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diff --git a/docs/chapter31/graphics.md b/docs/chapter31/graphics.md new file mode 100644 index 00000000..4977b490 --- /dev/null +++ b/docs/chapter31/graphics.md @@ -0,0 +1,132 @@ +# Optional graphics + +Simple owns the pixel array and drawing code. [MiniFB](https://github.com/emoon/minifb) +provides a window, input, and pixel presentation. The first interface is +`sys.gfx`: one fixed-size window, operated on the main thread. The +[Graphics example](examples/Graphics.smp) draws a color gradient in Simple. +The [drawing library and graphical tic-tac-toe](drawing.md) build on this pixel +interface. `make run-graphical-tictactoe CTAGS=` builds the optional backend and +opens the game; `make graphical-tictactoe CTAGS=` only builds its executable. +The game run target also builds optional [background audio](audio.md). + +## Default: no graphics dependency + +From `chapter31`, the usual `make release`, `make tests`, and `make tictactoe` +need no MiniFB, graphics headers, OpenGL, CMake, or running display. Nothing +downloads dependencies unless you explicitly request `make libs` or `make init` +(`make lib` remains a setup alias). Build and run targets never use the network. + +`make tests_nographics CTAGS=` runs the entire ordinary suite with +`SIMPLE_MINIFB=off`. This includes the missing-backend tests, which never open +windows. It excludes the interactive `run-graphics` target. + +The runtime contains a small loader using the OS dynamic-library facilities. +It does nothing until `sys.gfx.open`. Without an available backend, `open` +prints a diagnostic to stderr and returns `sys.gfx.ERROR` (-1). Programs can +return a nonzero status or fall back to text; the library does not terminate +the process. Non-graphics programs ignore even a broken graphics configuration. + +## Build the optional backend + +From `chapter31`: + +```sh +make libs CTAGS= # Once while online; fills the persistent lib/ cache. +make graphics graphics-example CTAGS= +make run-graphics CTAGS= +``` + +`libs` downloads the revision pinned in [graphics.mk](../graphics.mk) into +ignored `lib/minifb-<revision>.tar.gz` and extracts it under `lib/`. +`graphics` builds only its C framebuffer backend from these local sources. Windows +uses the MinGW-w64 GCC compiler (`x86_64-w64-mingw32-gcc`) and GDI; the rest of +Simple still uses the existing Cygwin GCC. Linux uses GCC and X11 (`libx11-dev` +on Ubuntu), including XWayland on a Wayland desktop. OpenGL, the C++ callback +wrappers, and upstream example programs are omitted. Native Wayland and macOS +builds are not provided here yet. + +Outputs: + +| Platform | Backend | Example | +| --- | --- | --- | +| Windows | `build/release/x86_64_v2_win64/simple_minifb.dll` | `build/examples/x86_64_v2_win64/Graphics.exe` | +| Linux | `build/release/x86_64_v2_SystemV/libsimple_minifb.so` | `build/examples/x86_64_v2_SystemV/Graphics` | + +`MiniFB-LICENSE` is copied alongside the backend; include it when distributing +the library. MiniFB sources remain outside the tracked Simple sources. +The cache survives `make clean`. Editing a makefile or rebuilding a backend +does not fetch or check GitHub. Missing dependencies fail promptly with +instructions to run `make libs` while online. + +`graphics-example` alone builds the executable without requiring MiniFB. It +also demonstrates the diagnostic and exit status 1 when graphics is absent. +`run-graphics` builds both, sets the backend path, and opens a window. Close it +or release Escape to exit. Passing any argument to the executable makes it +close after five polling iterations, for a quick smoke test. + +To run directly from PowerShell: + +```powershell +$env:SIMPLE_MINIFB = (Resolve-Path build/release/x86_64_v2_win64/simple_minifb.dll).Path +.\build\examples\x86_64_v2_win64\Graphics.exe +``` + +From Cygwin bash: + +```sh +export SIMPLE_MINIFB="$PWD/build/release/x86_64_v2_win64/simple_minifb.dll" +./build/examples/x86_64_v2_win64/Graphics.exe +``` + +For WSL, from the repository root: + +```sh +wsl -d Ubuntu-24.04 -- bash -lc 'cd chapter31 && make graphics graphics-example CLZDIR=build/classes-linux CTAGS=' +``` + +Inside WSL, set `SIMPLE_MINIFB` to the full path of the Linux `.so`, then run +the Linux example with a working X11 display. For an automated virtual display: + +```sh +SIMPLE_MINIFB="$PWD/build/release/x86_64_v2_SystemV/libsimple_minifb.so" \ + xvfb-run -a build/examples/x86_64_v2_SystemV/Graphics smoke +``` + +With no `SIMPLE_MINIFB` setting, the runtime searches beside the executable, +then its `../../release/<ABI>` and `../release/<ABI>` directories. These cover +the examples and test build layouts regardless of the current directory. +It also checks the current directory, `build/release/<ABI>`, and +`chapter31/build/release/<ABI>` relative to the current directory. Thus built +examples such as `Clock.exe` can be launched directly without configuration. + +`SIMPLE_MINIFB` overrides discovery; an invalid explicit path reports an error +without falling back. `SIMPLE_MINIFB=off` disables graphics for headless tests. +An absent, unloadable, or incompatible backend produces a diagnostic. +A backend that loads but cannot create a window also reports an error cleanly. + +## Initial interface + +| Operation | Meaning | +| --- | --- | +| `open(title,width,height)` | Open one window; returns `OK` or `ERROR`. | +| `present(pixels)` | Present a `u32[~]` of exactly `width*height` pixels, packed `0x00RRGGBB`. | +| `poll(wait)` | Process input; `true` waits up to 17ms, waking for input. | +| `wait(timeoutMs)` | Wait for input or timeout, then process events; 0 polls, -1 waits indefinitely. | +| `mouseX()`, `mouseY()` | Current mouse position, origin at upper left. | +| `button(LEFT)`, `key(code)` | Current pressed state; printable keys use uppercase ASCII. | +| `close()` | Release native window and pixel storage; safe to repeat. | + +`present`, `poll`, and `wait` return `OK` (0), `CLOSED` (1, normal close/Escape), or +`ERROR` (-1). Stop polling after either terminal result and call `close`. +The initial input API samples held state; it is not a queue of every transition. + +Waits may return early; values below -1 are errors. Recheck the monotonic +clock after waking. The [time library and animation example](time.md) combine +this wait with cooperative timer deadlines. Backend API version 2 adds the +wait operation; rebuild older MiniFB adapters from the cached sources. + +MiniFB retains its last framebuffer for repaint events. The adapter copies the +Simple array into native-owned storage before presenting; it never retains a +Simple heap pointer. Framebuffer allocation, the copy, and window/input calls +are the only native work here. Drawing primitives and the games can be built +in Simple on top of this boundary. |