path: root/src/lib/libgamma-facade.c.gpp

/* -*- c -*- */
/**
 * libgamma -- Display server abstraction layer for gamma ramp adjustments
 * Copyright (C) 2014, 2015  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This library 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 3 of the License, or
 * (at your option) any later version.
 * 
 * This library 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.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "libgamma-facade.h"

#include "libgamma-error.h"
#include "libgamma-method.h"
#include "gamma-helper.h"


/* Initialise the general preprocessor. */
$>cd src/extract
$>export PATH=".:${PATH}"

/* Some general preprocessor we will use frequently. */
$<
get-methods ()
{ ./libgamma-method-extract --list --method | cut -d _ -f 1,2 --complement
}
lowercase ()
{ echo "$*" | sed -e y/QWERTYUIOPASDFGHJKLZXCVBNM/qwertyuiopasdfghjklzxcvbnm/ | sed -e s:core_graphics:cg:g
}
$>

/* Include all adjustment methods that
   are enabled at compile-time. */
$>for method in $(get-methods); do
#ifdef HAVE_LIBGAMMA_METHOD_${method}
# include "gamma-$(lowercase $method | sed -e s:_:-:g).h"
# ifndef HAVE_LIBGAMMA_METHODS
#  define HAVE_LIBGAMMA_METHODS
# endif
#endif
$>done

#include <unistd.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>


/* Some things to reduce warnings when we do
   not have any adjustment methods enabled. */
#ifndef HAVE_LIBGAMMA_METHODS
# define HAVE_NO_LIBGAMMA_METHODS
# ifdef __GCC__
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wsuggest-attribute=const"
# endif
#endif



#ifdef HAVE_LIBGAMMA_METHODS
# ifdef HAVE_LIBGAMMA_METHOD_LINUX_DRM
/**
 * Test whether a file descriptor refers to a VT.
 * 
 * @param   fd  The file descriptor.
 * @return      Whether the file descriptor refers to a VT.
 */
static int libgamma_is_vt_proper(int fd)
{
  char buf[32];
  char digit0;
  
  /* Get TTY. */
  if (ttyname_r(fd, buf, sizeof(buf) / sizeof(char)))
    return 0;
  
  /* Validate TTY path. */
  if (strstr(buf, "/dev/tty") != buf)
    return 0;
  
  /* Validate TTY name. */
  digit0 = buf[strlen("/dev/tty")];
  return ('1' <= digit0) && (digit0 <= '9');
}
# endif


/**
 * Test the availability of an adjustment method.
 * 
 * @param  method     The adjustment method.
 * @param  operation  Allowed values:
 *                      0: Pass if the environment suggests it will work but is not fake.
 *                      1: Pass if the environment suggests it will work.
 *                      2: Pass if real and not fake.
 *                      3: Pass if real.
 *                      4: Always pass.
 *                    Other values invoke undefined behaviour.
 * @return            Whether the test passed.
 */
static int libgamma_list_method_test(int method, int operation)
{
  libgamma_method_capabilities_t caps;
  libgamma_method_capabilities(&caps, method);
  
  switch (operation)
    {
    case 0:
      /* Methods that the environment suggests will work, excluding fake. */
      if (caps.fake)
	return 0;
      /* Fall through. */
      
    case 1:
      /* Methods that the environment suggests will work, including fake. */
      if (caps.real == 0)
	return 0;
#ifdef HAVE_LIBGAMMA_METHOD_LINUX_DRM
      if (method == LIBGAMMA_METHOD_LINUX_DRM)
	return libgamma_is_vt_proper(STDIN_FILENO) ||
	       libgamma_is_vt_proper(STDOUT_FILENO) ||
	       libgamma_is_vt_proper(STDERR_FILENO);
#endif
#ifdef HAVE_LIBGAMMA_METHOD_DUMMY
      if (method == LIBGAMMA_METHOD_DUMMY)
	return 0;
#endif
      return caps.default_site_known;
      
    case 2:
      /* All real non-fake methods. */
      return caps.real && (caps.fake == 0);
      
    case 3:
      /* All real methods. */
      return caps.real;
      
