mod: move slider event handling to global command module

Since this event must be handled in all UIs, it is
better to register it on command object construction.

commands.lua

@@ -162,5 +162,24 @@ function Commands:new(obj)
 	end
 	setmetatable(obj.map, mt)
 
+	obj:add(KEY_INTO_SCREEN_SAVER, nil, "slider",
+		"toggle screen saver",
+		function()
+			Screen:saveCurrentBB()
+			Screen.kpv_rotation_mode = Screen.cur_rotation_mode
+			fb:setOrientation(Screen.native_rotation_mode)
+			--os.execute("killall -cont cvm")
+		end
+	)
+	obj:add(KEY_OUTOF_SCREEN_SAVER, nil, "slider",
+		"toggle screen saver",
+		function()
+			os.execute("sleep 3")
+			--os.execute("killall -stop cvm")
+			fb:setOrientation(Screen.kpv_rotation_mode)
+			Screen:resotreFromSavedBB()
+			fb:refresh(0)
+		end
+	)
 	return obj
 end

screen.lua

@@ -44,6 +44,8 @@ Screen = {
 	-- these two variabls are used to help switching from framework to reader
 	native_rotation_mode = nil,
 	kpv_rotation_mode = nil,
+
+	saved_bb = nil,
 }
 
 -- @orien: 1 for clockwise rotate, -1 for anti-clockwise
@@ -74,3 +76,27 @@ function Screen:updateRotationMode()
 	end
 end
 
+function Screen:saveCurrentBB()
+	if not self.saved_bb then
+		self.saved_bb = Blitbuffer.new(width, height)
+	end
+	if self.saved_bb:getWidth() ~= width then
+		self.saved_bb:free()
+		self.saved_bb = Blitbuffer.new(width, height)
+	end
+	self.saved_bb:blitFullFrom(fb.bb)
+end
+
+function Screen:resotreFromSavedBB()
+	self:restoreFromBB(self.saved_bb)
+end
+
+function Screen:getCurrentScreenBB()
+	local bb = Blitbuffer.new(width, height)
+	bb:blitFullFrom(fb.bb)
+	return bb
+end
+
+function Screen:restoreFromBB(bb)
+	fb.bb:blitFullFrom(bb)
+end