AltStatusBar: show page info similar as in footer

We now build the "page/total %" string ourselves,
with the same logic as used in the footer (including
when hidden flows or reference page numbers are used)
and give it to crengine to be displayed instead of
its own way of doing it.

frontend/apps/reader/modules/readercoptlistener.lua

@@ -41,6 +41,11 @@ function ReaderCoptListener:onReadSettings(config)
     self.document._document:setIntProperty("window.status.battery.percent", self.battery_percent)
     self.document._document:setIntProperty("window.status.pos.percent", self.reading_percent)
 
+    -- We will build the top status bar page info string ourselves,
+    -- if we have to display any chunk of it
+    self.page_info_override = self.page_number == 1 or self.page_count == 1 or self.reading_percent == 1
+    self.document:setPageInfoOverride("") -- an empty string lets crengine display its own page info
+
     self:onTimeFormatChanged()
 
     -- Enable or disable crengine header status line (note that for crengine, 0=header enabled, 1=header disabled)
@@ -76,6 +81,80 @@ function ReaderCoptListener:onReaderReady()
     end
 end
 
+function ReaderCoptListener:updatePageInfoOverride(pageno)
+    if not (self.document.configurable.status_line == 0 and self.view.view_mode == "page" and self.page_info_override) then
+        return
+    end
+    -- There are a few cases where we may not be updated on change, at least:
+    -- - when toggling ReaderPageMap's "Use reference page numbers"
+    -- - when changing footer's nb of digits after decimal point
+    -- but we will update on next page turn. Let's not bother.
+
+    local page_pre = ""
+    local page_number = pageno
+    local page_sep = " / "
+    local page_count = self.ui.document:getPageCount()
+    local page_post = ""
+    local percentage = page_number / page_count
+    local percentage_pre = ""
+    local percentage_post = ""
+    -- Let's use the same setting for nb of digits after decimal point as configured for the footer
+    local percentage_digits =  self.ui.view.footer.settings.progress_pct_format
+    local percentage_fmt = "%." .. percentage_digits .. "f%%"
+
+    -- We want the same output as with ReaderFooter's page_progress() and percentage()
+    -- but here each item (page number, page counte, percentage) is individually toggable,
+    -- so try to get something that make sense when not all are enabled
+    if self.ui.pagemap and self.ui.pagemap:wantsPageLabels() then
+        -- These become strings here
+        page_number = self.ui.pagemap:getCurrentPageLabel(true)
+        page_count = self.ui.pagemap:getLastPageLabel(true)
+    elseif self.ui.document:hasHiddenFlows() then
+        local flow = self.ui.document:getPageFlow(pageno)
+        page_number = tostring(self.ui.document:getPageNumberInFlow(pageno))
+        page_count = tostring(self.ui.document:getTotalPagesInFlow(flow))
+        percentage = page_number / page_count
+        if flow == 0 then
+            page_sep = " // "
+        else
+            page_pre = "["
+            page_post = "]"..tostring(flow)
+            percentage_pre = "["
+            percentage_post = "]"
+        end
+    end
+
+    local page_info = ""
+    if self.page_number or self.page_count then
+        page_info = page_info .. page_pre
+        if self.page_number then
+            page_info = page_info .. page_number
+            if self.page_count then
+                page_info = page_info .. page_sep
+            end
+        end
+        if self.page_count then
+            page_info = page_info .. page_count
+        end
+        page_info = page_info .. page_post
+        if self.reading_percent then
+            page_info = page_info .. "  " -- (double space as done by crengine's own drawing)
+        end
+    end
+    if self.reading_percent then
+        page_info = page_info .. percentage_pre .. percentage_fmt:format(percentage*100) .. percentage_post
+    end
+    self.document:setPageInfoOverride(page_info)
+end
+
+function ReaderCoptListener:onPageUpdate(pageno)
+    self:updatePageInfoOverride(pageno)
+end
+
+function ReaderCoptListener:onPosUpdate(pos, pageno)
+    self:updatePageInfoOverride(pageno)
+end
+
 function ReaderCoptListener:onBookMetadataChanged(prop_updated)
     -- custom metadata support for alt status bar and cre synthetic cover
     local prop_key = prop_updated and prop_updated.metadata_key_updated
@@ -191,6 +270,8 @@ ReaderCoptListener.onSuspend = ReaderCoptListener.unscheduleHeaderRefresh
 function ReaderCoptListener:setAndSave(setting, property, value)
     self.document._document:setIntProperty(property, value)
     G_reader_settings:saveSetting(setting, value)
+    self.page_info_override = self.page_number == 1 or self.page_count == 1 or self.reading_percent == 1
+    self.document:setPageInfoOverride("")
     -- Have crengine redraw it (even if hidden by the menu at this time)
     self.ui.rolling:updateBatteryState()
     self:updateHeader()