demo/stdmain.h

   1 // This file is part of the utio library, a terminal I/O library.
   2 //
   3 // Copyright (C) 2004 by Mike Sharov <msharov@users.sourceforge.net>
   4 // This file is free software, distributed under the MIT License.
   5 //
   6 // \file stdmain.h
   7 //
   8 // \brief Standard program main with error handling.
   9 //
  10 // The reason for using the singleton and all this error handling is that it
  11 // is very important for CKeyboard object to be able to clean up on exit. If
  12 // it fails to do so, the keyboard remains in the UI state and the shell will
  13 // not be very usable. There will be no echo, no cursor, and no scrollback.
  14 // (You can manually fix it with "stty sane" and "echo ^v ESC c")
  15 //
  16 // So main installs various cleanup handlers to catch fatal conditions, like
  17 // signals, exceptions, or terminates, and exit normally, calling destructors
  18 // on all objects. The singleton pattern is required because if the program
  19 // exits from a signal handler, destructors of local objects in main will not
  20 // be called, resulting in a garbled console. Hence the static Instance()
  21 // function, whose static member object is destructed on exit.
  22 //
  23 // This cleanup problem is common to all UI environments, be it console, the
  24 // framebuffer, or X. Crashing the UI environment without cleanup is a very
  25 // bad idea and you will have to write something like the code in this file
  26 // for every UI framework you choose to implement on top of utio.
  27 //
  28
  29 #ifndef STDMAIN_H_6A5A6F7B06CC2ED07880C5283C61797A
  30 #define STDMAIN_H_6A5A6F7B06CC2ED07880C5283C61797A
  31
  32 #include <utio.h>
  33 using namespace utio;
  34 using namespace utio::gdt;
  35 using namespace ustl;
  36
  37 extern "C" void InstallCleanupHandlers (void);
  38
  39 /// Declares singleton Instance() call in \p DemoClass.
  40 #define DECLARE_SINGLETON(DemoClass)    \
  41     static DemoClass& Instance (void) { static DemoClass obj; return (obj); }
  42
  43 /// Exception handling harness for demos
  44 template <typename T>
  45 int RunDemo (void) throw()
  46 {
  47     int rv = EXIT_FAILURE;
  48     try {
  49         T::Instance().Run();
  50         rv = EXIT_SUCCESS;
  51     } catch (ustl::exception& e) {
  52         cout.flush();
  53         cerr << "Error: " << e << endl;
  54     } catch (...) {
  55         cout.flush();
  56         cerr << "Unexpected error." << endl;
  57     }
  58     return (rv);
  59 }
  60
  61 /// Standard main with error handling.
  62 #define StdDemoMain(DemoClass)                  \
  63 int main (void)                                 \
  64 {                                               \
  65     InstallCleanupHandlers();                   \
  66     return (RunDemo<DemoClass>());              \
  67 }
  68
  69 #endif
  70