将SDL_PeepEvents从SDL1.2.14迁移到SDL1.3

Question

我正在将一个使用SDL1.2框架用C++编写的OS应用程序移植到使用SDL1.3框架的iOS。方法发生了一些变化，我在重写几段代码时遇到了麻烦。下面是1.2.14中SDL_PeepEvents方法的注释和声明：

/**
 *  Checks the event queue for messages and optionally returns them.
 *
 *  If 'action' is SDL_ADDEVENT, up to 'numevents' events will be added to
 *  the back of the event queue.
 *  If 'action' is SDL_PEEKEVENT, up to 'numevents' events at the front
 *  of the event queue, matching 'mask', will be returned and will not
 *  be removed from the queue.
 *  If 'action' is SDL_GETEVENT, up to 'numevents' events at the front 
 *  of the event queue, matching 'mask', will be returned and will be
 *  removed from the queue.
 *
 *  @return
 *  This function returns the number of events actually stored, or -1
 *  if there was an error.
 *
 *  This function is thread-safe.
 */
extern DECLSPEC int SDLCALL SDL_PeepEvents(SDL_Event *events, int numevents,
                SDL_eventaction action, Uint32 mask);

下面是1.3中相同方法的声明：

/**
 *  Checks the event queue for messages and optionally returns them.
 *  
 *  If \c action is ::SDL_ADDEVENT, up to \c numevents events will be added to
 *  the back of the event queue.
 *  
 *  If \c action is ::SDL_PEEKEVENT, up to \c numevents events at the front
 *  of the event queue, within the specified minimum and maximum type,
 *  will be returned and will not be removed from the queue.
 *  
 *  If \c action is ::SDL_GETEVENT, up to \c numevents events at the front 
 *  of the event queue, within the specified minimum and maximum type,
 *  will be returned and will be removed from the queue.
 *  
 *  \return The number of events actually stored, or -1 if there was an error.
 *  
 *  This function is thread-safe.
 */
extern DECLSPEC int SDLCALL SDL_PeepEvents(SDL_Event * events, int numevents,
                                           SDL_eventaction action,
                                           Uint32 minType, Uint32 maxType);

最后，下面是我尝试重写的方法：

/**
 * Returns true if the queue is empty of events that match 'mask'. 
 */
 bool EventHandler::timerQueueEmpty() {
    SDL_Event event;

    if (SDL_PeepEvents(&event, 1, SDL_PEEKEVENT, SDL_EVENTMASK(SDL_USEREVENT)))
        return false;
    else
        return true;
}

它当前在编译时抛出以下错误- 'SDL_EVENTMASK‘未在此作用域中声明。我完全理解之所以会发生这个错误，是因为SDL_EVENTMASK不再是SDL_PeepEvents函数的参数。我还了解到Uint32Mask已经被Uint32 minType，Uint32 maxType取代。我只是很难理解如何用这些新参数重写代码。

Answer 1

如您所述，SDL 1.3使用事件范围而不是事件掩码。此代码应适用于SDL 1.3：

SDL_PeepEvents(&event, 1, SDL_PEEKEVENT, SDL_USEREVENT, SDL_NUMEVENTS - 1);  // Peek events in the user range

另一件美化的事情--你不需要用if检查布尔变量，然后返回true/false：

/**
 * Returns true if the queue is empty of events that match 'mask'. 
 */
 bool EventHandler::timerQueueEmpty() {
    SDL_Event event;

    return SDL_PeepEvents(&event, 1, SDL_PEEKEVENT, SDL_USEREVENT, SDL_NUMEVENTS - 1) != 0;
}