pcbjam/docs/features/fork-cleanup/03-config-not-code.md

03 — Config, not code

Several #ifdef __EMSCRIPTEN__ patches re-implement, in C++, behavior that KiCad already exposes as a runtime setting or a CMake cache variable. Replacing the patch with a shipped config file (or a -D) gives identical behavior, removes the source edit, and keeps the knob user-changeable.

1. Zoom-to-cursor → input.center_on_zoom

Patch today: common/view/wx_view_controls.cpp (+9) and part of common/draw_panel_gal.cpp force m_warpCursor = false under __EMSCRIPTEN__ (browsers can't warp the OS pointer, so center-on-zoom is wrong; zoom-to-cursor is correct).

But this is already a user preference. common/settings/common_settings.cpp:228 defines PARAM<bool>("input.center_on_zoom", …, true) (the "Center and warp cursor on zoom" checkbox in Mouse & Touchpad). The two lines the fork patched are exactly the consumption sites: wx_view_controls.cpp:172 and draw_panel_gal.cpp:712. The wheel handler already implements point-under-cursor-stays-fixed when the pref is false.

Do instead: seed the browser FS with a first-run kicad_common.json containing "input": { "center_on_zoom": false }. Covers both sites, stays toggleable. Belt-and- suspenders: the wasm kiplatform WarpPointer() should return false — callers (wx_view_controls.cpp:342,972) already handle that gracefully, so even if a user re-enables the pref it degrades, not breaks. Removes 2 source patches.

2. Backspace-deletes → default user.hotkeys

Patch today: common/tool/actions.cpp (+7) adds DefaultHotkeyAlt(WXK_BACK) to the delete action under __EMSCRIPTEN__ so Mac-browser users' Backspace deletes.

Do instead: ship a default user.hotkeys file in the FS image mapping both Delete and Backspace to the delete action — pure runtime config.

⚠️ The companion change in common/tool/action_manager.cpp (+5) is not config — it's a genuine upstream bug fix (m_defaultHotKeyAlt is never applied, so DefaultHotkeyAlt() is dead upstream in default configs). That one belongs in 06, and the default-user.hotkeys route only needs it for the default-alt path; an explicit user-hotkeys mapping works without it.

3. Profile timer → HAVE_CLOCK_GETTIME

Patch today: libs/core/profile.cpp (+9) adds an #elif defined(__EMSCRIPTEN__) branch to GetRunningMicroSecs() using emscripten_get_now(). The existing upstream branches gate on the configure-time macros HAVE_CLOCK_GETTIME / HAVE_GETTIMEOFDAY_FUNC.

Do instead: Emscripten supports clock_gettime, so set HAVE_CLOCK_GETTIME in the wasm CMake cache / toolchain and the existing branch compiles. Zero source change.

4. Static KIFACE startup → call OnKifaceStart from the shell

Patch today: common/kiway.cpp (+33) special-cases KIWAY::KiFACE() under __EMSCRIPTEN__: it treats m_kiface_version == 0 as "OnKifaceStart not yet called" and either calls the statically-linked KIFACE_GETTER or backfills the version for a pre-set_kiface()'d face, then calls OnKifaceStart.

Do instead: the fork controls startup, so the wasm shell can call kiface->OnKifaceStart(&Pgm(), ctl, &kiway) itself at its set_kiface() call site. Then upstream's existing if(m_kiface[aFaceId]) return m_kiface[aFaceId]; early-return path works unmodified, and the single static KIFACE_GETTER fallback also lives in the shell. Removes the 33-line in-source block.

5. Keep the scripting member unconditional

include/pgm_base.h (+2) wraps std::unique_ptr<SCRIPTING> m_python_scripting in #ifdef KICAD_SCRIPTING. A unique_ptr to a forward-declared type compiles without the full header and is simply never populated when scripting is off — so the member can stay unconditional and the header reverts. (The .cpp creation site in common/pgm_base.cpp still needs its guard; that's part of the coherent scripting-optional patch in 05/06, not this doc.)

Net

Patch	Replacement	Removes
wx_view_controls.cpp, draw_panel_gal.cpp warpCursor	kicad_common.json default	2 sites
actions.cpp Backspace	default user.hotkeys	1 site (+ see 06)
profile.cpp timer	HAVE_CLOCK_GETTIME cache var	1 file
kiway.cpp static KIFACE	OnKifaceStart from shell	33 lines
pgm_base.h member guard	unconditional unique_ptr	1 header

The config files live in the wasm/ / web/ layer — no upstream footprint.