Functions in GtkNotebook

GtkNotebook is a very important object in the text file editor tfe. It connects the application and TfeTextView objects. A set of public functions are declared in tfenotebook.h. The name “tfenotebook” is used only for filenames; no “TfeNotebook” object type is defined. There’s no “TfeNotebook” object.

The source files are in the directory src/tfe5. You can get them by downloading the repository.

void
notebook_page_save(GtkNotebook *nb);

void
notebook_page_close (GtkNotebook *nb);

void
notebook_page_open (GtkNotebook *nb);

void
notebook_page_new_with_file (GtkNotebook *nb, GFile *file);

void
notebook_page_new (GtkNotebook *nb);

This header file describes the public functions in tfenotebook.c.

  • 1-2: notebook_page_save saves the current page to the file with the name specified in the tab.” If the name is untitled or untitled followed by digits, a file chooser dialog appears and a user can choose or specify a filename.
  • 4-5: notebook_page_close closes the current page.
  • 7-8: notebook_page_open shows a file chooser dialog and a user can choose a file. The contents of the file is inserted to a new page.
  • 10-11: notebook_page_new_with_file creates a new page and a file given as an argument is read and inserted into the page.
  • 13-14: notebook_page_new creates a new empty page.

You probably find that the functions except notebook_page_close are higher level functions of

  • tfe_text_view_save
  • tef_text_view_open
  • tfe_text_view_new_with_file
  • tfe_text_view_new

respectively.

There are two layers. One of them is tfe_text_view ..., which is the lower level layer. The other is notebook ..., which is the higher level layer.

Now let’s look at the program of each function.

notebook_page_new

static char *
get_untitled () {
  static int c = -1;
  if (++c == 0) 
    return g_strdup_printf("Untitled");
  else
    return g_strdup_printf ("Untitled%u", c);
}

static void
notebook_page_build (GtkNotebook *nb, GtkWidget *tv, const char *filename) {
  GtkWidget *scr = gtk_scrolled_window_new ();
  GtkNotebookPage *nbp;
  GtkWidget *lab;
  int i;

  gtk_scrolled_window_set_child (GTK_SCROLLED_WINDOW (scr), tv);
  lab = gtk_label_new (filename);
  i = gtk_notebook_append_page (nb, scr, lab);
  nbp = gtk_notebook_get_page (nb, scr);
  g_object_set (nbp, "tab-expand", TRUE, NULL);
  gtk_notebook_set_current_page (nb, i);
  g_signal_connect (GTK_TEXT_VIEW (tv), "change-file", G_CALLBACK (file_changed_cb), nb);
}

void
notebook_page_new (GtkNotebook *nb) {
  g_return_if_fail(GTK_IS_NOTEBOOK (nb));

  GtkWidget *tv;
  char *filename;

  tv = tfe_text_view_new ();
  filename = get_untitled ();
  notebook_page_build (nb, tv, filename);
  g_free (filename);
}
  • 26-37: The function notebook_page_new.
  • 28: The function g_return_if_fail checks the argument. It’s necessary because the function is public.
  • 33: Creates TfeTextView object.
  • 34: Creates filename, which is “Untitled”, “Untitled1”, … .
  • 1-8: The function get_untitled.
  • 3: Static variable c is initialized at the first call of this function. After that c keeps its value unless it is changed explicitly.
  • 4-7: Increases c by one and if it is zero, it returns “Untitled”. If it is a positive integer, it returns “Untitled<the integer>”, for example, “Untitled1”, “Untitled2”, and so on. The function g_strdup_printf creates a string and it should be freed by g_free when it becomes useless. The caller of get_untitled is in charge of freeing the string.
  • 36: Calls notebook_page_build to build a new page.
  • 37: Frees filename.
  • 10- 24: The function notebook_page_build. A parameter with the const qualifier cannot be modified within the function. It means that the argument filename is owned by the caller. The caller is responsible for freeing it when it is no longer needed.
  • 12: Creates GtkScrolledWindow.
  • 17: Inserts tv to GtkScrolledWindow as a child.
  • 18-19: Creates GtkLabel, then appends scr and lab to the GtkNotebook instance nb.
  • 20-21: Sets “tab-expand” property to TRUE. The function g_object_set sets properties on an object. The object can be any object derived from GObject. In many cases, an object has its own function to set its properties, but sometimes does not. In that case, use g_object_set to set the property.
  • 22: Sets the current page to the newly created page.
  • 23: Connects “change-file” signal and the handler file_changed_cb.

