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< title > GTK 4 tutorial< / title >
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< h1 id = "widgets-3" > Widgets (3)< / h1 >
< h2 id = "open-signal" > Open signal< / h2 >
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< h3 id = "g_application_handles_open-flag" > G_APPLICATION_HANDLES_OPEN
flag< / h3 >
< p > We made a very simple editor in the previous section with
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GtkTextView, GtkTextBuffer and GtkScrolledWindow. We will add file-read
ability to the program and improve it to a file viewer.< / p >
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< p > The easiest way to give a filename is to use a command line
argument.< / p >
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< pre > < code > $ ./a.out filename< / code > < / pre >
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< p > The program will open the file and insert its contents into the
GtkTextBuffer.< / p >
< p > To do this, we need to know how GtkApplication (or GApplication)
recognizes arguments. This is described in the < a
href="https://docs.gtk.org/gio/class.Application.html">GIO API Reference
– < / a > .< / p >
< p > When GtkApplication is created, a flag (GApplicationFlags) is given
as an argument.< / p >
< div class = "sourceCode" id = "cb2" > < pre class = "sourceCode c" > < code class = "sourceCode c" > < span id = "cb2-1" > < a href = "#cb2-1" aria-hidden = "true" tabindex = "-1" > < / a > GtkApplication < span class = "op" > *< / span > < / span >
< span id = "cb2-2" > < a href = "#cb2-2" aria-hidden = "true" tabindex = "-1" > < / a > gtk_application_new < span class = "op" > (< / span > < span class = "dt" > const< / span > gchar < span class = "op" > *< / span > application_id< span class = "op" > ,< / span > GApplicationFlags flags< span class = "op" > );< / span > < / span > < / code > < / pre > < / div >
< p > This tutorial explains only two flags,
< code > G_APPLICATION_DEFAULT_FLAGS< / code > and
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< code > G_APPLICATION_HANDLES_OPEN< / code > .< / p >
< p > < code > G_APPLICATION_FLAGS_NONE< / code > was used instead of
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< code > G_APPLICATION_DEFAULT_FLAGS< / code > before GIO version2.73.3 (GLib
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2.73.3 5/Aug/2022). Now it is deprecated and
< code > G_APPLICATION_DEFAULT_FLAGS< / code > is recommended.< / p >
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< p > For further information, see < a
href="https://docs.gtk.org/gio/flags.ApplicationFlags.html">GIO API
Reference – < / a > and < a
href="https://docs.gtk.org/gio/method.Application.run.html">GIO API
Reference – < / a > .< / p >
< p > We’ < code > G_APPLICATION_DEFAULT_FLAGS< / code > , as it is
the simplest option, and no command line arguments are allowed. If you
give arguments, an error will occur.< / p >
< p > The flag < code > G_APPLICATION_HANDLES_OPEN< / code > is the second
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simplest option. It allows arguments but only filenames.< / p >
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< div class = "sourceCode" id = "cb3" > < pre class = "sourceCode c" > < code class = "sourceCode c" > < span id = "cb3-1" > < a href = "#cb3-1" aria-hidden = "true" tabindex = "-1" > < / a > app < span class = "op" > =< / span > gtk_application_new < span class = "op" > (< / span > < span class = "st" > " com.github.ToshioCP.tfv3" < / span > < span class = "op" > ,< / span > G_APPLICATION_HANDLES_OPEN< span class = "op" > );< / span > < / span > < / code > < / pre > < / div >
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< h3 id = "open-signal-1" > open signal< / h3 >
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< p > When < code > G_APPLICATION_HANDLES_OPEN< / code > flag is given to the
application, two signals are available.< / p >
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< ul >
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< li > activate signal: This signal is emitted when there’
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argument.< / li >
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< li > open signal: This signal is emitted when there is at least one
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argument.< / li >
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< / ul >
< p > The handler of the “open” signal is defined as follows.< / p >
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< div class = "sourceCode" id = "cb4" > < pre class = "sourceCode c" > < code class = "sourceCode c" > < span id = "cb4-1" > < a href = "#cb4-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "dt" > void< / span > < / span >
< span id = "cb4-2" > < a href = "#cb4-2" aria-hidden = "true" tabindex = "-1" > < / a > open < span class = "op" > (< / span > < / span >
< span id = "cb4-3" > < a href = "#cb4-3" aria-hidden = "true" tabindex = "-1" > < / a > GApplication< span class = "op" > *< / span > self< span class = "op" > ,< / span > < / span >
< span id = "cb4-4" > < a href = "#cb4-4" aria-hidden = "true" tabindex = "-1" > < / a > gpointer files< span class = "op" > ,< / span > < / span >
< span id = "cb4-5" > < a href = "#cb4-5" aria-hidden = "true" tabindex = "-1" > < / a > gint n_files< span class = "op" > ,< / span > < / span >
< span id = "cb4-6" > < a href = "#cb4-6" aria-hidden = "true" tabindex = "-1" > < / a > gchar< span class = "op" > *< / span > hint< span class = "op" > ,< / span > < / span >
