Why am I unable to draw to a texture in SDL2?

I've been working on a project in SDL on nights and weekends for the past few months. I'm currently trying to get a menu system working. At the moment, I'm working on drawing text using SDL_TTF. As for my question, I'm seeing some strange behavior when I try to draw some textures to another texture.

The weirdness is that when I draw it, on a destination texture created with SDL_TEXTUREACCESS_TARGET (like it says to do in the docs) draws nothing, but returns no error. However, if I use SDL_TEXTUREACCESS_STATIC or SDL_TEXTUREACCESS_STREAM, it returns an error when I set the render target because of the access attribute, but draws just fine. After doing some digging, I heard some things about a bug in the Intel drivers (I'm on a Macbook with Intel graphics), so I was wondering if this was something I messed up, and how I might fix it. Alternately, if it isn't my fault, I'd still like to know what's going on, and if it would perform differently on different platforms and how I could work around it.

Here's my code, after removing unnecessary parts and :

I create the renderer:

renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);

Later on, when I go to render onto a canvas:

TTF_Font *fnt = loadFont(fontName.c_str(), fontSize);

In here I parse out some attributes and set them using TTF_SetFontStyle() and the clr for text color.

SDL_Texture *canvas; 
canvas = SDL_CreateTexture(rendy, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, contentRect.w, contentRect.h)
SDL_SetRenderTarget(rendy, canvas);

int pos = 0;
for (list<string>::iterator itr = lines.begin(); itr != lines.end(); itr++){
    SDL_Surface *temp;
    temp = TTF_RenderText_Blended(fnt, src.c_str(), clr);

    SDL_Texture *line;
    line = SDL_CreateTextureFromSurface(rendy, temp);
    int w,h;
    SDL_QueryTexture(line, NULL, NULL, &w, &h);

    SDL_Rect destR;

    //Assume that we're left justified
    destR.x = 0;
    destR.y = pos;
    destR.w = w;
    destR.h = h;

    SDL_RenderCopy(rendy, line, NULL, &destR);
    SDL_DestroyTexture(line);
    SDL_FreeSurface(temp);
    pos += TTF_FontLineSkip(fnt);
}

//Clean up
SDL_SetRenderTarget(rendy, NULL);

canvas gets returned to the calling function so it can be cached until this text box is modified. That function works by having a texture for the whole box, drawing a background texture onto it, and then drawing this image on top of that, and holding on to the whole thing.

That code looks like this:

(stuff to draw the background, which renders fine)

SDL_Texture *sum = SDL_CreateTexture(rendy, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, globalRect.w, globalRect.h);

SDL_SetTextureBlendMode(sum, SDL_BLENDMODE_BLEND);
SDL_SetRenderTarget(rendy, sum);

string lPad = getAttribute(EL_LEFT_PADDING);
string tPad = getAttribute(EL_TOP_PADDING);
int paddingL = strtol(lPad.c_str(), NULL, 10);
int paddingT = strtol(tPad.c_str(), NULL, 10);

SDL_Rect destR;
SDL_Rect srcR;
srcR.x = 0;
srcR.y = 0;
srcR.w = globalRect.w; //globalRect is the size size of the whole button
srcR.h = globalRect.h;
destR.x = 0;
destR.y = 0;
destR.w = globalRect.w;
destR.h = globalRect.h;

SDL_RenderCopy(rendy, bgTexture, NULL, &destR);
int maxX = contentRect.w;
fgTexture = getFGImage(rendy); //The call to the previous part

int w, h;
SDL_QueryTexture(fgTexture, NULL, NULL, &w, &h);

int width, height;
getTextSize(&width, &height, maxX);

srcR.x = 0;
srcR.y = 0;
srcR.w = width;
srcR.h = height;
destR.x = paddingL;
destR.y = paddingT;
destR.w = globalRect.w;
destR.h = globalRect.h;

SDL_RenderCopy(rendy, fgTexture, NULL, &destR);
SDL_DestroyTexture(fgTexture);
SDL_DestroyTexture(bgTexture);


return sum;

Sum is returned to another function which does the drawing.

Thanks in advance!

Update So I've figured out that the reason it only drew when I had the incorrect access setting was that, since the function was returning an error value, the render target was never set to the texture, so it was just drawing on the screen. I've also checked all my textures by writing a function AuditTexture which checks to see that the texture format for a texture is supported by the renderer, prints a string description of the access attribute, and prints the dimensions. I now know that all of their texture formats are supported, the two lines are static, canvas and sum are render targets, and none of them have dimensions of zero.

Solution

As it turns out, I had set the render target to be the composite texture, then called my function which set the render target to the text texture before drawing text. Then when I returned from the function, the render target was still the text texture instead of the composite one, so I basically drew the text over itself instead of drawing over the background.

A word to the wise: Don't ever assume something is taken care of for you, especially in c or c++.