From bc57d3e35ce0067a1098ef72857351fcf93469b3 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <slouken@libsdl.org>
Date: Thu, 15 Sep 2022 06:57:41 -0700
Subject: [PATCH] Fixed OpenGL ES shader compilation on Linux

---
 src/render/opengles2/SDL_render_gles2.c  |  6 +++++-
 src/render/opengles2/SDL_shaders_gles2.c | 24 +++++++++++++++++++-----
 src/render/opengles2/SDL_shaders_gles2.h |  7 ++++---
 3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
index 29b050d0b..e88257797 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -496,7 +496,7 @@ GLES2_CacheShader(GLES2_RenderData *data, GLES2_ShaderType type, GLenum shader_t
     GLuint id = 0;
     GLint compileSuccessful = GL_FALSE;
     int attempt, num_src;
-    const GLchar *shader_src_list[2];
+    const GLchar *shader_src_list[3];
     const GLchar *shader_body = GLES2_GetShader(type);
 
     if (!shader_body) {
@@ -506,6 +506,9 @@ GLES2_CacheShader(GLES2_RenderData *data, GLES2_ShaderType type, GLenum shader_t
 
     for (attempt = 0; attempt < 2 && !compileSuccessful; ++attempt) {
         num_src = 0;
+
+        shader_src_list[num_src++] = GLES2_GetShaderPrologue(type);
+
         if (shader_type == GL_FRAGMENT_SHADER) {
             if (attempt == 0) {
                 shader_src_list[num_src++] = GLES2_GetShaderInclude(data->texcoord_precision_hint);
@@ -513,6 +516,7 @@ GLES2_CacheShader(GLES2_RenderData *data, GLES2_ShaderType type, GLenum shader_t
                 shader_src_list[num_src++] = GLES2_GetShaderInclude(GLES2_SHADER_FRAGMENT_INCLUDE_UNDEF_PRECISION);
             }
         }
+
         shader_src_list[num_src++] = shader_body;
 
         SDL_assert(num_src <= SDL_arraysize(shader_src_list));
diff --git a/src/render/opengles2/SDL_shaders_gles2.c b/src/render/opengles2/SDL_shaders_gles2.c
index 4d48e36f4..54a589631 100644
--- a/src/render/opengles2/SDL_shaders_gles2.c
+++ b/src/render/opengles2/SDL_shaders_gles2.c
@@ -326,11 +326,13 @@ static const char GLES2_Fragment_TextureNV21BT709[] = \
 #endif
 
 /* Custom Android video format texture */
-static const char GLES2_Fragment_TextureExternalOES[] = " \
+static const char GLES2_Fragment_TextureExternalOES_Prologue[] = " \
     #extension GL_OES_EGL_image_external : require\n\
+";
+static const char GLES2_Fragment_TextureExternalOES[] = " \
     uniform samplerExternalOES u_texture; \
-    varying mediump vec4 v_color;\n\
-    varying SDL_TEXCOORD_PRECISION vec2 v_texCoord;\n\
+    varying mediump vec4 v_color; \
+    varying SDL_TEXCOORD_PRECISION vec2 v_texCoord; \
     \
     void main() \
     { \
@@ -344,7 +346,18 @@ static const char GLES2_Fragment_TextureExternalOES[] = " \
  * Shader selector                                                                               *
  *************************************************************************************************/
 
-const char *GLES2_GetShaderInclude(GLES2_ShaderIncludeType type) {
+const char *GLES2_GetShaderPrologue(GLES2_ShaderType type)
+{
+    switch (type) {
+    case GLES2_SHADER_FRAGMENT_TEXTURE_EXTERNAL_OES:
+        return GLES2_Fragment_TextureExternalOES_Prologue;
+    default:
+        return "";
+    }
+}
+
+const char *GLES2_GetShaderInclude(GLES2_ShaderIncludeType type)
+{
     switch (type) {
     case GLES2_SHADER_FRAGMENT_INCLUDE_UNDEF_PRECISION:
         return GLES2_Fragment_Include_Undef_Precision;
@@ -359,7 +372,8 @@ const char *GLES2_GetShaderInclude(GLES2_ShaderIncludeType type) {
     }
 }
 
-GLES2_ShaderIncludeType GLES2_GetTexCoordPrecisionEnumFromHint() {
+GLES2_ShaderIncludeType GLES2_GetTexCoordPrecisionEnumFromHint()
+{
     const char *texcoord_hint = SDL_GetHint("SDL_RENDER_OPENGLES2_TEXCOORD_PRECISION");
     GLES2_ShaderIncludeType value = GLES2_SHADER_FRAGMENT_INCLUDE_BEST_TEXCOORD_PRECISION;
     if (texcoord_hint) {
diff --git a/src/render/opengles2/SDL_shaders_gles2.h b/src/render/opengles2/SDL_shaders_gles2.h
index c3d59284e..5a688cc5c 100644
--- a/src/render/opengles2/SDL_shaders_gles2.h
+++ b/src/render/opengles2/SDL_shaders_gles2.h
@@ -60,9 +60,10 @@ typedef enum
     GLES2_SHADER_COUNT
 } GLES2_ShaderType;
 
-const char *GLES2_GetShader(GLES2_ShaderType type);
-const char *GLES2_GetShaderInclude(GLES2_ShaderIncludeType type);
-GLES2_ShaderIncludeType GLES2_GetTexCoordPrecisionEnumFromHint(void);
+extern const char *GLES2_GetShaderPrologue(GLES2_ShaderType type);
+extern const char *GLES2_GetShaderInclude(GLES2_ShaderIncludeType type);
+extern const char *GLES2_GetShader(GLES2_ShaderType type);
+extern GLES2_ShaderIncludeType GLES2_GetTexCoordPrecisionEnumFromHint(void);
 
 #endif /* SDL_VIDEO_RENDER_OGL_ES2 */