SessionManager.lua

-- A very simplistic session manager. It opens previously open files and restores
-- cursor position and scroll position. It is not perfect, for example it does 
-- not keep track of the order or in which view the files are in. This code must
-- be ran during startup. This is just a demonstration of how to use the API
-- and what can be done in a small amount of Lua.


local opened_files = {}
local is_shutting_down = false

-- If a session is found, load it. Note this cannot be done directly during
-- startup since N++ hasn't completely initialized yet.
npp.AddEventHandler("OnReady", function()
 local files = table.load(npp:GetPluginsConfigDir() .. "\\session.lua")
 if files ~= nil then
 for i,v in pairs(files) do
 npp:DoOpen(v.name)
 if v.lang then npp.BufferLangType[npp.CurrentBufferID] = v.lang end
 editor.FirstVisibleLine = v.top or 0
 editor.CurrentPos = v.pos or 0
 editor.Anchor = v.anchor or 0
 end
 end
 return false 
end)

-- Remove any files that are closed
npp.AddEventHandler("OnClose", function(f,i)
 -- If N++ is in the middle of shutting down, just ignore it
 if is_shutting_down then return false end
 opened_files[i] = nil
 return false
end)

-- This won't be called unless the user manually changes it, else it just
-- defaults to whatever value N++ decides is best
npp.AddEventHandler("OnLangChange", function()
 local i = npp.CurrentBufferID
 opened_files[i].lang = npp.BufferLangType[i]
end)

-- Keep track of some of the variables we want to restore in the file
-- This event will also catch any files being opened for the first time
npp.AddEventHandler("OnUpdateUI", function()
 local i = npp.CurrentBufferID
 if opened_files[i] == nil then
 opened_files[i] = {}
 opened_files[i].name = npp:GetFullCurrentPath()
 end
 opened_files[i].pos = editor.CurrentPos
 opened_files[i].anchor = editor.Anchor
 opened_files[i].top = editor.FirstVisibleLine

 return false
end)

npp.AddEventHandler("OnFileRenamed", function(f,i)
 opened_files[i].name = f -- update the name
 return false
end)

-- Set a flag so we know N++ is shutting down
npp.AddEventHandler("OnBeforeShutdown", function()
 is_shutting_down = true
 return false
end)

-- The user could cancel the shutdown
npp.AddEventHandler("OnCancelShutdown", function()
 is_shutting_down = false
 return false
end)

-- If it is actually shutting down, save the session file
npp.AddEventHandler("OnShutdown", function()
 -- Remove any dummy files, e.g. "new 1"
 for id, tab in pairs(opened_files) do
 if tab.name:find("^new %d+$") ~= nil then
 opened_files[id] = nil
 end
 end
 table.save(opened_files, npp:GetPluginsConfigDir() .. "\\session.lua")

 return false
end)


-- These below are merely helper fuctions to serialize tables. They were found
-- laying around on the Internet somewhere and worked for this case.

function table.save(tbl,filename )
 local function exportstring( s )
 return string.format("%q", s)
 end
 local charS,charE = "\t","\n"
 local file,err = io.open( filename, "wb" )
 if err then return err end

 -- initiate variables for save procedure
 local tables,lookup = { tbl },{ [tbl] = 1 }
 file:write( "return {"..charE )

 for idx,t in ipairs( tables ) do
 file:write( "-- Table: {"..idx.."}"..charE )
 file:write( "{"..charE )
 local thandled = {}

 for i,v in ipairs( t ) do
 thandled[i] = true
 local stype = type( v )
 -- only handle value
 if stype == "table" then
 if not lookup[v] then
 table.insert( tables, v )
 lookup[v] = #tables
 end
 file:write( charS.."{"..lookup[v].."},"..charE )
 elseif stype == "string" then
 file:write( charS..exportstring( v )..","..charE )
 elseif stype == "number" then
 file:write( charS..tostring( v )..","..charE )
 end
 end

 for i,v in pairs( t ) do
 -- escape handled values
 if (not thandled[i]) then
 
 local str = ""
 local stype = type( i )
 -- handle index
 if stype == "table" then
 if not lookup[i] then
 table.insert( tables,i )
 lookup[i] = #tables
 end
 str = charS.."[{"..lookup[i].."}]="
 elseif stype == "string" then
 str = charS.."["..exportstring( i ).."]="
 elseif stype == "number" then
 str = charS.."["..tostring( i ).."]="
 end
 
 if str ~= "" then
 stype = type( v )
 -- handle value
 if stype == "table" then
 if not lookup[v] then
 table.insert( tables,v )
 lookup[v] = #tables
 end
 file:write( str.."{"..lookup[v].."},"..charE )
 elseif stype == "string" then
 file:write( str..exportstring( v )..","..charE )
 elseif stype == "number" then
 file:write( str..tostring( v )..","..charE )
 end
 end
 end
 end
 file:write( "},"..charE )
 end
 file:write( "}" )
 file:close()
end

function table.load( sfile )
 local ftables,err = loadfile( sfile )
 if err then return _,err end
 local tables = ftables()
 for idx = 1,#tables do
 local tolinki = {}
 for i,v in pairs( tables[idx] ) do
 if type( v ) == "table" then
 tables[idx][i] = tables[v[1]]
 end
 if type( i ) == "table" and tables[i[1]] then
 table.insert( tolinki,{ i,tables[i[1]] } )
 end
 end
 -- link indices
 for _,v in ipairs( tolinki ) do
 tables[idx][v[2]],tables[idx][v[1]] = tables[idx][v[1]],nil
 end
 end
 return tables[1]
end