add progress bar

luigi/widget/progress.lua

@@ -0,0 +1,15 @@
+return function (self)
+
+    self.value = 0.5
+    self.flow = 'x' -- TODO: support vertical slider
+
+    local bar = self:addChild {
+        type = 'progressInner',
+        width = 0,
+    }
+
+    self:onReshape(function (event)
+        local x1, y1, x2, y2 = self:getRectangle(true, true)
+        bar.width = self.value * (x2 - x1)
+    end)
+end