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backends/graphics/opengl/framebuffer.h

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+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef BACKENDS_GRAPHICS_OPENGL_FRAMEBUFFER_H
+#define BACKENDS_GRAPHICS_OPENGL_FRAMEBUFFER_H
+
+#include "graphics/opengl/system_headers.h"
+
+#include "math/matrix4.h"
+
+#include "common/rotationmode.h"
+
+namespace OpenGL {
+
+class Pipeline;
+
+/**
+ * Object describing a framebuffer OpenGL can render to.
+ */
+class Framebuffer {
+public:
+	Framebuffer();
+	virtual ~Framebuffer() {};
+
+public:
+	enum BlendMode {
+		/**
+		 * Newly drawn pixels overwrite the existing contents of the framebuffer
+		 * without mixing with them.
+		 */
+		kBlendModeDisabled,
+
+		/**
+		 * Newly drawn pixels overwrite the existing contents of the framebuffer
+		 * without mixing with them. Alpha channel is discarded.
+		 */
+		kBlendModeOpaque,
+
+		/**
+		 * Newly drawn pixels mix with the framebuffer based on their alpha value
+		 * for transparency.
+		 */
+		kBlendModeTraditionalTransparency,
+
+		/**
+		 * Newly drawn pixels mix with the framebuffer based on their alpha value
+		 * for transparency.
+		 *
+		 * Requires the image data being drawn to have its color values pre-multiplied
+		 * with the alpha value.
+		 */
+		kBlendModePremultipliedTransparency,
+
+		/**
+		 * Newly drawn pixels add to the destination value.
+		 */
+		kBlendModeAdditive,
+
+		/**
+		 * Newly drawn pixels mask out existing pixels based on the alpha value and
+		 * add inversions of the pixels based on the color.
+		 */
+		kBlendModeMaskAlphaAndInvertByColor,
+	};
+
+	/**
+	 * Set the clear color of the framebuffer.
+	 */
+	void setClearColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a);
+
+	/**
+	 * Enable/disable GL_BLEND.
+	 */
+	void enableBlend(BlendMode mode);
+
+	/**
+	 * 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 Math::Matrix4 &getProjectionMatrix() const { return _projectionMatrix; }
+
+	enum CopyMask {
+		kCopyMaskClearColor   = (1 << 0),
+		kCopyMaskBlendState   = (1 << 1),
+		kCopyMaskScissorState = (1 << 2),
+		kCopyMaskScissorBox   = (1 << 4),
+
+		kCopyMaskAll          = kCopyMaskClearColor | kCopyMaskBlendState |
+		                        kCopyMaskScissorState | kCopyMaskScissorBox,
+	};
+
+	/**
+	 * Copy rendering state from another framebuffer
+	 */
+	void copyRenderStateFrom(const Framebuffer &other, uint copyMask);
+
+protected:
+	bool isActive() const { return _pipeline != nullptr; }
+
+	GLint _viewport[4];
+	void applyViewport();
+
+	Math::Matrix4 _projectionMatrix;
+	void applyProjectionMatrix();
+
+	/**
+	 * Activate framebuffer.
+	 *
+	 * This is supposed to set all state associated with the framebuffer.
+	 */
+	virtual void activateInternal() = 0;
+
+	/**
+	 * Deactivate framebuffer.
+	 *
+	 * This is supposed to make any cleanup required when unbinding the
+	 * framebuffer.
+	 */
+	virtual void deactivateInternal() {}
+
+public:
+	/**
+	 * Set the size of the target buffer.
+	 */
+	virtual bool setSize(uint width, uint height) = 0;
+
+	/**
+	 * Accessor to activate framebuffer for pipeline.
+	 */
+	void activate(Pipeline *pipeline);
+
+	/**
+	 * Accessor to deactivate framebuffer from pipeline.
+	 */
+	void deactivate();
+
+private:
+	Pipeline *_pipeline;
+
+	GLfloat _clearColor[4];
+	void applyClearColor();
+
+	BlendMode _blendState;
+	void applyBlendState();
+
+	bool _scissorTestState;
+	void applyScissorTestState();
+
+	GLint _scissorBox[4];
+	void applyScissorBox();
+};
+
+/**
+ * Default back buffer implementation.
+ */
+class Backbuffer : public Framebuffer {
+public:
+	/**
+	 * Set the size of the back buffer.
+	 */
+	bool setSize(uint width, uint height) override;
+
+protected:
+	void activateInternal() override;
+};
+
+#if !USE_FORCED_GLES
+class Texture;
+
+/**
+ * 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();
+	~TextureTarget() override;
+
+	/**
+	 * 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.
+	 */
+	bool setSize(uint width, uint height) override;
+
+	/**
+	 * Query pointer to underlying GL texture.
+	 */
+	Texture *getTexture() const { return _texture; }
+
+protected:
+	void activateInternal() override;
+
+private:
+	Texture *_texture;
+	GLuint _glFBO;
+	bool _needUpdate;
+};
+#endif
+
+} // End of namespace OpenGL
+
+#endif