View source for C++20


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

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

{| class="wikitable"
|-
! Feature                           !! Since !! Can use?                                    !! GCC    !! Apple Clang !! Comment
|-
| <code>std::span</code>            || C++20 || style="background: lightgreen;" | from 1.4  || 10     || 11.0.3 || Handle buffers like standard library containers without risk of overflow.
|-
| <code>std::format</code>          || C++20 || style="background: pink;"       |           || 13     || N/A    || Better and more efficient formatting of strings. [https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0645r10.html Text Formatting]
|-
| <code>std::lerp</code>            || C++20 || style="background: lightgreen;" | from 1.4  ||  9     || 11.0.3 || Linear interpolation. (ui/tools/pencil-tool.cpp)
|-
| <code>std::bit_floor</code>       || C++20 || style="background: lightgreen;" | from 1.4  || 9/10   || 11.0.3/13.0.0 || Compute floor(log2(x)). (helper/mathfns.h)
|-
| <code>Concepts</code>             || C++20 ||                                   from 1.4? || 6/10   || 12.0.0 Partial || Safer templating. (ui/controller.h)
|-
| <code>Coroutines</code>           || C++20 ||                                             || 10     || 10.0.1 Partial || Simpler asynchronous code. (trace/trace.cpp)
|-
| <code>std::make_unique_for_overwrite</code> || C++20 || style="background: pink;" |       || 11     || N/A    || Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
|-
| <code>Ranges</code>               || C++20 ||                                   from 1.4? ||        || ?      || for (init; decl : expr). (ui/dialog/swatches.cpp)
|-
| <code>[https://stackoverflow.com/a/60244416/5075760 Structural templates]</code> || C++20 || from 1.4? ||   || Partial      || Allow instances of arbitrary literal classes as template parameters. (display/drawing.cpp)
|-
| <code>Mathematical Constants</code>|| C++20 ||                                            || 10      || 12.0.5 || Constants like std::numbers::pi.     
|}

As of 6 September 2023, the CI runners for:
* Linux:
** appimage:linux GNU 10.5 (Building on "oldest supported Ubuntu LTS release", we must wait until April 2025 to use a newer GNU version!) Note: Gtkmm4 is not available in Ubuntu 20.04 or 22.04!
** inkscape:linux GNU 11.4.0
* Windows
** inkscape:windows:build Gnu 13.1.0
** inkscape:windows:dist Same as above.
* macOS:
** inkscape::macos:arm Apple Clang 13.1.6
** inkscape:macos:x64: Apple Clang 14.0.0.


We strive to support lastest Debian stable and latest Ubuntu LTS. But this may not be possible for a gtk4 based release. Ideally, we would target gtkmm4 4.10 as it has a critical scrolling bug fix.
{| class="wikitable"
|-
! 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
|}

Errors and Deprecated items that we use:
* error: call of overloaded ‘lerp(double, double&, double&)’ is ambiguous  (ui/knot/knot-holder-entity.cpp)
* 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]