掌機 - Miyoo A30 - C/C++ - SDL v2.0 - OpenGL ES 2.0 - Use Shader

main.c

#include <stdio.h>
#include <stdlib.h>
#include <SDL2/SDL.h>
#include <GLES2/gl2.h>
  
const char *vShaderSrc = 
    "attribute vec4 vPosition;    \n"
    "void main(void)              \n"
    "{                            \n"
    "    gl_Position = vPosition; \n"
    "}";
 
const char *fShaderSrc =
    "#ifdef GL_ES               \n"
    "precision mediump float;   \n"
    "#endif                     \n"
    "uniform vec4 vColor;       \n"
    "void main(void)            \n"
    "{                          \n"
    "    gl_FragColor = vColor; \n"
    "}";
  
int main(int argc, char **argv)
{
    SDL_Window *window = NULL;
    SDL_GLContext context = {0};
  
    SDL_Init(SDL_INIT_VIDEO);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
  
    window = SDL_CreateWindow("main", 0, 0, 320, 240, SDL_WINDOW_OPENGL);
    context = SDL_GL_CreateContext(window);
  
    GLuint vShader = 0;
    GLuint fShader = 0;
    GLuint pObject = 0;
  
    vShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vShader, 1, &vShaderSrc, NULL);
    glCompileShader(vShader);
  
    fShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fShader, 1, &fShaderSrc, NULL);
    glCompileShader(fShader);
  
    pObject = glCreateProgram();
    glAttachShader(pObject, vShader);
    glAttachShader(pObject, fShader);
    glLinkProgram(pObject);
    glUseProgram(pObject);
      
    GLfloat v[] = {
         0.0f,  0.5f, 0.0f,
        -0.5f, -0.5f, 0.0f,
         0.5f, -0.5f, 0.0f
    };
 
    GLuint vp = glGetAttribLocation(pObject, "vPosition");
    glVertexAttribPointer(vp, 3, GL_FLOAT, GL_FALSE, 0, v);
    glEnableVertexAttribArray(vp);
 
    GLuint vc = glGetUniformLocation(pObject, "vColor");
    glUniform4f(vc, 1.0f, 0.0f, 0.0f, 1.0f);
 
    glViewport(0, 0, 320, 240);
    glClear(GL_COLOR_BUFFER_BIT);
    glDrawArrays(GL_TRIANGLES, 0, 3);
 
    SDL_GL_SwapWindow(window);
    SDL_Delay(30000);
  
    SDL_DestroyWindow(window);
    SDL_GL_DeleteContext(context);
    SDL_Quit();
    return 0;
}

編譯、執行

$ /opt/a30/bin/arm-linux-gcc \
    -I/opt/a30/arm-a30-linux-gnueabihf/sysroot/usr/include/SDL2 \
    -lSDL2 -lSDL2_gfx -lSDL2_image -lSDL2_ttf -lSDL2_mixer \
    -lGLESv2 main.c -o main

/mnt/SDCARD# export LD_LIBRARY_PATH=.:/config/lib:/customer/lib:/usr/miyoo/lib
/mnt/SDCARD# ./main