    default:
      /* All methods. */
      return 1;
    }
}
#endif


/**
 * List available adjustment methods by their order of preference based on the environment.
 * 
 * @param  methods    Output array of methods, should be able to hold `LIBGAMMA_METHOD_COUNT` elements.
 * @param  buf_size   The number of elements that fits in `methods`, it should be `LIBGAMMA_METHOD_COUNT`,
 *                    This is used to avoid writing outside the output buffer if this library adds new
 *                    adjustment methods without the users of the library recompiling.
 * @param  operation  Allowed values:
 *                      0: Methods that the environment suggests will work, excluding fake.
 *                      1: Methods that the environment suggests will work, including fake.
 *                      2: All real non-fake methods.
 *                      3: All real methods.
 *                      4: All methods.
 *                    Other values invoke undefined behaviour.
 * @return            The number of element that have been stored in `methods`, or should
 *                    have been stored if the buffer was large enough.
 */
size_t libgamma_list_methods(int* restrict methods, size_t buf_size, int operation)
{
#ifdef HAVE_NO_LIBGAMMA_METHODS
  (void) methods;
  (void) buf_size;
  (void) operation;
  return 0;
#else
  size_t n = 0, len;
  int included[LIBGAMMA_METHOD_COUNT];
  char* begin;
  char* end;
  
  memset(included, 0, LIBGAMMA_METHOD_COUNT * sizeof(int));
  begin = getenv("PREFERRED_DISPLAY");
  while (begin && *begin)
    {
      end = strchr(begin, ' ');
      len = (size_t)(end - begin);
      if (len == 0);
#ifdef HAVE_LIBGAMMA_METHOD_WAYLAND
      else if ((len == 7) && !strncmp(begin, "wayland", len)) /* 7 is strlen("wayland") */
	{
	  if (libgamma_list_method_test(LIBGAMMA_METHOD_WAYLAND, operation) && (n++ < buf_size))
	    methods[n - 1] = LIBGAMMA_METHOD_WAYLAND, included[methods[n - 1]] = 1;
	}
#endif
#if defined(HAVE_LIBGAMMA_METHOD_X_RANDR) || defined(HAVE_LIBGAMMA_METHOD_X_VIDMODE)
      else if ((len == 3) && !strncmp(begin, "x11", len)) /* 3 is strlen("x11") */
	{
# ifdef HAVE_LIBGAMMA_METHOD_X_RANDR
	  if (libgamma_list_method_test(LIBGAMMA_METHOD_X_RANDR, operation) && (n++ < buf_size))
	    methods[n - 1] = LIBGAMMA_METHOD_X_RANDR, included[methods[n - 1]] = 1;
# endif
# ifdef HAVE_LIBGAMMA_METHOD_X_VIDMODE
	  if (libgamma_list_method_test(LIBGAMMA_METHOD_X_VIDMODE, operation) && (n++ < buf_size))
	    methods[n - 1] = LIBGAMMA_METHOD_X_VIDMODE, included[methods[n - 1]] = 1;
# endif
	}
#endif
      begin = end + 1;
    }
  
$>for method in $(get-methods); do
#ifdef HAVE_LIBGAMMA_METHOD_${method}
  if (included[LIBGAMMA_METHOD_${method}] == 0)
    if (libgamma_list_method_test(LIBGAMMA_METHOD_${method}, operation) && (n++ < buf_size))
      methods[n - 1] = LIBGAMMA_METHOD_${method};
#endif
$>done
  
  return n;
#endif
}


/**
 * Check whether an adjustment method is available, non-existing (invalid) methods will be
 * identified as not available under the rationale that the library may be out of date.
 * 
 * @param   method  The adjustment method.
 * @return          Whether the adjustment method is available.
 */
int libgamma_is_method_available(int method)
{
#ifdef HAVE_NO_LIBGAMMA_METHODS
  (void) method;
  return 0;
#else
  switch (method)
    {
$>for method in $(get-methods); do
#ifdef HAVE_LIBGAMMA_METHOD_${method}
    case LIBGAMMA_METHOD_${method}:
#endif
$>done
      return 1;
      
    default:
      return 0;
    }
#endif
}


/**
 * Call the adjustment method's implementation of the called function.
 * 
 * @param  1  The adjustment method, you may use `.` instead of `->` when resolving it.
 * @param  2  `return` if the function returns a value, `break` otherwise.
 * @param  3  The base name of the function to call, that is, the name of the function
 *            this is expended into without the libgamma namespace prefix.
 * @param  *  The function's parameters.
 */
$<switch ()
$>{
  /* Read out macro's parameters. */
$<method="${1//./->}"
  ctrl=$2
  fun=$3
  shift 3
  params="$*"
$>params="${params// /, }"
  
