Determine correct pixel format for SDL_CreateTexture()?

I am struggling to convert a simple pong game from SDL to SDL2 because I could not find a valid value for the pixel format argument (second parameter 'Uint32 format') when calling SDL_CreateTexture(). Finally I found success by using SDL_PIXELFORMAT_ARGB8888, and I also found that SDL_PIXELFORMAT_UNKNOWN works too. However, after reading a few articles on system endianness and determining byte-order, I'm still unsure how a valid pixel format can be found for a given system without guessing, using unknown, or running some separate shell scripts.

Is it safe to just rely on SDL_PIXELFORMAT_UNKNOWN? Could anyone provide some information (or a link) to help me better understand these concepts and implementing them? I'd like to understand the related concepts better for future graphics programming.

Here's what the code originally looked like:

screen = SDL_CreateRGBSurfaceWithFormat(0, width, height, 32, 
                                        SDL_PIXELTYPE_RGBA32); 

screen_texture = SDL_CreateTextureFromSurface(renderer, screen);

And what I used to make it work:

screen = SDL_CreateRGBSurface(0, 640, 480, 32,
                              0x00FF0000,
                              0x0000FF00,
                              0x000000FF,
                              0xFF000000);

screen_texture = SDL_CreateTexture(renderer,
                                   SDL_PIXELFORMAT_ARGB8888, 
                                   SDL_TEXTUREACCESS_TARGET,
                                   640, 480); // SDL_PIXELFORMAT_UNKNOWN also works

A given SDL_Renderer is going to support at least one SDL_PixelFormatEnum; Other formats will work but may incur a conversion penalty at creation and/or use.

Use SDL_GetRendererInfo() to populate a SDL_RendererInfo & use one of the formats in SDL_RendererInfo::texture_formats (from here):

SDL_RendererInfo info;
SDL_GetRendererInfo( renderer, &info );
cout << "Renderer name: " << info.name << endl;
cout << "Texture formats: " << endl;
for( Uint32 i = 0; i < info.num_texture_formats; i++ )
{
    cout << SDL_GetPixelFormatName( info.texture_formats[i] ) << endl;
}

Back when I ran that both the DirectX & OpenGL backends supported SDL_PIXELFORMAT_ARGB8888.

Double-checking the SDL code via git grep -A 25 SDL_RenderDriver I think the first texture_formats is the "preferred" format:

