Resubmit 35500: Added an application framework for demos. Ported hellotriangl...

third_party/gles_book_examples/Chapter_2/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 "Hello_Triangle.h"
+
 #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 )
+int htInit ( ESContext *esContext )
 {
-   UserData *userData = esContext->userData;
+   HTUserData *userData = esContext->userData;
+
    GLbyte vShaderStr[] =  
       "attribute vec4 vPosition;    \n"
       "void main()                  \n"
       "{                            \n"
       "   gl_Position = vPosition;  \n"
       "}                            \n";
    
+   // TODO(alokp): Shaders containing "precision" do not compile.
    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;
+   // TODO(alokp): Client-side vertex arrays do not work.
+   GLfloat vVertices[] = {  0.0f,  0.5f, 0.0f, 
+                           -0.5f, -0.5f, 0.0f,
+                            0.5f, -0.5f, 0.0f };
 
-   // 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 );
+   userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
+   if ( userData->programObject == 0 ) return FALSE;
 
    // Bind vPosition to attribute 0   
-   glBindAttribLocation ( programObject, 0, "vPosition" );
+   glBindAttribLocation ( userData->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;
+   glGenBuffers ( 1, &userData->vbo );
+   glBindBuffer ( GL_ARRAY_BUFFER, userData->vbo );
+   glBufferData ( GL_ARRAY_BUFFER, sizeof(vVertices), NULL, GL_STATIC_DRAW );
+   glBufferSubData ( GL_ARRAY_BUFFER, 0, sizeof(vVertices), vVertices );
 
    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 )
+void htDraw ( 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 };
-      
+   HTUserData *userData = esContext->userData;
+
    // 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 );
+   glBindBuffer ( GL_ARRAY_BUFFER, userData->vbo );
    glEnableVertexAttribArray ( 0 );
+   glVertexAttribPointer ( 0, 3, GL_FLOAT, GL_FALSE, 0, 0 );
 
    glDrawArrays ( GL_TRIANGLES, 0, 3 );
 
-   eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
+   // Nothing is drawn or application crashes without glFlush.
+   // TODO(alokp): glFlush should not be necessary with SwapBuffers().
+   glFlush();
 }
 
+///
+// Cleanup
+//
+void htShutDown ( ESContext *esContext )
+{
+   HTUserData *userData = esContext->userData;
 
-int main ( int argc, char *argv[] )
-{
-   ESContext esContext;
-   UserData  userData;
-
-   esInitContext ( &esContext );
-   esContext.userData = &userData;
-
-   esCreateWindow ( &esContext, "Hello Triangle", 320, 240, ES_WINDOW_RGB );
-   
-   if ( !Init ( &esContext ) )
-      return 0;
-
-   esRegisterDrawFunc ( &esContext, Draw );
-   
-   esMainLoop ( &esContext );
+   // Delete program object
+   if ( userData->programObject != 0 )
+   {
+      glDeleteProgram ( userData->programObject );
+      userData->programObject = 0;
+   }
+   if ( userData->vbo != 0 )
+   {
+      glDeleteBuffers ( 1, &userData->vbo );
+      userData->vbo = 0;
+   }
 }