

frontend/apps/filemanager/filemanagersearch.lua

@@ -504,6 +504,9 @@ function Search:onMenuHold(item)
     local thumbnail
     local doc = DocumentRegistry:openDocument(item.path)
     if doc then
+        if doc.loadDocument then -- CreDocument
+            doc:loadDocument(false) -- load only metadata
+        end
         thumbnail = doc:getCoverPageImage()
         doc:close()
     end

frontend/apps/reader/readerui.lua

@@ -263,6 +263,11 @@ function ReaderUI:init()
             document = self.document,
         })
     else
+        -- load crengine default settings (from cr3.ini, some of these
+        -- will be overriden by our settings by some reader modules below)
+        if self.document.setupDefaultView then
+            self.document:setupDefaultView()
+        end
         -- make sure we render document first before calling any callback
         self:registerPostInitCallback(function()
             if not self.document:loadDocument() then

frontend/document/credocument.lua

@@ -124,18 +124,6 @@ function CreDocument:init()
         error(self._document)  -- will contain error message
     end
 
-    -- adjust font sizes according to screen dpi
-    self._document:adjustFontSizes(Screen:getDPI())
-
-    if G_reader_settings:readSetting("cre_header_status_font_size") then
-        self._document:setIntProperty("crengine.page.header.font.size",
-            G_reader_settings:readSetting("cre_header_status_font_size"))
-    end
-
-    -- set fallback font face
-    self._document:setStringProperty("crengine.font.fallback.face",
-        G_reader_settings:readSetting("fallback_font") or self.fallback_font)
-
     -- We would have liked to call self._document:loadDocument(self.file)
     -- here, to detect early if file is a supported document, but we
     -- need to delay it till after some crengine settings are set for a
@@ -160,6 +148,34 @@ function CreDocument:requestDomVersion(version)
     cre.requestDomVersion(version)
 end
 
+function CreDocument:setupDefaultView()
+    if self.loaded then
+        -- Don't apply defaults if the document has already been loaded
+        -- as this must be done before calling loadDocument()
+        return
+    end
+    -- have crengine load defaults from cr3.ini
+    self._document:readDefaults()
+    logger.dbg("CreDocument: applied cr3.ini default settings.")
+
+    -- set fallback font face (this was formerly done in :init(), but it
+    -- affects crengine calcGlobalSettingsHash() and would invalidate the
+    -- cache from the main currently being read document when we just
+    -- loadDocument(only_metadata) another document go get its metadata
+    -- or cover image, eg. from History hold menu).
+    self._document:setStringProperty("crengine.font.fallback.face",
+        G_reader_settings:readSetting("fallback_font") or self.fallback_font)
+
+    -- adjust font sizes according to screen dpi
+    self._document:adjustFontSizes(Screen:getDPI())
+
+    -- set top status bar font size
+    if G_reader_settings:readSetting("cre_header_status_font_size") then
+        self._document:setIntProperty("crengine.page.header.font.size",
+            G_reader_settings:readSetting("cre_header_status_font_size"))
+    end
+end
+
 function CreDocument:loadDocument(full_document)
     if not self._loaded then
         local only_metadata = full_document == false

frontend/ui/screensaver.lua

@@ -249,6 +249,9 @@ function Screensaver:show(event, fallback_message)
         if exclude ~= true then
             if lfs.attributes(lastfile, "mode") == "file" then
                 local doc = DocumentRegistry:openDocument(lastfile)
+                if doc.loadDocument then -- CreDocument
+                    doc:loadDocument(false) -- load only metadata
+                end
                 local image = doc:getCoverPageImage()
                 doc:close()
                 if image ~= nil then