Add our own function to check whether a certain OpenGL extension is supported

simgear/screen/Makefile.am

@@ -28,6 +28,7 @@ libsgscreen_a_SOURCES = \
 	$(IMAGE_SERVER_SRCS) \
 	screen-dump.cxx \
         tr.cxx \
+	extensions.cxx \
 	win32-printer.h
 
 INCLUDES = -I$(top_srcdir)

simgear/screen/extensions.cxx

@@ -0,0 +1,66 @@
+/*
+ *
+ * Copyright (c) 2001 C<>sar Blecua Ud<55>as    All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * CESAR BLECUA UDIAS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
+ * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#include <string.h>
+
+#ifndef WIN32
+#include <dlfcn.h>
+#endif
+
+#include <extensions.hxx>
+
+bool SGSearchExtensionsString(char *extString, char *extName) {
+    // Returns GL_TRUE if the *extName string appears in the *extString string,
+    // surrounded by white spaces, or GL_FALSE otherwise.
+
+    char *p, *end;
+    int n, extNameLen;
+
+    extNameLen = strlen(extName);
+
+    p=extString;
+    end = p + strlen(p);
+
+    while (p < end) {
+        n = strcspn(p, " ");
+        if ((extNameLen == n) && (strncmp(extName, p, n) == 0))
+            return GL_TRUE;
+
+        p += (n + 1);
+    }
+
+    return GL_FALSE;
+}
+
+bool SGIsOpenGLExtensionSupported(char *extName) {
+   // Returns GL_TRUE if the OpenGL Extension whose name is *extName
+   // is supported by the system, or GL_FALSE otherwise.
+   //
+   // The *extName string must follow the OpenGL extensions naming scheme
+   // (ie: "GL_type_extension", like GL_EXT_convolution)
+
+    return SGSearchExtensionsString((char *)glGetString(GL_EXTENSIONS),
+extName);
+}
+

simgear/screen/extensions.hxx

@@ -1,10 +1,42 @@
+/*
+ *
+ * Copyright (c) 2001 C<>sar Blecua Ud<55>as    All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * CESAR BLECUA UDIAS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
+ * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
 #ifndef __SG_EXTENSIONS_HXX
 #define __SG_EXTENSIONS_HXX 1
 
-#ifndef WIN32
-#include <dlfcn.h>
+#include <GL/gl.h>
+
+#if defined(__cplusplus)
+extern "C" {
 #endif
 
+#ifndef APIENTRY
+#define APIENTRY
+#endif
+
+static bool SGSearchExtensionsString(char *extString, char *extName);
+bool SGIsOpenGLExtensionSupported(char *extName);
+
 inline void (*SGLookupFunction(const char *func))() {
 
 #if defined( WIN32 )
@@ -28,4 +60,15 @@ inline void (*SGLookupFunction(const char *func))() {
 #endif
 }
 
+
+
+/* OpenGL extension declarations */
+typedef void (APIENTRY * glPointParameterfProc)(GLenum pname, GLfloat param);
+typedef void (APIENTRY * glPointParameterfvProc)(GLenum pname, const GLfloat *params);
+
+#if defined(__cplusplus)
+}
 #endif
+
+#endif // !__SG_EXTENSIONS_HXX
+