/**

  * $Id$

  *

  * GL-based support functions 

  *

  * Copyright (c) 2005 Nathan Keynes.

  *

  * This program is free software; you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation; either version 2 of the License, or

  * (at your option) any later version.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  */

 #include <string.h>

 #include <stdlib.h>

 #include <glib/gstrfuncs.h>

 #include "pvr2/glutil.h"

 gboolean isOpenGLES2()

 {

     const char *str = glGetString(GL_VERSION);

     if( strncmp(str, "OpenGL ES 2.", 12) == 0 ) {

         return TRUE;

     }

 }

 gboolean isGLSecondaryColorSupported()

 {

     return isGLExtensionSupported("GL_EXT_secondary_color");

 }

 gboolean isGLVertexBufferSupported()

 {

     return isGLExtensionSupported("GL_ARB_vertex_buffer_object");

 }

 gboolean isGLPixelBufferSupported()

 {

     return isGLExtensionSupported("GL_ARB_pixel_buffer_object");

 }

 gboolean isGLMirroredTextureSupported()

 {

     return isGLExtensionSupported("GL_ARB_texture_mirrored_repeat");

 }

 gboolean isGLShaderSupported()

 {

     return isOpenGLES2() || (isGLExtensionSupported("GL_ARB_fragment_shader") &&

     isGLExtensionSupported("GL_ARB_vertex_shader") &&

     isGLExtensionSupported("GL_ARB_shading_language_100"));

 }

 /**

  * Check if there's at least 2 texture units

  */

 gboolean isGLMultitextureSupported()

 {

     if( !isOpenGLES2() && !isGLExtensionSupported("GL_ARB_multitexture") )

         return FALSE;

     int units = 0;

 #if defined(GL_MAX_TEXTURE_UNITS)

         glGetIntegerv(GL_MAX_TEXTURE_UNITS, &units);

 #elif defined(GL_MAX_TEXTURE_IMAGE_UNITS)

         glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &units);

 #endif

     return units >= 2;

 }

 gboolean isGLVertexRangeSupported()

 {

     return isGLExtensionSupported("GL_APPLE_vertex_array_range") ||

             isGLExtensionSupported("GL_NV_vertex_array_range");

 }

 /**

  * Test if a specific extension is supported. From opengl.org

  * @param extension extension name to check for

  * @return TRUE if supported, otherwise FALSE.

  */

 gboolean isGLExtensionSupported( const char *extension )

 {

     const GLubyte *extensions = NULL;

     const GLubyte *start;

     GLubyte *where, *terminator;

     /* Extension names should not have spaces. */

     where = (GLubyte *) strchr(extension, ' ');

     if (where || *extension == '\0')

         return 0;

     extensions = glGetString(GL_EXTENSIONS);

     if( extensions == NULL ) {

         /* No GL available, so we're pretty sure the extension isn't

          * available either. */

         return FALSE;

     }

     /* It takes a bit of care to be fool-proof about parsing the

        OpenGL extensions string. Don't be fooled by sub-strings,

        etc. */

     start = extensions;

     for (;;) {

         where = (GLubyte *) strstr((const char *) start, extension);

         if (!where)

             break;

         terminator = where + strlen(extension);

         if (where == start || *(where - 1) == ' ')

             if (*terminator == ' ' || *terminator == '\0')

                 return TRUE;

         start = terminator;

     }

     return FALSE;

 }

 int compare_charp( const void *a, const void *b )

 {

     const char **ca = (const char **)a;

     const char **cb = (const char **)b;

     return strcmp(*ca, *cb);

 }

 #define DEFAULT_TERMINAL_COLUMNS 80

 #define DEFAULT_COLUMN_WIDTH 34

 int glGetMaxColourAttachments()

 {

 #ifdef GL_MAX_COLOR_ATTACHMENTS

     GLint result = 0;

     glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS, &result);

     return result;

 #else

     return 1;

