gtk/gdk/gdkvisual.c

/* GDK - The GIMP Drawing Kit
 * gdkvisual.c
 *
 * Copyright 2001 Sun Microsystems Inc.
 *
 * Erwann Chenede <erwann.chenede@sun.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "gdkvisualprivate.h"
#include "gdkscreenprivate.h"


/**
 * SECTION:visuals
 * @Short_description: Low-level display hardware information
 * @Title: Visuals
 *
 * A #GdkVisual describes a particular video hardware display format.
 * It includes information about the number of bits used for each color,
 * the way the bits are translated into an RGB value for display, and
 * the way the bits are stored in memory. For example, a piece of display
 * hardware might support 24-bit color, 16-bit color, or 8-bit color;
 * meaning 24/16/8-bit pixel sizes. For a given pixel size, pixels can
 * be in different formats; for example the “red” element of an RGB pixel
 * may be in the top 8 bits of the pixel, or may be in the lower 4 bits.
 *
 * There are several standard visuals. The visual returned by
 * gdk_screen_get_system_visual() is the system’s default visual, and
 * the visual returned by gdk_screen_get_rgba_visual() should be used for
 * creating windows with an alpha channel.
 *
 * A number of functions are provided for determining the “best” available
 * visual. For the purposes of making this determination, higher bit depths
 * are considered better, and for visuals of the same bit depth,
 * %GDK_VISUAL_PSEUDO_COLOR is preferred at 8bpp, otherwise, the visual
 * types are ranked in the order of(highest to lowest)
 * %GDK_VISUAL_DIRECT_COLOR, %GDK_VISUAL_TRUE_COLOR,
 * %GDK_VISUAL_PSEUDO_COLOR, %GDK_VISUAL_STATIC_COLOR,
 * %GDK_VISUAL_GRAYSCALE, then %GDK_VISUAL_STATIC_GRAY.
 */

G_DEFINE_TYPE (GdkVisual, gdk_visual, G_TYPE_OBJECT)

static void
gdk_visual_init (GdkVisual *visual)
{
}

static void
gdk_visual_finalize (GObject *object)
{
  G_OBJECT_CLASS (gdk_visual_parent_class)->finalize (object);
}

static void
gdk_visual_class_init (GdkVisualClass *visual_class)
{
  GObjectClass *object_class = G_OBJECT_CLASS (visual_class);

  object_class->finalize = gdk_visual_finalize;
}

/**
 * gdk_list_visuals:
 *
 * Lists the available visuals for the default screen.
 * (See gdk_screen_list_visuals())
 * A visual describes a hardware image data format.
 * For example, a visual might support 24-bit color, or 8-bit color,
 * and might expect pixels to be in a certain format.
 *
 * Call g_list_free() on the return value when you’re finished with it.
 *
 * Returns: (transfer container) (element-type GdkVisual):
 *     a list of visuals; the list must be freed, but not its contents
 */
GList*
gdk_list_visuals (void)
{
  return gdk_screen_list_visuals (gdk_screen_get_default ());
}

/**
 * gdk_visual_get_system:
 *
 * Get the system’s default visual for the default GDK screen.
 * This is the visual for the root window of the display.
 * The return value should not be freed.
 *
 * Returns: (transfer none): system visual
 */
GdkVisual*
gdk_visual_get_system (void)
{
  return gdk_screen_get_system_visual (gdk_screen_get_default());
}

/**
 * gdk_visual_get_best_depth:
 *
 * Get the best available depth for the default GDK screen.  “Best”
 * means “largest,” i.e. 32 preferred over 24 preferred over 8 bits
 * per pixel.
 *
 * Returns: best available depth
 */
gint
gdk_visual_get_best_depth (void)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best_depth (screen);
}

/**
 * gdk_visual_get_best_type:
 *
 * Return the best available visual type for the default GDK screen.
 *
 * Returns: best visual type
 */
GdkVisualType
gdk_visual_get_best_type (void)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best_type (screen);
}