< span id = "cb4-7" > < a href = "#cb4-7" aria-hidden = "true" tabindex = "-1" > < / a > gpointer user_data< / span >
< span id = "cb4-8" > < a href = "#cb4-8" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "op" > )< / span > < / span > < / code > < / pre > < / div >
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< p > The parameters are:< / p >
< ul >
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< li > self: the application instance (usually GtkApplication)< / li >
< li > files: an array of GFiles. [array length=n_files] [element-type
GFile]< / li >
< li > n_files: the number of the elements of < code > files< / code > < / li >
< li > hint: a hint provided by the calling instance (usually it can be
ignored)< / li >
< li > user_data: user data that is set when the signal handler was
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connected.< / li >
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< / ul >
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< h2 id = "file-viewer" > File viewer< / h2 >
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< h3 id = "what-is-a-file-viewer" > What is a file viewer?< / h3 >
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< p > A file viewer is a program that displays text files. Our file viewer
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is as follows.< / p >
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< ul >
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< li > When arguments are given, it recognizes the first argument as a
filename and opens it.< / li >
< li > The second argument and after are ignored.< / li >
< li > If there’ < / li >
< li > If it successfully opens the file, it reads the contents of the
file, inserts them to GtkTextBuffer and shows the window.< / li >
< li > If it fails to open the file, it shows an error message and
quit.< / li >
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< / ul >
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< p > The program is shown below.< / p >
< div class = "sourceCode" id = "cb5" > < pre
class="sourceCode numberSource C numberLines">< code class = "sourceCode c" > < span id = "cb5-1" > < a href = "#cb5-1" > < / a > < span class = "pp" > #include < / span > < span class = "im" > < gtk/gtk.h> < / span > < / span >
< span id = "cb5-2" > < a href = "#cb5-2" > < / a > < / span >
< span id = "cb5-3" > < a href = "#cb5-3" > < / a > < span class = "dt" > static< / span > < span class = "dt" > void< / span > < / span >
< span id = "cb5-4" > < a href = "#cb5-4" > < / a > app_activate < span class = "op" > (< / span > GApplication < span class = "op" > *< / span > app< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-5" > < a href = "#cb5-5" > < / a > g_printerr < span class = "op" > (< / span > < span class = "st" > " You need a filename argument.< / span > < span class = "sc" > \n< / span > < span class = "st" > " < / span > < span class = "op" > );< / span > < / span >
< span id = "cb5-6" > < a href = "#cb5-6" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb5-7" > < a href = "#cb5-7" > < / a > < / span >
< span id = "cb5-8" > < a href = "#cb5-8" > < / a > < span class = "dt" > static< / span > < span class = "dt" > void< / span > < / span >
< span id = "cb5-9" > < a href = "#cb5-9" > < / a > app_open < span class = "op" > (< / span > GApplication < span class = "op" > *< / span > app< span class = "op" > ,< / span > GFile < span class = "op" > **< / span > files< span class = "op" > ,< / span > < span class = "dt" > int< / span > n_files< span class = "op" > ,< / span > < span class = "dt" > char< / span > < span class = "op" > *< / span > hint< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-10" > < a href = "#cb5-10" > < / a > GtkWidget < span class = "op" > *< / span > win< span class = "op" > ;< / span > < / span >
< span id = "cb5-11" > < a href = "#cb5-11" > < / a > GtkWidget < span class = "op" > *< / span > scr< span class = "op" > ;< / span > < / span >
< span id = "cb5-12" > < a href = "#cb5-12" > < / a > GtkWidget < span class = "op" > *< / span > tv< span class = "op" > ;< / span > < / span >
< span id = "cb5-13" > < a href = "#cb5-13" > < / a > GtkTextBuffer < span class = "op" > *< / span > tb< span class = "op" > ;< / span > < / span >
< span id = "cb5-14" > < a href = "#cb5-14" > < / a > < span class = "dt" > char< / span > < span class = "op" > *< / span > contents< span class = "op" > ;< / span > < / span >
< span id = "cb5-15" > < a href = "#cb5-15" > < / a > gsize length< span class = "op" > ;< / span > < / span >
< span id = "cb5-16" > < a href = "#cb5-16" > < / a > < span class = "dt" > char< / span > < span class = "op" > *< / span > filename< span class = "op" > ;< / span > < / span >
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< span id = "cb5-17" > < a href = "#cb5-17" > < / a > GError < span class = "op" > *< / span > err < span class = "op" > =< / span > NULL< span class = "op" > ;< / span > < / span >
< span id = "cb5-18" > < a href = "#cb5-18" > < / a > < / span >
< span id = "cb5-19" > < a href = "#cb5-19" > < / a > win < span class = "op" > =< / span > gtk_application_window_new < span class = "op" > (< / span > GTK_APPLICATION < span class = "op" > (< / span > app< span class = "op" > ));< / span > < / span >
< span id = "cb5-20" > < a href = "#cb5-20" > < / a > gtk_window_set_default_size < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > < span class = "dv" > 400< / span > < span class = "op" > ,< / span > < span class = "dv" > 300< / span > < span class = "op" > );< / span > < / span >
