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PopTracker Overview

This is a rough overview of internals and what we (have to) provide and what dependencies we have.

Check linked docs for specifics.

Goal

  • scriptable tracker and map tracker, similar to existing solutions
  • open source, platform independent
  • runs in browser and on desktop
    • have a Makefile that builds WASM blob, Linux binaries, Windows exe
    • OSX support?
  • auto-tracking support
    • usb2snes interface
    • more TBD
  • provide an interface that is compatible to existing packs

See TODO.md for current state of things.

WASM work-arounds

  • while(true) does not work in WASM, so we define an interface App that
    • implements a mainloop on desktop
    • hooks into AnimationFrame via emscripten_set_main_loop in WASM

UI requirements

  • item/status "icons" inside hbox/vbox/grid
  • map display: custom widget
  • map "icons" drawn in mapwidget's render()
  • hover -> tooltips -> floating regular widgets/containers
  • have "icons" be just widgets, state/image updated from back-end events/signals
  • use one TrackerView(Tracker*) widget to link up state with ui
  • we may require a "texture store" to support WebGL on mobile
  • layout.json => LayoutNodes => Widgets

see UILIB.md (outdated)

NOTE: UI needs a lot of rework.

Interface ideas

Packs

class Pack abstracts away Filesystem
    ::Pack("path") loads a pack, where path can be a directory or .zip file containing a manifest.json
    ::ReadFile(std::string fn,std::string& buf) will read file `fn` of the package into buffer `buf` and return a result code (no exceptions)
    static ::ListPacks() returns a list of packs
    ::ListVariants() returns a list of available variants for the pack
    ::getVariant() returns currently active variant (or "" if none is active)
    ::setVariant("variant") sets the active variant, used when resolving paths

Note that std::string allows easier integration with C code than a std::stream.

We may want to use mmap or raw pointer in the future, see Ideal ZIP.

Lua Glue

since packs use lua to do actual stuff, we map c++ classes into lua. See LUAGLUE.md for the lua interface code.

Game pack interface

see PACKS.md

We do not use the data directly, but instead load it into objects via Class::FromJSON, which are then used for to the actual (UI) implementation.

Back-end requirements

  • LUA VM
  • JSON parser
  • UI/Layout abstraction (JSON -> Widgets -> Pixels)

Base System / Dependencies

  • libsdl
  • libsdl_ttf
  • libfreetype as dependency of sdl_ttf
  • libsdl_image
  • libpng as dependency of sdl_image
  • zlib
  • liblua
  • json.hpp - https://github.com/nlohmann/json + patch to allow trailing commas

Linking

emcc for web/wasm deployment provides some (specialized) versions of some libs:

  • SDL2
  • SDL2_image
  • SDL2_ttf
  • libpng
  • zlib
  • and their dependencies

for now we link the libraries dynamically on Linux and use prebuilt SDL-devel (mingw) libs on Windows, but a more comlpex source tree + Makefile could integrate them as well

UI-Data-Bindings

  • signal Tracker::onLayoutChanged -> Ui::TrackerView::relayout
  • signal Tracker::onStateChanged -> Ui::Item update
  • signal Ui::Item::onClick -> ... -> Tracker::... -> Tracker::onStateChanged

Ideal ZIP

  • You would use anything (cloned repo or github-generated ZIP) during development and publish a "release ZIP" once done.
  • Ideally the release ZIP would come in two versions, one to be consumed on desktop, one to be consumed by Web browsers.
  • By having files aligned and uncompressed inside a ZIP, they can be accessed with mmap or void* without extraction (for a future version maybe).
  • (Desktop zip like apk, Web zip like usdz)

Desktop ZIP

  • Optimized ZIP (zopfli, advzip, 7z -mx=9, ...) for fastest download/disk loading
  • Optimized PNGs (zopflipng, optipng, pngcrush, ...) for fastes decompression
  • Store uncompressable/precompressed files (PNG, JPG) uncompressed in ZIP
  • Use zipalign to align all uncompressed files for direct consumption (mmap)

Web ZIP

see above, but ideally you want

  • uncompressed zip that is served over a compressed connection
  • zipalign all files (since all are uncompressed)
  • serve .br (brotli) or .gz (gzip) as indicated by the browser
  • both will compress the whole stream as one file, so duplicates in multiple files will have better compression than would be possible in a .zip
  • brotli has better compression than deflate (gzip,zip)
  • use .htaccess with mod_rewrite to serve precompressed files for optimum size and performance
  • after downloading, all files will be available uncompressed in the browser cache, aligned for direct consumption