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mirror of https://github.com/koreader/koreader synced 2024-11-16 06:12:56 +00:00
koreader/frontend/cacheitem.lua
NiLuJe fadee1f5dc
Clarify our OOP semantics across the codebase (#9586)
Basically:

* Use `extend` for class definitions
* Use `new` for object instantiations

That includes some minor code cleanups along the way:

* Updated `Widget`'s docs to make the semantics clearer.
* Removed `should_restrict_JIT` (it's been dead code since https://github.com/koreader/android-luajit-launcher/pull/283)
* Minor refactoring of LuaSettings/LuaData/LuaDefaults/DocSettings to behave (mostly, they are instantiated via `open` instead of `new`) like everything else and handle inheritance properly (i.e., DocSettings is now a proper LuaSettings subclass).
* Default to `WidgetContainer` instead of `InputContainer` for stuff that doesn't actually setup key/gesture events.
* Ditto for explicit `*Listener` only classes, make sure they're based on `EventListener` instead of something uselessly fancier.
* Unless absolutely necessary, do not store references in class objects, ever; only values. Instead, always store references in instances, to avoid both sneaky inheritance issues, and sneaky GC pinning of stale references.
  * ReaderUI: Fix one such issue with its `active_widgets` array, with critical implications, as it essentially pinned *all* of ReaderUI's modules, including their reference to the `Document` instance (i.e., that was a big-ass leak).
* Terminal: Make sure the shell is killed on plugin teardown.
* InputText: Fix Home/End/Del physical keys to behave sensibly.
* InputContainer/WidgetContainer: If necessary, compute self.dimen at paintTo time (previously, only InputContainers did, which might have had something to do with random widgets unconcerned about input using it as a baseclass instead of WidgetContainer...).
* OverlapGroup: Compute self.dimen at *init* time, because for some reason it needs to do that, but do it directly in OverlapGroup instead of going through a weird WidgetContainer method that it was the sole user of.
* ReaderCropping: Under no circumstances should a Document instance member (here, self.bbox) risk being `nil`ed!
* Kobo: Minor code cleanups.
2022-10-06 02:14:48 +02:00

29 lines
1.1 KiB
Lua

--[[
Inheritable abstraction for cache items
--]]
local CacheItem = {
size = 128, -- some reasonable default for a small table.
}
--- NOTE: As far as size estimations go, the assumption is that a key, value pair should roughly take two words,
--- and the most common items we cache are Geom-like tables (i.e., 4 key-value pairs).
--- That's generally a low estimation, especially for larger tables, where memory allocation trickery may be happening.
function CacheItem:extend(o)
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
-- NOTE: There's no object-specific initialization, the entirety of the new data *is* the table we pass to new.
-- We only keep the distinction as a matter of semantics, to differentiate class declarations from object instantiations.
CacheItem.new = CacheItem.extend
-- Called on eviction.
-- We generally use it to free C/FFI resources *immediately* (as opposed to relying on our Userdata/FFI finalizers to do it "later" on GC).
-- c.f., TileCacheItem
function CacheItem:onFree()
end
return CacheItem