< span id = "cb5-21" > < a href = "#cb5-21" > < / a > < / span >
< span id = "cb5-22" > < a href = "#cb5-22" > < / a > scr < span class = "op" > =< / span > gtk_scrolled_window_new < span class = "op" > ();< / span > < / span >
< span id = "cb5-23" > < a href = "#cb5-23" > < / a > gtk_window_set_child < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > scr< span class = "op" > );< / span > < / span >
< span id = "cb5-24" > < a href = "#cb5-24" > < / a > < / span >
< span id = "cb5-25" > < a href = "#cb5-25" > < / a > tv < span class = "op" > =< / span > gtk_text_view_new < span class = "op" > ();< / span > < / span >
< span id = "cb5-26" > < a href = "#cb5-26" > < / a > tb < span class = "op" > =< / span > gtk_text_view_get_buffer < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ));< / span > < / span >
< span id = "cb5-27" > < a href = "#cb5-27" > < / a > gtk_text_view_set_wrap_mode < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ),< / span > GTK_WRAP_WORD_CHAR< span class = "op" > );< / span > < / span >
< span id = "cb5-28" > < a href = "#cb5-28" > < / a > gtk_text_view_set_editable < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ),< / span > FALSE< span class = "op" > );< / span > < / span >
< span id = "cb5-29" > < a href = "#cb5-29" > < / a > gtk_scrolled_window_set_child < span class = "op" > (< / span > GTK_SCROLLED_WINDOW < span class = "op" > (< / span > scr< span class = "op" > ),< / span > tv< span class = "op" > );< / span > < / span >
< span id = "cb5-30" > < a href = "#cb5-30" > < / a > < / span >
< span id = "cb5-31" > < a href = "#cb5-31" > < / a > < span class = "cf" > if< / span > < span class = "op" > (< / span > g_file_load_contents < span class = "op" > (< / span > files< span class = "op" > [< / span > < span class = "dv" > 0< / span > < span class = "op" > ],< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > contents< span class = "op" > ,< / span > < span class = "op" > & < / span > length< span class = "op" > ,< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > err< span class = "op" > ))< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-32" > < a href = "#cb5-32" > < / a > gtk_text_buffer_set_text < span class = "op" > (< / span > tb< span class = "op" > ,< / span > contents< span class = "op" > ,< / span > length< span class = "op" > );< / span > < / span >
< span id = "cb5-33" > < a href = "#cb5-33" > < / a > g_free < span class = "op" > (< / span > contents< span class = "op" > );< / span > < / span >
< span id = "cb5-34" > < a href = "#cb5-34" > < / a > < span class = "cf" > if< / span > < span class = "op" > ((< / span > filename < span class = "op" > =< / span > g_file_get_basename < span class = "op" > (< / span > files< span class = "op" > [< / span > < span class = "dv" > 0< / span > < span class = "op" > ]))< / span > < span class = "op" > !=< / span > NULL< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-35" > < a href = "#cb5-35" > < / a > gtk_window_set_title < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb5-36" > < a href = "#cb5-36" > < / a > g_free < span class = "op" > (< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb5-37" > < a href = "#cb5-37" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb5-38" > < a href = "#cb5-38" > < / a > gtk_window_present < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
< span id = "cb5-39" > < a href = "#cb5-39" > < / a > < span class = "op" > }< / span > < span class = "cf" > else< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-40" > < a href = "#cb5-40" > < / a > g_printerr < span class = "op" > (< / span > < span class = "st" > " %s.< / span > < span class = "sc" > \n< / span > < span class = "st" > " < / span > < span class = "op" > ,< / span > err< span class = "op" > -> < / span > message< span class = "op" > );< / span > < / span >
< span id = "cb5-41" > < a href = "#cb5-41" > < / a > g_error_free < span class = "op" > (< / span > err< span class = "op" > );< / span > < / span >
< span id = "cb5-42" > < a href = "#cb5-42" > < / a > gtk_window_destroy < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
< span id = "cb5-43" > < a href = "#cb5-43" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb5-44" > < a href = "#cb5-44" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb5-45" > < a href = "#cb5-45" > < / a > < / span >
< span id = "cb5-46" > < a href = "#cb5-46" > < / a > < span class = "dt" > int< / span > < / span >
< span id = "cb5-47" > < a href = "#cb5-47" > < / a > main < span class = "op" > (< / span > < span class = "dt" > int< / span > argc< span class = "op" > ,< / span > < span class = "dt" > char< / span > < span class = "op" > **< / span > argv< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb5-48" > < a href = "#cb5-48" > < / a > GtkApplication < span class = "op" > *< / span > app< span class = "op" > ;< / span > < / span >
< span id = "cb5-49" > < a href = "#cb5-49" > < / a > < span class = "dt" > int< / span > stat< span class = "op" > ;< / span > < / span >
< span id = "cb5-50" > < a href = "#cb5-50" > < / a > < / span >
< span id = "cb5-51" > < a href = "#cb5-51" > < / a > app < span class = "op" > =< / span > gtk_application_new < span class = "op" > (< / span > < span class = "st" > " com.github.ToshioCP.tfv3" < / span > < span class = "op" > ,< / span > G_APPLICATION_HANDLES_OPEN< span class = "op" > );< / span > < / span >
< span id = "cb5-52" > < a href = "#cb5-52" > < / a > g_signal_connect < span class = "op" > (< / span > app< span class = "op" > ,< / span > < span class = "st" > " activate" < / span > < span class = "op" > ,< / span > G_CALLBACK < span class = "op" > (< / span > app_activate< span class = "op" > ),< / span > NULL< span class = "op" > );< / span > < / span >