/**
 * gdk_visual_get_best:
 *
 * Get the visual with the most available colors for the default
 * GDK screen. The return value should not be freed.
 *
 * Returns: (transfer none): best visual
 */
GdkVisual*
gdk_visual_get_best (void)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best (screen);
}

/**
 * gdk_visual_get_best_with_depth:
 * @depth: a bit depth
 *
 * Get the best visual with depth @depth for the default GDK screen.
 * Color visuals and visuals with mutable colormaps are preferred
 * over grayscale or fixed-colormap visuals. The return value should
 * not be freed. %NULL may be returned if no visual supports @depth.
 *
 * Returns: (transfer none): best visual for the given depth
 */
GdkVisual*
gdk_visual_get_best_with_depth (gint depth)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best_with_depth (screen, depth);
}

/**
 * gdk_visual_get_best_with_type:
 * @visual_type: a visual type
 *
 * Get the best visual of the given @visual_type for the default GDK screen.
 * Visuals with higher color depths are considered better. The return value
 * should not be freed. %NULL may be returned if no visual has type
 * @visual_type.
 *
 * Returns: (transfer none): best visual of the given type
 */
GdkVisual*
gdk_visual_get_best_with_type (GdkVisualType visual_type)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best_with_type (screen,
                                                                  visual_type);
}

/**
 * gdk_visual_get_best_with_both:
 * @depth: a bit depth
 * @visual_type: a visual type
 *
 * Combines gdk_visual_get_best_with_depth() and
 * gdk_visual_get_best_with_type().
 *
 * Returns: (nullable) (transfer none): best visual with both @depth
 *     and @visual_type, or %NULL if none
 */
GdkVisual*
gdk_visual_get_best_with_both (gint          depth,
			       GdkVisualType visual_type)
{
  GdkScreen *screen = gdk_screen_get_default();

  return GDK_SCREEN_GET_CLASS(screen)->visual_get_best_with_both (screen, depth, visual_type);
}

/**
 * gdk_query_depths:
 * @depths: (out) (array length=count) (transfer none): return
 *     location for available depths
 * @count: return location for number of available depths
 *
 * This function returns the available bit depths for the default
 * screen. It’s equivalent to listing the visuals
 * (gdk_list_visuals()) and then looking at the depth field in each
 * visual, removing duplicates.
 *
 * The array returned by this function should not be freed.
 */
void
gdk_query_depths (gint **depths,
                  gint  *count)
{
  GdkScreen *screen = gdk_screen_get_default();

  GDK_SCREEN_GET_CLASS(screen)->query_depths (screen, depths, count);
}

/**
 * gdk_query_visual_types:
 * @visual_types: (out) (array length=count) (transfer none): return
 *     location for the available visual types
 * @count: return location for the number of available visual types
 *
 * This function returns the available visual types for the default
 * screen. It’s equivalent to listing the visuals
 * (gdk_list_visuals()) and then looking at the type field in each
 * visual, removing duplicates.
 *
 * The array returned by this function should not be freed.
 */
void
gdk_query_visual_types (GdkVisualType **visual_types,
                        gint           *count)
{
  GdkScreen *screen = gdk_screen_get_default();

  GDK_SCREEN_GET_CLASS(screen)->query_visual_types (screen, visual_types, count);
}

/**
 * gdk_visual_get_visual_type:
 * @visual: A #GdkVisual.
 *
 * Returns the type of visual this is (PseudoColor, TrueColor, etc).
 *
 * Returns: A #GdkVisualType stating the type of @visual.
 *
 * Since: 2.22
 */
GdkVisualType
gdk_visual_get_visual_type (GdkVisual *visual)
{
  g_return_val_if_fail (GDK_IS_VISUAL (visual), 0);

  return visual->type;
}

/**
 * gdk_visual_get_depth:
 * @visual: A #GdkVisual.
 *
 * Returns the bit depth of this visual.
 *
 * Returns: The bit depth of this visual.
 *
 * Since: 2.22
 */
gint
gdk_visual_get_depth (GdkVisual *visual)
{
  g_return_val_if_fail (GDK_IS_VISUAL (visual), 0);

