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1st SDL Engine Drawing BMP Blank Screen

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Hello I have bought the book SDL game development from amazon to learn SDL2 game programming on Ubuntu.

I have my first game engine up and running but when I add code to draw a BMP in the top left of the screen I just get a black screen when I run it.

Can anybody help me solve this I would really appreciate it.

Also I am not sure if I have the texture creation code on lines 8-15 in the right place, I tried moving it around but it didn't make a difference.

 

main.cpp

 

<code>

#include <SDL2/SDL.h>
#include "Game.h"
#include "Game.cpp"


int main(int argc, char * args[])
{
Game * g_game = new Game;

g_game->init("Chapter 1", 100,100,640,480,false);

while(g_game->running())
{
    g_game->handleEvents();
    g_game->update();
    g_game->renderer();
}
g_game->clean();

return 0;

}


<code/>

 

Game.cpp

 

<code>

#include "Game.h"
#include <iostream>

bool Game::init(const char* title, int xpos, int ypos, int width,
int height, bool fullscreen)
{
    
    SDL_Surface * pTempSurface = SDL_LoadBMP("assets/rider.bmp");    
    m_pTexture = SDL_CreateTextureFromSurface(m_pRenderer,pTempSurface);
    SDL_FreeSurface(pTempSurface);
    SDL_QueryTexture(m_pTexture, NULL,NULL,&m_sourceRectangle.w,&m_sourceRectangle.h);
    m_destinationRectangle.x = m_sourceRectangle.x =0;
    m_destinationRectangle.y = m_sourceRectangle.y =0;
    m_destinationRectangle.w = m_sourceRectangle.w;
    m_destinationRectangle.h = m_sourceRectangle.h;    

    int flags = 0;

    if (fullscreen)
    {
    flags = SDL_WINDOW_FULLSCREEN;
    }

    // attempt to initialize SDL
    if(SDL_Init(SDL_INIT_EVERYTHING) == 0)
    {
    std::cout<<"SDL Init Success\n";
    // init the window
    m_pWindow = SDL_CreateWindow(title, xpos, ypos, width, height, flags);

    if(m_pWindow != 0) //window init success
    {
    std::cout<<"Window Creation Success\n";
    m_pRenderer = SDL_CreateRenderer(m_pWindow, -1, 0);

        if(m_pRenderer !=0) // render init success
        {
        std::cout<<"Renderer Creation Success\n";
        SDL_SetRenderDrawColor(m_pRenderer, 0,0,0,0);
        }    
        else
        {
        std::cout<<"Renderer Init Fail\n";
        return false; // renderer init fail
        }

    }
    
    else
    {
    std::cout<<"Window Init Fail\n";
    return false; //window init fail
    }

}

else
{
std::cout<<"SDL Init Fail\n";
return false; // SDL init fail
}


std::cout<<"Init success\n";
m_bRunning = true; // everything inited successfully
// start the main loop

return true;

}

 

void Game::renderer()
{
SDL_RenderClear(m_pRenderer); // clears the renderer
// to the draw colour

SDL_RenderCopy(m_pRenderer, m_pTexture, &m_sourceRectangle,&m_destinationRectangle);

SDL_RenderPresent(m_pRenderer); // draw to the screen
}


void Game::update()
{
}

void Game::clean()
{
std::cout<<"Cleaning game\n";
SDL_DestroyWindow(m_pWindow);
SDL_DestroyRenderer(m_pRenderer);
SDL_Quit();
}

 


void Game::handleEvents()
{
SDL_Event event;
    if(SDL_PollEvent(&event))
    {
        switch (event.type)
        {
        case SDL_QUIT:
         m_bRunning = false;
        break;
        }
    }
}

 

<code/>

 

game.h

 

<code>

 

#ifndef __Game__
#define __Game__

class Game
{
public:
Game() {}
~Game() {}

 

bool init(const char* title, int xpos, int ypos, int width,
int height, bool fullscreen);
void renderer();
void update();
void handleEvents();
void clean();

// a function to access the private running variable
bool running() {return m_bRunning;}

private:

SDL_Window * m_pWindow;
SDL_Renderer * m_pRenderer;
SDL_Texture * m_pTexture; //the new SDL Texture variable
SDL_Rect m_sourceRectangle; // the first rectangle
SDL_Rect m_destinationRectangle;// another rectangle

bool m_bRunning;
};


#endif /* defined(__Game_h__) */

 

<code/>

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Start by checking for errors wherever you have SDL calls, especially where you're loading and creating the texture.

Check the return value, then call SDL_GetError() if needed. Use the documentation to determine how to properly check for errors; the easiest way is to just type in the function call name in the search box, top left.

 

For example: Your very first call is SDL_LoadBMP. The documentation for this call says that this returns null if there was an error.

Thus, check the return value to see if it's null before going continuing on.

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