kc3-lang/angle/samples/gles2_book/Hello_Triangle/Hello_Triangle.c

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• Author : alokp@chromium.org
  Date : 2010-04-07 19:57:20
  Hash : 0270ef14
  Message : Changed the default character set to be UNICODE, the same as chromium. Changes to fix compile errors and warnings. Review URL: http://codereview.appspot.com/816046 git-svn-id: https://angleproject.googlecode.com/svn/trunk@103 736b8ea6-26fd-11df-bfd4-992fa37f6226

• samples/gles2_book/Hello_Triangle/Hello_Triangle.c

• //
  // Book:      OpenGL(R) ES 2.0 Programming Guide
  // Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
  // ISBN-10:   0321502795
  // ISBN-13:   9780321502797
  // Publisher: Addison-Wesley Professional
  // URLs:      http://safari.informit.com/9780321563835
  //            http://www.opengles-book.com
  //
  
  // Hello_Triangle.c
  //
  //    This is a simple example that draws a single triangle with
  //    a minimal vertex/fragment shader.  The purpose of this 
  //    example is to demonstrate the basic concepts of 
  //    OpenGL ES 2.0 rendering.
  #include <stdlib.h>
  #include "esUtil.h"
  
  typedef struct
  {
     // Handle to a program object
     GLuint programObject;
  
  } UserData;
  
  ///
  // Create a shader object, load the shader source, and
  // compile the shader.
  //
  GLuint LoadShader ( GLenum type, const char *shaderSrc )
  {
     GLuint shader;
     GLint compiled;
     
     // Create the shader object
     shader = glCreateShader ( type );
  
     if ( shader == 0 )
     	return 0;
  
     // Load the shader source
     glShaderSource ( shader, 1, &shaderSrc, NULL );
     
     // Compile the shader
     glCompileShader ( shader );
  
     // Check the compile status
     glGetShaderiv ( shader, GL_COMPILE_STATUS, &compiled );
  
     if ( !compiled ) 
     {
        GLint infoLen = 0;
  
        glGetShaderiv ( shader, GL_INFO_LOG_LENGTH, &infoLen );
        
        if ( infoLen > 1 )
        {
           char* infoLog = malloc (sizeof(char) * infoLen );
  
           glGetShaderInfoLog ( shader, infoLen, NULL, infoLog );
           esLogMessage ( "Error compiling shader:\n%s\n", infoLog );            
           
           free ( infoLog );
        }
  
        glDeleteShader ( shader );
        return 0;
     }
  
     return shader;
  
  }
  
  ///
  // Initialize the shader and program object
  //
  int Init ( ESContext *esContext )
  {
     UserData *userData = esContext->userData;
     GLbyte vShaderStr[] =  
        "attribute vec4 vPosition;    \n"
        "void main()                  \n"
        "{                            \n"
        "   gl_Position = vPosition;  \n"
        "}                            \n";
     
     GLbyte fShaderStr[] =  
        "precision mediump float;\n"\
        "void main()                                  \n"
        "{                                            \n"
        "  gl_FragColor = vec4 ( 1.0, 0.0, 0.0, 1.0 );\n"
        "}                                            \n";
  
     GLuint vertexShader;
     GLuint fragmentShader;
     GLuint programObject;
     GLint linked;
  
     // Load the vertex/fragment shaders
     vertexShader = LoadShader ( GL_VERTEX_SHADER, vShaderStr );
     fragmentShader = LoadShader ( GL_FRAGMENT_SHADER, fShaderStr );
  
     // Create the program object
     programObject = glCreateProgram ( );
     
     if ( programObject == 0 )
        return 0;
  
     glAttachShader ( programObject, vertexShader );
     glAttachShader ( programObject, fragmentShader );
  
     // Bind vPosition to attribute 0   
     glBindAttribLocation ( programObject, 0, "vPosition" );
  
     // Link the program
     glLinkProgram ( programObject );
  
     // Check the link status
     glGetProgramiv ( programObject, GL_LINK_STATUS, &linked );
  
     if ( !linked ) 
     {
        GLint infoLen = 0;
  
        glGetProgramiv ( programObject, GL_INFO_LOG_LENGTH, &infoLen );
        
        if ( infoLen > 1 )
        {
           char* infoLog = malloc (sizeof(char) * infoLen );
  
           glGetProgramInfoLog ( programObject, infoLen, NULL, infoLog );
           esLogMessage ( "Error linking program:\n%s\n", infoLog );            
           
           free ( infoLog );
        }
  
        glDeleteProgram ( programObject );
        return FALSE;
     }
  
     // Store the program object
     userData->programObject = programObject;
  
     glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
     return TRUE;
  }
  
  ///
  // Draw a triangle using the shader pair created in Init()
  //
  void Draw ( ESContext *esContext )
  {
     UserData *userData = esContext->userData;
     GLfloat vVertices[] = {  0.0f,  0.5f, 0.0f, 
                             -0.5f, -0.5f, 0.0f,
                              0.5f, -0.5f, 0.0f };
        
     // Set the viewport
     glViewport ( 0, 0, esContext->width, esContext->height );
     
     // Clear the color buffer
     glClear ( GL_COLOR_BUFFER_BIT );
  
     // Use the program object
     glUseProgram ( userData->programObject );
  
     // Load the vertex data
     glVertexAttribPointer ( 0, 3, GL_FLOAT, GL_FALSE, 0, vVertices );
     glEnableVertexAttribArray ( 0 );
  
     glDrawArrays ( GL_TRIANGLES, 0, 3 );
  
     eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
  }
  
  
  int main ( int argc, char *argv[] )
  {
     ESContext esContext;
     UserData  userData;
  
     esInitContext ( &esContext );
     esContext.userData = &userData;
  
     esCreateWindow ( &esContext, TEXT("Hello Triangle"), 320, 240, ES_WINDOW_RGB );
     
     if ( !Init ( &esContext ) )
        return 0;
  
     esRegisterDrawFunc ( &esContext, Draw );
     
     esMainLoop ( &esContext );
  }