【8】shader写入类中

上一篇将 vao vbo写入类中进行封装，本篇将shader进行封装。

 Shader shader("res/shaders/Basic.shader");
    shader.Bind(); 
    shader.SetUniform4f("u_Color", 0.2f, 0.3f, 0.8f, 1.0f);

shader.h

#pragma once

#include 
#include 

struct ShaderProgramSource
{
	std::string VertexSource;
	std::string FragmentSource;
};

class Shader
{
private:
	std::string m_FilePath;
	unsigned int m_RendererID;
	// caching for uniforms
	std::unordered_map<std::string, int> m_UniformLocationCache;
public:
	Shader(const std::string& filepath);
	~Shader();

	void Bind() const;
	void UnBind() const;

	//Set Uniform
	void SetUniform4f(const std::string& name, float v0, float v1, float v2, float v3);
private: 
	ShaderProgramSource ParseShader(const std::string& filepath); 
	unsigned int CompileShader(unsigned int type, const std::string& source);
	unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader);
	int GetUniformLocation(const std::string& name);
	

};

shader.cpp

#include "Shader.h"

#include 
#include 
#include 
#include 

#include "Renderer.h"



Shader::Shader(const std::string& filepath)
	: m_FilePath(filepath), m_RendererID(0)
{
    ShaderProgramSource source = ParseShader(filepath);
    m_RendererID = CreateShader(source.VertexSource, source.FragmentSource); 
}

Shader::~Shader()
{
    GLCall(glDeleteProgram(m_RendererID));
}

void Shader::Bind() const
{
    GLCall(glUseProgram(m_RendererID));
}

void Shader::UnBind() const
{
    GLCall(glUseProgram(0));
}

void Shader::SetUniform4f(const std::string& name, float v0, float v1, float v2, float v3)
{
    GLCall(glUniform4f(GetUniformLocation(name), v0, v1, v2, v3));
}


int Shader::GetUniformLocation(const std::string& name)
{
    if (m_UniformLocationCache.find(name) != m_UniformLocationCache.end())
    {
        return m_UniformLocationCache[name];
    }
    GLCall( int location = glGetUniformLocation(m_RendererID, name.c_str()));
    if (location == -1)
    {
        std::cout << "Warning: unifrom '" << name << "' doesn't exist!" << std::endl;
    } 
    m_UniformLocationCache[name] = location;
    return location;
}

ShaderProgramSource Shader::ParseShader(const std::string& filepath) {
    std::ifstream stream(filepath);

    enum class ShaderType { /* 带作用域的枚举类型，不是类*/
        NONE = -1, VERTEX = 0, FRAGMENT = 1
    };

    std::string line;
    std::stringstream ss[2];
    ShaderType type = ShaderType::NONE;
    while (getline(stream, line)) {
        if (line.find("#shader") != std::string::npos) { /* 找到了*/
            if (line.find("vertex") != std::string::npos) {
                // set mode to vertex
                type = ShaderType::VERTEX;
            }
            else if (line.find("fragment") != std::string::npos) {
                // set mode to fragment
                type = ShaderType::FRAGMENT;
            }
        }
        else {
            ss[(int)type] << line << '\n';
        }
    }

    return { ss[0].str(), ss[1].str() };
}

unsigned int Shader::CompileShader(unsigned int type, const std::string& source) {
    unsigned int id = glCreateShader(type);/*vertex 或者 fragment */
    const char* src = source.c_str(); /*或者写 &source[0]*/
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE) {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        // char message[length]; /*这里会发现因为长度不定，无法栈分配，但你仍要这么做*/
        char* message = (char*)alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Failed to compile " <<
            (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << "shader!请定位到此行" << std::endl;
        std::cout << message << std::endl;
        glDeleteShader(id);
        return 0;
    }

    return id;
}


unsigned int Shader::CreateShader(const std::string& vertexShader, const std::string& fragmentShader) {
    /*使用unsigned是因为它接受的参数就是这样，
    或者可以使用 GLuint，但是作者不喜欢这样，因为它要使用多个图像api*/
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);

    glDeleteShader(vs);
    glDeleteShader(fs);

    return program;
}