forked from AuroraMiddleware/gtk
Update some outdated content in the question index
Based on a patch by Jasper St. Pierre https://bugzilla.gnome.org/show_bug.cgi?id=639494
This commit is contained in:
Matthias Clasen
parent
b23839c7a5
commit
04248fbd39
@ -35,8 +35,8 @@ How do I get started with GTK+?
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</para></question>
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<answer><para>
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The GTK+ <ulink url="http://www.gtk.org">website</ulink> offers a
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<ulink url="http://www.gtk.org/tutorial">tutorial</ulink> and a
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The GTK+ <ulink url="http://www.gtk.org">website</ulink> offers a
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<ulink url="http://www.gtk.org/tutorial">tutorial</ulink> and a
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<ulink url="http://www.gtk.org/faq">FAQ</ulink>. More documentation ranging
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from whitepapers to online books can be found at the
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<ulink url="http://library.gnome.org/devel/">GNOME developer's site</ulink>.
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@ -47,7 +47,7 @@ this reference manual for details.
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<qandaentry>
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<question><para>
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Where can I get help with GTK+, submit a bug report, or make a feature
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Where can I get help with GTK+, submit a bug report, or make a feature
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request?
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</para></question>
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@ -102,11 +102,11 @@ state (explained in its documentation).
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</para>
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<para>
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For strings returned from functions, they will be declared "const" (using
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#G_CONST_RETURN) if they should not be freed. Non-const strings should be
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freed with g_free(). Arrays follow the same rule. (If you find an exception
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to the rules, please report a bug to <ulink
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url="http://bugzilla.gnome.org">http://bugzilla.gnome.org</ulink>.)
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For strings returned from functions, they will be declared "const" (using
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#G_CONST_RETURN) if they should not be freed. Non-const strings should be
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freed with g_free(). Arrays follow the same rule. If you find an
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undocumented exception to the rules, please report a bug to <ulink
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url="http://bugzilla.gnome.org">http://bugzilla.gnome.org</ulink>.
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</para>
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</answer>
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@ -164,8 +164,8 @@ How do I use GTK+ with threads?
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<answer>
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<para>
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This is covered in the <link linkend="gdk-Threads">GDK threads
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documentation</link>. See also the <link linkend="glib-Threads">GThread</link>
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This is covered in the <link linkend="gdk-Threads">GDK threads
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documentation</link>. See also the <link linkend="glib-Threads">GThread</link>
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documentation for portable threading primitives.
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</para>
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@ -182,33 +182,37 @@ How do I internationalize a GTK+ program?
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<para>
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Most people use <ulink url="http://www.gnu.org/software/gettext/">GNU
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gettext</ulink>, already required in order to install GLib. On a UNIX
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or Linux system with gettext installed, type <literal>info gettext</literal>
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or Linux system with gettext installed, type <literal>info gettext</literal>
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to read the documentation.
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</para>
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<para>
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The short checklist on how to use gettext is: call bindtextdomain() so gettext
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can find the files containing your translations, call textdomain() to set the
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default translation domain, call bind_textdomain_codeset() to request that
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all translated strings are returned in UTF-8, then call gettext() to look up
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each string to be translated in the default domain.
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The short checklist on how to use gettext is: call bindtextdomain() so
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gettext can find the files containing your translations, call textdomain()
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to set the default translation domain, call bind_textdomain_codeset() to
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request that all translated strings are returned in UTF-8, then call
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gettext() to look up each string to be translated in the default domain.
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</para>
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<para>
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<filename>gi18n.h</filename> provides the following shorthand macros for
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convenience.
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Conventionally, people define macros as follows for convenience:
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<informalexample>
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<programlisting>
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#define _(x) gettext (x)
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#define N_(x) x
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#define _(x) gettext (x)
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#define N_(x) x
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#define C_(ctx,x) pgettext (ctx, x)
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</programlisting>
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</informalexample>
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You use N_() (N stands for no-op) to mark a string for translation in a
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context where a function call to gettext() is not allowed, such as in an
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array initializer.
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You eventually have to call gettext() on the string to actually fetch the
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translation. _() both marks the string for translation and actually
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You use N_() (N stands for no-op) to mark a string for translation in
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a location where a function call to gettext() is not allowed, such as
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in an array initializer.
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You eventually have to call gettext() on the string to actually fetch
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the translation. _() both marks the string for translation and actually
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translates it.