< span id = "cb5-53" > < a href = "#cb5-53" > < / a > g_signal_connect < span class = "op" > (< / span > app< span class = "op" > ,< / span > < span class = "st" > " open" < / span > < span class = "op" > ,< / span > G_CALLBACK < span class = "op" > (< / span > app_open< span class = "op" > ),< / span > NULL< span class = "op" > );< / span > < / span >
< span id = "cb5-54" > < a href = "#cb5-54" > < / a > stat < span class = "op" > =< / span > g_application_run < span class = "op" > (< / span > G_APPLICATION < span class = "op" > (< / span > app< span class = "op" > ),< / span > argc< span class = "op" > ,< / span > argv< span class = "op" > );< / span > < / span >
< span id = "cb5-55" > < a href = "#cb5-55" > < / a > g_object_unref < span class = "op" > (< / span > app< span class = "op" > );< / span > < / span >
< span id = "cb5-56" > < a href = "#cb5-56" > < / a > < span class = "cf" > return< / span > stat< span class = "op" > ;< / span > < / span >
< span id = "cb5-57" > < a href = "#cb5-57" > < / a > < span class = "op" > }< / span > < / span > < / code > < / pre > < / div >
< p > Save it as < code > tfv3.c< / code > . If you’
the file is < code > src/tfv/tfv3.c< / code > . Compile and run it.< / p >
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< pre > < code > $ comp tfv3
$ ./a.out tfv3.c< / code > < / pre >
< figure >
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< img src = "image/screenshot_tfv3.png" alt = "File viewer" / >
< figcaption aria-hidden = "true" > File viewer< / figcaption >
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< / figure >
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< p > The function < code > main< / code > has only two changes from the previous
version.< / p >
< ul >
< li > < code > G_APPLICATION_DEFAULT_FLAGS< / code > is replaced by
< code > G_APPLICATION_HANDLES_OPEN< / code > < / li >
< li > < code > g_signal_connect (app, "open", G_CALLBACK (app_open), NULL)< / code >
is added.< / li >
< / ul >
< p > When the flag < code > G_APPLICATION_HANDLES_OPEN< / code > is given to
< code > gtk_application_new< / code > function, the application behaves like
this:< / p >
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< ul >
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< li > If the application is run without command line arguments, it emits
“activate” signal when it is activated.< / li >
< li > If the application is run with command line arguments, it emits
“open” signal when it is activated.< / li >
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< / ul >
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< p > The handler < code > app_activate< / code > becomes very simple. It just
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outputs an error message and returns to the caller. Then the application
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quits immediately because no window is created.< / p >
< p > The main work is done in the handler < code > app_open< / code > .< / p >
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< ul >
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< li > Creates GtkApplicationWindow, GtkScrolledWindow, GtkTextView and
GtkTextBuffer and connects them together< / li >
< li > Sets wrap mode to < code > GTK_WRAP_WORD_CHAR< / code > in
GtktextView< / li >
< li > Sets GtkTextView to non-editable because the program isn’
but only a viewer< / li >
< li > Reads the file and inserts the text into GtkTextBuffer (this will be
explained later)< / li >
< li > If the file is not opened, outputs an error message and destroys the
window. This makes the application quit.< / li >
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< / ul >
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< p > The following is the file reading part of the program.< / p >
< div class = "sourceCode" id = "cb7" > < pre class = "sourceCode c" > < code class = "sourceCode c" > < span id = "cb7-1" > < a href = "#cb7-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "cf" > if< / span > < span class = "op" > (< / span > g_file_load_contents < span class = "op" > (< / span > files< span class = "op" > [< / span > < span class = "dv" > 0< / span > < span class = "op" > ],< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > contents< span class = "op" > ,< / span > < span class = "op" > & < / span > length< span class = "op" > ,< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > err< span class = "op" > ))< / span > < span class = "op" > {< / span > < / span >
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< span id = "cb7-2" > < a href = "#cb7-2" aria-hidden = "true" tabindex = "-1" > < / a > gtk_text_buffer_set_text < span class = "op" > (< / span > tb< span class = "op" > ,< / span > contents< span class = "op" > ,< / span > length< span class = "op" > );< / span > < / span >
< span id = "cb7-3" > < a href = "#cb7-3" aria-hidden = "true" tabindex = "-1" > < / a > g_free < span class = "op" > (< / span > contents< span class = "op" > );< / span > < / span >
