SDL Multiple Function Rendering - c++

Question

I want my game engine to be nice and tidy and rather than coding a bunch of redundant lines, I would rather include functions that do this for me.
void draw::image(){
SDL_Surface *bmp = SDL_LoadBMP("C:\\Users\\Joe\\Documents\\Visual Studio 2013\\Projects\\SDL_APP1\\map1.bmp");
SDL_Texture*bmptx;
SDL_Renderer * renderer = SDL_CreateRenderer(_window, -1, 0);
bmptx = SDL_CreateTextureFromSurface(renderer, bmp);
SDL_FreeSurface(bmp);
SDL_RenderCopy(renderer, bmptx, NULL, NULL);
SDL_RenderPresent(renderer);
}
void draw::text(string q, float x, float y, float w, float h){
SDL_SetRenderDrawColor(renderer, 64, 64, 64, 255);
SDL_RenderDrawLine(renderer, x, y, w, h);
SDL_RenderPresent(renderer);
}
My problem is that I don't know how to format the text() function so that it draws to the same renderer as the image() function. I want it so that in my main loop, I can call both the text and the image functions and they will draw to the same renderer at the same time. This way I wont have to directly code these into my main loop. Side note I am using SDL 2.

Answer 1

You would want to pass a pointer to the renderer you previously created (probably in main()) to each of your drawing functions. Creating a new renderer for every object you draw would be very inefficient.
void draw::image(SDL_Renderer *renderer)
{
// ...
}
void draw::text(SDL_Renderer *renderer, string q, float x, float y, float w, float h)
{
SDL_SetRenderDrawColor(renderer, 64, 64, 64, 255);
// ...
}
Then, within your main() after you've created the window, you'd create your renderer:
renderer = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED);
and then pass it to your drawing functions. Assuming your methods are static, then:
draw::image(renderer);
or if you have an object on the stack:
myDrawObject.image(renderer);
or if you have a pointer to one of your draw objects:
myDrawPtr->image(renderer);
Also, you probably need to think about this approach a bit more. Presumably you want to draw these things every frame, so with your current approach you are requiring SDL to load the BMP file from disk (or disk cache) and convert it to whatever internal format it requires for the texture, every single frame. It's unlikely this will give you acceptable performance, especially when you want to render multiple images per frame.
More than likely, a better approach will be to store some of these resources in member variables within your draw class. But this is basic C++ stuff, so you might want to do some more reading and tutorials around the subject of classes.