Set vertex position and color at the same time


I would like to set the vertex position and color at the same time.

My opengl2 codes are:

static char* vertexShaderCode = "attribute vec4 vPosition;" 
      "mat4 projectionMatrix = mat4( 2.0/480.0, 0.0, 0.0, -1.0,"
                           "0.0, -2.0/800.0, 0.0, 1.0,"
                           "0.0, 0.0, -1.0, 0.0,"
                           "0.0, 0.0, 0.0, 1.0);"
      "void main() {gl_Position = vPosition*projectionMatrix;}";

static char* fragmentShaderCode =
   "precision mediump float;" 
   "uniform vec4 vColor;" 
   "void main() {gl_FragColor = vColor;}";


   gColorHandle = glGetUniformLocation(gProgram, "vColor");
   gPositionHandle = glGetAttribLocation(gProgram, "vPosition");

Then i use these two functions to set the color and the position:

void glSetColorA(GLfloat* color, int32 rgb, int32 a)
   PixelConv pc;
   pc.pixel = rgb;
   color[0] = (GLfloat)pc.r / (GLfloat)255;
   color[1] = (GLfloat)pc.g / (GLfloat)255;
   color[2] = (GLfloat)pc.b / (GLfloat)255;
   color[3] = (GLfloat)a / (GLfloat)255;   
   glUniform4fv(gColorHandle, 1, color); // Set color for drawing the line

void glDrawPixel(GLfloat* coords, int32 x, int32 y)
   coords[0] = x;
   coords[1] = y;
   coords[2] = 0;

   glVertexAttribPointer(gPositionHandle, COORDS_PER_VERTEX, GL_FLOAT, GL_FALSE, COORDS_PER_VERTEX * sizeof(float), coords); // Prepare the triangle coordinate data
   glDrawArrays(GL_POINTS, 0,1);

However, i plan to set a bunch of pixels, like 100 at a time, and i belive that if i could set both the color and the position in the same instruction, it would be faster.

What has to be changed? I’m an opengl newbie.



There is a reference implementation, see
It is a complete single file minimal OpenGL program that draws with a color.