support renderbuffer based display (#52)

* support renderbuffer based display

Add optional callback to Disp constructor to specify OS binding for renderbuffer storage during allocation.   If this is specified the renderbuffer will be used (via framebuffer) for rendering to the display, rather than framebuffer == 0 screen rendering.

* #include <functional>

CMakeLists.txt

@@ -14,7 +14,7 @@ HunterGate(
   LOCAL
 )
 
-project(ogles_gpgpu VERSION 0.3.3)
+project(ogles_gpgpu VERSION 0.3.4)
 
 hunter_add_package(check_ci_tag)
 find_package(check_ci_tag CONFIG REQUIRED)

ogles_gpgpu/common/proc/disp.cpp

@@ -28,9 +28,30 @@ void main()
 );
 // clang-format on
 
+Disp::Disp() = default;
+
+Disp::Disp(const Callback &renderbufferStorage)
+    : renderbufferStorage(renderbufferStorage)
+{
+
+}
+
+Disp::~Disp()
+{
+    if (renderbufferStorage)
+    {
+        glDeleteRenderbuffers(1, &renderbuffer);
+    }
+}
+
 int Disp::init(int inW, int inH, unsigned int order, bool prepareForExternalInput) {
     OG_LOGINF(getProcName(), "initialize");
 
+    if(renderbufferStorage)
+    {
+        createFBO();
+    }
+
     // ProcBase init - set defaults
     baseInit(inW, inH, order, prepareForExternalInput, procParamOutW, procParamOutH, procParamOutScale);
 
@@ -50,12 +71,48 @@ int Disp::render(int position) {
     filterRenderSetCoords();
     Tools::checkGLErr(getProcName(), "render set coords");
 
-    //glBindBuffer(GL_FRAMEBUFFER, 0);
     filterRenderDraw();
     Tools::checkGLErr(getProcName(), "render draw");
+
+    if(renderbufferStorage)
+    {
+        glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+        Tools::checkGLErr(getProcName(), "glBindRenderbuffer");
+    }
 
     filterRenderCleanup();
     Tools::checkGLErr(getProcName(), "render cleanup");
 
     return 0;
 }
+
+void Disp::createFBO()
+{
+    FilterProcBase::createFBO();
+
+    if (renderbufferStorage) {
+
+        fbo->bind();
+        Tools::checkGLErr(getProcName(), "glBindFramebuffer");
+
+        // Create a Renderbuffer
+        glGenRenderbuffers(1, &renderbuffer);
+        Tools::checkGLErr(getProcName(), "glGenRenderbuffers");
+
+        glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+        Tools::checkGLErr(getProcName(), "glBindRenderbuffer");
+
+        renderbufferStorage();
+        Tools::checkGLErr(getProcName(), "renderbufferStorage");
+
+        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
+        Tools::checkGLErr(getProcName(), "glFramebufferRenderbuffer");
+
+        auto fboStatus = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+        if (fboStatus != GL_FRAMEBUFFER_COMPLETE) {
+            std::stringstream ss;
+            ss << "Framebuffer incomplete :" << int(fboStatus);
+            throw std::runtime_error(ss.str());
+        }
+    }
+}

ogles_gpgpu/common/proc/disp.h

@@ -17,6 +17,8 @@
 
 #include "base/filterprocbase.h"
 
+#include <functional>
+
 namespace ogles_gpgpu {
 
 /**
@@ -25,6 +27,24 @@ namespace ogles_gpgpu {
  */
 class Disp : public FilterProcBase {
 public:
+
+    using Callback = std::function<void()>;
+
+    /**
+     * Default constructor
+     */
+    Disp();
+
+    /**
+     * Constructor for renderbuffer based display
+     */
+    Disp(const Callback &renderbufferStorage);
+
+    /**
+     * Destructor
+     */
+    virtual ~Disp();
+
     /**
      * Output resolution of display.
      *
@@ -87,13 +107,23 @@ class Disp : public FilterProcBase {
         return NULL;
     }
 
+    /**
+     * Create an FBO for this processor. This will contain the result after rendering in its attached texture.
+     *
+     * (optional) create renderbuffer if renderbufferStorage callback was specified in constructor.
+     */
+    virtual void createFBO();
+
 private:
     float tx = 0.f;
     float ty = 0.f;
     float resolutionX = 1.f;
     float resolutionY = 1.f;
 
     static const char* fshaderDispSrc; // fragment shader source
+
+    GLuint renderbuffer; // (optional) renderbuffer based display
+    Callback renderbufferStorage;
 };
 }