src/mesa/main/querymatrix.c

/**************************************************************************
 *
 * Copyright 2008 VMware, Inc.
 * All Rights Reserved.
 *
 **************************************************************************/


/**
 * Code to implement GL_OES_query_matrix.  See the spec at:
 * http://www.khronos.org/registry/gles/extensions/OES/OES_query_matrix.txt
 */


#include <stdlib.h>
#include "c99_math.h"
#include "glheader.h"
#include "querymatrix.h"
#include "main/get.h"
#include "util/macros.h"


/**
 * This is from the GL_OES_query_matrix extension specification:
 *
 *  GLbitfield glQueryMatrixxOES( GLfixed mantissa[16],
 *                                GLint   exponent[16] )
 *  mantissa[16] contains the contents of the current matrix in GLfixed
 *  format.  exponent[16] contains the unbiased exponents applied to the
 *  matrix components, so that the internal representation of component i
 *  is close to mantissa[i] * 2^exponent[i].  The function returns a status
 *  word which is zero if all the components are valid. If
 *  status & (1<<i) != 0, the component i is invalid (e.g., NaN, Inf).
 *  The implementations are not required to keep track of overflows.  In
 *  that case, the invalid bits are never set.
 */

#define INT_TO_FIXED(x) ((GLfixed) ((x) << 16))
#define FLOAT_TO_FIXED(x) ((GLfixed) ((x) * 65536.0))


GLbitfield GLAPIENTRY
_mesa_QueryMatrixxOES(GLfixed mantissa[16], GLint exponent[16])
{
   GLfloat matrix[16];
   GLint tmp;
   GLenum currentMode = GL_FALSE;
   GLenum desiredMatrix = GL_FALSE;
   /* The bitfield returns 1 for each component that is invalid (i.e.
    * NaN or Inf).  In case of error, everything is invalid.
    */
   GLbitfield rv;
   unsigned i, bit;

   /* This data structure defines the mapping between the current matrix
    * mode and the desired matrix identifier.
    */
   static const struct {
      GLenum currentMode;
      GLenum desiredMatrix;
   } modes[] = {
      {GL_MODELVIEW, GL_MODELVIEW_MATRIX},
      {GL_PROJECTION, GL_PROJECTION_MATRIX},
      {GL_TEXTURE, GL_TEXTURE_MATRIX},
   };

   /* Call Mesa to get the current matrix in floating-point form.  First,
    * we have to figure out what the current matrix mode is.
    */
   _mesa_GetIntegerv(GL_MATRIX_MODE, &tmp);
   currentMode = (GLenum) tmp;

   /* The mode is either GL_FALSE, if for some reason we failed to query
    * the mode, or a given mode from the above table.  Search for the
    * returned mode to get the desired matrix; if we don't find it,
    * we can return immediately, as _mesa_GetInteger() will have
    * logged the necessary error already.
    */
   for (i = 0; i < ARRAY_SIZE(modes); i++) {
      if (modes[i].currentMode == currentMode) {
         desiredMatrix = modes[i].desiredMatrix;
         break;
      }
   }
   if (desiredMatrix == GL_FALSE) {
      /* Early error means all values are invalid. */
      return 0xffff;
   }

   /* Now pull the matrix itself. */
   _mesa_GetFloatv(desiredMatrix, matrix);

   rv = 0;
   for (i = 0, bit = 1; i < 16; i++, bit<<=1) {
      float normalizedFraction;
      int exp;

      switch (fpclassify(matrix[i])) {
      case FP_SUBNORMAL:
      case FP_NORMAL:
      case FP_ZERO:
         /* A "subnormal" or denormalized number is too small to be
          * represented in normal format; but despite that it's a
          * valid floating point number.  FP_ZERO and FP_NORMAL
          * are both valid as well.  We should be fine treating
          * these three cases as legitimate floating-point numbers.
          */
         normalizedFraction = (GLfloat)frexp(matrix[i], &exp);
         mantissa[i] = FLOAT_TO_FIXED(normalizedFraction);
         exponent[i] = (GLint) exp;
         break;

      case FP_NAN:
         /* If the entry is not-a-number or an infinity, then the
          * matrix component is invalid.  The invalid flag for
          * the component is already set; might as well set the
          * other return values to known values.  We'll set
          * distinct values so that a savvy end user could determine
          * whether the matrix component was a NaN or an infinity,
          * but this is more useful for debugging than anything else
          * since the standard doesn't specify any such magic
          * values to return.
          */
         mantissa[i] = INT_TO_FIXED(0);
         exponent[i] = (GLint) 0;
         rv |= bit;
         break;

      case FP_INFINITE:
         /* Return +/- 1 based on whether it's a positive or
          * negative infinity.
          */
         if (matrix[i] > 0) {
            mantissa[i] = INT_TO_FIXED(1);
         }
         else {
            mantissa[i] = -INT_TO_FIXED(1);
         }
         exponent[i] = (GLint) 0;
         rv |= bit;
         break;

      default:
         /* We should never get here; but here's a catching case
          * in case fpclassify() is returnings something unexpected.
          */
         mantissa[i] = INT_TO_FIXED(2);
         exponent[i] = (GLint) 0;
         rv |= bit;
         break;
      }

   } /* for each component */

   /* All done */
   return rv;
}