notebook_page_new_with_file

void
notebook_page_new_with_file (GtkNotebook *nb, GFile *file) {
  g_return_if_fail(GTK_IS_NOTEBOOK (nb));
  g_return_if_fail(G_IS_FILE (file));

  GtkWidget *tv;
  char *filename;

  if ((tv = tfe_text_view_new_with_file (file)) == NULL)
    return; /* read error */
  filename = g_file_get_basename (file);
  notebook_page_build (nb, tv, filename);
  g_free (filename);
}
  • 9-10: Calls tfe_text_view_new_with_file. If the function returns NULL, an error has happened. Then, it does nothing and returns.
  • 11-13: Gets the filename, builds a new page and frees filename.

notebook_page_open

static void
open_response_cb (TfeTextView *tv, int response, GtkNotebook *nb) {
  GFile *file;
  char *filename;

  if (response != TFE_OPEN_RESPONSE_SUCCESS) {
    g_object_ref_sink (tv);
    g_object_unref (tv);
  }else {
    file = tfe_text_view_get_file (tv);
    filename = g_file_get_basename (file);
    g_object_unref (file);
    notebook_page_build (nb, GTK_WIDGET (tv), filename);
    g_free (filename);
  }
}

void
notebook_page_open (GtkNotebook *nb) {
  g_return_if_fail(GTK_IS_NOTEBOOK (nb));

  GtkWidget *tv;

  tv = tfe_text_view_new ();
  g_signal_connect (TFE_TEXT_VIEW (tv), "open-response", G_CALLBACK (open_response_cb), nb);
  tfe_text_view_open (TFE_TEXT_VIEW (tv), GTK_WINDOW (gtk_widget_get_ancestor (GTK_WIDGET (nb), GTK_TYPE_WINDOW)));
}
  • 18-27: The function notebook_page_open.
  • 24: Creates TfeTextView object.
  • 25: Connects the signal “open-response” and the handler open_response_cb.
  • 26: Calls tfe_text_view_open. The “open-response” signal will be emitted later in this function to inform the result.
  • 1-16: The handler open_response_cb.
  • 6-8: If the response code is not TFE_OPEN_RESPONSE_SUCCESS, the instance tv will be destroyed. It has floating reference, which will be explained later. A floating reference needs to be converted into an ordinary reference before releasing it. The function g_object_ref_sink does that. After that, the function g_object_unref releases tv and decreases the reference count by one. Finally the reference count becomes zero and tv is destroyed.
  • 9-15: Otherwise, it builds a new page with tv.

Floating Reference

All the widgets are derived from GInitiallyUnowned. GObject and GInitiallyUnowned are almost the same. The difference is like this. When an instance of GInitiallyUnowned is created, the instance has a “floating reference”. On the other hand, when an instance of GObject (not GInitiallyUnowned) is created, it has “normal reference”. Their descendants inherits them, so every widget has a floating reference just after the creation. Non-widget class, for example, GtkTextBuffer is a direct sub class of GObject and it has normal reference.

The function g_object_ref_sink converts the floating reference into a normal reference. If the instance does not have a floating reference, g_object_ref_sink simply increases the reference count by one. It is used when an widget is added to another widget as a child.

GtkTextView *tv = gtk_text_view_new (); // Floating reference
GtkScrolledWindow *scr = gtk_scrolled_window_new ();
gtk_scrolled_window_set_child (scr, tv); // Scrolled window sinks the tv's floating reference and tv's reference count becomes one.