< span id = "cb7-4" > < a href = "#cb7-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "cf" > if< / span > < span class = "op" > ((< / span > filename < span class = "op" > =< / span > g_file_get_basename < span class = "op" > (< / span > files< span class = "op" > [< / span > < span class = "dv" > 0< / span > < span class = "op" > ]))< / span > < span class = "op" > !=< / span > NULL< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb7-5" > < a href = "#cb7-5" aria-hidden = "true" tabindex = "-1" > < / a > gtk_window_set_title < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb7-6" > < a href = "#cb7-6" aria-hidden = "true" tabindex = "-1" > < / a > g_free < span class = "op" > (< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb7-7" > < a href = "#cb7-7" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "op" > }< / span > < / span >
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< span id = "cb7-8" > < a href = "#cb7-8" aria-hidden = "true" tabindex = "-1" > < / a > gtk_window_present < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
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< span id = "cb7-9" > < a href = "#cb7-9" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "op" > }< / span > < span class = "cf" > else< / span > < span class = "op" > {< / span > < / span >
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< span id = "cb7-10" > < a href = "#cb7-10" aria-hidden = "true" tabindex = "-1" > < / a > g_printerr < span class = "op" > (< / span > < span class = "st" > " %s.< / span > < span class = "sc" > \n< / span > < span class = "st" > " < / span > < span class = "op" > ,< / span > err< span class = "op" > -> < / span > message< span class = "op" > );< / span > < / span >
< span id = "cb7-11" > < a href = "#cb7-11" aria-hidden = "true" tabindex = "-1" > < / a > g_error_free < span class = "op" > (< / span > err< span class = "op" > );< / span > < / span >
< span id = "cb7-12" > < a href = "#cb7-12" aria-hidden = "true" tabindex = "-1" > < / a > gtk_window_destroy < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
< span id = "cb7-13" > < a href = "#cb7-13" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "op" > }< / span > < / span > < / code > < / pre > < / div >
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< p > The function < code > g_file_load_contents< / code > loads the file
contents into a temporary buffer, which is automatically allocated and
sets < code > contents< / code > to point the buffer. The length of the buffer
is assigned to < code > length< / code > . It returns < code > TRUE< / code > if the
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file’
< code > FALSE< / code > and sets the variable < code > err< / code > to point a
newly created GError structure. The caller takes ownership of the GError
structure and is responsible for freeing it. If you want to know the
details about g_file_load_contents, see < a
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href="https://docs.gtk.org/gio/method.File.load_contents.html">g file
load contents< / a > .< / p >
< p > If it has successfully read the file, it inserts the contents into
GtkTextBuffer, frees the temporary buffer pointed by
< code > contents< / code > , sets the title of the window, frees the memories
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pointed by < code > filename< / code > and then shows the window.< / p >
< p > If it fails, < code > g_file_load_contents< / code > sets < code > err< / code >
to point a newly created GError structure. The structure is:< / p >
< div class = "sourceCode" id = "cb8" > < pre class = "sourceCode c" > < code class = "sourceCode c" > < span id = "cb8-1" > < a href = "#cb8-1" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "kw" > struct< / span > GError < span class = "op" > {< / span > < / span >
< span id = "cb8-2" > < a href = "#cb8-2" aria-hidden = "true" tabindex = "-1" > < / a > GQuark domain< span class = "op" > ;< / span > < / span >
< span id = "cb8-3" > < a href = "#cb8-3" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "dt" > int< / span > code< span class = "op" > ;< / span > < / span >
< span id = "cb8-4" > < a href = "#cb8-4" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "dt" > char< / span > < span class = "op" > *< / span > message< span class = "op" > ;< / span > < / span >
< span id = "cb8-5" > < a href = "#cb8-5" aria-hidden = "true" tabindex = "-1" > < / a > < span class = "op" > }< / span > < / span > < / code > < / pre > < / div >
< p > The < code > message< / code > member is used most often. It points an
error message. A function < code > g_error_free< / code > is used to free the
memory of the structure. See < a
href="https://docs.gtk.org/glib/struct.Error.html">GError< / a > .< / p >
< p > The program above outputs an error message, frees < code > err< / code >
and destroys the window and finally make the program quit.< / p >
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< h2 id = "gtknotebook" > GtkNotebook< / h2 >
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< p > GtkNotebook is a container widget that contains multiple widgets with
tabs. It shows only one child at a time. Another child will be shown
when its tab is clicked.< / p >
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< figure >
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< img src = "image/screenshot_gtk_notebook.png" alt = "GtkNotebook" / >
< figcaption aria-hidden = "true" > GtkNotebook< / figcaption >
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< / figure >
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< p > The left image is the window at the startup. The file
< code > pr1.c< / code > is shown and its filename is in the left tab. After
clicking on the right tab, the contents of the file < code > tfv1.c< / code >
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is shown (the right image).< / p >
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< p > The following is < code > tfv4.c< / code > . It has GtkNoteBook widget. It
