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All Projects → hydro-sdk → Hydro Sdk

hydro-sdk / Hydro Sdk

Licence: agpl-3.0
Author native Flutter experiences in Typescript and deliver updates directly to users over the air and out of band

Programming Languages

typescript
32286 projects
dart
5743 projects
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709 projects

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Hydro-SDK

Author native Flutter experiences in Typescript and deliver updates directly to users over the air and out of band.
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Sponsored by:

What

Hydro provides a projection of Dart and Flutter into Typescript. Not everything Flutter provides has been projected yet. See https://hydro-sdk.github.io/hydro-sdk/
Hydro compiles your code into a single .hc bytecode file which can be easily packed into an existing Flutter app or loaded over the network.

What About Performance?

While your code is interpreted, ensuring it will work on all platforms that Flutter will, most of the heavy lifting is done in Dart code by Flutter itself. You don't need to sacrifice FPS or portability for quick iteration. See "Advanced Uses" below for documentation about compiling directly from Typescript to Dart for maximum performance.

Features

Hot Reload, Incremental Compilation

Stateful Hot-reload Demo

Source Maps

Source maps screenshot

Why

Easier Delivery

Serve complete experiences over HTTP. Deliver updates to parts of your app, or deliver your entire app as a packaged bytecode image over the air to users. No app stores or long reviews.

How

Hydo-SDK provides a Common Flutter Runtime (CFR), composed of a virtual machine implementing a subset of a Lua 5.2 environment, bindings for Flutter, Dart, some Javascript builtins, and a set of Flutter widgets exposing it all to embedders. All written in pure Dart. Hydro-SDK combines the CFR with guest language projections and a compilation toolchain for compiling supported languages into Lua bytecode, and Lua bytecode into Dart.

Examples

Each example can be run over the air directly off of Github using it's corresponding .hc file under dist/.

examples/pokeApp

An adaptation of https://github.com/iampawan/PokemonApp
Shows off how to load data over HTTP using a port of the http package, wait until it's ready with Futures, parse it from JSON into interfaces with dart:convert, pass it down the widget tree with a port of ScopedModel, let the user search on it with TextFormFields and animate transitions between screens with Hero animations.

examples/hotel-booking

A line for line port of https://github.com/cybdom/hotel_booking_ui
Shows off a highly customised UI with Clips and Stacks.

examples/animated-list

A line for line port of the Flutter catalog example showing off basic transition animations.

examples/basic-app-bar

A line for line port of the Flutter catalog example showing off app bars and material icons.

examples/counter

Obligatory Flutter stateful counter showcase showing a simple use of state.

examples/hostArgs

An example demonstrating how to pass non-trivial arguments, including Widget trees from a host Flutter application through to embedded Hydro content. See also https://github.com/chgibb/hydro-sdk/blob/master/test/smoke/hostArgs_test.dart

examples/unityGallery

Shows off how to use CustomScrollViews with Slivers and override ScrollPhysics to create a selection screen with all the other examples embedded.

Getting Started

Check out the example project at https://github.com/hydro-sdk/hydro_demo for documentation about getting started

Current Development

Current development is focused on the Structured Wrapper and Interface generator for Dart (SWID) sub-project under lib/swid. This project will allow for automatic projection of Dart packages (like Flutter). See https://github.com/hydro-sdk/hydro-sdk/projects/5

Advanced Uses

Transpile Typescript to Dart, Run Code in Mixed Mode With Mixed Native and Virtual (bytecode) Functions

Hydro includes a CLI utility under bin to compile .hc bytecode files into Dart code. The resulting Dart code exports a single variable called thunks which can be passed to any Dart-level Hydro widget, allowing the CFR's code-loader to swap out virtual functions with their native counterparts at run time. This effectively provides a Typescript -> Dart transpiler. The ouput doesn't look very similiar to the input Typescript, but is semantically equivalent. This can be leveraged for applications which rely on many separate .hc files at runtime, or to help keep the edit-debug experience for large .hc files fast and responsive.

