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# Package Gdk.Font

This is the base package for handling fonts. GtkAda knows about bitmap and vectorial fonts, and can draw both. The list of fonts available to you depends on what is installed on your system.

The name of the font is indicated in the standard X11 fashion, namely: (example extracted from the Xlib manual):

-adobe-courier-bold-o-normal--10-100-75-75-m-60-iso8859-1 where:

- adobe : foundry
- courier : font family
- bold : weight (e.g. bold, medium)
- o : slant (e.g. roman, italic, oblique)
- normal : set width (e.g. normal, condensed, narrow, double)
- 10 : pixels
- 100 : points (in tenths of a point)
- 75 : horizontal resolution in dpi
- 75 : vertical resolution in dpi
- m : spacing (e.g. monospace or proportional)
- 60 : average width (in tenths of a pixel)
- iso8859-1 : character set

Any of the fields can have a '*' instead, so that the system will automatically find a font that matches the rest of the string, and won't care about that specific field.

But the easiest way to select a font is by using some external programs, for instance xfontsel, xlsfont, gfontsel, or even the font selection dialog example in the testgtk/ directory of the GtkAda distribution.

see section Package Gtk.Extra.PsFont for a package that processes postscript fonts, with their more usual names, and can easily convert them to standard Gdk_Font structures.

Some of the functions below should be used only for wide-character strings. This is needed for languages with more than 256 characters.

Wide character values between 0 and 127 are always identical in meaning to the ASCII character codes. An alternative to wide characters is multi-byte characters, which extend normal char strings to cope with larger character sets. As the name suggests, multi-byte characters use a different number of bytes to store different character codes. For example codes 0-127 (i.e. the ASCII codes) often use just one byte of memory, while other codes may use 2, 3 or even 4 bytes. Multi-byte characters have the advantage that they can often be used in an application with little change, since strings are still represented as arrays of char values. However multi-byte strings are much easier to manipulate since the character are all of the same size.

On Unix systems, the external utility 'xfd' can be used to display all the characters in a font.

- Gdk.Font Types
- Gdk.Font Subprograms

## Types

    type Gdk_Font is new Gdk.C_Proxy;

A font used to draw text. This can represent a bitmap font, a scalable (vectorial) font, or a fontset. A fontset is a list of comma-separated fonts, that permits GtkAda to obtain the fonts needed for a variety of locales from a single locale-independent base font name. The single base font name should name a family of fonts whose members are encoded in the various charsets needed by the locales of interest. The algorithm used to select the font is described in the manual page for XCreateFontSet(3X).

## Subprograms

    procedure Load
      (Font               : out    Gdk_Font;
       Font_Name          : in     String);

| Load a new font, given its name. This is the first step before using a font. The font is first looked up in the cache, and if it was already loaded, it is not reloaded again. Thus, it does not harm to call this function multiple times with the same Font_Name. Null_Font is returned if the font could not be loaded.

    procedure Fontset_Load
      (Font               : out    Gdk_Font;
       Fontset_Name       : in     String);

| Load a new font set. Fontset_Name is a comma-separated list of fonts that will be loaded as part of the fontset.

    procedure Ref
      (Font               : in     Gdk_Font);

| Increment the reference counter for the font. You should not make any assumption of the initial value of the fonts returned by Load or Fontset_Load, since these can be extracted from a cache.

    procedure Unref
      (Font               : in     Gdk_Font);

| Decrement the reference counter for the font. When this counter reaches 0, the font is deleted from memory.

    function Id
      (Font               : in     Gdk_Font)
       return Gint;

| Return the X font id for the font. This Id will only be needed if you want to call directly X11 functions, you won't need it with GtkAda.

    function Equal
      (Fonta, Fontb       : in     Gdk_Font)
       return Boolean;

| Compare two fonts or two fontsets for equality. Two fonts are equal if they have the same font Id. Two fontsets are equal if the name given to Fontset_Load was the same.

    function Get_Ascent
      (Font               : in     Gdk_Font)
       return Gint;

| Return the maximal ascent for the font. This is the logical extent above the baseline for spacing between two lines.

