How to use SDL_CreateTexture - c++

Question

I would like to know ho to use SDL_CreateTexture function.
I just want to create texture, give it a color and draw it somewhere on the screen. I dont wanna load any picture into it.
I thought I can use SDL_CreateTexture, SDL_SetTextureColorMod, SDL_RenderCopy, SDL_RenderPresent in that order, but I always get just a black rectangle instead of red one.
#include <SDL.h>
int main(int argc, char* argv[]) {
SDL_Init(SDL_INIT_EVERYTHING);
SDL_Window *MainWindow = SDL_CreateWindow("My Game Window",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
1024, 768,
SDL_WINDOW_SHOWN
);
SDL_Renderer *renderer = SDL_CreateRenderer(MainWindow, -1, 0);
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
SDL_RenderClear(renderer);
SDL_Texture *Tile = SDL_CreateTexture(renderer,SDL_PIXELFORMAT_RGBA8888,SDL_TEXTUREACCESS_TARGET,8,8);
//I want my texture to be red
SDL_SetTextureColorMod(Tile,255,0,0);
//I just try this i dont know if I have to do that
SDL_SetTextureAlphaMod(Tile,255);
SDL_Rect destination = {320,240,8,8};
SDL_RenderCopy(renderer,Tile,NULL,&destination);
SDL_RenderPresent(renderer);
SDL_Delay(3000);
//Clean up
SDL_DestroyTexture(Tile);
SDL_DestroyWindow(MainWindow);
SDL_Quit();
return 0;
}
I also dont know if I am using right format (SDL_PixelFormatEnum) value in SDL_CreateTexture. There is a lot of them and I dont understand what they mean. Which one can I use form this purpose?

Answer 1

SDL_SetTextureColorMod will make sure subsequent render copy operations will have the specified multiplier taken into account. It doesn't change color to the texture texels.
You should rather either load a bitmap or initialize your texture with a red color as in the following example
int main(int argc, char* argv[]) {
SDL_Init(SDL_INIT_EVERYTHING);
SDL_Window *MainWindow = SDL_CreateWindow("My Game Window",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
1024, 768,
SDL_WINDOW_SHOWN
);
SDL_Renderer *renderer = SDL_CreateRenderer(MainWindow, -1, 0);
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
SDL_RenderClear(renderer);
SDL_Texture *Tile = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888,
SDL_TEXTUREACCESS_STREAMING, 8, 8);
// Initialize texture pixels to a red opaque RGBA value
unsigned char* bytes = nullptr;
int pitch = 0;
SDL_LockTexture(Tile, nullptr, reinterpret_cast<void**>(&bytes), &pitch);
unsigned char rgba[4] = { 255, 0, 0, 255 };
for(int y = 0; y < 8; ++y) {
for (int x = 0; x < 8; ++x) {
memcpy(&bytes[(y * 8 + x)*sizeof(rgba)], rgba, sizeof(rgba));
}
}
SDL_UnlockTexture(Tile);
SDL_Rect destination = { 320, 240, 8, 8 };
SDL_RenderCopy(renderer, Tile, NULL, &destination);
SDL_RenderPresent(renderer);
SDL_Delay(3000);
//Clean up
SDL_DestroyTexture(Tile);
SDL_DestroyWindow(MainWindow);
SDL_Quit();
return 0;
}