Footer: added "memory usage" item

Helps following KOReader memory usage (and memory leaks).

frontend/apps/reader/modules/readerfooter.lua

@@ -27,11 +27,14 @@ local MODE = {
     book_time_to_read = 6,
     chapter_time_to_read = 7,
     frontlight = 8,
+    mem_usage = 9,
 }
 
+local MODE_NB = 0
 local MODE_INDEX = {}
 for k,v in pairs(MODE) do
     MODE_INDEX[v] = k
+    MODE_NB = MODE_NB + 1
 end
 
 -- functions that generates footer text for each mode
@@ -85,6 +88,18 @@ local footerTextGeneratorMap = {
         return footer:getDataFromStatistics(
             "TC: ", (left and left or footer.pages - footer.pageno))
     end,
+    mem_usage = function(footer)
+        local statm = io.open("/proc/self/statm", "r")
+        if statm then
+            local infos = statm:read("*all")
+            statm:close()
+            local rss = infos:match("^%S+ (%S+) ")
+            -- we got the nb of 4Kb-pages used, that we convert to Mb
+            rss = math.floor(tonumber(rss) * 4096 / 1024 / 1024)
+            return string.format("M:%d", rss)
+        end
+        return ""
+    end,
 }
 
 local ReaderFooter = WidgetContainer:extend{
@@ -120,6 +135,7 @@ function ReaderFooter:init()
         book_time_to_read = true,
         chapter_time_to_read = true,
         frontlight = false,
+        mem_usage = false,
     }
 
     if self.settings.disabled then
@@ -304,6 +320,7 @@ local option_titles = {
     book_time_to_read = _("Book time to read"),
     chapter_time_to_read = _("Chapter time to read"),
     frontlight = _("Frontlight level"),
+    mem_usage = _("KOReader memory usage"),
 }
 
 function ReaderFooter:addToMainMenu(tab_item_table)
@@ -400,6 +417,7 @@ function ReaderFooter:addToMainMenu(tab_item_table)
     table.insert(sub_items, getMinibarOption("book_time_to_read"))
     table.insert(sub_items, getMinibarOption("chapter_time_to_read"))
     table.insert(sub_items, getMinibarOption("frontlight"))
+    table.insert(sub_items, getMinibarOption("mem_usage"))
 end
 
 -- this method will be updated at runtime based on user setting
@@ -530,6 +548,7 @@ function ReaderFooter:applyFooterMode(mode)
     -- 6 for from statistics book time to read
     -- 7 for from statistics chapter time to read
     -- 8 for front light level
+    -- 9 for memory usage
     if mode ~= nil then self.mode = mode end
     self.view.footer_visible = (self.mode ~= MODE.off)
     if not self.view.footer_visible or self.settings.all_at_once then return end
@@ -568,14 +587,14 @@ function ReaderFooter:onTapFooter(arg, ges)
                 self.mode = MODE.page_progress
             end
         else
-            self.mode = (self.mode + 1) % 9
+            self.mode = (self.mode + 1) % MODE_NB
             for i, m in ipairs(MODE_INDEX) do
                 if self.mode == MODE.off then break end
                 if self.mode == i then
                     if self.settings[m] then
                         break
                     else
-                        self.mode = (self.mode + 1) % 9
+                        self.mode = (self.mode + 1) % MODE_NB
                     end
                 end
             end