grain

A modern C++ framework for building native, cross-platform applications with a clean platform-independent API.

Linux backends

Linux builds use X11 by default. The optional Linux GTK4 backend uses GTK4 windows and native GSK paths rendered through a custom widget's snapshot. Select one backend per build; application code uses the same App, Window, View, and GraphicContext APIs.

Install GTK4 4.14 or later development packages, CMake 3.30 or later, Ninja, and a C++23 compiler. On Ubuntu/Debian, the GTK4 development package is libgtk-4-dev.

cmake --preset linux-gtk4
cmake --build --preset linux-gtk4
ctest --preset linux-gtk4
./build/linux-gtk4/examples/basic/grain_basic

For a custom build directory, use -DGRAIN_LINUX_BACKEND=GTK4; select X11 for the existing backend. GTK4 chooses the display backend at runtime; set GDK_BACKEND=wayland or GDK_BACKEND=x11 to select it explicitly when available.

The GTK4 backend supports native path fills and strokes (including Bézier curves), transforms, saved graphics state, resize/focus/close events, and exits the application loop when its last window closes. Keyboard, text, and pointer event forwarding are not implemented yet. GTK initialization, window operations, and the application loop must run on the main thread. GTK4 callback exceptions are rethrown by App::run().

GTK4 receives GSK fill/stroke nodes and selects the renderer. Grain does not rasterize GTK4 views with Cairo; the separate X11 backend still uses Cairo.

GTK4 integration tests run with Xvfb when xvfb-run is installed. They check native render nodes and pixels for fills, strokes, curves, and transforms using GTK's software renderer. They exercise the X11 display backend; testing native Wayland requires a Wayland session. To also test the OpenGL renderer:

GDK_BACKEND=x11 GSK_RENDERER=gl GTK_A11Y=none xvfb-run -a ./build/linux-gtk4/tests/GrainGtk4Tests