SDL_render_d3d.c:SDL_RenderDriver D3D_RenderDriver = {
SDL_render_d3d.c-    D3D_CreateRenderer,
SDL_render_d3d.c-    {
SDL_render_d3d.c-     "direct3d",
SDL_render_d3d.c-     (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
SDL_render_d3d.c-     1,
SDL_render_d3d.c-     {SDL_PIXELFORMAT_ARGB8888},
SDL_render_d3d.c-     0,
SDL_render_d3d.c-     0}
--
SDL_render_d3d11.c:SDL_RenderDriver D3D11_RenderDriver = {
SDL_render_d3d11.c-    D3D11_CreateRenderer,
SDL_render_d3d11.c-    {
SDL_render_d3d11.c-        "direct3d11",
SDL_render_d3d11.c-        (
SDL_render_d3d11.c-            SDL_RENDERER_ACCELERATED |
SDL_render_d3d11.c-            SDL_RENDERER_PRESENTVSYNC |
SDL_render_d3d11.c-            SDL_RENDERER_TARGETTEXTURE
SDL_render_d3d11.c-        ),                          /* flags.  see SDL_RendererFlags */
SDL_render_d3d11.c-        6,                          /* num_texture_formats */
SDL_render_d3d11.c-        {                           /* texture_formats */
SDL_render_d3d11.c-            SDL_PIXELFORMAT_ARGB8888,
SDL_render_d3d11.c-            SDL_PIXELFORMAT_RGB888,
SDL_render_d3d11.c-            SDL_PIXELFORMAT_YV12,
SDL_render_d3d11.c-            SDL_PIXELFORMAT_IYUV,
SDL_render_d3d11.c-            SDL_PIXELFORMAT_NV12,
SDL_render_d3d11.c-            SDL_PIXELFORMAT_NV21
SDL_render_d3d11.c-        },
SDL_render_d3d11.c-        0,                          /* max_texture_width: will be filled in later */
SDL_render_d3d11.c-        0                           /* max_texture_height: will be filled in later */
SDL_render_d3d11.c-    }
SDL_render_d3d11.c-};
--
SDL_render_metal.m:SDL_RenderDriver METAL_RenderDriver = {
SDL_render_metal.m-    METAL_CreateRenderer,
SDL_render_metal.m-    {
SDL_render_metal.m-        "metal",
SDL_render_metal.m-        (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
SDL_render_metal.m-        6,
SDL_render_metal.m-        {
SDL_render_metal.m-            SDL_PIXELFORMAT_ARGB8888,
SDL_render_metal.m-            SDL_PIXELFORMAT_ABGR8888,
SDL_render_metal.m-            SDL_PIXELFORMAT_YV12,
SDL_render_metal.m-            SDL_PIXELFORMAT_IYUV,
SDL_render_metal.m-            SDL_PIXELFORMAT_NV12,
SDL_render_metal.m-            SDL_PIXELFORMAT_NV21
SDL_render_metal.m-        },
SDL_render_metal.m-    0, 0,
SDL_render_metal.m-    }
SDL_render_metal.m-};
--
SDL_render_gl.c:SDL_RenderDriver GL_RenderDriver = {
SDL_render_gl.c-    GL_CreateRenderer,
SDL_render_gl.c-    {
SDL_render_gl.c-     "opengl",
SDL_render_gl.c-     (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
SDL_render_gl.c-     1,
SDL_render_gl.c-     {SDL_PIXELFORMAT_ARGB8888},
SDL_render_gl.c-     0,
SDL_render_gl.c-     0}
SDL_render_gl.c-};
--
SDL_render_gles.c:SDL_RenderDriver GLES_RenderDriver = {
SDL_render_gles.c-    GLES_CreateRenderer,
SDL_render_gles.c-    {
SDL_render_gles.c-     "opengles",
SDL_render_gles.c-     (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC),
SDL_render_gles.c-     1,
SDL_render_gles.c-     {SDL_PIXELFORMAT_ABGR8888},
SDL_render_gles.c-     0,
SDL_render_gles.c-     0
SDL_render_gles.c-    }
SDL_render_gles.c-};
--
SDL_render_gles2.c:SDL_RenderDriver GLES2_RenderDriver = {
SDL_render_gles2.c-    GLES2_CreateRenderer,
SDL_render_gles2.c-    {
SDL_render_gles2.c-        "opengles2",
SDL_render_gles2.c-        (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
SDL_render_gles2.c-        4,
SDL_render_gles2.c-        {
SDL_render_gles2.c-        SDL_PIXELFORMAT_ARGB8888,
SDL_render_gles2.c-        SDL_PIXELFORMAT_ABGR8888,
SDL_render_gles2.c-        SDL_PIXELFORMAT_RGB888,
SDL_render_gles2.c-        SDL_PIXELFORMAT_BGR888
SDL_render_gles2.c-        },
SDL_render_gles2.c-        0,
SDL_render_gles2.c-        0
SDL_render_gles2.c-    }
SDL_render_gles2.c-};
--
SDL_render_psp.c:SDL_RenderDriver PSP_RenderDriver = {
SDL_render_psp.c-    .CreateRenderer = PSP_CreateRenderer,
SDL_render_psp.c-    .info = {
SDL_render_psp.c-        .name = "PSP",
SDL_render_psp.c-        .flags = SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE,
SDL_render_psp.c-        .num_texture_formats = 4,
SDL_render_psp.c-        .texture_formats = { [0] = SDL_PIXELFORMAT_BGR565,
SDL_render_psp.c-                                                 [1] = SDL_PIXELFORMAT_ABGR1555,
SDL_render_psp.c-                                                 [2] = SDL_PIXELFORMAT_ABGR4444,
SDL_render_psp.c-                                                 [3] = SDL_PIXELFORMAT_ABGR8888,
SDL_render_psp.c-        },
SDL_render_psp.c-        .max_texture_width = 512,
SDL_render_psp.c-        .max_texture_height = 512,
SDL_render_psp.c-     }
SDL_render_psp.c-};
--
SDL_render_sw.c:SDL_RenderDriver SW_RenderDriver = {
SDL_render_sw.c-    SW_CreateRenderer,
SDL_render_sw.c-    {
SDL_render_sw.c-     "software",
SDL_render_sw.c-     SDL_RENDERER_SOFTWARE | SDL_RENDERER_TARGETTEXTURE,
SDL_render_sw.c-     8,
SDL_render_sw.c-     {
SDL_render_sw.c-      SDL_PIXELFORMAT_ARGB8888,
SDL_render_sw.c-      SDL_PIXELFORMAT_ABGR8888,
SDL_render_sw.c-      SDL_PIXELFORMAT_RGBA8888,
SDL_render_sw.c-      SDL_PIXELFORMAT_BGRA8888,
SDL_render_sw.c-      SDL_PIXELFORMAT_RGB888,
SDL_render_sw.c-      SDL_PIXELFORMAT_BGR888,
SDL_render_sw.c-      SDL_PIXELFORMAT_RGB565,
SDL_render_sw.c-      SDL_PIXELFORMAT_RGB555
SDL_render_sw.c-     },
SDL_render_sw.c-     0,
SDL_render_sw.c-     0}
SDL_render_sw.c-};
--
SDL_DirectFB_render.c:SDL_RenderDriver DirectFB_RenderDriver = {
SDL_DirectFB_render.c-    DirectFB_CreateRenderer,
SDL_DirectFB_render.c-    {
SDL_DirectFB_render.c-     "directfb",
SDL_DirectFB_render.c-     (SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_ACCELERATED),
SDL_DirectFB_render.c-     /* (SDL_TEXTUREMODULATE_NONE | SDL_TEXTUREMODULATE_COLOR |
SDL_DirectFB_render.c-      SDL_TEXTUREMODULATE_ALPHA),
SDL_DirectFB_render.c-      (SDL_BLENDMODE_NONE | SDL_BLENDMODE_MASK | SDL_BLENDMODE_BLEND |
SDL_DirectFB_render.c-      SDL_BLENDMODE_ADD | SDL_BLENDMODE_MOD),
SDL_DirectFB_render.c-     (SDL_SCALEMODE_NONE | SDL_SCALEMODE_FAST |
SDL_DirectFB_render.c-      SDL_SCALEMODE_SLOW | SDL_SCALEMODE_BEST), */
SDL_DirectFB_render.c-     0,
SDL_DirectFB_render.c-     {
SDL_DirectFB_render.c-             /* formats filled in later */
SDL_DirectFB_render.c-     },
SDL_DirectFB_render.c-     0,
SDL_DirectFB_render.c-     0}
SDL_DirectFB_render.c-};