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</para>
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<para>
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Nowadays, GLib provides the common shorthand macros in the header file
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<filename>gi18n.h</filename>, so you don't have to define them yourself,
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just include that header.
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The C_() macro (C stands for context) adds an additional context to
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the string that is marked for translation, which can help to disambiguate
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short strings that might need different translations in different
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parts of your program.
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</para>
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<para>
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Code using these macros ends up looking like this:
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@ -231,21 +235,21 @@ Code using these macros ends up looking like this:
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</informalexample>
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</para>
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<para>
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Libraries using gettext should use dgettext() instead of gettext(), which
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allows them to specify the translation domain each time they ask for a
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translation. Libraries should also avoid calling textdomain(), since they
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will be specifying the domain instead of using the default. For dgettext()
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the _() macro can be defined as:
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<informalexample>
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<programlisting>
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#define _(x) dgettext ("MyDomain", x)
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</programlisting>
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</informalexample>
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Libraries using gettext should use dgettext() instead of gettext(), which
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allows them to specify the translation domain each time they ask for a
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translation. Libraries should also avoid calling textdomain(), since
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they will be specifying the domain instead of using the default.
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</para>
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<para>
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Again, GLib comes with the <filename>gi18n-lib.h</filename>, saving you the
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trouble of defining the macros by hand. The macros in that header expect the
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translation domain to be specified by the %GETTEXT_PACKAGE macro.
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With the convention that the macro <literal>GETTEXT_PACKAGE</literal> is
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defined to hold your libraries translation domain,
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<filename>gi18n-lib.h</filename> can be included to provide
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the following convenience:
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<informalexample>
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<programlisting>
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#define _(x) dgettext (GETTEXT_PACKAGE, x)
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</programlisting>
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</informalexample>
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</para>
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</answer>
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</qandaentry>
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@ -259,9 +263,9 @@ How do I use non-ASCII characters in GTK+ programs ?
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<answer>
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<para>
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GTK+ uses <ulink url="http://www.unicode.org">Unicode</ulink> (more exactly
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UTF-8) for all text. UTF-8 encodes each Unicode codepoint as a sequence of
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one to six bytes and has a number of nice properties which make it a good
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GTK+ uses <ulink url="http://www.unicode.org">Unicode</ulink> (more exactly
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UTF-8) for all text. UTF-8 encodes each Unicode codepoint as a sequence of
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one to six bytes and has a number of nice properties which make it a good
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choice for working with Unicode text in C programs:
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<itemizedlist>
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<listitem><para>
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@ -271,30 +275,30 @@ ASCII characters are encoded by their familiar ASCII codepoints.
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ASCII characters never appear as part of any other character.
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</para></listitem>
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<listitem><para>
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The zero byte doesn't occur as part of a character, so that UTF-8 strings
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can be manipulated with the usual C library functions for handling
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The zero byte doesn't occur as part of a character, so that UTF-8 strings
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can be manipulated with the usual C library functions for handling
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zero-terminated strings.
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</para></listitem>
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</itemizedlist>
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More information about Unicode and UTF-8 can be found in the
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<ulink url="http://www.cl.cam.ac.uk/~mgk25/unicode.html">UTF-8 and Unicode i
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More information about Unicode and UTF-8 can be found in the
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<ulink url="http://www.cl.cam.ac.uk/~mgk25/unicode.html">UTF-8 and Unicode
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FAQ for Unix/Linux</ulink>.
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GLib provides functions for converting strings between UTF-8 and other
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encodings, see g_locale_to_utf8() and g_convert().
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</para>
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<para>
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Text coming from external sources (e.g. files or user input), has to be
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converted to UTF-8 before being handed over to GTK+. The following example
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writes the content of a IS0-8859-1 encoded text file to
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converted to UTF-8 before being handed over to GTK+. The following example
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writes the content of a IS0-8859-1 encoded text file to
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<literal>stdout</literal>:
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<informalexample><programlisting>
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gchar *text, *utf8_text;
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gsize length;
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GError *error = NULL;
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if (g_file_get_contents (filename, &text, &length, NULL))
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if (g_file_get_contents (filename, &text, &length, NULL))
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{
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utf8_text = g_convert (text, length, "UTF-8", "ISO-8859-1",
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utf8_text = g_convert (text, length, "UTF-8", "ISO-8859-1",
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NULL, NULL, &error);
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if (error != NULL)
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{
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@ -304,7 +308,7 @@ if (g_file_get_contents (filename, &text, &length, NULL))
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else
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g_print (utf8_text);
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}
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else
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else
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fprintf (stderr, "Unable to read file %s\n", filename);
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</programlisting></informalexample>
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</para>
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@ -315,36 +319,37 @@ handling non-ASCII content:
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<varlistentry><term>direct UTF-8</term>
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<listitem><para>
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If your editor and compiler are capable of handling UTF-8 encoded sources,
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it is very convenient to simply use UTF-8 for string literals, since it allows
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you to edit the strings in "wysiwyg". Note that choosing this option may
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reduce the portability of your code.