Edge-Cases and Errors at Compile Time

method-name and other-method-name Defined at some-file:line,column (x,y) and some-other-file:other-line,other-column (a,b) both mangled to the following: big-hashed-name

In debug mode, the compiler tracks the identity of functions across different compiles by mangling function names. This information is passed on to (and required by) the CFR's virtual machine in debug mode in order to enable hot-reload. The above error is a santiy check performed by the compiler during compilation to ensure it hasn't accidentally assigned the same identity to two functions that it knows are not the same. This is NOT an error with your code. If you encounter this, please file an issue so we can make the compiler smarter.

Edge-Cases and Errors at Runtime

Dispatched function prototypes are required to have debug symbols but the prototype from x-y in big-hashed-name could not be matched to a debug symbol

In debug mode, the CFR's virtual machine needs code being called into from the Flutter framework as part of Flutter's normal widget lifecycle to have debugging information attached to it in order to provide hot reload. This error can usually be observed being raised when trying to execute build methods in Typescript classes which extend StatelessWidget or State. This is NOT an error with your code. This usually means the compiler wasn't quite smart enough to find all of the anonymous functions/tear offs you're using in your build methods and report them to the VM for debugging and hot-reload. If you encounter this, please file an issue so we can make the compiler smarter.

Failed to dispatch to big-hashed-method-name from x-y in big-hashed-name

In debug mode, the CFR's virtual machine will enforce that all code being called into from the Flutter framework as part of Flutter's normal widget lifecycle is looked up just in time before it's executed. If the virtual machine fails to lookup a function that is being called, this error will be thrown. This error can be observed when running code that is in the middle of attempting to call code that has just been deleted as part of a hot-reload.

attempt to index a nil value null foo

This error can be seen by regular Typescript code that attempts to access a field foo on an uninitialized object. If this error is observed originating in hydro-sdk/runtime Typescript code, after a hot-reload is performed, it may indicate a limitation of hot-reload. In debug mode, functions have their enclosing scopes refreshed before they are executed. This error can sometimes be caused by adding an import statement for a file which has never been imported before anywhere in the life of the currently running program. In this case, the code being executed is having it's enclosing scope refreshed to include the new symbols being imported, but the imported file itself is not being executed in order to initialise the new symbols being used, resulting in trying to index into nil values. This issue can be remedied by performing a hot-restart of the Dart code running the CFR virtual machine. This error does NOT necessarily indicate an error with your code.

Limitations

  • General

    • Flutter, and some of it's most popular third party packages (Like Provider and ScopedModel) rely on a lot of widget tree walking with RTTI to identify ancestors. The interface between guest code -> host code is a natural type-erasure barrier. This could be overcome to some degree if Dart supported generic constructors.
    • Most patterns that look like Widget<OtherWidget> aren't possible to express in guest code
    • Stateful hot-reload of guest code works with some limits. Incoming code with a higher number of function prototypes than what is currently running, or incoming code which would force a relocation of a running function prototype to a much higher source mapping will cause an abort and full restart.
    • Incoming code built in release mode will cause a full restart.
    • It's not yet possible to pass arguments at startup from Dart -> guest code

  • Typescript

    • The compiler toolchain needs to control tsconfig options in order to control compilation for different build profiles. strict is always turned on by default.
    • No async or await. Though, asynchronous programming is possible using a projection of Dart's Future class.
    • No yield or generators
    • We make best efforts to create an environment where APIs written for Dart's nominal, reified type system feel natural being consumed from Typescript's structural, erased type system. In some cases, this involves passing extra parameters into an API which in Dart would have expected only a type parameter. This is most used in widget tree walking APIs like ScopedModel. An example from the PokeApp example:
    public build(context: BuildContext) 
{
    const pokeHubService = ScopedModel.of<PokeHubService>(context, PokeHubService.staticType);
    ...

    Our port of ScopedModel can be found here https://github.com/chgibb/hydro-sdk/tree/master/runtime/scopedModel Full PokeApp example here https://github.com/chgibb/hydro-sdk/tree/master/examples/pokeApp

    • The current compiler toolchain is really bad at tree-shaking. For example,
    import {SizedBox} from "hydro-sdk/runtime/flutter/widgets/sizedBox/index"

    will be more efficient than

    import {SizedBox} from "hydro-sdk/runtime/flutter/widgets/index"

    and

    import {SizedBox} from "hydro-sdk/runtime/flutter/index"

Supported Languages

Prior Art for Common Flutter Runtime

Prior Art for Structured Wrapper and Interface generator for Dart

Interesting Links and Resources

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