  switch (${method})
    {
$>for adjmethod in $(get-methods); do
#ifdef HAVE_LIBGAMMA_METHOD_${adjmethod}
    case LIBGAMMA_METHOD_${adjmethod}:
      /* Call the adjustment method's implementation, either
	 return or break after it depending on macro parameter's. */
$>[ $ctrl = return ] &&
      return
      libgamma_$(lowercase $adjmethod)_${fun}(${params});
$>[ ! $ctrl = return ] &&
      break;
#endif
$>done
    
    default:
      /* If the adjustment method does not exists, either return
	 that error, or do nothing because the function this is
	 expanded into does return errors. */
$>if [ $ctrl = return ]; then
      return LIBGAMMA_NO_SUCH_ADJUSTMENT_METHOD;
$>else
      /* Method does not exists/excluded at compile-time.
	 We will assume that this is not done... */
      break;
$>fi
    }
$>}


/**
 * Return the capabilities of an adjustment method.
 * 
 * @param  this    The data structure to fill with the method's capabilities.
 * @param  method  The adjustment method (display server and protocol.)
 */
void libgamma_method_capabilities(libgamma_method_capabilities_t* restrict this, int method)
{
  memset(this, 0, sizeof(libgamma_method_capabilities_t));
$>switch method break method_capabilities this
}


/**
 * Return the default site for an adjustment method.
 * 
 * @param   method  The adjustment method (display server and protocol.)
 * @return          The default site, `NULL` if it cannot be determined or
 *                  if multiple sites are not supported by the adjustment
 *                  method. This value should not be `free`:d.
 */
char* libgamma_method_default_site(int method)
{
  const char* restrict var = libgamma_method_default_site_variable(method);
  char* restrict env;
  
  /* Return `NULL` there is not variable to read. */
  if (var == NULL)
    return NULL;
  
  /* Read the variable. */
  env = getenv(var);
  /* Return `NULL` if it does not exist (or is empty). */
  if ((env == NULL) || (*env == '\0'))
    return NULL;
  
  /* Return the variable's value. */
  return env;
}


/**
 * Return the default variable that determines
 * the default site for an adjustment method.
 * 
 * @param   method  The adjustment method (display server and protocol.)
 * @return          The environ variables that is used to determine the
 *                  default site. `NULL` if there is none, that is, if
 *                  the method does not support multiple sites.
 *                  This value should not be `free`:d.
 */
const char* libgamma_method_default_site_variable(int method)
{
  switch (method)
    {
#ifdef HAVE_LIBGAMMA_METHOD_X_RANDR
    case LIBGAMMA_METHOD_X_RANDR:
      return "DISPLAY";
#endif
#ifdef HAVE_LIBGAMMA_METHOD_X_VIDMODE
    case LIBGAMMA_METHOD_X_VIDMODE:
      return "DISPLAY";
#endif
#ifdef HAVE_LIBGAMMA_METHOD_WAYLAND
    case LIBGAMMA_METHOD_WAYLAND:
      return "WAYLAND_DISPLAY";
#endif
    default:
      return NULL;
    }
}


/**
 * Initialise an allocated site state.
 * 
 * @param   this    The site state to initialise.
 * @param   method  The adjustment method (display server and protocol.)
 * @param   site    The site identifier, unless it is `NULL` it must a
 *                  `free`:able. One the state is destroyed the library
 *                  will attempt to free it. There you should not free
 *                  it yourself, and it must not be a string constant
 *                  or allocated on the stack. Note however that it will
 *                  not be `free`:d if this function fails.
 * @return          Zero on success, otherwise (negative) the value of an
 *                  error identifier provided by this library.
 */
int libgamma_site_initialise(libgamma_site_state_t* restrict this,
			     int method, char* restrict site)
{
  this->method = method;
  this->site = site;
$>switch method return site_initialise this site
}


/**
 * Release all resources held by a site state.
 * 
 * @param  this  The site state.
 */
void libgamma_site_destroy(libgamma_site_state_t* restrict this)
{
$>switch this.method break site_destroy this
  free(this->site);
}


/**
 * Release all resources held by a site state
 * and free the site state pointer.
 * 
 * @param  this  The site state.
 */
void libgamma_site_free(libgamma_site_state_t* restrict this)
{
  libgamma_site_destroy(this);
  free(this);
}


/**
 * Restore the gamma ramps all CRTC:s with a site to the system settings.
 * 
 * @param   this  The site state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_site_restore(libgamma_site_state_t* restrict this)
{
$>switch this.method return site_restore this
}