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it is very convenient to simply use UTF-8 for string literals, since it
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allows you to edit the strings in "wysiwyg". Note that choosing this option
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may reduce the portability of your code.
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</para></listitem>
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</varlistentry>
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<varlistentry><term>escaped UTF-8</term>
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<listitem><para>
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Even if your toolchain can't handle UTF-8 directly, you can still encode string
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literals in UTF-8 by using octal or hexadecimal escapes like
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<literal>\212</literal> or <literal>\xa8</literal> to
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encode each byte. This is portable, but modifying the escaped strings is not
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very convenient. Be careful when mixing hexadecimal escapes with ordinary text;
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Even if your toolchain can't handle UTF-8 directly, you can still encode
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string literals in UTF-8 by using octal or hexadecimal escapes like
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<literal>\212</literal> or <literal>\xa8</literal> to encode each byte.
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This is portable, but modifying the escaped strings is not very convenient.
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Be careful when mixing hexadecimal escapes with ordinary text;
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<literal>"\xa8abcd"</literal> is a string of length 1 !
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</para></listitem>
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</varlistentry>
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<varlistentry><term>runtime conversion</term>
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<listitem><para>
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If the string literals can be represented in an encoding which your toolchain
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can handle (e.g. IS0-8859-1), you can write your source files in that encoding
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and use g_convert() to convert the strings to UTF-8 at runtime. Note that this
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has some runtime overhead, so you may want to move the conversion out of inner
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loops.
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If the string literals can be represented in an encoding which your
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toolchain can handle (e.g. IS0-8859-1), you can write your source files
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in that encoding and use g_convert() to convert the strings to UTF-8 at
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runtime. Note that this has some runtime overhead, so you may want to move
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the conversion out of inner loops.
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</para></listitem>
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</varlistentry>
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</variablelist>
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Here is an example showing the three approaches using the copyright sign
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© which has Unicode and ISO-8859-1 codepoint 169 and is represented in
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UTF-8 by the two bytes 194, 169:
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Here is an example showing the three approaches using the copyright sign
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© which has Unicode and ISO-8859-1 codepoint 169 and is represented
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in UTF-8 by the two bytes 194, 169, or <literal>"\302\251"</literal> as
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a string literal:
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<informalexample><programlisting>
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g_print ("direct UTF-8: ©");
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g_print ("escaped UTF-8: \302\251");
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@ -368,9 +373,9 @@ How do I use GTK+ with C++?
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<answer>
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<para>
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There are two ways to approach this. The GTK+ header files use the subset
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of C that's also valid C++, so you can simply use the normal GTK+ API
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in a C++ program. Alternatively, you can use a "C++ binding"
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There are two ways to approach this. The GTK+ header files use the subset
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of C that's also valid C++, so you can simply use the normal GTK+ API
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in a C++ program. Alternatively, you can use a "C++ binding"
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such as <ulink url="http://gtkmm.sourceforge.net/">gtkmm</ulink>
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which provides a native C++ API.
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</para>
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@ -380,20 +385,20 @@ connected to signals, not methods. So you will need to use global
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functions or "static" class functions for signal connections.
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</para>
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<para>
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Another common issue when using GTK+ directly is that
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C++ will not implicitly convert an integer to an enumeration.
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Another common issue when using GTK+ directly is that
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C++ will not implicitly convert an integer to an enumeration.
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This comes up when using bitfields; in C you can write the following
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code:
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<informalexample>
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<programlisting>
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gdk_window_set_events (gdk_window,
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gdk_window_set_events (gdk_window,
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GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK);
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</programlisting>
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</informalexample>
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while in C++ you must write:
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<informalexample>
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<programlisting>
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gdk_window_set_events (gdk_window,
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gdk_window_set_events (gdk_window,
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(GdkEventMask) GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK);
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</programlisting>
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</informalexample>
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@ -427,19 +432,19 @@ How do I load an image or animation from a file?
