separated dialog.lua into source files for each individual function

frontend/ui/button.lua

@@ -0,0 +1,45 @@
+require "ui/widget"
+
+--[[
+a button widget
+]]
+Button = WidgetContainer:new{
+	text = nil, -- mandatory
+	preselect = false
+}
+
+function Button:init()
+	-- set FrameContainer content
+	self[1] = FrameContainer:new{
+		margin = 0,
+		bordersize = 3,
+		background = 0,
+		radius = 15,
+		padding = 2,
+
+		HorizontalGroup:new{
+			HorizontalSpan:new{ width = 8 },
+			TextWidget:new{
+				text = self.text,
+				face = Font:getFace("cfont", 20)
+			},
+			HorizontalSpan:new{ width = 8 },
+		}
+	}
+	if self.preselect then
+		self[1].color = 15
+	else
+		self[1].color = 5
+	end
+end
+
+function Button:onFocus()
+	self[1].color = 15
+	return true
+end
+
+function Button:onUnfocus()
+	self[1].color = 5
+	return true
+end
+