C++20

See also C++11, C++17.

Some things that will be interesting to use once C++20 is common:

Feature	Since	Can use?	GCC	Apple Clang	Comment
std::span	C++20	from 1.4	10	11.0.3	Handle buffers like standard library containers without risk of overflow.
std::format	C++20	not yet	13	N/A	Better and more efficient formatting of strings. Text Formatting
std::lerp	C++20	from 1.4	9	11.0.3	Linear interpolation. (ui/tools/pencil-tool.cpp)
std::bit_floor	C++20	from 1.4	9/10	11.0.3/13.0.0	Compute floor(log2(x)). (helper/mathfns.h)
Concepts	C++20	from 1.4?	6/10	12.0.0 Partial	Safer templating. (ui/controller.h)
Coroutines	C++20	not yet	10	10.0.1 Partial	Simpler asynchronous code. (trace/trace.cpp)
std::make_unique_for_overwrite	C++20	not yet	11	N/A	Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
Ranges	C++20	not yet		?	for (init; decl : expr). (ui/dialog/swatches.cpp)
Structural templates	C++20	from 1.4?		Partial	Allow instances of arbitrary literal classes as template parameters. (display/drawing.cpp)
Mathematical Constants	C++20		10	12.0.5	Constants like std::numbers::pi.

References:

• General: https://en.cppreference.com/w/Template:cpp/compiler_support/20
• Apple Clang: https://developer.apple.com/documentation/xcode-release-notes

As of 27 March 2024, the CI runners for the various supported platforms are

• Linux:
  • appimage:linux: GNU 13.2.0 (building on Ubuntu 23.10)
  • inkscape:linux: Same as above
• Windows
  • inkscape:windows:build: GNU 13.2.0 (temporarily disabled since GTK4 port)
  • inkscape:windows:dist: Same as above
• macOS:
  • inkscape::macos:arm: Apple Clang 15.0.0
  • inkscape:macos:x64: Apple Clang 13.0.0 (temporarily disabled since GTK4 port)

We strive to support latest Debian stable and latest Ubuntu LTS. However, we had to break that promise since the GTK4 port, which requires gtkmm4 >= 4.14:

Distro	gcc	clang	gtkmm4
Debian 12 (Bookworm, stable)	12.2.0	15.0.6	4.8.3
Ubuntu 22.04 (Jammy Jellyfish)	12.3.0	15.0.7	Not packaged!
Ubuntu 23.04 (Lunar)	13.1.0	16.0.0	4.10.1

Ubuntu users therefore have the following options:

• Wait for Ubuntu 24.04, expected around 25 April 2024.
• Upgrade to Ubuntu 24.04 now.
• Upgrade to Ubuntu 23.10 and build gtkmm4 from source, as is currently done by CI.
• ???

Deprecated items that we still use:

• warning: implicit capture of ‘this’ via ‘[=]’ is deprecated in C++20 [-Wdeprecated] https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0806r2.html
• warning: bitwise operation between different enumeration types ‘Box3D::Axis’ and ‘Box3D::FrontOrRear’ is deprecated [-Wdeprecated-enum-enum-conversion]