Can't draw simple bitmap to window in SDL2 - c++

Question

I'm currently trying to set up a few C++ libraries for a future project. Namely, SDL2.
Here's my code:
#include <iostream>
#include <fstream>
#include <SDL.h>
int SCREEN_WIDTH = 457;
int SCREEN_HEIGHT = 497;
const char* imgpath = "Sprite.bmp";
std::string errmsg;
SDL_Window* window = NULL;
SDL_Surface* screensurface = NULL;
SDL_Surface* image = NULL;
SDL_Rect rect;
struct {
bool wdown;
bool adown;
bool sdown;
bool ddown;
bool edown;
bool escdown;
} kpresses;
void clearkpresses() {
kpresses.wdown = false;
kpresses.adown = false;
kpresses.sdown = false;
kpresses.ddown = false;
kpresses.edown = false;
kpresses.escdown = false;
}
void setrect() {
rect.x = 0;
rect.y = 0;
rect.w = 457;
rect.h = 497;
}
bool gameinit() {
std::ofstream errfile;
errfile.open("errlog.txt");
clearkpresses();
setrect();
if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER) < 0 ) {
errmsg = "SDL could not initialize! SDL_Error:";
std::cout << errmsg << SDL_GetError() << std::endl;
errfile << errmsg << SDL_GetError() << std::endl;
errfile.std::ofstream::close();
return false;
}
screensurface = SDL_GetWindowSurface(window);
window = SDL_CreateWindow("Transcend", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
if( window == NULL ){
errmsg = "Window could not be created! SDL_Error:";
std::cout << errmsg << SDL_GetError() << std::endl;
errfile << errmsg << SDL_GetError() << std::endl;
errfile.std::ofstream::close();
return false;
}
image = SDL_LoadBMP(imgpath);
if (image == NULL) {
errmsg = "Media unable to load! IMG Error: ";
std::cout << errmsg << SDL_GetError() << std::endl;
errfile << errmsg << SDL_GetError() << std::endl;
errfile.std::ofstream::close();
return false;
}
return true;
}
void gamehalt()
{
SDL_DestroyWindow(window);
window = NULL;
SDL_Quit();
}
int main(int argc, char* args[]) {
if (!gameinit()) {
gamehalt();
return 0;
}
bool quit = false;
SDL_Event event;
while (!quit) {
while (SDL_PollEvent(&event) != 0) {
if (event.type == SDL_QUIT) {
quit = true;
}
switch(event.type) {
case SDLK_w:
kpresses.wdown = true;
case SDLK_a:
kpresses.adown = true;
case SDLK_s:
kpresses.sdown = true;
case SDLK_d:
kpresses.ddown = true;
case SDLK_e:
kpresses.edown = true;
case SDLK_ESCAPE:
kpresses.escdown = true;
}
}
//TODOUpdate
//TODORender
SDL_BlitSurface(image, NULL, screensurface, &rect);
SDL_UpdateWindowSurface(window);
//reset
clearkpresses();
}
gamehalt();
return 0;
}
Compiled, assembled, and linked with this windows cmd command:
g++ Main.cpp -static-libgcc -static-libstdc++ -I..\include\SDL2\include\SDL2 -I..\include\SDL2_image\include\SDL2 -L..\include\SDL2\lib -L..\include\SDL2_image\lib -w -lmingw32 -lSDL2main -lSDL2 -o ../Transcend.exe
It compiles and runs with no errors, but only displays a blank screen.

Answer 1

The problem is that you are trying to get the window surface, but the window isn't already created.
Please swap those two lines:
screensurface = SDL_GetWindowSurface(window);
window = SDL_CreateWindow("Transcend", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
This way:
window = SDL_CreateWindow("Transcend", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
screensurface = SDL_GetWindowSurface(window);