Fix SDL color encoding.

Little-endian + RGBA means that red is located at the lowest-order bits,
not the highest.

The hello_world_sdl test is now portable, because we no longer write to
individual bytes.

We also add a test for a completely blank screen, which should be black, not
red.

Closes #1287, #761, #765.

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/sdl_canvas_blank.c b/tests/sdl_canvas_blank.c
new file mode 100644
index 00000000..0e7607a6
--- /dev/null
+++ b/tests/sdl_canvas_blank.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <SDL/SDL.h>
+
+
+int main() {
+  SDL_Init(SDL_INIT_VIDEO);
+  SDL_Surface *screen = SDL_SetVideoMode(256, 256, 32, SDL_SWSURFACE);
+
+  if (SDL_MUSTLOCK(screen)) SDL_LockSurface(screen);
+  if (SDL_MUSTLOCK(screen)) SDL_UnlockSurface(screen);
+  SDL_Flip(screen); 
+
+  SDL_Quit();
+
+  return 0;
+}
+