/**

 * $Id$

 *

 * 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;

}