/**
 * Initialise an allocated partition state.
 * 
 * @param   this       The partition state to initialise.
 * @param   site       The site state for the site that the partition belongs to.
 * @param   partition  The index of the partition within the site.
 * @return             Zero on success, otherwise (negative) the value of an
 *                     error identifier provided by this library.
 */
int libgamma_partition_initialise(libgamma_partition_state_t* restrict this,
				  libgamma_site_state_t* restrict site, size_t partition)
{
  this->site = site;
  this->partition = partition;
$>switch site.method return partition_initialise this site partition
}


/**
 * Release all resources held by a partition state.
 * 
 * @param  this  The partition state.
 */
void libgamma_partition_destroy(libgamma_partition_state_t* restrict this)
{
$>switch this.site.method break partition_destroy this
}


/**
 * Release all resources held by a partition state
 * and free the partition state pointer.
 * 
 * @param  this  The partition state.
 */
void libgamma_partition_free(libgamma_partition_state_t* restrict this)
{
  libgamma_partition_destroy(this);
  free(this);
}


/**
 * Restore the gamma ramps all CRTC:s with a partition to the system settings.
 * 
 * @param   this  The partition state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_partition_restore(libgamma_partition_state_t* restrict this)
{
$>switch this.site.method return partition_restore this
}



/**
 * Initialise an allocated CRTC state.
 * 
 * @param   this       The CRTC state to initialise.
 * @param   partition  The partition state for the partition that the CRTC belongs to.
 * @param   crtc       The index of the CRTC within the partition.
 * @return             Zero on success, otherwise (negative) the value of an
 *                     error identifier provided by this library.
 */
int libgamma_crtc_initialise(libgamma_crtc_state_t* restrict this,
			     libgamma_partition_state_t* restrict partition, size_t crtc)
{
  this->partition = partition;
  this->crtc = crtc;
$>switch partition.site.method return crtc_initialise this partition crtc
}


/**
 * Release all resources held by a CRTC state.
 * 
 * @param  this  The CRTC state.
 */
void libgamma_crtc_destroy(libgamma_crtc_state_t* restrict this)
{
$>switch this.partition.site.method break crtc_destroy this
}


/**
 * Release all resources held by a CRTC state
 * and free the CRTC state pointer.
 * 
 * @param  this  The CRTC state.
 */
void libgamma_crtc_free(libgamma_crtc_state_t* restrict this)
{
  libgamma_crtc_destroy(this);
  free(this);
}


/**
 * Restore the gamma ramps for a CRTC to the system settings for that CRTC.
 * 
 * @param   this  The CRTC state.
 * @return        Zero on success, otherwise (negative) the value of an
 *                error identifier provided by this library.
 */
int libgamma_crtc_restore(libgamma_crtc_state_t* restrict this)
{
$>switch this.partition.site.method return crtc_restore this
}



/**
 * Read information about a CRTC.
 * 
 * @param   this    Instance of a data structure to fill with the information about the CRTC.
 * @param   crtc    The state of the CRTC whose information should be read.
 * @param   fields  OR:ed identifiers for the information about the CRTC that should be read.
 * @return          Zero on success, -1 on error. On error refer to the error reports in `this`.
 */
int libgamma_get_crtc_information(libgamma_crtc_information_t* restrict this,
				  libgamma_crtc_state_t* restrict crtc, int32_t fields)
{
#ifdef HAVE_NO_LIBGAMMA_METHODS
  (void) fields;
#endif
  this->edid = NULL;
  this->connector_name = NULL;
$>switch crtc.partition.site.method return get_crtc_information this crtc fields
}


/**
 * Release all resources in an information data structure for a CRTC.
 * 
 * @param  this  The CRTC information.
 */
void libgamma_crtc_information_destroy(libgamma_crtc_information_t* restrict this)
{
  free(this->edid);
  free(this->connector_name);
}


/**
 * Release all resources in an information data structure for a CRTC
 * and free the data structure pointer.
 * 
 * @param  this  The CRTC information.
 */
void libgamma_crtc_information_free(libgamma_crtc_information_t* restrict this)
{
  libgamma_crtc_information_destroy(this);
  free(this);
}