is inserted as a child of GtkApplicationWindow and contains multiple
GtkScrolledWindow.< / p >
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< div class = "sourceCode" id = "cb9" > < pre
class="sourceCode numberSource C numberLines">< code class = "sourceCode c" > < span id = "cb9-1" > < a href = "#cb9-1" > < / a > < span class = "pp" > #include < / span > < span class = "im" > < gtk/gtk.h> < / span > < / span >
< span id = "cb9-2" > < a href = "#cb9-2" > < / a > < / span >
< span id = "cb9-3" > < a href = "#cb9-3" > < / a > < span class = "dt" > static< / span > < span class = "dt" > void< / span > < / span >
< span id = "cb9-4" > < a href = "#cb9-4" > < / a > app_activate < span class = "op" > (< / span > GApplication < span class = "op" > *< / span > app< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-5" > < a href = "#cb9-5" > < / a > g_printerr < span class = "op" > (< / span > < span class = "st" > " You need filename arguments.< / span > < span class = "sc" > \n< / span > < span class = "st" > " < / span > < span class = "op" > );< / span > < / span >
< span id = "cb9-6" > < a href = "#cb9-6" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb9-7" > < a href = "#cb9-7" > < / a > < / span >
< span id = "cb9-8" > < a href = "#cb9-8" > < / a > < span class = "dt" > static< / span > < span class = "dt" > void< / span > < / span >
< span id = "cb9-9" > < a href = "#cb9-9" > < / a > app_open < span class = "op" > (< / span > GApplication < span class = "op" > *< / span > app< span class = "op" > ,< / span > GFile < span class = "op" > **< / span > files< span class = "op" > ,< / span > gint n_files< span class = "op" > ,< / span > gchar < span class = "op" > *< / span > hint< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-10" > < a href = "#cb9-10" > < / a > GtkWidget < span class = "op" > *< / span > win< span class = "op" > ;< / span > < / span >
< span id = "cb9-11" > < a href = "#cb9-11" > < / a > GtkWidget < span class = "op" > *< / span > nb< span class = "op" > ;< / span > < / span >
< span id = "cb9-12" > < a href = "#cb9-12" > < / a > GtkWidget < span class = "op" > *< / span > lab< span class = "op" > ;< / span > < / span >
< span id = "cb9-13" > < a href = "#cb9-13" > < / a > GtkNotebookPage < span class = "op" > *< / span > nbp< span class = "op" > ;< / span > < / span >
< span id = "cb9-14" > < a href = "#cb9-14" > < / a > GtkWidget < span class = "op" > *< / span > scr< span class = "op" > ;< / span > < / span >
< span id = "cb9-15" > < a href = "#cb9-15" > < / a > GtkWidget < span class = "op" > *< / span > tv< span class = "op" > ;< / span > < / span >
< span id = "cb9-16" > < a href = "#cb9-16" > < / a > GtkTextBuffer < span class = "op" > *< / span > tb< span class = "op" > ;< / span > < / span >
< span id = "cb9-17" > < a href = "#cb9-17" > < / a > < span class = "dt" > char< / span > < span class = "op" > *< / span > contents< span class = "op" > ;< / span > < / span >
< span id = "cb9-18" > < a href = "#cb9-18" > < / a > gsize length< span class = "op" > ;< / span > < / span >
< span id = "cb9-19" > < a href = "#cb9-19" > < / a > < span class = "dt" > char< / span > < span class = "op" > *< / span > filename< span class = "op" > ;< / span > < / span >
< span id = "cb9-20" > < a href = "#cb9-20" > < / a > < span class = "dt" > int< / span > i< span class = "op" > ;< / span > < / span >
< span id = "cb9-21" > < a href = "#cb9-21" > < / a > GError < span class = "op" > *< / span > err < span class = "op" > =< / span > NULL< span class = "op" > ;< / span > < / span >
< span id = "cb9-22" > < a href = "#cb9-22" > < / a > < / span >
< span id = "cb9-23" > < a href = "#cb9-23" > < / a > win < span class = "op" > =< / span > gtk_application_window_new < span class = "op" > (< / span > GTK_APPLICATION < span class = "op" > (< / span > app< span class = "op" > ));< / span > < / span >
< span id = "cb9-24" > < a href = "#cb9-24" > < / a > gtk_window_set_title < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > < span class = "st" > " file viewer" < / span > < span class = "op" > );< / span > < / span >
< span id = "cb9-25" > < a href = "#cb9-25" > < / a > gtk_window_set_default_size < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > < span class = "dv" > 600< / span > < span class = "op" > ,< / span > < span class = "dv" > 400< / span > < span class = "op" > );< / span > < / span >
< span id = "cb9-26" > < a href = "#cb9-26" > < / a > nb < span class = "op" > =< / span > gtk_notebook_new < span class = "op" > ();< / span > < / span >
< span id = "cb9-27" > < a href = "#cb9-27" > < / a > gtk_window_set_child < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ),< / span > nb< span class = "op" > );< / span > < / span >
< span id = "cb9-28" > < a href = "#cb9-28" > < / a > < / span >
< span id = "cb9-29" > < a href = "#cb9-29" > < / a > < span class = "cf" > for< / span > < span class = "op" > (< / span > i < span class = "op" > =< / span > < span class = "dv" > 0< / span > < span class = "op" > ;< / span > i < span class = "op" > < < / span > n_files< span class = "op" > ;< / span > i< span class = "op" > ++)< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-30" > < a href = "#cb9-30" > < / a > < span class = "cf" > if< / span > < span class = "op" > (< / span > g_file_load_contents < span class = "op" > (< / span > files< span class = "op" > [< / span > i< span class = "op" > ],< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > contents< span class = "op" > ,< / span > < span class = "op" > & < / span > length< span class = "op" > ,< / span > NULL< span class = "op" > ,< / span > < span class = "op" > & < / span > err< span class = "op" > ))< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-31" > < a href = "#cb9-31" > < / a > scr < span class = "op" > =< / span > gtk_scrolled_window_new < span class = "op" > ();< / span > < / span >
