Add linear flow wisdom to screensaver message magic variables (#9905)

If there are hidden flows, this calculates the current page, total pages, percent, time left in chapter, and time left in the magic variables used in screensaver message only for the current flow. If there are no hidden flows, the behavior is the same as before.

frontend/ui/screensaver.lua

@@ -170,8 +170,18 @@ function Screensaver:expandSpecial(message, fallback)
     if ui and ui.document then
         -- If we have a ReaderUI instance, use it.
         local doc = ui.document
-        currentpage = ui.view.state.page or currentpage
-        totalpages = doc:getPageCount() or totalpages
+        if doc:hasHiddenFlows() then
+            local currentpageAll = ui.view.state.page or currentpage
+            currentpage = doc:getPageNumberInFlow(ui.view.state.page or currentpageAll)
+            totalpages = doc:getTotalPagesInFlow(doc:getPageFlow(currentpageAll))
+            time_left_chapter = self:_calcAverageTimeForPages(ui.toc:getChapterPagesLeft(currentpageAll) or (totalpages - currentpage))
+            time_left_document = self:_calcAverageTimeForPages(totalpages - currentpage)
+        else
+            currentpage = ui.view.state.page or currentpage
+            totalpages = doc:getPageCount() or totalpages
+            time_left_chapter = self:_calcAverageTimeForPages(ui.toc:getChapterPagesLeft(currentpage) or doc:getTotalPagesLeft(currentpage))
+            time_left_document = self:_calcAverageTimeForPages(doc:getTotalPagesLeft(currentpage))
+        end
         percent = Math.round((currentpage * 100) / totalpages)
         local props = doc:getProps()
         if props then
@@ -179,8 +189,6 @@ function Screensaver:expandSpecial(message, fallback)
             authors = props.authors and props.authors ~= "" and props.authors or authors
             series = props.series and props.series ~= "" and props.series or series
         end
-        time_left_chapter = self:_calcAverageTimeForPages(ui.toc:getChapterPagesLeft(currentpage) or doc:getTotalPagesLeft(currentpage))
-        time_left_document = self:_calcAverageTimeForPages(doc:getTotalPagesLeft(currentpage))
     elseif DocSettings:hasSidecarFile(lastfile) then
         -- If there's no ReaderUI instance, but the file has sidecar data, use that
         local docinfo = DocSettings:open(lastfile)