Command line options for GL context.

Adding command line options to glViewer to make it easy
to control the requested GL version and profile.  While
it is only enabled for glViewer in this change, it will
be easy to extend to all our example viewers.  The new
command line options are:

    -glCoreProfile on|off
    -glForwardCompat on|off
    -glVersion M.n

examples/common/glUtils.cpp

@@ -24,6 +24,7 @@
 
 #include <sstream>
 #include <string>
+#include <cstring>
 #include "glUtils.h"
 
 #include <GLFW/glfw3.h>
@@ -37,34 +38,104 @@ namespace GLUtils {
    (glewIsSupported(x) == GL_TRUE)
 #endif
 
+static void
+_argParseBool(bool *ret, const char *lbl, int i, int argc, char **argv)
+{
+    if (i < argc-1) {
+        if (!strcmp(argv[i+1], "on")) {
+            *ret = true;
+        } else if (!strcmp(argv[i+1], "off")) {
+            *ret = false;
+        } else {
+            fprintf(stderr, "Unknown setting for %s: %s\n", lbl, argv[i+1]);
+            exit(1);
+        }
+    } else {
+        fprintf(stderr,
+            "Please specify \"on\" or \"off\" for %s.\n", lbl);
+        exit(1);
+    }
+}
+
 void
-SetMinimumGLVersion() {
+SetMinimumGLVersion(int argc, char ** argv) {
+
+#if defined(__APPLE__)
+    // Here 3.2 is the minimum GL version supported, GLFW will allocate a
+    // higher version if possible. This works on OS X, but instead limits
+    // the version to 3.2 on Linux. On Linux & Windows, specifying no 
+    // version hint should use the highest version available.
+    //
+    // http://www.glfw.org/faq.html#how-do-i-create-an-opengl-30-context
+    // http://www.glfw.org/faq.html#what-versions-of-opengl-are-supported-by-glfw
+    bool coreProfile = true;
+    bool forwardCompat = true;
+    bool versionSet = true;
+    int  major = 3;
+    int  minor = 2;
+#else
+    bool coreProfile = false;
+    bool forwardCompat = false;
+    bool versionSet = false;
+    int  major = 4;
+    int  minor = 2;
+#endif
+
+    for (int i = 1; i < argc; ++i) {
+
+        if (!strcmp(argv[i], "-glCoreProfile")) {
+            _argParseBool(&coreProfile, argv[i], i, argc, argv);
+        }
+        if (!strcmp(argv[i], "-glForwardCompat")) {
+            _argParseBool(&forwardCompat, argv[i], i, argc, argv);
+        }
+        if (!strcmp(argv[i], "-glVersion")) {
+            if (i < argc-1) {
+                char *versionStr = argv[i+1];
+                size_t len = strlen(versionStr);
+                if (len == 3 && versionStr[1] == '.' &&
+                    versionStr[0] >= '0' && versionStr[0] <= '9' &&
+                    versionStr[2] >= '0' && versionStr[2] <= '9') {
+                        
+                    major = versionStr[0] - '0';
+                    minor = versionStr[2] - '0';
+                    versionSet = true;
+
+                } else {
+                    fprintf(stderr,
+                        "Invalid version number: %s, please specify a number "
+                        "in the format M.n, e.g., -glVersion 4.2.\n",
+                        versionStr);
+                    exit(1);
+                }
+            } else {
+                fprintf(stderr,
+                    "Please specify a version number for glVersion "
+                    "in the form M.n, e.g., -glVersion 4.2.\n");
+                exit(1);
+            }
+        }
+    }
+
+
     #define glfwOpenWindowHint glfwWindowHint
     #define GLFW_OPENGL_VERSION_MAJOR GLFW_CONTEXT_VERSION_MAJOR
     #define GLFW_OPENGL_VERSION_MINOR GLFW_CONTEXT_VERSION_MINOR
 
-    #if defined(__APPLE__)
-
-        #ifdef CORE_PROFILE
+#ifdef CORE_PROFILE
+    if (coreProfile) {
         glfwOpenWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+    }
+
+    if (forwardCompat) {
         glfwOpenWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
-        #endif
-
-        // Here 3.2 is the minimum GL version supported, GLFW will allocate a
-        // higher version if possible. This works on OS X, but instead limits
-        // the version to 3.2 on Linux. On Linux & Windows, specifying no 
-        // version hint should use the highest version available.
-        //
-        // http://www.glfw.org/faq.html#how-do-i-create-an-opengl-30-context
-        // http://www.glfw.org/faq.html#what-versions-of-opengl-are-supported-by-glfw
-        //
-        int major = 3,
-            minor = 2;
+    }
+#endif
 
+    if (versionSet) {
         glfwOpenWindowHint(GLFW_OPENGL_VERSION_MAJOR, major);
         glfwOpenWindowHint(GLFW_OPENGL_VERSION_MINOR, minor);
-
-    #endif
+    }
 }
 
 void

examples/common/glUtils.h

@@ -51,7 +51,7 @@
 
 namespace GLUtils {
 
-void SetMinimumGLVersion();
+void SetMinimumGLVersion(int argc=0, char **argv=NULL);
 
 void PrintGLVersion();
 

examples/glViewer/glViewer.cpp

@@ -1829,7 +1829,7 @@ int main(int argc, char ** argv) {
 
     static const char windowTitle[] = "OpenSubdiv glViewer " OPENSUBDIV_VERSION_STRING;
 
-    GLUtils::SetMinimumGLVersion();
+    GLUtils::SetMinimumGLVersion(argc, argv);
 
     if (fullscreen) {