Use OpenGL functions under extension names, if not present under regu…

…lar names.

lib/ivis_opengl/screen.cpp

@@ -204,12 +204,19 @@ void screenShutDown(void)
 }
 
 // Make OpenGL's VBO functions available under the core names for drivers that support OpenGL 1.4 only but have the VBO extension
-void screen_EnableVBO()
+void screen_EnableMissingFunctions()
 {
-	// no need if there is OpenGL 1.5 available
+	if (!GLEW_VERSION_1_3 && GLEW_ARB_multitexture)
+	{
+		debug(LOG_WARNING, "Pre-OpenGL 1.3: Fixing ARB_multitexture extension function names.");
+
+		__glewActiveTexture = __glewActiveTextureARB;
+		__glewMultiTexCoord2fv = __glewMultiTexCoord2fvARB;
+	}
+
 	if (!GLEW_VERSION_1_5 && GLEW_ARB_vertex_buffer_object)
 	{
-		debug(LOG_WARNING, "OpenGL 1.4+: Using VBO extension functions under the core names.");
+		debug(LOG_WARNING, "Pre-OpenGL 1.5: Fixing ARB_vertex_buffer_object extension function names.");
 
 		__glewBindBuffer = __glewBindBufferARB;
 		__glewBufferData = __glewBufferDataARB;
@@ -223,6 +230,27 @@ void screen_EnableVBO()
 		__glewMapBuffer = __glewMapBufferARB;
 		__glewUnmapBuffer = __glewUnmapBufferARB;
 	}
+
+	if (!GLEW_VERSION_2_0 && GLEW_ARB_shader_objects)
+	{
+		debug(LOG_WARNING, "Pre-OpenGL 2.0: Fixing ARB_shader_objects extension function names.");
+
+		__glewGetUniformLocation = __glewGetUniformLocationARB;
+		__glewAttachShader = __glewAttachObjectARB;
+		__glewCompileShader = __glewCompileShaderARB;
+		__glewCreateProgram = __glewCreateProgramObjectARB;
+		__glewCreateShader = __glewCreateShaderObjectARB;
+		__glewGetProgramInfoLog = __glewGetInfoLogARB;
+		__glewGetShaderInfoLog = __glewGetInfoLogARB;  // Same as previous.
+		__glewGetProgramiv = __glewGetObjectParameterivARB;
+		__glewUseProgram = __glewUseProgramObjectARB;
+		__glewGetShaderiv = __glewGetObjectParameterivARB;
+		__glewLinkProgram = __glewLinkProgramARB;
+		__glewShaderSource = __glewShaderSourceARB;
+		__glewUniform1f = __glewUniform1fARB;
+		__glewUniform1i = __glewUniform1iARB;
+		__glewUniform4fv = __glewUniform4fvARB;
+	}
 }
 
 void screen_SetBackDropFromFile(const char* filename)

lib/ivis_opengl/screen.h

@@ -63,8 +63,8 @@ extern void screenDoDumpToDiskIfRequired(void);
 void screen_enableMapPreview(char *name, int width, int height, Vector2i *playerpositions);
 void screen_disableMapPreview(void);
 bool screen_getMapPreview(void);
+void screen_EnableMissingFunctions();
 
-void screen_EnableVBO();
 struct OPENGL_DATA
 {
 	char vendor[256];

src/init.cpp

@@ -35,6 +35,7 @@
 #include "lib/framework/wzapp.h"
 #include "lib/ivis_opengl/piemode.h"
 #include "lib/ivis_opengl/piestate.h"
+#include "lib/ivis_opengl/screen.h"
 #include "lib/ivis_opengl/tex.h"
 #include "lib/ivis_opengl/ivi.h"
 #include "lib/netplay/netplay.h"
@@ -520,6 +521,9 @@ bool systemInitialise(void)
 	// Initialize the iVis text rendering module
 	iV_TextInit();
 
+	// Fix badly named OpenGL functions. Must be done after iV_TextInit, to avoid the renames being clobbered by an extra glewInit() call.
+	screen_EnableMissingFunctions();
+
 	iV_Reset();								// Reset the IV library.
 
 	readAIs();

src/terrain.cpp

@@ -711,9 +711,6 @@ bool initTerrain(void)
 	int decalSize;
 	int maxSectorSizeIndices, maxSectorSizeVertices;
 	bool decreasedSize = false;
-
-	// call VBO support hack before using it
-	screen_EnableVBO();
 
 	// this information is useful to prevent crashes with buggy opengl implementations
 	glGetIntegerv(GL_MAX_ELEMENTS_VERTICES, &GLmaxElementsVertices);