/**
 * Convert a raw representation of an EDID to a hexadecimal representation.
 * 
 * @param   1       Casing name.
 * @param   2       The hexadecimal alphabet.
 * @param   edid    The EDID in raw representation.
 * @param   length  The length of `edid`.
 * @return          The EDID in hexadecimal representation,
 *                  `NULL` on allocation error, `errno` will be set accordingly.
 */
$>behex_edid ()
$>{
char* libgamma_behex_edid_${1}(const unsigned char* restrict edid, size_t length)
{
  char* restrict out;
  size_t i;
  
  /* Allocate memory area for the output string. */
  if ((out = malloc((length * 2 + 1) * sizeof(char))) == NULL)
    return NULL;
  
  /* Translate from raw octets to hexadecimal. */
  for (i = 0; i < length; i++)
    {
      out[i * 2 + 0] = "${2}"[(edid[i] >> 4) & 15];
      out[i * 2 + 1] = "${2}"[(edid[i] >> 0) & 15];
    }
  /* NUL-terminate the output string. */
  out[length * 2] = '\0';
  
  return out;
}
$>}


/**
 * Convert a raw representation of an EDID to a lowercase hexadecimal representation.
 * 
 * @param   edid    The EDID in raw representation.
 * @param   length  The length of `edid`.
 * @return          The EDID in lowercase hexadecimal representation,
 *                  `NULL` on allocation error, `errno` will be set accordingly.
 */
$>behex_edid lowercase 0123456789abcdef


/**
 * Convert a raw representation of an EDID to an uppercase hexadecimal representation.
 * 
 * @param   edid    The EDID in raw representation.
 * @param   length  The length of `edid`.
 * @return          The EDID in uppercase hexadecimal representation,
 *                  NULL` on allocation error, `errno` will be set accordingly.
 */
$>behex_edid uppercase 0123456789ABCDEF


/**
 * Convert an hexadecimal representation of an EDID to a raw representation.
 * 
 * @param   edid  The EDID in hexadecimal representation.
 * @return        The EDID in raw representation, it will be half the length
 *                of `edid` (the input value). `NULL` on allocation error or
 *                if the EDID is malformated, `errno` will be set accordingly.
 */
unsigned char* libgamma_unhex_edid(const char* restrict edid)
{
#define not_range(lower, V, upper)  ((V < lower) || (upper < V))
#define is_not_hex(V)  (not_range('0', V, '9') && not_range('a', V, 'f') && not_range('A', V, 'F'))
  
  unsigned char* restrict out;
  size_t n = strlen(edid);
  size_t i;
  
  /* Check that the length of the strings is even,
     otherwise it cannot represent bytes. */
  if ((n & 1))
    return errno = EINVAL, NULL;
  
  /* Allocate memory area for output octet array. */
  if ((out = malloc(n /= 2 * sizeof(unsigned char))) == NULL)
    return NULL;
  
  /* Convert to raw octet array. */
  for (i = 0; i < n; i++)
    {
      /* Get the next character pair that, it represents an octet.o */
      char a = edid[i * 2 + 0];
      char b = edid[i * 2 + 1];
      
      /* Verify that the input is in hexadecimal. */
      if (is_not_hex(a) || is_not_hex(b))
	{
	  free(out);
	  return errno = EINVAL, NULL;
	}
      
      /* Convert each chararacter to raw format. */
      a = (char)((a & 15) + (a > '9' ? 9 : 0));
      b = (char)((b & 15) + (b > '9' ? 9 : 0));
      
      /* Combine the two characters into one octet. */
      out[i] = (unsigned char)((a << 4) | b);
    }
  
  return out;
  
#undef is_hex
#undef not_range
}


/**
 * Get the current gamma ramps for a CRTC, 16-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
int libgamma_crtc_get_gamma_ramps16(libgamma_crtc_state_t* restrict this,
				    libgamma_gamma_ramps16_t* restrict ramps)
{
#ifdef HAVE_NO_LIBGAMMA_METHODS
  (void) ramps;
#endif
  
  switch (this->partition->site->method)
    {
      /* Methods other than Quartz/CoreGraphics uses 16-bit integers. */
$>for method in $(get-methods | grep -v QUARTZ_CORE_GRAPHICS); do
#ifdef HAVE_LIBGAMMA_METHOD_${method}
    case LIBGAMMA_METHOD_${method}:
      return libgamma_$(lowercase $method)_crtc_get_gamma_ramps16(this, ramps);
#endif
     
