Inital context stuff and tests

Linking and  building is successfull and inital tests pass

docs/dd.md

@@ -72,9 +72,20 @@ color emoji are out of scope for the first versions.
 
 ## Rendering
 
-Rectangles, borders, and glyphs all reduce to quads. A backend only needs to
-manage textures, draw quad batches, and apply a scissor rect. Rendering
-backends are replaceable, and the SDL3 and OpenGL backend is the default.
+The core never calls a backend. Each frame `rg_render` returns a draw list
+made of texture operations (create, update region, destroy) followed by
+batches of colored and textured quads with scissor rects. A backend is any
+code that consumes that list. The SDL3 and OpenGL backend is the default, and
+the null backend records the list for headless tests. A WASM host can consume
+the list from JavaScript. The shipped backends share a small convenience
+interface, and the core does not depend on it.
+
+## Viewport and scale
+
+All API coordinates are logical pixels. The host calls
+`rg_set_viewport(ctx, w, h, scale)` when the window resizes or the display
+scale changes. A scale change invalidates the glyph atlas and glyphs are
+rasterized again at the new size.
 
 ## Documents
 
@@ -144,27 +155,6 @@ across the FFI boundary.
   never by raw pointers.
 - The user can supply an allocator, and internal allocation uses arenas.
 
-## Build and environment
-
-The build system is CMake with Ninja. Development happens on NixOS using
-direnv and flakes, and the devShell provides CMake, Ninja, pkg-config, clang,
-clang-tools, SDL3, Emscripten, and lua-language-server. Emscripten's cache
-directory is set to `.emscripten-cache` inside the project. WASM builds go
-through `emcmake` into `build-wasm/`. Sources live in a flat `src/` with no
-generated files, so Zig and Odin users can compile them with their own
-toolchain.
-
-## Milestone 1
-
-A `main.lua` builds a `VBox` of `Label` and `Button` nodes. A stylesheet with
-classes and a `:hover` state styles them. Layout runs through Clay and draws
-through the SDL3 and OpenGL backend with stb_truetype text. A button click
-fires both a Lua handler and a named event in the polled queue. One
-transition eases a button background on hover. A data-bound label shows a
-counter that the button increments.
-
-Text inputs and scrolling follow in milestone 2, along with focus handling.
-
 ## Context and ownership
 
 All state lives in an `rg_context`, which is created with `rg_create` and
@@ -194,8 +184,47 @@ Gamepad navigation will be added as a semantic layer (up, down, left, right,
 accept, cancel) that drives focus movement, so a game can map any device to
 it.
 
-## Open questions
+## Errors and logging
 
-- Whether texture uploads travel inside the draw list.
-- Viewport and display scale handling.
-- Error reporting and logging.
+Functions that can fail return an `int` status where zero is success and
+negative values are errors. `rg_last_error(ctx)` returns the message for the
+most recent failure on that context. The config carries a log callback, a log
+level, and a userdata pointer. The default callback writes to stderr and the
+default level is trace, so logging is verbose until I lower it. Lua errors
+such as syntax errors and handler failures are logged and never replace the
+live tree, so a broken save during hot reload leaves the last good tree on
+screen.
+
+## Testing
+
+`ctest` runs the smoke tests. The core smoke test installs a counting
+allocator and fails if any bytes are live after `rg_destroy`. Every
+allocation, including Lua's, goes through the context allocator.
+
+### Build and environment
+
+The build system is CMake with Ninja. Development happens on NixOS using
+direnv and flakes, and the devShell provides CMake, Ninja, pkg-config, clang,
+clang-tools, SDL3, Emscripten, and lua-language-server. Emscripten's cache
+directory is set to `.emscripten-cache` inside the project. WASM builds go
+through `emcmake` into `build-wasm/`. Sources live in a flat `src/` with no
+generated files, so Zig and Odin users can compile them with their own
+toolchain.
+
+### Milestone 1
+
+A `main.lua` builds a `VBox` of `Label` and `Button` nodes. A stylesheet with
+classes and a `:hover` state styles them. Layout runs through Clay and draws
+through the SDL3 and OpenGL backend with stb_truetype text. A button click
+fires both a Lua handler and a named event in the polled queue. One
+transition eases a button background on hover. A data-bound label shows a
+counter that the button increments.
+
+Text inputs and scrolling follow in milestone 2, along with focus handling.
+
+
+
+### Open questions
+
+- Node handle format.
+- Property system: how properties are named, typed, and stored.