UIDesign - surefish/koreader GitHub Wiki

NOTICE!

Please always refer to the code first! Content in this page is not actively maintained and might be outdated.

How to Debug

We have a helper function called DEBUG to help with debugging. You can use that function to print string and tables:

a = {"1", "2", "3"}
DEBUG("table a: ", a)

Anything printed by DEBUG will starts with a # sign.

Event system

Event system is used for widgets to communicate with each others.

Each event is an object that has two properties: args and handler. handler is the name of function that will be called on receive. args is a table that contains all the arguments needed to be passed to the event handler. When a widget receives a event, it will first check to see if self[event.handler] exists. If yes, the self[event.handler] function will be called and the return value of the handler will be returned to UIManager.

Notice that If you don't want the event propagate after consumed in your handler, your handler must return True. Otherwise, the event will be passed to other widgets' handlers until one of the handlers returns True.

WidgetContainer is a special kind of widget. When it receives an event, it will first propagate the event to all its children. If the event is still not consumed (handler returns True), then it will try to handle by itself.

When you call UIManager:show on an widget, this widget will be added to the top of UIManager._window_stack. Events are sent to the first widget in UIManager._window_stack. If it is not consumed, then UIManager will try to send it to all active widgets (widget.is_always_active equals true) in the _window_stack.

Draw Page Code Path

  • in readerview.lua: ReaderView widget flag itself dirty in ReaderView:recalculate
  • in ui.lua: UI main loop calls ReaderView:paintTo
  • in readerview.lua: ReaderView:paintTo calls document:drawPage
  • in document.lua: document:drawPage check for cache, if found, return cache
  • in document.lua: if cache not found, document:drawPage calls document:renderPage
  • in document.lua: document:renderPage calls _document:openPage, page:draw and put the result into cache