OOPS_FEATURES: Declarative Subsystem Capabilities

OOPS_FEATURES is the declarative capability interface provided by oops-sdk for applications built with oops-apps/common/app.mk.

An application declares what capabilities it requires (intent), rather than hand-listing SDK source files (implementation):

# In your application's Makefile:
OOPS_FEATURES += keyboard net http audio

1. Motivation & Architecture

Historically, application Makefiles hand-listed individual SDK source files in PAYLOAD_SRCS:

# ANTI-PATTERN: Leaking SDK implementation into applications
PAYLOAD_SRCS = main.c \
               $(OOPS_SDK_DIR)/src/input/input.c \
               $(OOPS_SDK_DIR)/src/input/keyboard.c \
               $(OOPS_SDK_DIR)/src/net/net.c \
               $(OOPS_SDK_DIR)/src/net/netctl.c \
               $(OOPS_SDK_DIR)/src/net/dns.c \
               $(OOPS_SDK_DIR)/src/net/http.c \
               $(OOPS_SDK_DIR)/src/system/zip.c

This caused multiple points of friction:

Fragility: When an SDK subsystem was refactored into additional files (such as oops-gl adding shader compiler modules), every application's link broke with undefined symbol errors until their Makefiles were individually updated.
Hidden Symbol Dependencies: Subsystems depend on platform libraries (libSceKeyboard, libSceHttp, etc.). If an app forgot to ensure common/symbols.txt mapped those imports, obscene-tool mkmodule could not tag them for the loader, causing silent runtime failures on hardware.
Leaked Implementation: Title authors had to know the internal file layout and module structure of the SDK.

The Single Source of Truth

The SDK owns its source files, their dependencies, and their libSce* import claims. Therefore, oops-sdk/oops-sdk.mk defines:

OOPS_FEATURE_<name>_SRCS: The source files implementing capability <name>.
OOPS_FEATURE_<name>_SYMS: The required libSce* library imports.
OOPS_FEATURES_AVAILABLE: The roster of all supported capabilities.

oops-apps/common/app.mk is the consumer front-door:

Validates requested features against OOPS_FEATURES_AVAILABLE.
Appends $(OOPS_FEATURE_<f>_SRCS) to PAYLOAD_SRCS.
Passes $(OOPS_FEATURE_<f>_SYMS) to mkmodule for module tagging.
Emits a fatal $(error ...) if an unknown feature is requested.

2. Complete Capabilities Reference

Feature	Header API	Description	SDK Sources (`OOPS_FEATURE_<f>_SRCS`)	Platform Imports (`_SYMS`)
`base`	`<oops/system.h>`	Core runtime (implicit always-on)	`system.c`, `freestd.c`, `syscall.c`, `offsets.c`, `fs.c`, `sysmodule.c`, `procparam.c`, `memory.c`, `heap.c`, `time.c`	`libkernel`, `libSceLibcInternal`, `libSceSystemService`, `libSceUserService`, `libSceSysUtil`
`display`	`<oops/display.h>`	Video scanout & AGC/GNM command buffers	`src/display.c`, `src/agc/.c` (or `src/gnm/.c`)	`libSceVideoOut`, `libSceAgc`, `libSceAgcDriver`, `libSceGnmDriver`
`draw`	`<oops/draw.h>`	2D CPU software drawing canvas	`src/draw/draw.c`	(none)
`png`	`<oops/draw.h>`	PNG image decompressor	`src/draw/png.c`	(none)
`hud`	`<oops/hud.h>`	On-screen debug HUD overlay	`src/hud/hud.c`	(none)
`input`	`<oops/input.h>`	DualSense / DualShock gamepad polling	`src/input/input.c`	`libScePad`, `libSceUserService`
`keyboard`	`<oops/keyboard.h>`	USB & Bluetooth keyboard events	`src/input/keyboard.c`	`libSceKeyboard`
`mouse`	`<oops/mouse.h>`	USB & Bluetooth mouse polling	`src/input/mouse.c`	`libSceMouse`
`audio`	`<oops/audio.h>`	Low-latency PCM audio streaming	`src/audio/audio.c`	`libSceAudioOut`
`audiodec`	`<oops/audiodec.h>`	Hardware audio decoding (AT9, AAC, MP3)	`src/audio/audiodec.c`	`libSceAudiodec`, `libSceAjm`
`videodec`	`<oops/videodec.h>`	Hardware H.264 / AVC video decoding	`src/videodec/videodec.c`	`libSceVideodec2`
`net`	`<oops/net.h>`, `<oops/netctl.h>`	BSD sockets, link status & DNS client	`src/net/net.c`, `src/net/netctl.c`, `src/net/dns.c`	`libSceNet`, `libSceNetCtl`, `libkernel`
`dns`	`<oops/dns.h>`	Standalone RFC 1035 DNS resolver	`src/net/dns.c`	`libSceNet`
`http`	`<oops/http.h>`	HTTP/HTTPS client & streaming download	`src/net/http.c`, `src/system/zip.c`	`libSceHttp`, `libSceSsl`, `libSceNet`
`zip`	`<oops/zip.h>`	Freestanding Deflate & ZIP extractor	`src/system/zip.c`	(none)
`savedata`	`<oops/savedata.h>`	User save data storage & mounts	`src/system/savedata.c`	`libSceSaveData`
`dialog`	`<oops/dialog.h>`	System IME (OSK) & message dialogs	`src/system/dialog.c`	`libSceCommonDialog`, `libSceImeDialog`, `libSceMsgDialog`
`thread`	`<oops/thread.h>`	POSIX threads, semaphores & mutexes	`src/thread/thread.c`	`libkernel`
`jit`	`<oops/jit.h>`	Dynamic JIT shared memory allocation	`src/system/jit.c`	`libkernel`
`escalate`	`<oops/escalate.h>`	Privilege escalation & jailbreak	`src/system/escalate.c`	`libkernel`
`inject`	`<oops/krw.h>`	Kernel R/W & target process injection	`src/system/krw.c`, `procctl.c`, `loader.c`, `target.c`, `inject.c`	`libkernel`
`pkg`	`<oops/pkg.h>`	Background package installer client	`src/system/pkg.c`	`libSceAppInstUtil`
`suspend`	`<oops/system.h>`	System suspend/resume event hooks	`src/system/suspend.c`	`libSceSystemService`
`glu`	`<GL/glu.h>`	OpenGL GLU utility matrix/projection	`src/gl/gl_glu.c`	(none)
`glut`	`<GL/glut.h>`	OpenGL GLUT toolkit & bitmap fonts	`src/gl/glut.c`, `src/gl/glut_font.c`	(none)
`js`	`<oops/js.h>`	Standalone QuickJS JavaScript engine (ES2020)	`src/js/js.c`, `src/js/quickjs/*.c`	(none)
`html`	`<oops/html.h>`	Standalone litehtml HTML5/CSS layout & renderer	`src/html/oops_html.cpp`, `src/html/html_container.cpp`, `src/html/litehtml/src/.cpp`, `src/html/litehtml/src/gumbo/.c`	(none)
`webview`	`<oops/webview.h>`	Assembled Webview browser (QuickJS + litehtml + DOM + fetch)	`src/webview/*.cpp`	(none; depends on `js`, `html`, `http`, `input`)

