support for OpenGL 2.0

* use OpenGL 2.0 auxiliary buffers when FBO is not supported, thus this means that OpenGL 3 is not a requirement anymore, so otclient might work in older video cards
* map zooming will never work well with Opengl 2.0 because of glCopyTexSubImage2D limitation

src/framework/graphics/coordsbuffer.cpp

@@ -86,6 +86,10 @@ void CoordsBuffer::addRepeatedRects(const Rect& dest, const Rect& src)
 
 void CoordsBuffer::enableHardwareCaching(HardwareBuffer::UsagePattern usagePattern)
 {
+#ifndef OPENGL_ES2
+    if(!GL_ARB_vertex_buffer_object)
+        return;
+#endif
     m_hardwareCacheMode = usagePattern;
     m_hardwareCaching = true;
     m_hardwareCached = false;

src/framework/graphics/framebuffer.cpp

@@ -25,30 +25,52 @@
 #include "texture.h"
 
 uint FrameBuffer::boundFbo = 0;
+std::vector<bool> auxBuffers;
 
 FrameBuffer::FrameBuffer()
 {
     m_clearColor = Color::alpha;
-
-    glGenFramebuffers(1, &m_fbo);
-    if(!m_fbo)
-        logFatal("Unable to create framebuffer object");
+    internalCreate();
 }
 
 FrameBuffer::FrameBuffer(const Size& size)
 {
     m_clearColor = Color::alpha;
-
-    glGenFramebuffers(1, &m_fbo);
-    if(!m_fbo)
-        logFatal("Unable to create framebuffer object");
-
+    internalCreate();
     resize(size);
 }
 
+void FrameBuffer::internalCreate()
+{
+    if(g_graphics.hasFBO()) {
+        glGenFramebuffers(1, &m_fbo);
+        if(!m_fbo)
+            logFatal("Unable to create framebuffer object");
+    } else { // use auxiliar buffers when FBOs are not supported
+        m_fbo = 0;
+        if(auxBuffers.size() == 0) {
+            int maxAuxs;
+            glGetIntegerv(GL_AUX_BUFFERS, &maxAuxs);
+            auxBuffers.resize(maxAuxs+1, false);
+        }
+        for(uint i=1;i<auxBuffers.size();++i) {
+            if(auxBuffers[i] == false) {
+                m_fbo = i;
+                auxBuffers[i] = true;
+            }
+        }
+        if(!m_fbo)
+            logFatal("There is no available auxiliar buffer for a new framebuffer");
+    }
+}
+
 FrameBuffer::~FrameBuffer()
 {
-    glDeleteFramebuffers(1, &m_fbo);
+    if(g_graphics.hasFBO()) {
+        glDeleteFramebuffers(1, &m_fbo);
+    } else {
+        auxBuffers[m_fbo] = false;
+    }
 }
 
 void FrameBuffer::resize(const Size& size)
@@ -59,15 +81,19 @@ void FrameBuffer::resize(const Size& size)
     if(m_texture && m_texture->getSize() == size)
         return;
 
-    internalBind();
     m_texture = TexturePtr(new Texture(size.width(), size.height(), 4));
     m_texture->setSmooth(true);
-    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_texture->getId(), 0);
 
-    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
-    if(status != GL_FRAMEBUFFER_COMPLETE)
-        logFatal("Unable to setup framebuffer object");
-    internalRelease();
+    if(g_graphics.hasFBO()) {
+        internalBind();
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_texture->getId(), 0);
+
+        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+        if(status != GL_FRAMEBUFFER_COMPLETE)
+            logFatal("Unable to setup framebuffer object");
+        internalRelease();
+    }
+
 }
 
 void FrameBuffer::bind(bool clear)
@@ -115,7 +141,15 @@ void FrameBuffer::internalBind()
     if(boundFbo == m_fbo)
         return;
     assert(boundFbo != m_fbo);
-    glBindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+
+    if(g_graphics.hasFBO()) {
+        glBindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+    } else {
+        int buffer = GL_AUX0 + m_fbo - 1;
+        glDrawBuffer(buffer);
+        glReadBuffer(buffer);
+    }
+
     m_prevBoundFbo = boundFbo;
     boundFbo = m_fbo;
 }
@@ -123,6 +157,18 @@ void FrameBuffer::internalBind()
 void FrameBuffer::internalRelease()
 {
     assert(boundFbo == m_fbo);
-    glBindFramebuffer(GL_FRAMEBUFFER, m_prevBoundFbo);
+    if(g_graphics.hasFBO()) {
+        glBindFramebuffer(GL_FRAMEBUFFER, m_prevBoundFbo);
+    } else {
+        m_texture->bind();
+        glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, m_texture->getWidth(), m_texture->getHeight());
+
+        int buffer = GL_BACK;
+        if(m_prevBoundFbo != 0)
+            buffer = GL_AUX0 + m_fbo - 1;
+
+        glDrawBuffer(buffer);
+        glReadBuffer(buffer);
+    }
     boundFbo = m_prevBoundFbo;
 }

src/framework/graphics/framebuffer.h

@@ -46,6 +46,7 @@ public:
     const Size& getSize() { return m_texture->getSize(); }
 
 private:
+    void internalCreate();
     void internalBind();
     void internalRelease();
 

src/framework/graphics/graphics.cpp

@@ -37,9 +37,8 @@ void Graphics::init()
         logFatal("Unable to init GLEW: ", glewGetErrorString(err));
     if(!GLEW_ARB_vertex_program || !GLEW_ARB_vertex_shader ||
        !GLEW_ARB_fragment_program || !GLEW_ARB_fragment_shader ||
-       !GLEW_ARB_framebuffer_object ||
-       !GLEW_ARB_multitexture)
-        logFatal("Your video driver is not supported");
+       !GLEW_ARB_texture_non_power_of_two || !GLEW_ARB_multitexture)
+        logFatal("Some OpenGL 2.0 extensions is not supported by your system graphics, please try updating your video drivers or buy a new hardware.");
 #endif
 
     glEnable(GL_BLEND);
@@ -59,11 +58,13 @@ void Graphics::terminate()
     m_emptyTexture.reset();
 }
 
-bool Graphics::isExtensionSupported(const char *extension)
+bool Graphics::hasFBO()
 {
-    std::string extensionsString = (const char*)glGetString(GL_EXTENSIONS);
-    auto extensions = Fw::split(extensionsString);
-    return std::find(extensions.begin(), extensions.end(), extension) != extensions.end();
+#ifndef OPENGL_ES2
+    return GLEW_ARB_framebuffer_object;
+#else
+    return true;
+#endif
 }
 
 void Graphics::resize(const Size& size)

src/framework/graphics/graphics.h

@@ -32,7 +32,7 @@ public:
     void init();
     void terminate();
 
-    bool isExtensionSupported(const char *extension);
+    bool hasFBO();
 
     void resize(const Size& size);
     void beginRender();