add koreader plugin mechanism

This should implement #505.

frontend/apps/reader/modules/readermenu.lua

@@ -28,6 +28,9 @@ function ReaderMenu:init()
         typeset = {
             icon = "resources/icons/appbar.page.text.png",
         },
+        plugins = {
+            icon = "resources/icons/appbar.tools.png",
+        },
         home = {
             icon = "resources/icons/appbar.home.png",
             callback = function()
@@ -105,6 +108,7 @@ function ReaderMenu:onShowReaderMenu()
                 self.tab_item_table.navi,
                 self.tab_item_table.typeset,
                 self.tab_item_table.main,
+                self.tab_item_table.plugins,
                 self.tab_item_table.home,
             },
             show_parent = menu_container,

frontend/apps/reader/pluginloader.lua

@@ -0,0 +1,44 @@
+local DEBUG = require("dbg")
+-- lfs
+
+local PluginLoader = {
+    plugin_path = lfs.currentdir().."/plugins"
+}
+
+function PluginLoader:loadPlugins()
+    if self.plugins then return self.plugins end
+
+    self.plugins = {}
+    for f in lfs.dir(self.plugin_path) do
+        local path = self.plugin_path.."/"..f
+        local mode = lfs.attributes(path, "mode")
+        -- valid koreader plugin directory
+        if mode == "directory" and f:find(".+%.koplugin$") then
+            local mainfile = path.."/".."main.lua"
+            local package_path = package.path
+            local package_cpath = package.cpath
+            package.path = path.."/?.lua;"..package.path
+            package.cpath = path.."/lib/?.so;"..package.cpath
+            local ok, module = pcall(require, "main")
+            if not ok then
+                DEBUG("Error when loading", mainfile, module)
+            end
+            package.path = package_path
+            package.cpath = package_cpath
+            if ok then
+                module.path = path
+                table.insert(self.plugins, module)
+            end
+        end
+    end
+
+    for _,plugin in ipairs(self.plugins) do
+        package.path = package.path..";"..plugin.path.."/?.lua"
+        package.cpath = package.cpath..";"..plugin.path.."/lib/?.so"
+    end
+
+    return self.plugins
+end
+
+return PluginLoader
+

frontend/apps/reader/readerui.lua

@@ -31,6 +31,7 @@ local ReaderDictionary = require("apps/reader/modules/readerdictionary")
 local ReaderHyphenation = require("apps/reader/modules/readerhyphenation")
 local ReaderActivityIndicator = require("apps/reader/modules/readeractivityindicator")
 local ReaderLink = require("apps/reader/modules/readerlink")
+local PluginLoader = require("apps/reader/pluginloader")
 
 --[[
 This is an abstraction for a reader interface
@@ -261,6 +262,18 @@ function ReaderUI:init()
             document = self.document,
         })
     end
+
+    -- koreader plugins
+    for _,module in ipairs(PluginLoader:loadPlugins()) do
+        DEBUG("Loaded plugin", module.path)
+        table.insert(self, module:new{
+            dialog = self.dialog,
+            view = self[1],
+            ui = self,
+            document = self.document,
+        })
+    end
+
     --DEBUG(self.doc_settings)
     -- we only read settings after all the widgets are initialized
     self:handleEvent(Event:new("ReadSettings", self.doc_settings))

reader.lua

@@ -1,8 +1,8 @@
 #!./koreader-base
 
 require "defaults"
-package.path = "./frontend/?.lua;./?.lua"
-package.cpath = "?.so;/usr/lib/lua/?.so"
+package.path = "?.lua;common/?.lua;frontend/?.lua"
+package.cpath = "?.so;common/?.so;/usr/lib/lua/?.so"
 
 local DocSettings = require("docsettings")
 local _ = require("gettext")