gdk-Visuals              package:RGtk2              R Documentation

_V_i_s_u_a_l_s

_D_e_s_c_r_i_p_t_i_o_n:

     Low-level display hardware information

_M_e_t_h_o_d_s _a_n_d _F_u_n_c_t_i_o_n_s:

     'gdkQueryDepths()'
      'gdkQueryVisualTypes()'
      'gdkListVisuals()'
      'gdkVisualGetBestDepth()'
      'gdkVisualGetBestType()'
      'gdkVisualGetSystem()'
      'gdkVisualGetBest()'
      'gdkVisualGetBestWithDepth(depth)'
      'gdkVisualGetBestWithType(visual.type)'
      'gdkVisualGetBestWithBoth(depth, visual.type)'
      'gdkVisualGetScreen(object)'

_D_e_t_a_i_l_e_d _D_e_s_c_r_i_p_t_i_o_n:

     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.

     Usually you can avoid thinking about visuals in GTK+. Visuals are
     useful to interpret the contents of a 'GdkImage', but you should
     avoid 'GdkImage' precisely because its contents depend on the
     display hardware; use 'GdkPixbuf' instead, for all but the most
     low-level purposes. Also, anytime you provide a 'GdkColormap', the
     visual is implied as part of the colormap
     ('gdkColormapGetVisual'), so you won't have to provide a visual in
     addition.

     There are several standard visuals. The visual returned by
     'gdkVisualGetSystem' is the system's default visual.
     'gdkRgbGetVisual' return the visual most suited to displaying
     full-color image data. If you use the calls in 'GdkRGB', you
     should create your windows using this visual (and the colormap
     returned by 'gdkRgbGetColormap').

     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'.

_S_t_r_u_c_t_u_r_e_s:


     '_G_d_k_V_i_s_u_a_l' The 'GdkVisual' structure contains information about a
          particular visual.

          '_t_y_p_e' ['GdkVisualType'] inherited portion from 'GObject'

          '_d_e_p_t_h' [integer] The type of this visual.

          '_b_y_t_e_O_r_d_e_r' ['GdkByteOrder'] The number of bits per pixel.

          '_c_o_l_o_r_m_a_p_S_i_z_e' [integer] The byte-order for this visual.

          '_b_i_t_s_P_e_r_R_g_b' [integer] The number of entries in the colormap,
               for visuals of type 'GDK_VISUAL_PSEUDO_COLOR' or
               'GDK_VISUAL_GRAY_SCALE'. For other visual types, it is
               the number of possible levels per color component. If
               the visual has different numbers of levels for different
               components, the value of this field is undefined.

          '_r_e_d_M_a_s_k' [numeric] The number of significant bits per red,
               green, or blue when specifying colors for this visual.
               (For instance, for  'gdkColormapAllocColor')

          '_r_e_d_S_h_i_f_t' [integer] A mask giving the bits in a pixel value
               that correspond to the red field. Significant only for
               'GDK_VISUAL_PSEUDOCOLOR' and 'GDK_VISUAL_DIRECTCOLOR'.

          '_r_e_d_P_r_e_c' [integer] The 'red_shift' and 'red_prec' give an
               alternate presentation of the information in 'red_mask'.
               'red_mask' is a contiguous sequence of 'red_prec' bits
               starting at bit number 'red_shift'. For example, shows
               constructing a pixel value out of three 16 bit color
               values.

          '_g_r_e_e_n_M_a_s_k' [numeric] See above.

          '_g_r_e_e_n_S_h_i_f_t' [integer] A mask giving the bits in a pixel
               value that correspond to the green field.

          '_g_r_e_e_n_P_r_e_c' [integer] The 'green_shift' and 'green_prec' give
               an alternate presentation of the information in
               'green_mask'.

          '_b_l_u_e_M_a_s_k' [numeric] See above.

          '_b_l_u_e_S_h_i_f_t' [integer] A mask giving the bits in a pixel value
               that correspond to the blue field.

          '_b_l_u_e_P_r_e_c' [integer] The 'blue_shift' and 'blue_prec' give an
               alternate presentation of the information in
               'blue_mask'.


_E_n_u_m_s _a_n_d _F_l_a_g_s:


     '_G_d_k_V_i_s_u_a_l_T_y_p_e' A set of values that describe the manner in which
          the pixel values for a visual are converted into RGB values
          for display.

          '_s_t_a_t_i_c-_g_r_a_y' Each pixel value indexes a grayscale value
               directly.

          '_g_r_a_y_s_c_a_l_e' Each pixel is an index into a color map that maps
               pixel  values into grayscale values. The color map can
               be changed by an application.

          '_s_t_a_t_i_c-_c_o_l_o_r' Each pixel value is an index into a
               predefined, unmodifiable color map that maps pixel
               values into RGB values.

          '_p_s_e_u_d_o-_c_o_l_o_r' Each pixel is an index into a color map that
               maps pixel values into rgb values. The color map can be
               changed by an application.

          '_t_r_u_e-_c_o_l_o_r' Each pixel value directly contains red, green,
               and blue components. The 'red_mask', 'green_mask', and 
               'blue_mask' fields of the 'GdkVisual' structure describe
               how the components are assembled into a pixel value.

          '_d_i_r_e_c_t-_c_o_l_o_r' Each pixel value contains red, green, and blue
               components as for 'GDK_VISUAL_TRUE_COLOR', but the
               components are mapped via a  color table into the final
               output table instead of being converted directly.


     '_G_d_k_B_y_t_e_O_r_d_e_r' A set of values describing the possible byte-orders
          for storing pixel values in memory.

          '_l_s_b-_f_i_r_s_t' The values are stored with the least-significant
               byte first. For instance, the 32-bit value 0xffeecc
               would be stored in memory as 0xcc, 0xee, 0xff, 0x00.

          '_m_s_b-_f_i_r_s_t' The values are stored with the most-significant
               byte first. For instance, the 32-bit value 0xffeecc
               would be stored in memory as 0x00, 0xcc, 0xee, 0xff.


_A_u_t_h_o_r(_s):

     Derived by RGtkGen from GTK+ documentation

_R_e_f_e_r_e_n_c_e_s:

     <URL: http://developer.gnome.org/doc/API/2.0/gdk/gdk-Visuals.html>

_S_e_e _A_l_s_o:

     'GdkImage' 'GdkColormap'