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<answer>
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<para>
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To load an image file straight into a display widget, use
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gtk_image_new_from_file() <footnote><para> If the file load fails,
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gtk_image_new_from_file() will display no image graphic — to detect
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a failed load yourself, use gdk_pixbuf_new_from_file() directly, then
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gtk_image_new_from_pixbuf().</para></footnote>.
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To load an image file straight into a display widget, use
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gtk_image_new_from_file() <footnote><para> If the file load fails,
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gtk_image_new_from_file() will display no image graphic — to detect
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a failed load yourself, use gdk_pixbuf_new_from_file() directly, then
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gtk_image_new_from_pixbuf().</para></footnote>.
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To load an image for another purpose, use gdk_pixbuf_new_from_file(). To i
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load an animation, use gdk_pixbuf_animation_new_from_file().
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gdk_pixbuf_animation_new_from_file() can also load non-animated images, so
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use it in combination with gdk_pixbuf_animation_is_static_image() to load a
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file of unknown type.
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gdk_pixbuf_animation_new_from_file() can also load non-animated images, so
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use it in combination with gdk_pixbuf_animation_is_static_image() to load a
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file of unknown type.
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</para>
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<para>
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To load an image or animation file asynchronously (without blocking), use
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To load an image or animation file asynchronously (without blocking), use
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#GdkPixbufLoader.
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</para>
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</answer>
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@ -453,14 +458,13 @@ How do I draw text ?
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<answer>
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<para>
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To draw a piece of text, use a Pango layout and gdk_draw_layout(),
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using code like the following:
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To draw a piece of text, use a Pango layout and gdk_draw_layout().
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<informalexample>
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<programlisting>
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layout = gtk_widget_create_pango_layout (widget, text);
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fontdesc = pango_font_description_from_string ("Luxi Mono 12");
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pango_layout_set_font_description (layout, fontdesc);
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gdk_draw_layout (..., layout);
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pango_layout_set_font_description (layout, fontdesc);
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pango_cairo_show_layout (cr, layout);
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pango_font_description_free (fontdesc);
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g_object_unref (layout);
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</programlisting>
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@ -485,13 +489,13 @@ How do I measure the size of a piece of text ?
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<answer>
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<para>
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To obtain the size of a piece of text, use a Pango layout and
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To obtain the size of a piece of text, use a Pango layout and
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pango_layout_get_pixel_size(), using code like the following:
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<informalexample>
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<programlisting>
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layout = gtk_widget_create_pango_layout (widget, text);
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fontdesc = pango_font_description_from_string ("Luxi Mono 12");
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pango_layout_set_font_description (layout, fontdesc);
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pango_layout_set_font_description (layout, fontdesc);
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pango_layout_get_pixel_size (layout, &width, &height);
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pango_font_description_free (fontdesc);
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g_object_unref (layout);
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@ -510,21 +514,21 @@ section of <ulink url="http://library.gnome.org/devel/pango/stable/">Pango manua
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<qandaentry>
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<question>
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<para>
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Why are types not registered if I use their <literal>GTK_TYPE_BLAH</literal>
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Why are types not registered if I use their <literal>GTK_TYPE_BLAH</literal>
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macro ?
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</para>
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</question>
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<answer>
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<para>
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The <literal>GTK_TYPE_BLAH</literal> macros are defined as calls to
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The <literal>GTK_TYPE_BLAH</literal> macros are defined as calls to
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<literal>gtk_blah_get_type()</literal>, and the <literal>_get_type()</literal> i
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functions are declared as %G_GNUC_CONST which allows the compiler to optimize
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the call away if it appears that the value is not being used.
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</para>
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<para>
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A common workaround for this problem is to store the result in a volatile
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A common workaround for this problem is to store the result in a volatile
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variable, which keeps the compiler from optimizing the call away.
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<informalexample><programlisting>
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volatile GType dummy = GTK_TYPE_BLAH;
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@ -543,7 +547,7 @@ How do I create a transparent toplevel window ?
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<answer>
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<para>
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To make a window transparent, it needs to use a visual which supports that.