  return visual->depth;
}

static void
gdk_visual_get_pixel_details (GdkVisual *visual,
                              gulong     pixel_mask,
                              guint32   *mask,
                              gint      *shift,
                              gint      *precision)
{
  gulong m = 0;
  gint s = 0;
  gint p = 0;

  if (pixel_mask != 0)
    {
      m = pixel_mask;
      while (!(m & 0x1))
        {
          s++;
          m >>= 1;
        }

      while (m & 0x1)
        {
          p++;
          m >>= 1;
        }
    }

  if (mask)
    *mask = pixel_mask;

  if (shift)
    *shift = s;

  if (precision)
    *precision = p;
}

/**
 * gdk_visual_get_red_pixel_details:
 * @visual: A #GdkVisual
 * @mask: (out) (allow-none): A pointer to a #guint32 to be filled in, or %NULL
 * @shift: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 * @precision: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 *
 * Obtains values that are needed to calculate red pixel values in TrueColor
 * and DirectColor. The “mask” is the significant bits within the pixel.
 * The “shift” is the number of bits left we must shift a primary for it
 * to be in position (according to the "mask"). Finally, "precision" refers
 * to how much precision the pixel value contains for a particular primary.
 *
 * Since: 2.22
 */
void
gdk_visual_get_red_pixel_details (GdkVisual *visual,
                                  guint32   *mask,
                                  gint      *shift,
                                  gint      *precision)
{
  g_return_if_fail (GDK_IS_VISUAL (visual));

  gdk_visual_get_pixel_details (visual, visual->red_mask, mask, shift, precision);
}

/**
 * gdk_visual_get_green_pixel_details:
 * @visual: a #GdkVisual
 * @mask: (out) (allow-none): A pointer to a #guint32 to be filled in, or %NULL
 * @shift: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 * @precision: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 *
 * Obtains values that are needed to calculate green pixel values in TrueColor
 * and DirectColor. The “mask” is the significant bits within the pixel.
 * The “shift” is the number of bits left we must shift a primary for it
 * to be in position (according to the "mask"). Finally, "precision" refers
 * to how much precision the pixel value contains for a particular primary.
 *
 * Since: 2.22
 */
void
gdk_visual_get_green_pixel_details (GdkVisual *visual,
                                    guint32   *mask,
                                    gint      *shift,
                                    gint      *precision)
{
  g_return_if_fail (GDK_IS_VISUAL (visual));

  gdk_visual_get_pixel_details (visual, visual->green_mask, mask, shift, precision);
}

/**
 * gdk_visual_get_blue_pixel_details:
 * @visual: a #GdkVisual
 * @mask: (out) (allow-none): A pointer to a #guint32 to be filled in, or %NULL
 * @shift: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 * @precision: (out) (allow-none): A pointer to a #gint to be filled in, or %NULL
 *
 * Obtains values that are needed to calculate blue pixel values in TrueColor
 * and DirectColor. The “mask” is the significant bits within the pixel.
 * The “shift” is the number of bits left we must shift a primary for it
 * to be in position (according to the "mask"). Finally, "precision" refers
 * to how much precision the pixel value contains for a particular primary.
 *
 * Since: 2.22
 */
void
gdk_visual_get_blue_pixel_details (GdkVisual *visual,
                                   guint32   *mask,
                                   gint      *shift,
                                   gint      *precision)
{
  g_return_if_fail (GDK_IS_VISUAL (visual));

  gdk_visual_get_pixel_details (visual, visual->blue_mask, mask, shift, precision);
}

/**
 * gdk_visual_get_screen:
 * @visual: a #GdkVisual
 *
 * Gets the screen to which this visual belongs
 *
 * Returns: (transfer none): the screen to which this visual belongs.
 *
 * Since: 2.2
 */
GdkScreen *
gdk_visual_get_screen (GdkVisual *visual)
{
  g_return_val_if_fail (GDK_IS_VISUAL (visual), NULL);

  return visual->screen;
}