< span id = "cb9-32" > < a href = "#cb9-32" > < / a > tv < span class = "op" > =< / span > gtk_text_view_new < span class = "op" > ();< / span > < / span >
< span id = "cb9-33" > < a href = "#cb9-33" > < / a > tb < span class = "op" > =< / span > gtk_text_view_get_buffer < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ));< / span > < / span >
< span id = "cb9-34" > < a href = "#cb9-34" > < / a > gtk_text_view_set_wrap_mode < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ),< / span > GTK_WRAP_WORD_CHAR< span class = "op" > );< / span > < / span >
< span id = "cb9-35" > < a href = "#cb9-35" > < / a > gtk_text_view_set_editable < span class = "op" > (< / span > GTK_TEXT_VIEW < span class = "op" > (< / span > tv< span class = "op" > ),< / span > FALSE< span class = "op" > );< / span > < / span >
< span id = "cb9-36" > < a href = "#cb9-36" > < / a > gtk_scrolled_window_set_child < span class = "op" > (< / span > GTK_SCROLLED_WINDOW < span class = "op" > (< / span > scr< span class = "op" > ),< / span > tv< span class = "op" > );< / span > < / span >
< span id = "cb9-37" > < a href = "#cb9-37" > < / a > < / span >
< span id = "cb9-38" > < a href = "#cb9-38" > < / a > gtk_text_buffer_set_text < span class = "op" > (< / span > tb< span class = "op" > ,< / span > contents< span class = "op" > ,< / span > length< span class = "op" > );< / span > < / span >
< span id = "cb9-39" > < a href = "#cb9-39" > < / a > g_free < span class = "op" > (< / span > contents< span class = "op" > );< / span > < / span >
< span id = "cb9-40" > < a href = "#cb9-40" > < / a > < span class = "cf" > if< / span > < span class = "op" > ((< / span > filename < span class = "op" > =< / span > g_file_get_basename < span class = "op" > (< / span > files< span class = "op" > [< / span > i< span class = "op" > ]))< / span > < span class = "op" > !=< / span > NULL< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-41" > < a href = "#cb9-41" > < / a > lab < span class = "op" > =< / span > gtk_label_new < span class = "op" > (< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb9-42" > < a href = "#cb9-42" > < / a > g_free < span class = "op" > (< / span > filename< span class = "op" > );< / span > < / span >
< span id = "cb9-43" > < a href = "#cb9-43" > < / a > < span class = "op" > }< / span > < span class = "cf" > else< / span > < / span >
< span id = "cb9-44" > < a href = "#cb9-44" > < / a > lab < span class = "op" > =< / span > gtk_label_new < span class = "op" > (< / span > < span class = "st" > " " < / span > < span class = "op" > );< / span > < / span >
< span id = "cb9-45" > < a href = "#cb9-45" > < / a > gtk_notebook_append_page < span class = "op" > (< / span > GTK_NOTEBOOK < span class = "op" > (< / span > nb< span class = "op" > ),< / span > scr< span class = "op" > ,< / span > lab< span class = "op" > );< / span > < / span >
< span id = "cb9-46" > < a href = "#cb9-46" > < / a > nbp < span class = "op" > =< / span > gtk_notebook_get_page < span class = "op" > (< / span > GTK_NOTEBOOK < span class = "op" > (< / span > nb< span class = "op" > ),< / span > scr< span class = "op" > );< / span > < / span >
< span id = "cb9-47" > < a href = "#cb9-47" > < / a > g_object_set < span class = "op" > (< / span > nbp< span class = "op" > ,< / span > < span class = "st" > " tab-expand" < / span > < span class = "op" > ,< / span > TRUE< span class = "op" > ,< / span > NULL< span class = "op" > );< / span > < / span >
< span id = "cb9-48" > < a href = "#cb9-48" > < / a > < span class = "op" > }< / span > < span class = "cf" > else< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-49" > < a href = "#cb9-49" > < / a > g_printerr < span class = "op" > (< / span > < span class = "st" > " %s.< / span > < span class = "sc" > \n< / span > < span class = "st" > " < / span > < span class = "op" > ,< / span > err< span class = "op" > -> < / span > message< span class = "op" > );< / span > < / span >
< span id = "cb9-50" > < a href = "#cb9-50" > < / a > g_clear_error < span class = "op" > (& < / span > err< span class = "op" > );< / span > < / span >
< span id = "cb9-51" > < a href = "#cb9-51" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb9-52" > < a href = "#cb9-52" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb9-53" > < a href = "#cb9-53" > < / a > < span class = "cf" > if< / span > < span class = "op" > (< / span > gtk_notebook_get_n_pages < span class = "op" > (< / span > GTK_NOTEBOOK < span class = "op" > (< / span > nb< span class = "op" > ))< / span > < span class = "op" > > < / span > < span class = "dv" > 0< / span > < span class = "op" > )< / span > < / span >
< span id = "cb9-54" > < a href = "#cb9-54" > < / a > gtk_window_present < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
< span id = "cb9-55" > < a href = "#cb9-55" > < / a > < span class = "cf" > else< / span > < / span >
< span id = "cb9-56" > < a href = "#cb9-56" > < / a > gtk_window_destroy < span class = "op" > (< / span > GTK_WINDOW < span class = "op" > (< / span > win< span class = "op" > ));< / span > < / span >
< span id = "cb9-57" > < a href = "#cb9-57" > < / a > < span class = "op" > }< / span > < / span >
< span id = "cb9-58" > < a href = "#cb9-58" > < / a > < / span >
< span id = "cb9-59" > < a href = "#cb9-59" > < / a > < span class = "dt" > int< / span > < / span >