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This is done by getting the RGBA colormap of the screen with
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This is done by getting the RGBA colormap of the screen with
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gdk_screen_get_rgba_colormap() and setting it on the window. Note that
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gdk_screen_get_rgba_colormap() will return %NULL if transparent windows
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are not supported on the screen; also note that this may change from
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@ -563,8 +567,8 @@ gdk_draw_rgb_32_image().
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</para>
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||||
<para>
|
||||
Note that the presence of an RGBA visual is no guarantee that the
|
||||
window will actually appear transparent on screen. On X11, this
|
||||
requires a compositing manager to be running. See
|
||||
window will actually appear transparent on screen. On X11, this
|
||||
requires a compositing manager to be running. See
|
||||
gtk_widget_is_composited() for a way to find out if the alpha
|
||||
channel will be respected.
|
||||
</para>
|
||||
@ -583,7 +587,7 @@ channel will be respected.
|
||||
<answer>
|
||||
<para>
|
||||
See <link linkend="TreeWidget">tree widget overview</link> — you
|
||||
should use the #GtkTreeView widget. (A list is just a tree with no branches,
|
||||
should use the #GtkTreeView widget. (A list is just a tree with no branches,
|
||||
so the tree widget is used for lists as well).
|
||||
</para>
|
||||
</answer>
|
||||
@ -600,8 +604,8 @@ See <link linkend="TextWidget">text widget overview</link> — you
|
||||
should use the #GtkTextView widget.
|
||||
</para>
|
||||
<para>
|
||||
If you only have a small amount of text, #GtkLabel may also be appropriate
|
||||
of course. It can be made selectable with gtk_label_set_selectable(). For a
|
||||
If you only have a small amount of text, #GtkLabel may also be appropriate
|
||||
of course. It can be made selectable with gtk_label_set_selectable(). For a
|
||||
single-line text entry, see #GtkEntry.
|
||||
</para>
|
||||
</answer>
|
||||
@ -615,8 +619,8 @@ single-line text entry, see #GtkEntry.
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
#GtkImage can display images in just about any format GTK+ understands.
|
||||
You can also use #GtkDrawingArea if you need to do something more complex,
|
||||
#GtkImage can display images in just about any format GTK+ understands.
|
||||
You can also use #GtkDrawingArea if you need to do something more complex,
|
||||
such as draw text or graphics over the top of the image.
|
||||
</para>
|
||||
</answer>
|
||||
@ -648,17 +652,14 @@ How do I change the color of a widget?
|
||||
</para></question>
|
||||
|
||||
<answer><para>
|
||||
See gtk_widget_modify_fg(), gtk_widget_modify_bg(), gtk_widget_modify_base(),
|
||||
and gtk_widget_modify_text(). See <link linkend="gtk-Resource-Files">GTK+
|
||||
resource files</link> for more discussion. You can also change widget color
|
||||
by installing a resource file and parsing it with gtk_rc_add_default_file().
|
||||
The advantage of a resource file is that users can then override the
|
||||
color you've chosen.
|
||||
See gtk_widget_override_color() and gtk_widget_override_background_color().
|
||||
You can also change the appearance of a widget by installing a
|
||||
custom style provider, see gtk_style_context_add_provider().
|
||||
</para>
|
||||
|
||||
<para>To change the background color for widgets such as #GtkLabel that have
|
||||
no background, place them in a #GtkEventBox and set the background of the
|
||||
event box.
|
||||
<para>To change the background color for widgets such as #GtkLabel that
|
||||
have no background, place them in a #GtkEventBox and set the background
|
||||
of the event box.
|
||||
</para></answer>
|
||||
</qandaentry>
|
||||
|
||||
@ -668,35 +669,38 @@ How do I change the font of a widget?
|
||||
</para></question>
|
||||
|
||||
<answer><para>
|
||||
This has several possible answers, depending on what exactly you want to
|
||||
achieve. One option is gtk_widget_modify_font(). Note that this function
|
||||
can be used to change only the font size, as in the following example:
|
||||
This has several possible answers, depending on what exactly you want to
|
||||
achieve. One option is gtk_widget_override_font().
