adds component to ease use of OpenGL programs (that is pipelines of shaders)

interface/src/OGlProgram.h

@@ -0,0 +1,130 @@
+#ifndef __interface__OpenGlSupport__
+#define __interface__OpenGlSupport__
+
+#include "InterfaceConfig.h"
+
+/**
+ * Macro to log OpenGl errors to stderr.
+ * Example: oglLog( glPushMatrix() );
+ */
+#define oGlLog(stmt) \
+    stmt; \
+    { \
+        GLenum e = glGetError(); \
+        if (e != GL_NO_ERROR) { \
+            fprintf(stderr, __FILE__ ":"  oGlLog_stringize(__LINE__) \
+                    " [OpenGL] %s\n", gluErrorString(e)); \
+        } \
+    } \
+    (void) 0
+
+#define oGlLog_stringize(x) oGlLog_stringize_i(x)
+#define oGlLog_stringize_i(x) # x
+
+/**
+ * Encapsulation of the otherwise lengthy call sequence to compile
+ * and link shading pipelines.
+ */
+class OGlProgram {
+
+    GLuint _hndProg;
+
+public:
+
+    OGlProgram() : _hndProg(0) { }
+
+    ~OGlProgram() { if (_hndProg != 0u) { glDeleteProgram(_hndProg); } }
+
+    // no copy/assign
+    OGlProgram(OGlProgram const&); // = delete;
+    OGlProgram& operator=(OGlProgram const&); // = delete;
+
+#if 0 // let's keep this commented, for now (C++11)
+
+    OGlProgram(OGlProgram&& disposable) : _hndProg(disposable._hndProg) {
+
+        disposable._hndProg = 0;
+    }
+
+    OGlProgram& operator=(OGlProgram&& disposable) {
+
+        GLuint tmp = _hndProg;
+        _hndProg = disposable._hndProg;
+        disposable._hndProg = tmp;
+    }
+#endif
+
+    /**
+     * Activates the executable for rendering.
+     * Shaders must be added and linked before this will work.
+     */
+    void activate() const {
+
+        if (_hndProg != 0u)
+            oGlLog( glUseProgram(_hndProg) );
+    }
+
+    /**
+     * Adds a shader to the program.
+     */
+    bool addShader(GLenum type, GLchar const* cString) { 
+
+        addShader(type, 1, & cString);        
+    }
+
+    /**
+     * Adds a shader to the program and logs to stderr.
+     */
+    bool addShader(GLenum type, GLsizei nStrings, GLchar const** strings) {
+
+        if (! _hndProg) { _hndProg = glCreateProgram(); }
+
+        GLuint s = glCreateShader(type);
+        glShaderSource(s, nStrings, strings, 0l);
+        glCompileShader(s);
+        GLint status; 
+        glGetShaderiv(s, GL_COMPILE_STATUS, & status);
+        if (!! status)
+            glAttachShader(_hndProg, s);
+#ifdef NDEBUG
+        else
+#endif
+            fetchLog(s, glGetShaderiv, glGetShaderInfoLog);
+        glDeleteShader(s);
+        return !! status;
+    }
+
+    /**
+     * Links the program and logs to stderr.
+     */
+    bool link() {
+
+        if (! _hndProg) { return false; }
+
+        glLinkProgram(_hndProg);
+        GLint status; 
+        glGetProgramiv(_hndProg, GL_LINK_STATUS, & status);
+#ifdef NDEBUG
+        if (status == 0)
+#endif
+            fetchLog(_hndProg, glGetProgramiv, glGetProgramInfoLog);
+
+        return status != 0;
+    }
+
+private:
+
+    template< typename ParamFunc, typename GetLogFunc >
+    void fetchLog(GLint handle, ParamFunc getParam, GetLogFunc getLog) {
+        GLint logLength = 0;
+        getParam(handle, GL_INFO_LOG_LENGTH, &logLength);
+        if (!! logLength) {
+            GLchar* message = new GLchar[logLength];
+            getLog(handle, logLength, 0l, message);
+            fprintf(stderr, "%s\n", message);
+            delete[] message;
+        }
+    }
+};
+
+#endif