add a script to transpile imgui header from cpp to lua

cmake/imgui4lua.cmake

@@ -0,0 +1,23 @@
+function(_imgui4lua_main)
+  set(dir "${CMAKE_CURRENT_BINARY_DIR}/generated")
+  set(py  "${PROJECT_SOURCE_DIR}/cmake/imgui4lua.py")
+  set(src "${imgui_SOURCE_DIR}/imgui.h")
+  set(dst "${dir}/imgui4lua.inc")
+
+  find_program(SH      sh      REQUIRED)
+  find_program(PYTHON3 python3 REQUIRED)
+  find_program(CLANGXX clang++ REQUIRED)
+
+  make_directory("${dir}")
+  add_custom_command(
+    COMMAND  ${SH} -c "${PYTHON3} '${py}' '${src}' > '${dst}'"
+    OUTPUT  "${dst}"
+    DEPENDS "${src}" "${py}"
+    VERBATIM
+  )
+
+  add_library(imgui4lua INTERFACE)
+  target_sources(imgui4lua PUBLIC "${dst}")
+  target_include_directories(imgui4lua INTERFACE ${CMAKE_CURRENT_BINARY_DIR})
+endfunction()
+_imgui4lua_main()

cmake/imgui4lua.py

@@ -0,0 +1,133 @@
+import json
+import subprocess
+import sys
+
+# ---- GENERATOR DEFINITIONS
+def gen_func(item):
+  name = item["name"]
+  if name not in kFuncWhitelist:
+    return
+
+  pops   = []
+  params = []
+  pcount = 0
+  for arg in item.get("inner", []):
+    pop, param, push = gen_argument(pcount, arg)
+    pcount += 1
+    pops  .extend(pop)
+    params.extend(param)
+    push  .extend(push)
+
+  pushes  = gen_return(item)
+  use_ret = 0 < len(pushes)
+
+  # text output
+  nl = "\n  "
+  cm = ", "
+  if 0 < len(pops) or 0 < len(pushes):
+    print("lua_pushcfunction(L, [](auto L) {")
+  else:
+    print("lua_pushcfunction(L, [](auto) {")
+  if 0 < len(pops):
+    print(f"  {nl.join(pops)}")
+  if use_ret:
+    print(f"  const auto r = ImGui::{name}({cm.join(params)});")
+  else:
+    print(f"  ImGui::{name}({cm.join(params)});")
+  if 0 < len(pushes):
+    print(f"  {nl.join(pushes)}")
+  print(f"  return {len(pushes)};")
+  print("});")
+  print(f"lua_setfield(L, -2, \"{name}\");")
+  print()
+
+def gen_return(item):
+  ftype = item["type"]["qualType"]
+  type  = ftype[0:ftype.find("(")-1]
+
+  if "void" == type:
+    return []
+  if "bool" == type:
+    return ["lua_pushboolean(L, r);"]
+  if "float" == type:
+    return ["lua_pushnumber(L, static_cast<lua_Number>(r));"]
+  if "ImVec2" == type:
+    return [
+        "lua_pushnumber(L, static_cast<lua_Number>(r.x));",
+        "lua_pushnumber(L, static_cast<lua_Number>(r.y));",
+    ]
+
+  print(f"unknown return type: {type}", file=sys.stderr)
+  return []
+
+def gen_argument(pc, item):
+  type = item["type"].get("desugaredQualType", item["type"]["qualType"])
+  n    = pc+1
+  pn   = f"p{pc}"
+
+  if type in ["int", "unsigned int"]:
+    return ([f"const int {pn} = static_cast<{type}>(luaL_checkinteger(L, {n}));"], [pn], [])
+
+  if "bool" == type:
+    return ([f"const bool {pn} = lua_toboolean(L, {n});"], [pn], [])
+
+  if "const char *" == type:
+    return ([f"const char* {pn} = luaL_checkstring(L, {n});"], [pn], [])
+
+  if "const ImVec2 &" == type:
+    return ([
+        f"const float {pn}_1 = static_cast<float>(luaL_checknumber(L, {n}));",
+        f"const float {pn}_2 = static_cast<float>(luaL_checknumber(L, {n}));",
+    ], [f"ImVec2 {{{pn}_1, {pn}_2}}"], [])
+
+  if "bool *" == type:
+    return ([f"bool {pn};"], [f"&{pn}"], [f"lua_pushboolean(L, {pn});"])
+
+  print(f"unknown argument type: {type}", file=sys.stderr)
+  return ([], [], [])
+
+
+# ---- WALKER DEFINITIONS
+def walk_symbols(item):
+  kind = item.get("kind")
+
+  if kind == "FunctionDecl":
+    gen_func(item)
+  else:
+    walk(item)
+
+def walk(item):
+  kind = item.get("kind")
+
+  w = walk
+  if kind == "NamespaceDecl":
+    w = walk_symbols
+
+  for child in item.get("inner", []):
+    w(child)
+
+
+# ---- DATA DEFINITIONS
+kFuncWhitelist = [
+  "Begin",
+  "End",
+  "BeginChild",
+  "EndChild",
+  "IsWindowAppearing",
+  "IsWindowCollapsed",
+  "IsWindowFocused",
+  "IsWindowHovered",
+  "GetWindowPos",
+  "GetWindowSize",
+  "GetWindowWidth",
+  "GetWindowHeight",
+]
+
+
+# ---- ENTRYPOINT
+proc = subprocess.run(["clang++", "-x", "c++", "-std=c++2b", "-Xclang", "-ast-dump=json", "-fsyntax-only", sys.argv[1]], capture_output=True)
+if 0 == proc.returncode:
+  walk(json.loads(proc.stdout))
+else:
+  print(proc.stderr.decode("utf-8"))
+  exit(1)

core/CMakeLists.txt

@@ -3,6 +3,7 @@ target_link_libraries(nf7_core
   PUBLIC
     git_hash
     imgui
+    imgui4lua
     luajit
     nf7_config
     nf7_iface

thirdparty/CMakeLists.txt

@@ -19,6 +19,7 @@ FetchContent_Declare(
 )
 FetchContent_Populate(imgui)
 include(imgui.cmake)
+include(../cmake/imgui4lua.cmake)
 
 # ---- luajit (MIT)
 FetchContent_Declare(