|
||||
<informalexample><programlisting>
|
||||
PangoFontDesc *font_desc = pango_font_description_new (<!-- -->);
|
||||
pango_font_description_set_size (font_desc, 40);
|
||||
gtk_widget_modify_font (widget, font);
|
||||
gtk_widget_override_font (widget, font);
|
||||
pango_font_description_free (font_desc);
|
||||
</programlisting></informalexample>
|
||||
</para>
|
||||
<para>
|
||||
If you want to make the text of a label larger, you can use
|
||||
If you want to make the text of a label larger, you can use
|
||||
gtk_label_set_markup():
|
||||
<informalexample><programlisting>
|
||||
gtk_label_set_markup (label, "<big>big text</big>");
|
||||
</programlisting></informalexample>
|
||||
This is preferred for many apps because it's a relative size to the
|
||||
user's chosen font size. See g_markup_escape_text() if you are
|
||||
This is preferred for many apps because it's a relative size to the
|
||||
user's chosen font size. See g_markup_escape_text() if you are
|
||||
constructing such strings on the fly.
|
||||
</para>
|
||||
<para>
|
||||
You can also change the font of a widget by putting
|
||||
<programlisting>
|
||||
gtk-font-name = "Sans 30"
|
||||
.my-widget-class {
|
||||
font: Sans 30;
|
||||
}
|
||||
</programlisting>
|
||||
in a resource file and parsing it with gtk_rc_add_default_file().
|
||||
The advantage of a resource file is that users can then override the font you
|
||||
have chosen. See <link linkend="gtk-Resource-Files">GTK+ resource files</link>
|
||||
for more discussion.
|
||||
in a CSS file, loading it with gtk_css_provider_load_from_file(), and
|
||||
adding the provider with gtk_style_context_add_provider_for_screen().
|
||||
To associate this style information with your widget, set a style class
|
||||
on its #GtkStyleContext using gtk_style_context_add_class().
|
||||
The advantage of this approach is that users can then override the font
|
||||
you have chosen. See the #GtkStyleContext documentation for more discussion.
|
||||
</para>
|
||||
</answer>
|
||||
</qandaentry>
|
||||
@ -706,8 +710,9 @@ for more discussion.
|
||||
How do I disable/ghost/desensitize a widget?
|
||||
</para></question>
|
||||
|
||||
<answer><para> In GTK+ a disabled widget is termed "insensitive." See
|
||||
gtk_widget_set_sensitive().
|
||||
<answer><para>
|
||||
In GTK+ a disabled widget is termed "insensitive."
|
||||
See gtk_widget_set_sensitive().
|
||||
</para></answer>
|
||||
</qandaentry>
|
||||
|
||||
@ -746,14 +751,14 @@ How do I make a text widget display its complete contents in a specific font?
|
||||
</para></question>
|
||||
|
||||
<answer><para>
|
||||
If you use gtk_text_buffer_insert_with_tags() with appropriate tags to select
|
||||
the font, the inserted text will have the desired appearance, but text typed
|
||||
in by the user before or after the tagged block will appear in the default
|
||||
style.
|
||||
If you use gtk_text_buffer_insert_with_tags() with appropriate tags to
|
||||
select the font, the inserted text will have the desired appearance, but
|
||||
text typed in by the user before or after the tagged block will appear in
|
||||
the default style.
|
||||
</para>
|
||||
<para>
|
||||
To ensure that all text has the desired appearance, use gtk_widget_modify_font()
|
||||
to change the default font for the widget.
|
||||
To ensure that all text has the desired appearance, use
|
||||
gtk_widget_override_font() to change the default font for the widget.
|
||||
</para></answer>
|
||||
</qandaentry>
|
||||
|
||||
@ -770,17 +775,17 @@ A good way to keep a text buffer scrolled to the end is to place a
|
||||
<link linkend="GtkTextMark">mark</link> at the end of the buffer, and
|
||||
give it right gravity. The gravity has the effect that text inserted
|
||||
at the mark gets inserted <emphasis>before</emphasis>, keeping the mark
|
||||
at the end.
|
||||
at the end.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<para>
|
||||
To ensure that the end of the buffer remains visible, use
|
||||
gtk_text_view_scroll_to_mark() to scroll to the mark after
|
||||
inserting new text.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The gtk-demo application contains an example of this technique.
|
||||
The gtk-demo application contains an example of this technique.
|
||||
</para>
|
||||
</answer>
|
||||
</qandaentry>
|
||||
@ -797,25 +802,10 @@ How do I associate some data with a row in the tree?
