目录

什么是状态机？

基于状态机模式进行重构

Canvas.h源码

什么是状态机？

回顾之前两部分内容，我们做了：

• 绘制点
• 绘制线（Brensenham）
• 绘制三角形（拆分法）
• 图片操作（stb_image.h）
• 纹理贴图
• 效果处理

我们思考OpenGL是基于什么思想来做的，或者说什么样的设计模式？

答：状态机。那么什么是状态机？

状态机：

• 记录状态参数
• 更改状态参数
• 使用状态参数做事

白话解释：你给我什么参数，我就做什么事。给我true我就去做，false就不去做。

为什么用状态机？

• 图形学的程序结构特殊性，每个阶段关心的事情不一样
• 渲染管线的设置后处理的方便性
• 接口的整洁性

基于状态机模式进行重构

基于以上考虑和分析，我们对现有代码进行小小的重构:

canvas.h：

添加数据元类型，绘图模式，数据元素类:

	enum DATA_TYPE {GT_FLOAT=0,GT_INT=1};enum DRAW_MODE {GT_LINE=0,GL_TRIANGLE=1};struct DataElement {int			m_size;DATA_TYPE	m_type;int			m_stride;//每次取点的步长byte*		m_data;//数据空间指针DataElement() {m_size = -1;m_type = GT_FLOAT;m_stride = 0;m_data = nullptr;}};

 将之前Canvan类中的一些变量，抽象出来，到一个Statement类中：

随后添加部分状态机接口：

//===========状态机接口===============
void gtVertexPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);
void gtColorPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);
void gtTexCoordPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);
void gtDrawArray(DRAW_MODE _mode,int _first,int _count);//从first的点，画count个点

	void Canvas::gtVertexPointer(int _size, DATA_TYPE _type, int _stride, byte* _data){m_state.m_vertexData.m_size = _size;m_state.m_vertexData.m_type = _type;m_state.m_vertexData.m_stride = _stride;m_state.m_vertexData.m_data = _data;}void Canvas::gtColorPointer(int _size, DATA_TYPE _type, int _stride, byte* _data){m_state.m_colorData.m_size = _size;m_state.m_colorData.m_type = _type;m_state.m_colorData.m_stride = _stride;m_state.m_colorData.m_data = _data;}void Canvas::gtTexCoordPointer(int _size, DATA_TYPE _type, int _stride, byte* _data){m_state.m_texCoordData.m_size = _size;m_state.m_texCoordData.m_type = _type;m_state.m_texCoordData.m_stride = _stride;m_state.m_texCoordData.m_data = _data;}void Canvas::gtDrawArray(DRAW_MODE _mode, int _first, int _count){}

Canvas.h源码

为了方便查看，这里贴出Canvas.h的整体源码，也是对之前的一个总结梳理：

#pragma once
#include "GTMATH.hpp"
#include 
#include 
#include "Image.h"namespace GT {//点类class Point {public:int m_x;int m_y;RGBA m_color;floatV2 m_uv;Point(int _x = 0, int _y = 0, RGBA _color = RGBA(0, 0, 0, 0), floatV2 _uv = floatV2(0.0, 0.0)) {m_x = _x, m_y = _y, m_color = _color, m_uv = _uv;}~Point() {}};enum DATA_TYPE {GT_FLOAT=0,GT_INT=1};enum DRAW_MODE {GT_LINE=0,GL_TRIANGLE=1};struct DataElement {int			m_size;DATA_TYPE	m_type;int			m_stride;//每次取点的步长byte*		m_data;//数据空间指针DataElement() {m_size = -1;m_type = GT_FLOAT;m_stride = 0;m_data = nullptr;}};struct Statement {bool				 m_useBlend;//是否启用alpha混合模式bool				 m_enableTexture;//是否启用纹理贴图const Image*	     m_texture;//纹理贴图素材Image::TEXTURE_TYPE  m_texType;//纹理过滤byte				 m_alphaLimit;//大于此像素值才可以进行绘制DataElement			 m_vertexData;DataElement			 m_colorData;DataElement			 m_texCoordData;Statement() {m_useBlend = false;m_enableTexture = false;m_texture = nullptr;m_texType = Image::TX_REPEAT;m_alphaLimit = 0;}};//画布类，封装一些之后的图形APIclass Canvas {private:int			 m_width;int			 m_height;RGBA*		 m_buffer;Statement	 m_state;public:Canvas(int _width, int _height, void* _buffer) {if (_width <= 0 || _height <= 0) {m_width = -1;m_height = -1;m_buffer = nullptr;}m_width = _width;m_height = _height;m_buffer = (RGBA*)_buffer;m_state.m_useBlend = false;m_state.m_enableTexture = false;}~Canvas(){}//=========画布清洗============void clear() {if (m_buffer != nullptr) {memset(m_buffer, 0, sizeof(RGBA) * m_width * m_height);}}//=========画点操作============void drawPoint(int x, int y, RGBA _color) {if (x < 0 || x >= m_width || y < 0 || y >= m_height) {return;}m_buffer[y * m_width + x] = _color;}//根据真正的背景值取pixelRGBA getColor(int x, int y) {if (x < 0 || x >= m_width || y < 0 || y >= m_height) {return RGBA(0, 0, 0, 0);}return m_buffer[y * m_width + x];}//=========画线算法Brensenhem===void drawLine(Point pt1,Point pt2);//=========线性插值Lerp=========inline RGBA colorLerp(RGBA _color1, RGBA _color2, float _scale) {RGBA _color;_color.m_r = _color.m_r + (float)(_color2.m_r - _color1.m_r) * _scale;_color.m_g = _color.m_g + (float)(_color2.m_g - _color1.m_g) * _scale;_color.m_b = _color.m_b + (float)(_color2.m_b - _color1.m_b) * _scale;_color.m_a = _color.m_a + (float)(_color2.m_a - _color1.m_a) * _scale;return _color;}//=========画三角形==============void drawTriange(Point p1, Point p2, Point p3);void drawTriangeFlat(Point pFlat1, Point pFlat2, Point pt);//=========判断三角形是否与屏幕相交======bool judgeInRect(Point p, GT_RECT _rect);bool judgeInTriangle(Point pt, std::vector _ptArray);//==========图片操作=============void drawImage(int _x, int _y, Image* _image);void setAlphaLimit(byte _limit) { m_state.m_alphaLimit = _limit; }void setBlend(bool _useBlend) { m_state.m_useBlend = _useBlend; }//===========纹理===============void enableTexture(bool _enable) { m_state.m_enableTexture = _enable; }void bindTexture(const Image* _image) { m_state.m_texture = _image; }void setTextureType(Image::TEXTURE_TYPE _type) { m_state.m_texType = _type; }inline floatV2 uvLerp(floatV2 _uv1, floatV2 _uv2, float _scale) {floatV2 _uv;_uv.x = _uv1.x + (_uv2.x - _uv1.x) * _scale;_uv.y = _uv1.y + (_uv2.y - _uv1.y) * _scale;return _uv;}//===========状态机接口===============void gtVertexPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);void gtColorPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);void gtTexCoordPointer(int _size, DATA_TYPE _type, int _stride, byte* _data);void gtDrawArray(DRAW_MODE _mode,int _first,int _count);//从first的点，画count个点};
}