ludic/changes/state.md

bump: major type: feature No function writes a global: a module's changing data is a state. state Hiker { hips: int = -1 } is a record with exactly one instance, which no code can name; it reaches code as a parameter, h: mut Hiker to change it or h: Hiker to read it, and the runtime supplies it at the entry points (entry (h: mut Hiker), a handler's, a listener's or a lifecycle hook's parameters, a scene's on enter (h: mut Hiker), a test's, a ui block's Hiker.hips, a function value - a system's, a port bind's, a package's callback - an engine system, a namespace method's target and every call into the runtime). A module-level var is refused; a module-level let is immutable all the way down. A read-only state is checked where it is written - an assignment or a push through it or through a local holding part of it, passing it where mut is wanted, a machine over its field - and so is a module-level let. Each test block gets fresh states. A program's type named like one the runtime declares (property PadButton beside the runtime's enum PadButton) is refused instead of failing in clang.

ludic migrate state [file|dir...] [--runtime] [--dry-run] moves programs there: a var nothing writes becomes a let, each module's other vars one state (FishingState, Render3dState, SceneDemoState), every reference fishing_st.name, each function's states - to a fixed point over what it calls - its leading parameters, mut where anything below it writes, and each entry point declares them; the plans of every program given are merged before a file is edited. gpp's 35 mechanic packages, ludic.ui, ludic.render3d, every example, the docs' fences and the runtime were moved with it. The toolchain's own programs build with --globals until they move too.

Outside the runtime, the drawable's size and scale, the screen's framebuffer and the tilemap's tile size are read and set through its functions (gl_width(), gl_set_drawable(w, h), gl_screen_fbo(), gl_pixel_scale(), rt_map_tile_size()), and ludic.ui's render3d backend installs itself through the UiRenderers registry.