Cannot draw a filled circle with SDL2 gfx - c++

Question

There is the following code. The desired result is that a window is created and a filled circle is drawn:
#include <SDL2/SDL.h>
#include <iostream>
#include <SDL2/SDL2_gfxPrimitives.h>
int main()
{
SDL_Window* window = nullptr;
SDL_Renderer* renderer = nullptr;
if(SDL_Init(SDL_INIT_EVERYTHING) < 0)
{
std::cout << "Could not initialise" << std::endl;
return 1;
}
window = SDL_CreateWindow("MyGame",
SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED,
640,
480,
SDL_WINDOW_SHOWN);
if(!window)
{
std::cout << "Could not create the window" << std::endl;
return 1;
}
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
SDL_RenderClear(renderer);
Sint16 circleR = 100;
Sint16 circleX = 300;
Sint16 circleY = 300;
SDL_Surface* windowSurface = SDL_GetWindowSurface(window);
Uint32 circleColour = SDL_MapRGB(windowSurface->format, 255, 0, 0);
int result = filledCircleColor(renderer, circleX, circleY, circleR, circleColour);
std::cout << "drawing the circle r " << circleR << " x " << circleX << " y " << circleY << " circleColour " << circleColour << std::endl;
std::cout << "draw circle result " << result << std::endl;
SDL_RenderPresent(renderer);
bool run = true;
while(run)
{
SDL_Event event;
while (SDL_PollEvent(&event))
{
if(event.type == SDL_QUIT)
{
run = false;
}
}
}
SDL_Quit();
return 0;
}
The problem is that the circle is not drawn - the window is all black.
The output:
drawing the circle r 100 x 300 y 300 circleColour 16711680
draw circle result 0
filledCircleColor returns 0 what should mean that there's no error.
What should be done so that the circle is drawn? I'm using SDL 2.0.2 on Ubuntu with SDL2 gfx extension.

Answer 1

About SDL_GetWindowSurface, the documentation says : "You may not combine this with 3D or the rendering API on this window."
For me, in your example, SDL_GetWindowSurface returns null.
The filledCircleColor() function takes a color of the form 0xRRGGBBAA.
It works after removing the surface part, and changing to :
int result = filledCircleColor(renderer, circleX, circleY, circleR, 0xFF0000FF);