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
Remember that the #GtkTreeModel columns don't necessarily have to be displayed.
|
||||
So you can put non-user-visible data in your model just like any other data,
|
||||
and retrieve it with gtk_tree_model_get(). See the
|
||||
<link linkend="TreeWidget">tree widget overview</link>.
|
||||
</para>
|
||||
</answer>
|
||||
</qandaentry>
|
||||
|
||||
<qandaentry>
|
||||
<question><para>
|
||||
What's the #GtkTreeView equivalent of gtk_clist_find_row_from_data()?
|
||||
</para></question>
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
As there is no separate data column in the #GtkTreeModel, there's no
|
||||
built in function to find the iter from data. You can write a custom
|
||||
searching function to walk the tree and find the data, or use
|
||||
gtk_tree_model_foreach().
|
||||
Remember that the #GtkTreeModel columns don't necessarily have to be
|
||||
displayed. So you can put non-user-visible data in your model just
|
||||
like any other data, and retrieve it with gtk_tree_model_get().
|
||||
See the <link linkend="TreeWidget">tree widget overview</link>.
|
||||
</para>
|
||||
</answer>
|
||||
</qandaentry>
|
||||
@ -827,9 +817,9 @@ How do I put an image and some text in the same column?
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
You can pack more than one #GtkCellRenderer into a single #GtkTreeViewColumn
|
||||
using gtk_tree_view_column_pack_start() or gtk_tree_view_column_pack_end().
|
||||
So pack both a #GtkCellRendererPixbuf and a #GtkCellRendererText into the
|
||||
You can pack more than one #GtkCellRenderer into a single #GtkTreeViewColumn
|
||||
using gtk_tree_view_column_pack_start() or gtk_tree_view_column_pack_end().
|
||||
So pack both a #GtkCellRendererPixbuf and a #GtkCellRendererText into the
|
||||
column.
|
||||
</para>
|
||||
</answer>
|
||||
@ -837,15 +827,15 @@ column.
|
||||
|
||||
<qandaentry>
|
||||
<question><para>
|
||||
I can set data easily on my #GtkTreeStore/#GtkListStore models using
|
||||
I can set data easily on my #GtkTreeStore/#GtkListStore models using
|
||||
gtk_list_store_set() and gtk_tree_store_set(), but can't read it back?
|
||||
</para></question>
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
Both the #GtkTreeStore and the #GtkListStore implement the #GtkTreeModel
|
||||
interface. Consequentially, the can use any function this interface
|
||||
implements. The easiest way to read a set of data back is to use
|
||||
interface. Consequentially, you can use any function this interface
|
||||
implements. The easiest way to read a set of data back is to use
|
||||
gtk_tree_model_get().
|
||||
</para>
|
||||
</answer>
|
||||
@ -857,14 +847,14 @@ How do I change the way that numbers are formatted by #GtkTreeView?
|
||||
</para></question>
|
||||
<answer><para>
|
||||
Use gtk_tree_view_insert_column_with_data_func()
|
||||
or gtk_tree_view_column_set_cell_data_func() and do the conversion from i
|
||||
number to string yourself (with, say, g_strdup_printf()).
|
||||
or gtk_tree_view_column_set_cell_data_func() and do the conversion
|
||||
from number to string yourself (with, say, g_strdup_printf()).
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The following example demonstrates this:
|
||||
<informalexample><programlisting>
|
||||
enum
|
||||
enum
|
||||
{
|
||||
DOUBLE_COLUMN,
|
||||
N_COLUMNS
|
||||
@ -873,11 +863,11 @@ enum
|
||||
GtkListStore *mycolumns;
|
||||
GtkTreeView *treeview;
|
||||
|
||||
void
|
||||
void
|
||||
my_cell_double_to_text (GtkTreeViewColumn *tree_column,
|
||||
GtkCellRenderer *cell,
|
||||
GtkCellRenderer *cell,
|
||||
GtkTreeModel *tree_model,
|
||||
GtkTreeIter *iter,
|
||||
GtkTreeIter *iter,
|
||||
gpointer data)
|
||||
{
|
||||
GtkCellRendererText *cell_text = (GtkCellRendererText *)cell;
|
||||
@ -892,7 +882,7 @@ my_cell_double_to_text (GtkTreeViewColumn *tree_column,
|
||||
g_free (text);
|
||||
}
|
||||
|
||||
void
|
||||
void
|
||||
set_up_new_columns (GtkTreeView *myview)
|
||||
{
|
||||
GtkCellRendererText *renderer;
|
||||
@ -908,7 +898,7 @@ set_up_new_columns (GtkTreeView *myview)
|
||||
|
||||
/* Create a new column that has a title ("Example column"),
|
||||
* uses the above created renderer that will render the double
|
||||
* value into text from the associated model's rows.