     /* The Quartz/CoreGraphics method uses single precision float. */
$>done
#ifdef HAVE_LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS
    case LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS:
      {
	libgamma_gamma_ramps_any_t ramps_;
	ramps_.bits16 = *ramps;
	return libgamma_translated_ramp_get(this, &ramps_, 16, -1,
					    libgamma_crtc_get_gamma_rampsf);
      }
#endif
      
      /* The selected method does not exist. */
    default:
      return LIBGAMMA_NO_SUCH_ADJUSTMENT_METHOD;
    }
}


/**
 * Set the gamma ramps for a CRTC, 16-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
int libgamma_crtc_set_gamma_ramps16(libgamma_crtc_state_t* restrict this,
				    libgamma_gamma_ramps16_t ramps)
{
#ifdef HAVE_NO_LIBGAMMA_METHODS
  (void) ramps;
#endif
  
  switch (this->partition->site->method)
    {
      /* Methods other than Quartz/CoreGraphics uses 16-bit integers. */
$>for method in $(get-methods | grep -v QUARTZ_CORE_GRAPHICS); do
#ifdef HAVE_LIBGAMMA_METHOD_${method}
    case LIBGAMMA_METHOD_${method}:
      return libgamma_$(lowercase $method)_crtc_set_gamma_ramps16(this, ramps);
#endif
$>done
     
     /* The Quartz/CoreGraphics method uses single precision float. */
#ifdef HAVE_LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS
    case LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS:
      {
	libgamma_gamma_ramps_any_t ramps_;
	ramps_.bits16 = ramps;
	return libgamma_translated_ramp_set(this, ramps_, 16, -1,
					    libgamma_crtc_set_gamma_rampsf);
      }
#endif
      
      /* The selected method does not exist. */
    default:
      return LIBGAMMA_NO_SUCH_ADJUSTMENT_METHOD;
    }
}



/**
 * Set or get the gamma ramps for a CRTC, non-16-bit gamma-depth version.
 * 
 * @param   1      Either `get` or `set`, for the action that the name of value implies.
 * @param   2      The `ramp*` pattern for the ramp structure and function to call.
 * @param   3      Either of `bit8`, `bit16`, `bit32`, `bit64`, `float_single`, `float_double`;
 *                 rather self-explanatory.
 * @param   4      The number of bits in the gamma depth, -1 for single precision float,
 *                 (`float`) and -2 for double percition float (`double`).
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply, or
 *                 the gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps ()
$>{
$<
  action=$1
  ramps=$2
  type=$3
  bits=$4
  p=
  [ $action = get ] && p='*'
$>
int libgamma_crtc_${action}_gamma_${ramps}(libgamma_crtc_state_t* restrict this,
					   libgamma_gamma_${ramps}_t${p:+* restrict} ramps)
{
  libgamma_gamma_ramps_any_t ramps_;
  switch (this->partition->site->method)
    {
      /* The dummy method supports all ramp depths. */
#ifdef HAVE_LIBGAMMA_METHOD_DUMMY
    case LIBGAMMA_METHOD_DUMMY:
      return libgamma_dummy_crtc_${action}_gamma_${ramps}(this, ramps);
#endif
      
      /* The Quartz/CoreGraphics method uses single precision float. */
#ifdef HAVE_LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS
    case LIBGAMMA_METHOD_QUARTZ_CORE_GRAPHICS:
$>if [ $bits = -1 ]; then
      /* Single precision float is used. */
      return libgamma_quartz_cg_crtc_${action}_gamma_${ramps}(this, ramps);
$>else
      /* Something else is used and we convert to Single precision float. */
      ramps_.${type} = ${p}ramps;
      return libgamma_translated_ramp_${action}(this, ${p:+&}ramps_, ${bits}, -1,
						libgamma_crtc_${action}_gamma_rampsf);
$>fi
#endif
      
      /* Other methods use 16-bit integers. */
    default:
      ramps_.${type} = ${p}ramps;
      return libgamma_translated_ramp_${action}(this, ${p:+&}ramps_, ${bits}, 16,
						libgamma_crtc_${action}_gamma_ramps16);
    }
}
$>}



/**
 * Get the current gamma ramps for a CRTC, 8-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps get ramps8 bits8 8


/**
 * Set the gamma ramps for a CRTC, 32-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps set ramps8 bits8 8



/**
 * Get the current gamma ramps for a CRTC, 32-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps get ramps32 bits32 32


/**
 * Set the gamma ramps for a CRTC, 32-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps set ramps32 bits32 32