 #endif

 }

 /**

  * Define an orthographic projection matrix

  * Note: row-major order

  */

 void defineOrthoMatrix( GLfloat *matrix, GLfloat width, GLfloat height, GLfloat znear, GLfloat zfar )

 {

     matrix[0] =  2/width;

     matrix[1] =  0;

     matrix[2] =  0;

     matrix[3] =  0;

     matrix[4] =  0;

     matrix[5] = -2/height;

     matrix[6] =  0;

     matrix[7] =  0;

     matrix[8] =  0;

     matrix[9] =  0;

     matrix[10]= -2/(zfar-znear);

     matrix[11]=  0;

     matrix[12]= -1;

     matrix[13]=  1;

     matrix[14]= -(zfar+znear)/(zfar-znear);

     matrix[15]=  1;

 }

 /**

  * Format a GL extension list (or other space-separated string) nicely, and

  * print to the given output stream.

  */

 void fprint_extensions( FILE *out, const char *extensions )

 {

     unsigned int i, j, count, maxlen = DEFAULT_COLUMN_WIDTH, columns, per_column, terminal_columns;

     const char *terminal_columns_str = getenv("COLUMNS");

     if( terminal_columns_str == NULL || (terminal_columns = strtol(terminal_columns_str,0,10)) == 0 )

         terminal_columns = DEFAULT_TERMINAL_COLUMNS;

     if( extensions == NULL || extensions[0] == '\0' )

         return;

     gchar *ext_dup = g_strdup(extensions);

     gchar **ext_split = g_strsplit(g_strstrip(extensions), " ", 0);

     for( count = 0; ext_split[count] != NULL; count++ ) {

         unsigned len = strlen(ext_split[count]);

         if( len > maxlen )

             maxlen = len;

     }

     columns = terminal_columns / (maxlen+2);

     if( columns == 0 )

         columns = 1;

     per_column = (count+columns-1) / columns;

     qsort(ext_split, count, sizeof(gchar *), compare_charp);

     for( i=0; i<per_column; i++ ) {

         for( j=0; j<columns; j++ ) {

             unsigned idx = i + (j*per_column);

             if( idx < count )

                 fprintf( out, "  %-*s", maxlen, ext_split[idx] );

         }

         fprintf( out, "\n" );

     }

     g_strfreev(ext_split);

     g_free(ext_dup);

 }

 void glPrintInfo( FILE *out )

 {

     fprintf( out, "GL Vendor: %s\n", glGetString(GL_VENDOR) );

     fprintf( out, "GL Renderer: %s\n", glGetString(GL_RENDERER) );

     fprintf( out, "GL Version: %s\n", glGetString(GL_VERSION) );

     if( isGLShaderSupported() ) {

          fprintf( out, "SL Version: %s\n", glGetString(GL_SHADING_LANGUAGE_VERSION) );

     }

     fprintf( out, "GL Extensions:\n" );

     fprint_extensions( out, (const gchar *)glGetString(GL_EXTENSIONS) );

     if( display_driver && display_driver->print_info ) {

         fprintf( out, "\n");

         display_driver->print_info(out);

     }

 }

 gboolean gl_check_error(const char *context)

 {

     GLint err = glGetError();

     if( err != 0 ) {

         const char *s;

         switch( err ) {

         case GL_INVALID_ENUM: s = "Invalid enum"; break;

         case GL_INVALID_VALUE: s = "Invalid value"; break;

         case GL_INVALID_OPERATION: s = "Invalid operation"; break;

 #ifdef GL_STACK_OVERFLOW

         case GL_STACK_OVERFLOW: s = "Stack overflow"; break;

 #endif

 #ifdef GL_STACK_UNDERFLOW

         case GL_STACK_UNDERFLOW: s = "Stack underflow"; break;

 #endif

         case GL_OUT_OF_MEMORY:   s = "Out of memory"; break;

         default: s = "Unknown error"; break;

         }

         if( context ) {

             WARN( "%s: GL error: %x (%s)\n", context, err, s );

         } else {

             WARN( "GL error: %x (%s)\n", err, s );

         }

         return FALSE;

     }

     return TRUE;

 }