|
||||
* value into text from the associated model's rows.
|
||||
*/
|
||||
column = gtk_tree_view_column_new (<!-- -->);
|
||||
gtk_tree_view_column_set_title (column, "Example column");
|
||||
@ -922,10 +912,10 @@ set_up_new_columns (GtkTreeView *myview)
|
||||
*/
|
||||
/* Set up a custom function that will be called when the column content
|
||||
* is rendered. We use the func_data pointer as an index into our
|
||||
* model. This is convenient when using multi column lists.
|
||||
* model. This is convenient when using multi column lists.
|
||||
*/
|
||||
gtk_tree_view_column_set_cell_data_func (column, renderer,
|
||||
my_cell_double_to_text,
|
||||
my_cell_double_to_text,
|
||||
(gpointer)DOUBLE_COLUMN, NULL);
|
||||
}
|
||||
</programlisting></informalexample>
|
||||
@ -953,42 +943,15 @@ How do I use cairo to draw in GTK+ applications ?
|
||||
</para></question>
|
||||
|
||||
<answer><para>
|
||||
Use gdk_cairo_create() to obtain a cairo context for drawing
|
||||
on a GDK window or pixmap. See <link linkend="gdk-Cairo-Interaction">Cairo
|
||||
Interaction</link> for some more useful functions.
|
||||
</para></answer>
|
||||
</qandaentry>
|
||||
|
||||
<qandaentry>
|
||||
<question><para>
|
||||
I have created a cairo context with gdk_cairo_create(), but when I
|
||||
later use it, my drawing does not show up. Why is that ?
|
||||
</para></question>
|
||||
|
||||
<answer>
|
||||
<para>
|
||||
All drawing in GTK+ is normally done in an expose handler, and GTK+
|
||||
creates a temporary pixmap for double-buffering the drawing. If you
|
||||
create a cairo context outside the expose handler, it is backed
|
||||
by the GDK window itself, not the double-buffering pixmap. Consequently,
|
||||
any drawing you do with that cairo context gets overwritten at the
|
||||
end of the expose handler, when the double-buffering pixmap is copied
|
||||
back.
|
||||
The #GtkWidget::draw signal gets a ready-to-use cairo context
|
||||
as parameter that you should use.
|
||||
</para>
|
||||
<para>
|
||||
Possible solutions to this problem are:
|
||||
<itemizedlist>
|
||||
<listitem><para>
|
||||
Turn off double-buffering, with gtk_widget_set_double_buffered().
|
||||
This is not ideal, since it can cause some flickering.
|
||||
</para></listitem>
|
||||
<listitem><para>
|
||||
Create the cairo context inside the expose handler. If you do this,
|
||||
gdk_cairo_create() arranges for it to be backed by the double-buffering
|
||||
pixmap. This is the preferred solution, and is used throughout GTK+
|
||||
itself.
|
||||
</para></listitem>
|
||||
</itemizedlist>
|
||||
All drawing in GTK+ is normally done in a draw handler, and GTK+
|
||||
creates a temporary pixmap for double-buffering the drawing.
|
||||
It is possible to turn off double-buffering, with
|
||||
gtk_widget_set_double_buffered(), but this is not ideal,
|
||||
since it can cause some flickering.
|
||||
</para>
|
||||
</answer>
|
||||
</qandaentry>
|
||||
@ -996,7 +959,7 @@ itself.
|
||||
<qandaentry>
|
||||
<question><para>
|
||||
Can I improve the performance of my application by using the
|
||||
Glitz backend of cairo ?
|
||||
Glitz or GL backend of cairo ?
|
||||
</para></question>
|
||||
|
||||
<answer><para>
|
||||
@ -1016,7 +979,7 @@ Can I use cairo to draw on a #GdkPixbuf ?
|
||||
|
||||
<answer><para>
|
||||
No, at least not yet. The cairo image surface does not support the
|
||||
pixel format used by GdkPixbuf.
|
||||
pixel format used by GdkPixbuf.
|
||||
</para></answer>
|
||||
</qandaentry>
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user