use getProvider and openDocument in reader.lua

we use getProvider for file extension filter

reader.lua

@@ -10,7 +10,7 @@ require "alt_getopt"
 
 
 function showReader(file, pass)
-	local document = DocumentRegistry:getProvider(file)
+	local document = DocumentRegistry:openDocument(file)
 	if not document then
 		UIManager:show(InfoMessage:new{ text = "No reader engine for this file" })
 		return
@@ -39,7 +39,12 @@ function showFileManager(path)
 	local FileManager = FileChooser:new{
 		path = path,
 		dimen = Screen:getSize(),
-		is_borderless = true
+		is_borderless = true,
+		filter = function(filename) 
+			if DocumentRegistry:getProvider(filename) then
+				return true
+			end
+		end
 	}
 
 	function FileManager:onFileSelect(file)

wtest.lua

@@ -145,9 +145,9 @@ readerwindow = CenterContainer:new{
 reader = ReaderUI:new{
 	dialog = readerwindow,
 	dimen = Geom:new{ w = Screen:getWidth() - 100, h = Screen:getHeight() - 100 },
-	document = DocumentRegistry:getProvider("test/2col.pdf")
-	--document = DocumentRegistry:getProvider("test/djvu3spec.djvu")
-	--document = DocumentRegistry:getProvider("./README.TXT")
+	document = DocumentRegistry:openDocument("test/2col.pdf")
+	--document = DocumentRegistry:openDocument("test/djvu3spec.djvu")
+	--document = DocumentRegistry:openDocument("./README.TXT")
 }
 readerwindow[1][1] = reader