Comment détecter correctement appuyer sur la touche et relâchez dans sdl2

Question

Mon code complet -

#include <SDL.h> 
#include <SDL_opengl.h> 
#include <GL\GLU.h> 
#include <fstream> 

using namespace std; 


int index = 0; 
int speed = 0; 
int frames = 0; 
int lasttime = 0; 
int mousex = 0; 
int mousey = 0; 
bool postRedraw = true; 

int screenWidth = 640; 
int screenHeight = 480; 
float screenAspect = screenWidth/screenHeight; 

bool init(); 
bool initGL(); 
void handleKeys(unsigned char key, int x, int y); 
void update(); 
void render(); 
void close(); 
void Initialize(); 
void handleEvents(); 


ofstream logFile; 

SDL_Window* gWindow = NULL; 
bool isRunning = true; 
SDL_GLContext gContext; 
float xpos = 0.0; 
float ypos = 0.0; 
float zpos = 0.0; 


void Initialize() 
{ 
    gluPerspective(60.0f, screenAspect, 1.0, 400.0); 
    glEnable(GL_COLOR_MATERIAL); 
    glEnable(GL_NORMALIZE); 
    glTranslatef(0.0f, 0.0f, -5.0f); 
    glFrontFace(GL_CCW); 
    glEnable(GL_LIGHT0); 
} 


void render() 
{ 
    glTranslatef(xpos, ypos, zpos); 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glColor3f(1.0, 0.0, 0.0); 
    glBegin(GL_TRIANGLES); 
     glVertex3f(-1.0f,0.0f,-1.0f); 
     glVertex3f(0.0f, 1.0f, -1.0f); 
     glVertex3f(0.0f, 2.0f, -2.0f); 
    glEnd(); 
    postRedraw = true; 
} 


void handleEvents() 
{ 
    const Uint8* keystates = SDL_GetKeyboardState(NULL); 
    if(keystates[SDL_GetScancodeFromKey(SDLK_w)]) 
    { 
     zpos += 0.01; 
    } 
    if(keystates[SDL_GetScancodeFromKey(SDLK_s)]) 
    { 
     zpos -= 0.01; 
    } else { 
    } 
} 

bool init() 
{ 
    bool success = true; 
    if(SDL_Init(SDL_INIT_VIDEO) < 0) 
    { 
     logFile<<"SDL could not initialize! SDL Error: "<<SDL_GetError()<<endl; 
     success = false; 
    } 
    else 
    { 
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2); 
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1); 
     gWindow = SDL_CreateWindow("SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, screenWidth, screenHeight, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE); 
     if(gWindow == NULL) 
     { 
      logFile<<"Window could not be created! SDL Error: "<<SDL_GetError()<<endl; 
      success = false; 
     } 
     else 
     { 
      gContext = SDL_GL_CreateContext(gWindow); 
      if(gContext == NULL) 
      { 
       logFile<<"OpenGL context could not be created! SDL Error: "<<SDL_GetError()<<endl; 
       success = false; 
      } 
      else 
      { 
       if(SDL_GL_SetSwapInterval(1) < 0) 
       { 
        logFile<<"Warning: Unable to set VSync! SDL Error: "<<SDL_GetError()<<endl; 
       } 
       if(!initGL()) 
       { 
        logFile<<"Unable to initialize OpenGL!"<<endl; 
        success = false; 
       } 
      } 
     } 
    } 
    logFile.open("log.txt"); 
    if(logFile.is_open()) 
    { 
     success = true; 
    } else { 
     success = false; 
    } 
    return success; 
} 

bool initGL() 
{ 
    bool success = true; 
    GLenum error = GL_NO_ERROR; 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    error = glGetError(); 
    if(error != GL_NO_ERROR) 
    { 
     logFile<<"Error initializing OpenGL! "<<gluErrorString(error)<<endl; 
     success = false; 
    } 
    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
    glEnable(GL_CULL_FACE); 
    glEnable(GL_DEPTH_TEST); 
    error = glGetError(); 
    if(error != GL_NO_ERROR) 
    { 
     logFile<<"Error initializing OpenGL! "<<gluErrorString(error)<<endl; 
     success = false; 
    } 
    glClearColor(0.f, 0.f, 0.f, 1.f); 
    error = glGetError(); 
    if(error != GL_NO_ERROR) 
    { 
     logFile<<"Error initializing OpenGL! "<<gluErrorString(error); 
     success = false; 
    } 

    return success; 
} 


void close() 
{ 
    logFile.close(); 
    SDL_DestroyWindow(gWindow); 
    gWindow = NULL; 
    SDL_Quit(); 
} 

int main(int argc, char* args[]) 
{ 
    if(!init()) 
    { 
     logFile<<"Failed to initialize!"<<endl; 
    } 
    else 
    { 

     SDL_Event event; 
     Initialize(); 
     lasttime = SDL_GetTicks(); 
     while(isRunning) 
     { 
      while(SDL_PollEvent(&event) != 0) 
      { 
       if(event.type == SDL_QUIT) 
       { 
        isRunning = false; 
       } else if(event.type == SDL_MOUSEMOTION) { 
        SDL_GetMouseState(&mousex, &mousey); 
       } else if(event.type == SDL_MOUSEBUTTONDOWN) { 
        SDL_GetMouseState(&mousex, &mousey); 
       } else if(event.type == SDL_MOUSEBUTTONUP) { 
        SDL_GetMouseState(&mousex, &mousey); 
       } 
      } 
      handleEvents(); 
      if(postRedraw) 
      { 
       postRedraw = false; 
       render(); 
       SDL_GL_SwapWindow(gWindow); 
      } 
      if((SDL_GetTicks()-lasttime)>=1000) 
      { 
       lasttime = SDL_GetTicks(); 
       speed = frames; 
       logFile<<speed<<endl; 
       frames = 0; 
      } else { 
       frames++; 
      } 
     } 
    } 

    close(); 

    return 0; 
} 

Le code ci-dessus est juste pour le test, le code minimaliste où j'ai problème est -

void handleEvents() 
{ 
    const Uint8* keystates = SDL_GetKeyboardState(NULL); 
    if(keystates[SDL_GetSancodeFromKey(SDLK_w)]) { 
     zpos += 0.01; 
    } 
    if(keystates[SDL_GetScancodeFromKey(SDLK_s)]) 
    { 
     zpos -= 0.01; 
    } else { 
    } 
} 

à prévoir: le trangle dessiné bougera vers l'avant/vers l'arrière tandis que la touche w/s est enfoncée.

Sortie: le triangle continue de se déplacer dans la direction souhaitée même si la touche a été relâchée.

Answer 1

Vous accumulez vos changements de matrice au fil du temps. glTranslatef modifie actuelle matrice avec traduction. L'image suivante le modifie à nouveau. Et encore, ....

Vous devez réinitialiser la matrice avec appel glLoadIdentity(). Sachez qu'il modifie la matrice actuellement sélectionnée et annulera les changements de matrice que vous avez effectués dans Initialize (au moins votre glTranslatef ici - la perspective devrait aller à la matrice GL_PROJECTION, ce que vous n'avez pas fait).