OPENGL: Introduce abstraction for framebuffer.

This allows us to use various framebuffer settings easily. Now the GPU
accelerated CLUT8 surface implementation does not need to query former
framebuffer state anymore.

backends/graphics/opengl/framebuffer.h

@@ -0,0 +1,157 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef BACKENDS_GRAPHICS_OPENGL_FRAMEBUFFER_H
+#define BACKENDS_GRAPHICS_OPENGL_FRAMEBUFFER_H
+
+#include "backends/graphics/opengl/opengl-sys.h"
+
+namespace OpenGL {
+
+/**
+ * Object describing a framebuffer OpenGL can render to.
+ */
+class Framebuffer {
+public:
+	Framebuffer();
+	virtual ~Framebuffer() {};
+
+	/**
+	 * Activate framebuffer.
+	 *
+	 * This is supposed to set all state associated with the framebuffer.
+	 */
+	virtual void activate() = 0;
+
+	/**
+	 * Deactivate framebuffer.
+	 *
+	 * This is supposed to make any cleanup required when unbinding the
+	 * framebuffer.
+	 */
+	virtual void deactivate();
+
+	/**
+	 * Set the clear color of the framebuffer.
+	 */
+	void setClearColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a);
+
+	/**
+	 * Enable/disable GL_BLEND.
+	 */
+	void enableBlend(bool enable);
+
+	/**
+	 * Enable/disable GL_SCISSOR_TEST.
+	 */
+	void enableScissorTest(bool enable);
+
+	/**
+	 * Set scissor box dimensions.
+	 */
+	void setScissorBox(GLint x, GLint y, GLsizei w, GLsizei h);
+
+	/**
+	 * Obtain projection matrix of the framebuffer.
+	 */
+	const GLfloat *getProjectionMatrix() const { return _projectionMatrix; }
+protected:
+	bool isActive() const { return _isActive; }
+
+	GLint _viewport[4];
+	void applyViewport();
+
+	GLfloat _projectionMatrix[4*4];
+private:
+	bool _isActive;
+
+	GLfloat _clearColor[4];
+	void applyClearColor();
+
+	bool _blendState;
+	void applyBlendState();
+
+	bool _scissorTestState;
+	void applyScissorTestState();
+
+	GLint _scissorBox[4];
+	void applyScissorBox();
+};
+
+/**
+ * Default back buffer implementation.
+ */
+class Backbuffer : public Framebuffer {
+public:
+	virtual void activate();
+
+	/**
+	 * Set the dimensions (a.k.a. size) of the back buffer.
+	 */
+	void setDimensions(uint width, uint height);
+};
+
+#if !USE_FORCED_GLES
+class GLTexture;
+
+/**
+ * Render to texture framebuffer implementation.
+ *
+ * This target allows to render to a texture, which can then be used for
+ * further rendering.
+ */
+class TextureTarget : public Framebuffer {
+public:
+	TextureTarget();
+	virtual ~TextureTarget();
+
+	virtual void activate();
+
+	/**
+	 * Notify that the GL context is about to be destroyed.
+	 */
+	void destroy();
+
+	/**
+	 * Notify that the GL context has been created.
+	 */
+	void create();
+
+	/**
+	 * Set size of the texture target.
+	 */
+	void setSize(uint width, uint height);
+
+	/**
+	 * Query pointer to underlying GL texture.
+	 */
+	GLTexture *getTexture() const { return _texture; }
+private:
+	GLTexture *_texture;
+	GLuint _glFBO;
+	bool _needUpdate;
+};
+#endif
+
+} // End of namespace OpenGL
+
+#endif