3. Base Runtime (Implicit Always-On)

Every application links the base feature automatically, even if OOPS_FEATURES is unset:

system.c: Process lifecycle, firmware detection, klog logging, /app0/oops-log channels.
freestd.c: Clean-room libc primitives (obs_strlen, obs_memcpy, obs_format_hex, etc.).
syscall.c & offsets.c: Direct system call dispatch and kernel data structures.
fs.c: Sandboxed and persistent filesystem traversal and POSIX file IO.
sysmodule.c: Dynamic library loading (sceSysmoduleLoadModule).
procparam.c: Title execution environment and process parameters.
memory.c & heap.c: Direct memory (sceKernelAllocateDirectMemory) and userland allocator.
time.c: Monotonic high-resolution clock and TSC frequency.
libc.c, scanf.c, math.c: Freestanding C runtime stubs (for non-Mesa titles).

4. How to Use in an Application

In Makefile:

APP_NAME    := my-homebrew
ENTRY_POINT := my_app_start

# Declare capabilities:
OOPS_FEATURES := display draw input keyboard audio

# If using OpenGL, declare renderer:
# OOPS_RENDERER = gl1 | gl2 | mesa

# Only list your own application sources:
PAYLOAD_SRCS := main.c app_logic.c

include $(OOPS_APPS_ROOT)/common/app.mk

Relationship with `OOPS_RENDERER`

OOPS_RENDERER = gl1 | gl2 automatically pulls oops-gl sources (OOPS_GL_SRCS).
OOPS_RENDERER = mesa automatically pulls oops-mesa hosted sysroot and libraries.
Subsystems used alongside graphics (e.g. keyboard, audio, savedata) are declared via OOPS_FEATURES.

5. Adding a New Feature to the SDK

To add a new capability <feat>:

Define Sources: In oops-sdk/oops-sdk.mk, define:

OOPS_FEATURE_<feat>_SRCS := $(OOPS_SDK_DIR)/src/path/to/source.c

Define Symbol Claims: Specify the required platform library imports:
```
OOPS_FEATURE_<feat>_SYMS := libSce<LibraryName>
```
Add Symbol Manifest: Create oops-sdk/symbols/<feat>.syms containing the <library> <symbol> lines.
Register in Roster: Append <feat> to OOPS_FEATURES_AVAILABLE in oops-sdk.mk.
Document: Add the entry to the table in docs/FEATURES.md and regenerate the API index (bash tools/api-index.sh).