Introduction

Bindline is a suite of several header-only libraries which are designed to avoid common mistakes with asynchronous code, e.g. event handlers and coroutines:

• FredEmmott::bindline - a library for composing functions
• FredEmmott::weak_refs - concepts and functional helpers for:
  • writing code that transparently supports different implementations of strong/weak refs
  • creating functors that store a weak reference, but invoke with a valid strong reference
• FredEmmott::cppwinrt - concepts and functional helpers for working with C++/WinRT

FredEmmott::bindline wraps the other libraries and is intended as the primary interface to them, but they can be used separately, or in any combination.

These libraries were originally an internal implementation detail of OpenKneeboard, which uses them heavily.

Requirements

• C++20 is required
• additional features are available with C++23
• these libraries are tested with recent versions of Clang, Visual Studio, and G++
• these libraries are tested on 64-bit Windows, Linux, and macOS

This project only aims to support recent compilers and standards; in particular, it is only tested with the versions of compilers that are available in GitHub’s runners.

Example

Event handlers, callbacks, and asynchronously-called code often have repetitive boilerplate for safety, or to fit a given signature; bindline aims to make this less error-prone:

auto f = &MyClass::some_func
  // Store an `std::weak_ptr` or `winrt::weak_ref`, but when invoking:
  // 1. convert back to a strong ref
  // 2. return without invoking if the ref is stale (i.e. `nullptr`)
  | bind_refs_front(this)
  // Automatically switch thread when invoked
  | bind_winrt_context(winrt_apartment_context_or_dispatcher_queue())
  // if some_func() takes N parameters, require invocing with N + 2
  // parameters; this can be useful for event handlers
  | drop_n_back<2>();

f(args...);