< span id = "cb9-60" > < a href = "#cb9-60" > < / a > main < span class = "op" > (< / span > < span class = "dt" > int< / span > argc< span class = "op" > ,< / span > < span class = "dt" > char< / span > < span class = "op" > **< / span > argv< span class = "op" > )< / span > < span class = "op" > {< / span > < / span >
< span id = "cb9-61" > < a href = "#cb9-61" > < / a > GtkApplication < span class = "op" > *< / span > app< span class = "op" > ;< / span > < / span >
< span id = "cb9-62" > < a href = "#cb9-62" > < / a > < span class = "dt" > int< / span > stat< span class = "op" > ;< / span > < / span >
< span id = "cb9-63" > < a href = "#cb9-63" > < / a > < / span >
< span id = "cb9-64" > < a href = "#cb9-64" > < / a > app < span class = "op" > =< / span > gtk_application_new < span class = "op" > (< / span > < span class = "st" > " com.github.ToshioCP.tfv4" < / span > < span class = "op" > ,< / span > G_APPLICATION_HANDLES_OPEN< span class = "op" > );< / span > < / span >
< span id = "cb9-65" > < a href = "#cb9-65" > < / a > g_signal_connect < span class = "op" > (< / span > app< span class = "op" > ,< / span > < span class = "st" > " activate" < / span > < span class = "op" > ,< / span > G_CALLBACK < span class = "op" > (< / span > app_activate< span class = "op" > ),< / span > NULL< span class = "op" > );< / span > < / span >
< span id = "cb9-66" > < a href = "#cb9-66" > < / a > g_signal_connect < span class = "op" > (< / span > app< span class = "op" > ,< / span > < span class = "st" > " open" < / span > < span class = "op" > ,< / span > G_CALLBACK < span class = "op" > (< / span > app_open< span class = "op" > ),< / span > NULL< span class = "op" > );< / span > < / span >
< span id = "cb9-67" > < a href = "#cb9-67" > < / a > stat < span class = "op" > =< / span > g_application_run < span class = "op" > (< / span > G_APPLICATION < span class = "op" > (< / span > app< span class = "op" > ),< / span > argc< span class = "op" > ,< / span > argv< span class = "op" > );< / span > < / span >
< span id = "cb9-68" > < a href = "#cb9-68" > < / a > g_object_unref < span class = "op" > (< / span > app< span class = "op" > );< / span > < / span >
< span id = "cb9-69" > < a href = "#cb9-69" > < / a > < span class = "cf" > return< / span > stat< span class = "op" > ;< / span > < / span >
< span id = "cb9-70" > < a href = "#cb9-70" > < / a > < span class = "op" > }< / span > < / span > < / code > < / pre > < / div >
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< p > Most of the changes are in the function < code > app_open< / code > . The
numbers at the left of the following items are line numbers in the
source code.< / p >
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< ul >
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< li > 11-13: Variables < code > nb< / code > , < code > lab< / code > and
< code > nbp< / code > are defined. They point GtkNotebook, GtkLabel and
GtkNotebookPage respectively.< / li >
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< li > 24: The window’ < / li >
< li > 25: The default size of the window is 600x400.< / li >
< li > 26-27: GtkNotebook is created and inserted to the
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GtkApplicationWindow as a child.< / li >
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< li > 29-57: For-loop. The variable < code > files[i]< / code > points i-th
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GFile, which is created by the GtkApplication from the i-th command line
argument.< / li >
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< li > 31-36: GtkScrollledWindow, GtkTextView are created. GtkTextBuffer is
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got from the GtkTextView. The GtkTextView is connected to the
GtkScrolledWindow as a child.< / li >
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< li > 38-39: inserts the contents of the file into GtkTextBuffer and frees
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the memory pointed by < code > contents< / code > .< / li >
< li > 40-42: If the filename is taken from the GFile, GtkLabel is created
with the filename. The string < code > filename< / code > is freed..< / li >
< li > 43-44: If it fails to take the filename, empty string GtkLabel is
created.< / li >
< li > 45-46: Appends a GtkScrolledWindow to the GtkNotebook as a child.
And the GtkLabel is set as the child’
GtkNoteBookPage is created automatically. The function
< code > gtk_notebook_get_page< / code > returns the GtkNotebookPage of the
child (GtkScrolledWindow).< / li >
< li > 47: GtkNotebookPage has “tab-expand” property. If it is set to TRUE
then the tab expands horizontally as long as possible. If it is FALSE,
then the width of the tab is determined by the size of the label.
< code > g_object_set< / code > is a general function to set properties of
objects. See < a
href="https://docs.gtk.org/gobject/method.Object.set.html">GObject API
Reference – < / a > .< / li >
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< li > 48-50: If it fails to read the file, the error message is shown. The
function < code > g_clear_error (& err)< / code > works like
< code > g_error_free (err); err = NULL< / code > .< / li >
< li > 53-56: If at least one page exists, the window is shown. Otherwise,
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the window is destroyed and the application quits.< / li >
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< / ul >
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< / div >
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