From aa99b4a63ea0469f264733f0a5688a2258d91c72 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Thu, 28 Feb 2019 09:43:17 -0500
Subject: [PATCH] SDL_GL_LoadLibrary() has slightly different behavior between
 1.2 and 2.0.

---
 src/SDL12_compat.c | 30 ++++++++++++++++++++++++++++++
 src/SDL20_syms.h   |  2 +-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 3c61f3ee8..c62c5b60c 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -3054,6 +3054,36 @@ SDL_FreeYUVOverlay(SDL12_Overlay * overlay)
     FIXME("write me");
 }
 
+DECLSPEC int SDLCALL
+SDL_GL_LoadLibrary(const char *libname)
+{
+    /* SDL 1.2 would unload the previous library if one was loaded. SDL2
+       reports an error if one is already loaded, and sometimes loads it
+       internally for some video targets, so unloading it probably isn't safe.
+       There really isn't a good reason to be using anything other than the
+       system OpenGL in 2019, so we ignore the error in this case to match 1.2
+       behavior, even if you were going to load a different library this time.
+       Oh well. */
+    const int rc = SDL20_GL_LoadLibrary(libname);
+    if (rc == -1) {
+        const char *err = SDL20_GetError();
+        if (SDL20_strcmp(err, "OpenGL library already loaded") == 0) {
+            return 0;
+        }
+
+        /* reset the actual error. */
+        char *dup = SDL_strdup(err);
+        if (!dup) {
+            SDL20_SetError("Out of memory");
+        } else {
+            SDL20_SetError(dup);
+            SDL_free(dup);
+        }
+    }
+    return rc;
+}
+
+
 DECLSPEC int SDLCALL
 SDL_GL_SetAttribute(SDL12_GLattr attr, int value)
 {
diff --git a/src/SDL20_syms.h b/src/SDL20_syms.h
index 7487cba11..fb36137f0 100644
--- a/src/SDL20_syms.h
+++ b/src/SDL20_syms.h
@@ -98,7 +98,7 @@ SDL20_SYM(int,GetColorKey,(SDL_Surface *a, Uint32 *b),(a,b),return)
 SDL20_SYM(void,FreeSurface,(SDL_Surface *a),(a),)
 SDL20_SYM(SDL_Surface*,LoadBMP_RW,(SDL_RWops *a, int b),(a,b),return)
 SDL20_SYM(int,SaveBMP_RW,(SDL_Surface *a, SDL_RWops *b, int c),(a,b,c),return)
-SDL20_SYM_PASSTHROUGH(int,GL_LoadLibrary,(const char *a),(a),return)
+SDL20_SYM(int,GL_LoadLibrary,(const char *a),(a),return)
 SDL20_SYM_PASSTHROUGH(void *,GL_GetProcAddress,(const char *a),(a),return)
 SDL20_SYM(int,GL_SetAttribute,(SDL_GLattr a, int b),(a,b),return)
 SDL20_SYM(int,GL_GetAttribute,(SDL_GLattr a, int *b),(a,b),return)