/**
 * Get the current gamma ramps for a CRTC, 64-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps get ramps64 bits64 64


/**
 * Set the gamma ramps for a CRTC, 64-bit gamma-depth version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps set ramps64 bits64 64


/**
 * Get the current gamma ramps for a CRTC, `float` version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps get rampsf float_single -1


/**
 * Set the gamma ramps for a CRTC, `float` version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps set rampsf float_single -1



/**
 * Get the current gamma ramps for a CRTC, `double` version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to fill with the current values.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps get rampsd float_double -2


/**
 * Set the gamma ramps for a CRTC, `double` version.
 * 
 * @param   this   The CRTC state.
 * @param   ramps  The gamma ramps to apply.
 * @return         Zero on success, otherwise (negative) the value of an
 *                 error identifier provided by this library.
 */
$>crtc_set_get_gamma_ramps set rampsd float_double -2



/**
 * Set the gamma ramps for a CRTC.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   1               The data type for the ramp stop elements.
 * @param   2               The `ramp*` pattern for the ramp structure and function to call.
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f ()
$>{
int libgamma_crtc_set_gamma_${2}_f(libgamma_crtc_state_t* restrict this,
				   libgamma_gamma_${2}_fun* red_function,
				   libgamma_gamma_${2}_fun* green_function,
				   libgamma_gamma_${2}_fun* blue_function)
{
  libgamma_crtc_information_t info;
  libgamma_gamma_${2}_t ramps;
  size_t i, n;
  int e;
  
  /* Get the size of the gamma ramps. */
  if (libgamma_get_crtc_information(&info, this, LIBGAMMA_CRTC_INFO_GAMMA_SIZE))
    {
      if ((e = info.gamma_size_error) < 0)
	return e;
      return errno = e, LIBGAMMA_ERRNO_SET;
    }
  
  /* Copy the size of the gamma ramps and calculte the grand size. */
  n  = ramps.  red_size = info.  red_gamma_size;
  n += ramps.green_size = info.green_gamma_size;
  n += ramps. blue_size = info. blue_gamma_size;
  
  /* Allocate gamma ramps. */
  ramps.  red = malloc(n * sizeof(${1}));
  ramps.green = ramps.  red + ramps.  red_size;
  ramps. blue = ramps.green + ramps.green_size;
  if (ramps.red == NULL)
    return LIBGAMMA_ERRNO_SET;
  
  /* Generate the gamma ramp for the red chennel. */
  for (i = 0, n = ramps.red_size; i < n; i++)
    ramps.red[i] = red_function((float)i / (float)(n - 1));
  
  /* Generate the gamma ramp for the green chennel. */
  for (i = 0, n = ramps.green_size; i < n; i++)
    ramps.green[i] = green_function((float)i / (float)(n - 1));
  
  /* Generate the gamma ramp for the blue chennel. */
  for (i = 0, n = ramps.blue_size; i < n; i++)
    ramps.blue[i] = blue_function((float)i / (float)(n - 1));
  
  /* Apply the gamma ramps. */
  e = libgamma_crtc_set_gamma_${2}(this, ramps);
  free(ramps.red);
  return e;
}
$>}


/**
 * Set the gamma ramps for a CRTC, 8-bit gamma-depth function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f uint8_t ramps8


/**
 * Set the gamma ramps for a CRTC, 16-bit gamma-depth function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f uint16_t ramps16


/**
 * Set the gamma ramps for a CRTC, 32-bit gamma-depth function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f uint32_t ramps32


/**
 * Set the gamma ramps for a CRTC, 64-bit gamma-depth function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f uint64_t ramps64


/**
 * Set the gamma ramps for a CRTC, `float` function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f float rampsf


/**
 * Set the gamma ramps for a CRTC, `double` function version.
 * 
 * Note that this will probably involve the library allocating temporary data.
 * 
 * @param   this            The CRTC state.
 * @param   red_function    The function that generates the gamma ramp for the red channel.
 * @param   green_function  The function that generates the gamma ramp for the green channel.
 * @param   blue_function   The function that generates the gamma ramp for the blue channel.
 * @return                  Zero on success, otherwise (negative) the value of an
 *                          error identifier provided by this library.
 */
$>crtc_set_gamma_ramps_f double rampsd



#ifdef HAVE_NO_LIBGAMMA_METHODS
# ifdef __GCC__
#  pragma GCC diagnostic pop
# endif
#endif