    function Get_Descent
      (Font               : in     Gdk_Font)
       return Gint;

| Return the maximal descent for the font. This is the logical extent below the baseline for spacing between two lines.

    function String_Width
      (Font               : in     Gdk_Font;
       Str                : in     String)
       return Gint;

| Return the width in pixels that Str will occupy if drawn with Font. The value returned is the distance between the origin of the text and the position at which the next string should be drawn.

    function Text_Width
      (Font               : in     Gdk_Font;
       Text               : in     String)
       return Gint;

| This is the same function as String_Width. In C, this function is intended to measure only the width of a part of the string, but you can simply pass it a substring in Ada.

    function Text_Width
      (Font               : in     Gdk_Font;
       Text               : in     Gdk.Types.Gdk_WString)
       return Gint;

| Return the width in pixels that Text will occupy on the screen. This function should be used with strings that contain Unicode characters

    function Char_Width
      (Font               : in     Gdk_Font;
       Char               : in     Character)
       return Gint;

| Return the width in pixels occupied by a single character on the screen. The value returned is the distance between Char's origin on the screen and the origin of the next character in the string.

    function Char_Width
      (Font               : in     Gdk_Font;
       Char               : in     Gdk.Types.Gdk_WChar)
       return Gint;

| Return the width in pixels occupied by a single wide-character.

    function String_Measure
      (Font               : in     Gdk_Font;
       Str                : in     String)
       return Gint;

| Determine the distance from the origin to the rightmost portion of Str. This is not the correct value for determining the origin of the next portion when drawing text in multiple pieces. See String_Width instead.

    function Text_Measure
      (Font               : in     Gdk_Font;
       Text               : in     String)
       return Gint;

| Same function a String_Measure. In C, this function is intended to measure only the width of a part of the string, but you can simply pass it a substring in Ada. This is also called the right bearing of the string.

    function Char_Measure
      (Font               : in     Gdk_Font;
       Char               : in     Character)
       return Gint;

| Return the width in pixels of Char. As opposed to Char_Width, the value returned is not the distance at which the next character should be drawn. This is also called the right bearing of the character.

    procedure String_Extents
      (Font               : in     Gdk.Font.Gdk_Font;
       Str                : in     String;
       Lbearing           : out    Gint;
       Rbearing           : out    Gint;
       Width              : out    Gint;
       Ascent             : out    Gint;
       Descent            : out    Gint);

| Return the metrics for a given text. See the picture for more explanations on all the fields. Lbearing : Origin to left edge of character. Rbearing : Origin to right edge of character. Width : Advance to next character's origin. Ascent : Baseline to top edge of character. Descent : Baseline to bottom edge of character.

    procedure Text_Extents
      (Font               : in     Gdk_Font;
       Text               : in     String;
       Lbearing           : out    Gint;
       Rbearing           : out    Gint;
       Width              : out    Gint;
       Ascent             : out    Gint;
       Descent            : out    Gint);

| Return all the metrics for a given text. See the picture for more explanations on all the fields. in C, this function would be used for part of a string, which you can simulate in Ada with a substring.

    procedure Text_Extents
      (Font               : in     Gdk_Font;
       Text               : in     Gdk.Types.Gdk_WString;
       Lbearing           : out    Gint;
       Rbearing           : out    Gint;
       Width              : out    Gint;
       Ascent             : out    Gint;
       Descent            : out    Gint);

| Return all the metrics for a given wide-character string. See the picture for more explanations on the returned values.

    function String_Height
      (Font               : in     Gdk_Font;
       Str                : in     String)
       return Gint;

| Return the height in pixels of the string. This is the total height, and you can not easily tell how this height is split around the baseline.

    function Text_Height
      (Font               : in     Gdk_Font;
       Str                : in     String)
       return Gint;

| Same as String_Height. In C, this function is intended to measure only the width of a part of the string, but you can simply pass it a substring in Ada. This is also called the right bearing of the string.

    function Char_Height
      (Font               : in     Gdk_Font;
       Char               : in     Character)
       return Gint;

| Return the total height in pixels of a single character.

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