When tv is added to scr as a child, g_object_ref_sink is used.

g_object_ref_sink (tv);

So, the floating reference is converted into an ordinary reference. That is to say, floating reference is removed, and the normal reference count is one. Thanks to this, the caller does not need to decrease tv’s reference count. If an Object_A were not a descendant of GInitiallyUnowned, the program would be like this:

Object_A *obj_a = object_a_new (); // reference count is one
GtkScrolledWindow *scr = gtk_scrolled_window_new ();
gtk_scrolled_window_set_child (scr, obj_a); // obj_a's reference count is two
// obj_a is referred by the caller (this program) and scrolled window
g_object_unref (obj_a); // obj_a's reference count is one because the caller no longer refers obj_a.

This example tells us that the caller needs to unref obj_a.

If you use g_object_unref to an instance that has a floating reference, you need to convert the floating reference to a normal reference in advance. See GObject API reference for further information.

notebook_page_close

void
notebook_page_close (GtkNotebook *nb) {
  g_return_if_fail(GTK_IS_NOTEBOOK (nb));

  GtkWidget *win;
  int i;

  if (gtk_notebook_get_n_pages (nb) == 1) {
    win = gtk_widget_get_ancestor (GTK_WIDGET (nb), GTK_TYPE_WINDOW);
    gtk_window_destroy(GTK_WINDOW (win));
  } else {
    i = gtk_notebook_get_current_page (nb);
    gtk_notebook_remove_page (GTK_NOTEBOOK (nb), i);
  }
}

This function closes the current page. If the page is the only page the notebook has, then the function destroys the top-level window and quits the application.

  • 8-10: If the page is the only page the notebook has, it calls gtk_window_destroy to destroy the top-level window.
  • 11-13: Otherwise, removes the current page. The child widget (TfeTextView) is also destroyed.

notebook_page_save

static TfeTextView *
get_current_textview (GtkNotebook *nb) {
  int i;
  GtkWidget *scr;
  GtkWidget *tv;

  i = gtk_notebook_get_current_page (nb);
  scr = gtk_notebook_get_nth_page (nb, i);
  tv = gtk_scrolled_window_get_child (GTK_SCROLLED_WINDOW (scr));
  return TFE_TEXT_VIEW (tv);
}

void
notebook_page_save (GtkNotebook *nb) {
  g_return_if_fail(GTK_IS_NOTEBOOK (nb));

  TfeTextView *tv;

  tv = get_current_textview (nb);
  tfe_text_view_save (tv);
}
  • 13-21: notebook_page_save.
  • 19: Gets the TfeTextView instance belongs to the current page. The caller does not have the ownership of tv so you don’t need to care about the reference count of tv.
  • 20: Calls tfe_text_view_save.
  • 1-11: get_current_textview. This function gets the TfeTextView object belongs to the current page.
  • 7: Gets the page number of the current page.
  • 8: Gets the child widget scr, which is a GtkScrolledWindow instance, of the current page. The object scr is owned by the notebook nb.
  • 9-10: Gets the child widget of scr, which is a TfeTextView instance, and returns it. The returned instance is owned by scr.

file_changed_cb Handler

The function file_changed_cb is a handler connected to “change-file” signal. If a file in a TfeTextView instance is changed, the instance emits this signal. This handler changes the label of the GtkNotebookPage.

static void
file_changed_cb (TfeTextView *tv, GtkNotebook *nb) {
  GtkWidget *scr;
  GtkWidget *label;
  GFile *file;
  char *filename;

  file = tfe_text_view_get_file (tv);
  scr = gtk_widget_get_parent (GTK_WIDGET (tv));
  if (G_IS_FILE (file)) {
    filename = g_file_get_basename (file);
    g_object_unref (file);
  } else
    filename = get_untitled ();
  label = gtk_label_new (filename);
  g_free (filename);
  gtk_notebook_set_tab_label (nb, scr, label);
}
  • 8: Gets the GFile instance from tv.
  • 9: Gets the GkScrolledWindow instance which is the parent widget of tv.
  • 10-12: If file points to a GFile instance, the filename of the GFile is assigned to filename. Then, unref the GFile object file.
  • 13-14: Otherwise (file is NULL), a string Untitled(number) is assigned to filename.
  • 15-17: Creates a GtkLabel instance label with the filename and set the label of the GtkNotebookPage with label.