rendergl: Check for GL 4.6 anisotropic TF extension

OpenGL 4.6 has brought an extension for anisotropic filtering that can work
alongside our existing GL_EXT_texture_filter_anisotropic code: check for
this new extension and, if supported, make use of it.

Link: https://registry.khronos.org/OpenGL/extensions/ARB/ARB_texture_filter_anisotropic.txt

Author: voidanix

src/engine/rendergl.cpp

@@ -562,13 +562,14 @@ void gl_checkextensions()
         if(glversion < 300 && dbgexts) conoutf("\frUsing GL_ARB_texture_compression_rgtc extension.");
     }
 
-    if(hasext("GL_EXT_texture_filter_anisotropic"))
-    {
+    if ((glversion >= 460 || hasext("GL_ARB_texture_filter_anisotropic")) ||
+                             hasext("GL_EXT_texture_filter_anisotropic")) {
         GLint val;
-        glGetIntegerv(GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT, &val);
+        glGetIntegerv(GL_MAX_TEXTURE_MAX_ANISOTROPY, &val);
         hwmaxanisotropy = val;
         hasAF = true;
-        if(dbgexts) conoutf("\frUsing GL_EXT_texture_filter_anisotropic extension.");
+        if (dbgexts)
+            conoutf("\frUsing GL_*_texture_filter_anisotropic extension.");
     }
 
     if(glversion >= 300 || hasext("GL_EXT_gpu_shader4"))

src/engine/texture.cpp

@@ -784,7 +784,10 @@ void setuptexparameters(int tnum, void *pixels, int clamp, int filter, GLenum fo
     glBindTexture(target, tnum);
     glTexParameteri(target, GL_TEXTURE_WRAP_S, clamp&1 ? GL_CLAMP_TO_EDGE : (clamp&0x100 ? GL_MIRRORED_REPEAT : GL_REPEAT));
     if(target!=GL_TEXTURE_1D) glTexParameteri(target, GL_TEXTURE_WRAP_T, clamp&2 ? GL_CLAMP_TO_EDGE : (clamp&0x200 ? GL_MIRRORED_REPEAT : GL_REPEAT));
-    if(target==GL_TEXTURE_2D && hasAF && min(anisotropy, hwmaxanisotropy) > 0 && filter > 1) glTexParameteri(target, GL_TEXTURE_MAX_ANISOTROPY_EXT, min(anisotropy, hwmaxanisotropy));
+
+    if (target == GL_TEXTURE_2D && hasAF && min(anisotropy, hwmaxanisotropy) > 0 && filter > 1)
+        glTexParameteri(target, GL_TEXTURE_MAX_ANISOTROPY, min(anisotropy, hwmaxanisotropy));
+
     glTexParameteri(target, GL_TEXTURE_MAG_FILTER, filter && bilinear ? GL_LINEAR : GL_NEAREST);
     glTexParameteri(target, GL_TEXTURE_MIN_FILTER,
         filter > 1 ?

src/shared/glexts.h

@@ -289,10 +289,10 @@ extern PFNGLDRAWBUFFERSPROC glDrawBuffers_;
 #define GL_PIXEL_UNPACK_BUFFER            0x88EC
 #endif
 
-#ifndef GL_EXT_texture_filter_anisotropic
-#define GL_EXT_texture_filter_anisotropic 1
-#define GL_TEXTURE_MAX_ANISOTROPY_EXT     0x84FE
-#define GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT 0x84FF
+#ifndef GL_ARB_texture_filter_anisotropic
+#define GL_ARB_texture_filter_anisotropic 1
+#define GL_TEXTURE_MAX_ANISOTROPY         0x84FE
+#define GL_MAX_TEXTURE_MAX_ANISOTROPY     0x84FF
 #endif
 
 #ifndef GL_EXT_texture_compression_s3tc