Proof of concept: Add prevent UI refresh to REAPER native custom actions

main.cpp

#include <cstring>

#define REAPERAPI_IMPLEMENT
#include <reaper_plugin_functions.h>

const char *(*__localizeFunc)(const char *str, const char *subctx, int flags);

static bool IsCustomAction(KbdSectionInfo *section, const int id)
{
  // logic from SWS's IsMacroOrScript
  const char *prefix = __localizeFunc("Custom", "actions", 0);
  const size_t prefixLen = strlen(prefix);
  const char *actionName = kbd_getTextFromCmd(id, section);

  return !strncmp(actionName, prefix, prefixLen) && actionName[prefixLen] == ':';
}

static bool commandHook(KbdSectionInfo *section, const int command, int, int, int, HWND)
{
  static int runCustomAction = 0;

  if(section->uniqueID != 0 || runCustomAction == command || !IsCustomAction(section, command))
    return false;

  runCustomAction = command;
  PreventUIRefresh(1);
  Main_OnCommand(command, 0); // FIXME: non-main sections!
  PreventUIRefresh(-1);
  runCustomAction = 0;
  return true;
}

extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
  REAPER_PLUGIN_HINSTANCE instance, reaper_plugin_info_t *rec)
{
  if(!rec) {
    plugin_register("-hookcommand2", reinterpret_cast<void *>(commandHook));
    return 0;
  }

  if(rec->caller_version != REAPER_PLUGIN_VERSION || !rec->GetFunc)
    return 0;

  __localizeFunc     = (decltype(__localizeFunc))    rec->GetFunc("__localizeFunc");
  kbd_getTextFromCmd = (decltype(kbd_getTextFromCmd))rec->GetFunc("kbd_getTextFromCmd");
  Main_OnCommand     = (decltype(Main_OnCommand))    rec->GetFunc("Main_OnCommand");
  plugin_register    = (decltype(plugin_register))   rec->GetFunc("plugin_register");
  PreventUIRefresh   = (decltype(PreventUIRefresh))  rec->GetFunc("PreventUIRefresh");

  plugin_register("hookcommand2", reinterpret_cast<void *>(commandHook));

  return 1;
}