SDL2 Invalid Renderer | 易学教程

问题

I believe I have an SDL2 bug here and I wanted some verification. When I create a renderer it is invalid and I cannot initialize SDL_ttf because of this. Here is a quick demo program that exhibits the issue on my xubuntu 14.04 distribution. My graphics card is an NVIDIA GTX 550 Ti. Driver version 331.113 proprietary, tested.

#include <SDL2/SDL.h>

#include <string>
#include <stdexcept>
#include <iostream>

using namespace std;

int main() {
SDL_Window* _window;
SDL_Renderer* _renderer;

if( SDL_Init( SDL_INIT_EVERYTHING ) != 0 ) {
    string error( SDL_GetError() );
    throw runtime_error( "SDL could not initialize! SDL Error: " + error );
}

_window = SDL_CreateWindow( "Conscious", SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED, 500, 500, SDL_WINDOW_SHOWN );
if( _window == NULL ) {
    string error( SDL_GetError() );
    throw runtime_error( "Window could not be created! SDL Error: " + error );
}

_renderer = SDL_CreateRenderer( _window , -1,
        SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC );
if( _renderer == NULL ) {
    string error( SDL_GetError() );
    throw runtime_error( "Renderer could not be created! SDL Error: " + error );
}

cout << SDL_GetError() << endl;

return 0;
}

Let me know what you think!

Thanks, Jonathon

--EDIT--

If you take out SDL_image and SDL_ttf the renderer is still returned as invalid. Also this does not happen on windows with the same exact hardware. If this is not a bug would somebody please explain what could be wrong with such a simple example?

--EDIT EDIT-- This code prints out "Invalid renderer" on my system. If you have SDL2 please run it and let me know if you do too.

回答1:

While it is indeed produces 'Invalid renderer' message, it isn't a problem because as SDL_GetError documentation states You must check the return values of SDL function calls to determine when to appropriately call SDL_GetError()., and SDL gave you no reason to look for error description in GetError.

Why it happens, by the way:

Breakpoint 1, 0x00007ffff7b00e90 in SDL_SetError_REAL () from /usr/lib64/libSDL2-2.0.so.0
(gdb) backtrace
#0  0x00007ffff7b00e90 in SDL_SetError_REAL () from /usr/lib64/libSDL2-2.0.so.0
#1  0x00007ffff7b8f124 in SDL_GL_GetProcAddress_REAL () from /usr/lib64/libSDL2-2.0.so.0
#2  0x00007ffff7b8f80b in SDL_GL_GetAttribute_REAL () from /usr/lib64/libSDL2-2.0.so.0
#3  0x00007ffff7b41bcf in GL_CreateRenderer () from /usr/lib64/libSDL2-2.0.so.0
#4  0x00007ffff7b3b66c in SDL_CreateRenderer_REAL () from /usr/lib64/libSDL2-2.0.so.0
#5  0x0000000000401383 in main ()

GL_CreateRenderer calls SDL_GetAttribute to get context version and such, which tries to load GL functions, which requires active renderer, but it isn't there yet. While not most eye-pleasant solution, it works well and it isn't a bug. Probable reason why you don't have it on windows is e.g. because it uses different renderer (d3d?).

来源：https://stackoverflow.com/questions/31628174/sdl2-invalid-renderer

标签

sdl-2

true-type-fonts

renderer