C++20

See also C++11, C++17, C++23.

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	15.3	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, 15.3 Full	Simpler asynchronous code. (trace/trace.cpp)
std::make_unique_for_overwrite	C++20	not yet	11	15.0.0	Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
Ranges	C++20	not yet		?	(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.
Heterogenous lookup in std::unordered_map	C++20	not yet			Faster lookup, use of smart pointers as keys.
consteval static member functions	C++20	not yet			Guaranteed compile time evaluation of member functions (stronger than constexpr)

References:

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

As of 21 September 2025, the CI runners for the various supported platforms are

• Linux: GCC 13.3.0 (on Ubuntu 24.04)
• Windows: GCC 15.1.0
• macOS: Apple Clang 17.0.0
• Android: Clang 19.0.0 (on Ubuntu 24.04)

We support the latest Debian stable and latest Ubuntu LTS.

Distro	gcc	clang	glib	glibmm	gtk4	gtkmm4
Debian 13 (Trixie)	14.2.0	19.0	2.84.4	2.84.0	4.18.6	4.18.0
Ubuntu 24.04 (Noble)	13.3.0	18.1.3	2.80.0	2.78.1	4.14.2	4.10.1

The build requires glibmm >= 2.78.1 and gtkmm4 >= 4.14, however Inkscape will compile its own gtkmm4 if the system version is too old, so building on Ubuntu 24.04 still works out of the box.

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]