SDL: blit: Add a case for 8-bit blits that sdl12-compat exposed. (b5cd0)

From b5cd0749b2d04fbab07be46a5167eac3083b04fb Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 16 May 2023 14:38:44 -0400
Subject: [PATCH] blit: Add a case for 8-bit blits that sdl12-compat exposed.

sdl12-compat can get into a state where a color-keyed surface is
marked for blending, but wants to blend with full alpha (which
is the same as _not_ blending), so rather than fail to find a
blitter in that case, it just selects the colorkey blitter.


(cherry picked from commit 0eea92c8fcc4b5c572a0dd9848ca8886978ee0a2)
 src/video/SDL_blit_1.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/video/SDL_blit_1.c b/src/video/SDL_blit_1.c
index f3f95abc79e1..c59a417622dd 100644
--- a/src/video/SDL_blit_1.c
+++ b/src/video/SDL_blit_1.c
@@ -531,6 +531,9 @@ SDL_CalculateBlit1(SDL_Surface *surface)
         return one_blitkey[which];
+    case SDL_COPY_COLORKEY | SDL_COPY_BLEND:  /* this is not super-robust but handles a specific case we found sdl12-compat. */
+        return (surface->map->info.a == 255) ? one_blitkey[which] : (SDL_BlitFunc)NULL;
         /* Supporting 8bpp->8bpp alpha is doable but requires lots of
            tables which consume space and takes time to precompute,