SDL_WaitEvent() don't seems to empty the event buffer

[OldFram]

Hi everyone

I don't know is this issue have been sent before, but I find something wrong when trying to open a new window after the closure of a precedent one. I use the SDL2 with Code::Blocks running Lubuntu 18.04 (32 bits) and 22.04 (64 bits).

When I close the first window (Q or ESC key), SDL_WaitEvent() don't seems to empty the event buffer and the second window closes immediately on the same key...

Let's see the code:

#include <iostream>
#include <SDL2/SDL.h>

using namespace std;

int main()
{
    cerr<<"Start Problem"<<endl;

    SDL_Window *WindowPtr=nullptr; //window ptr
    SDL_Event event; //an event
    int waitEventBool = 1; //flag to stay in the event loop

    //Simple init SDL2
    if(SDL_Init(SDL_INIT_VIDEO)==-1)
    {
        cerr<<"SDL 2 initialization failure... "<<SDL_GetError()<<endl;
        exit(EXIT_FAILURE);
    }

    WindowPtr=SDL_CreateWindow("First window; Q or ESC key to exit", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 360, SDL_WINDOW_SHOWN);
    if(WindowPtr==nullptr)
    {
        cerr<<"First window creation failure..."<<SDL_GetError()<<endl;
        exit(EXIT_FAILURE);
    }

    waitEventBool = 1;
    while(waitEventBool)
    {
        SDL_WaitEvent(&event); //stop and wait an event

        switch(event.type)
        {
        case SDL_QUIT: //Quit event
            waitEventBool=0;
            break;
        case SDL_KEYDOWN: //key press
            switch(event.key.keysym.sym) //which key ?
            {
            case SDLK_ESCAPE:
                cout<<"Exit #1 ESC key"<<endl;
                waitEventBool=0;
                break;
            case SDLK_q:
                cout<<"Exit #1 on Q key"<<endl;
                waitEventBool=0;
                break;
            default:
                break;
            }
            break;
        }
    }

    //Destroy the first window
    SDL_DestroyWindow(WindowPtr);

    WindowPtr=SDL_CreateWindow("Second window; Q or ESC key to exit", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 400, 240, SDL_WINDOW_SHOWN);
    if(WindowPtr==nullptr)
    {
        cerr<<"Second window creation failure..."<<SDL_GetError()<<endl;
        exit(EXIT_FAILURE);
    }

    waitEventBool = 1;
    while(waitEventBool)
    {
        SDL_WaitEvent(&event); //stop and wait an event

        switch(event.type)
        {
        case SDL_QUIT: //Quit event
            waitEventBool=0;
            break;
        case SDL_KEYDOWN: //key press
            switch(event.key.keysym.sym) //which key ?
            {
            case SDLK_ESCAPE:
                cout<<"Exit #2 ESC key"<<endl;
                waitEventBool=0;
                break;
            case SDLK_q:
                cout<<"Exit #2 on Q key"<<endl;
                waitEventBool=0;
                break;
            default:
                break;
            }
            break;
        }
    }

    //Destroy the second window
    SDL_DestroyWindow(WindowPtr);

    //Quit SDL
    SDL_Quit();

    cerr<<"End Problem"<<endl;

    return EXIT_SUCCESS;
}

I added the following lines before the second event loop (line 66) and it seems to solve the problem... So why SDL_WaitEvent() maintains the key pressed in the event buffer ?

    SDL_PumpEvents();
    SDL_FlushEvent(SDL_KEYDOWN);

I thank you if you can tell me where I'm wrong.

Francis