Only render when dirty

gfx/element.lua

@@ -31,11 +31,15 @@ function Element:new(o)
 end
 
 function Element:draw()
-  local win = self:_getWindow()
--- Calling draw() without a valid window is a logical error
----@diagnostic disable-next-line: need-check-nil
-  win.setCursorPos(1, 1)
+  local dirty = self:_isDirty()
+  if dirty then
+    local win = self:_getWindow()
+  -- Calling draw() without a valid window is a logical error
+  ---@diagnostic disable-next-line: need-check-nil
+    win.setCursorPos(1, 1)
+  end
   self.dirty = false
+  return dirty
 end
 
 function Element:getX()
@@ -76,6 +80,7 @@ function Element:setParent(parent)
   if self.parent ~= parent then
     self:setDirty()
     self.parent = parent
+    self:_reload()
   end
 end
 
@@ -115,6 +120,10 @@ function Element:setVisible(visible)
   self:_getWindow().setVisible(visible)
 end
 
+function Element:_isDirty()
+  return self.dirty
+end
+
 function Element:resize(opts)
   if (opts.width ~= nil and self.x ~= opts.width) or (opts.height ~= nil and self.y ~= opts.height) then
     self:setDirty()
@@ -189,10 +198,12 @@ function Element:setOnClick(onClick)
 end
 
 function Element:_reload()
-  local window = window.create(self.parent, self:getX(), self:getY(), self:getWidth(), self:getHeight(), self:isVisible())
-  window.setBackgroundColor(self:getBgColor())
-  window.setTextColor(self:getFgColor())
-  self:_setWindow(window)
+  if self.parent ~= nil then
+    local window = window.create(self.parent, self:getX(), self:getY(), self:getWidth(), self:getHeight(), self:isVisible())
+    window.setBackgroundColor(self:getBgColor())
+    window.setTextColor(self:getFgColor())
+    self:_setWindow(window)
+  end
 end
 
 return Element

gfx/list.lua

@@ -21,9 +21,22 @@ end
 function List:insertChild(child, atIndex)
   local index = math.min(math.max(1, atIndex or #self.children), #self.children)
   table.insert(self.children, index, child)
+
+  -- Update window references
+  self:_reload()
+
+  -- Update render positions
   adjustPositions(self.children, self:isVertical(), index)
 end
 
+function List:setParent(parent)
+  Element.setParent(self, parent)
+  local win = self:_getWindow()
+  for _,child in ipairs(self.children) do
+    child:setParent(win)
+  end
+end
+
 function List:removeChild(child)
   local index
   local searchType = type(child)
@@ -51,6 +64,7 @@ function List:removeChild(child)
   end
 
   local removed = table.remove(self.children, index)
+  self:_reload()
   if index <= #self.children then
     adjustPositions(self.children, self:isVertical(), index)
   end
@@ -67,11 +81,14 @@ function List:isHorizontal()
 end
 
 function List:draw()
-  Element.draw(self)
-  self:_getWindow().clear()
-  for _,v in ipairs(self.children) do
-    v:draw()
+  local dirty = Element.draw(self)
+  if dirty then
+    self:_getWindow().clear()
+    for _,child in ipairs(self.children) do
+      child:draw()
+    end
   end
+  return dirty
 end
 
 function List:getHeight()
@@ -105,4 +122,29 @@ function List:findById(id)
   return nil
 end
 
+function List:_isDirty()
+  if Element._isDirty(self) then
+    return true
+  end
+
+  for _,child in ipairs(self.childrent) do
+    if child:_isDirty() then
+      return true
+    end
+  end
+  return false
+end
+
+function List:_reload()
+  Element._reload(self)
+
+  -- Reload child windows
+  local win = self:_getWindow()
+  for _,child in ipairs(self.children) do
+    if child:_getWindow() ~= win then
+      child:setParent(win)
+    end
+  end
+end
+
 return List

gfx/padding.lua

@@ -28,10 +28,13 @@ function Padding:resize(opts)
 end
 
 function Padding:draw()
-  Element.draw(self)
-  local win = self:_getWindow()
-  win.clear()
-  self.element:draw()
+  if Element.draw(self) or self.element:_isDirty() then
+    local win = self:_getWindow()
+    win.clear()
+    self.element:draw()
+    return true
+  end
+  return false
 end
 
 function Padding:getPaddingLeft()

gfx/text.lua

@@ -26,8 +26,11 @@ function Text:getText()
 end
 
 function Text:draw()
-  Element.draw(self)
-  self:_getWindow().write(self:getText())
+  local dirty = Element.draw(self)
+  if dirty then
+    self:_getWindow().write(self:getText())
+  end
+  return dirty
 end
 
 function Text:getHeight()