ci(review): add Copilot code review instructions (#10012)

.github/copilot-instructions.md

@@ -0,0 +1,63 @@
+# LVGL Code Review Instructions
+
+LVGL is an embedded C99 graphics library for MCUs, MPUs, and simulators.
+Code must be portable, memory-efficient, and bare-metal safe.
+
+## Critical Issues (always flag)
+
+- NULL dereference: every `lv_malloc`/`lv_realloc` result must be checked
+- Buffer overflow or out-of-bounds array access
+- Memory leak: every `lv_malloc` needs matching `lv_free` on all exit paths
+- Use-after-free, uninitialized variable use
+- Integer overflow in size/coordinate calculations
+- Missing `#if LV_USE_xxx` / `#endif` guards for optional features
+- Global variables not in `lv_global_t` — must use `LV_GLOBAL_DEFAULT()`
+- Test headers included in production source (`#include "lv_test_..."` in `src/`)
+
+## Embedded Performance (flag in hot paths)
+
+- No heap allocation in draw loops, event handlers, timer callbacks
+- Avoid `lv_obj_is_valid()` in internal callbacks — walks entire object tree
+- `lv_free(NULL)` is safe — no redundant NULL check before it
+
+## Naming & Style
+
+- `lv_<module>_<action>_<subject>` for public API
+- ALL_CAPS for enums/defines; `_t` suffix for typedefs
+- 4 spaces, no tabs; function brace on new line; `if`/`for` brace on same line
+- `<stdint.h>` types; C files use block comments `/* */` only (no `//`), C++ files may use `//`; `"%" LV_PRId32` for format strings
+- File-scope variables must be `static`; no globals outside `lv_global_t`
+
+## Code Organization
+
+- Extract helpers when functions exceed ~50 lines, but don't over-engineer single-use helpers
+- Eliminate code duplication across branches
+- Struct layout: pointers first, then int32, then small types/bitfields (minimize padding)
+- New files follow `src/misc/lv_templ.c` section template
+- `#if LV_USE_xxx` near top, `#endif /* LV_USE_xxx */` at bottom
+
+## Memory & Error Patterns
+
+- Prefer graceful degradation over assert for recoverable failures (e.g. cache alloc fail → log + disable, not crash)
+- `LV_LOG_WARN` for unexpected recoverable conditions; `LV_LOG_ERROR` for bugs
+
+## GPU / Draw Units
+
+- All `vg_lite_*` calls: check with `LV_VG_LITE_CHECK_ERROR`
+- Use current API names (`vg_lite_set_path_type` not deprecated variants)
+- GL state: save and restore (scissor, framebuffer binding, clear color)
+- `#if LV_USE_DRAW_*` guards required
+
+## PR Requirements
+
+- Commit: `<type>(<scope>): <subject>` — imperative, lowercase, no period, max 90 chars
+- Types with source code changes: `fix`, `feat`, `refactor`, `arch`, `perf`, `style`, `test`
+- Types without source code changes: `chore`, `ci`, `docs`, `build`
+- Exception: inline source documentation (Doxygen) uses `docs` even though it lives in source files
+- CI analyzes and reports patch coverage on new coverable lines
+- New features need tests; bug fixes need regression tests when feasible
+- New features and API changes should include examples in `examples/`
+- If `lv_conf_template.h` was modified, check that `lv_conf_internal_gen.py` was run and `Kconfig` updated
+- Code must be formatted with `scripts/code-format.py` (astyle) — flag obvious style violations
+- Doxygen `/** */` with `@param`/`@return` for all public functions in `.h` files
+- Comments explain **why**, not what

.github/instructions/c-code.instructions.md

@@ -0,0 +1,43 @@
+---
+applyTo: "src/**/*.c,src/**/*.h"
+---
+
+# LVGL C Source Review Rules
+
+## Memory Safety
+
+- Every `lv_malloc` / `lv_realloc` must have a NULL check immediately after
+- Every allocation must have a matching `lv_free` on all exit paths (including error paths)
+- `lv_free(NULL)` is safe — don't add redundant NULL checks before it
+- Pointer parameters: NULL-check before dereference when caller could reasonably pass NULL
+- Array access must be bounds-checked
+
+## Error Handling
+
+- Functions returning `lv_result_t` must be checked by callers
+- Error paths must clean up all allocated resources before returning
+- Graceful runtime fallback is preferred over assert for recoverable failures (e.g. cache allocation failure should degrade, not crash)
+- Add `LV_LOG_WARN` for unexpected but recoverable conditions
+- Add `LV_LOG_ERROR` for conditions that indicate a bug
+
+## Performance
+
+- No heap allocation in hot paths (draw loops, event handlers, timer callbacks)
+- Prefer stack allocation for small temporary buffers
+- Avoid `lv_obj_is_valid()` in internal callbacks — it walks the entire object tree
+- Cache-friendly access: sequential over random
+- Struct member ordering: pointers first, then int32_t, then smaller types/bitfields — minimizes padding
+
+## Portability
+
+- No platform headers without `#if` guards
+- No compiler extensions without fallback
+- No `float`/`double` in core code unless behind `LV_USE_FLOAT`
+- Use `LV_ATTRIBUTE_*` macros for alignment/section placement
+- Use `"%" LV_PRId32` for `int32_t` format strings, not `"%d"`
+
+## Include Structure
+
+- `.h` files: `#ifndef LV_<MODULE>_H` / `#define` / `#endif`
+- Feature-gated files: keep `#if LV_USE_<FEATURE>` near the top and the matching `#endif` at the bottom; necessary includes (module headers, private headers) may appear before the feature guard
+- Never include test headers in production source files