SH-2908 Potential fix for pink textures on some OpenGL 3.1 implementations.

indra/llrender/llshadermgr.cpp

@@ -614,6 +614,7 @@ GLhandleARB LLShaderMgr::loadShaderFile(const std::string& filename, S32 & shade
 
 			//some implementations of GLSL 1.30 require integer precision be explicitly declared
 			text[count++] = strdup("precision mediump int;\n");
+			text[count++] = strdup("precision highp float;\n");
 		}
 		else
 		{ //set version to 400
@@ -668,20 +669,22 @@ GLhandleARB LLShaderMgr::loadShaderFile(const std::string& filename, S32 & shade
 		
 		VARYING_FLAT ivec4 vary_texture_index;
 
+		vec4 ret = vec4(1,0,1,1);
+
 		vec4 diffuseLookup(vec2 texcoord)
 		{
 			switch (vary_texture_index.r))
 			{
-				case 0: return texture2D(tex0, texcoord);
-				case 1: return texture2D(tex1, texcoord);
-				case 2: return texture2D(tex2, texcoord);
+				case 0: ret = texture2D(tex0, texcoord); break;
+				case 1: ret = texture2D(tex1, texcoord); break;
+				case 2: ret = texture2D(tex2, texcoord); break;
 				.
 				.
 				.
-				case N: return texture2D(texN, texcoord);
+				case N: return texture2D(texN, texcoord); break;
 			}
 
-			return vec4(0,0,0,0);
+			return ret;
 		}
 		*/
 
@@ -708,18 +711,19 @@ GLhandleARB LLShaderMgr::loadShaderFile(const std::string& filename, S32 & shade
 		}
 		else if (major_version > 1 || minor_version >= 30)
 		{  //switches are supported in GLSL 1.30 and later
+			text[count++] = strdup("\tvec4 ret = vec4(1,0,1,1);\n");
 			text[count++] = strdup("\tswitch (vary_texture_index.r)\n");
 			text[count++] = strdup("\t{\n");
 		
 			//switch body
 			for (S32 i = 0; i < texture_index_channels; ++i)
 			{
-				std::string case_str = llformat("\t\tcase %d: return texture2D(tex%d, texcoord);\n", i, i);
+				std::string case_str = llformat("\t\tcase %d: ret = texture2D(tex%d, texcoord); break;\n", i, i);
 				text[count++] = strdup(case_str.c_str());
 			}
 
 			text[count++] = strdup("\t}\n");
-			text[count++] = strdup("\treturn vec4(1,0,1,1);\n");
+			text[count++] = strdup("\treturn ret;\n");
 			text[count++] = strdup("}\n");
 		}
 		else