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172 lines
6 KiB
Markdown
172 lines
6 KiB
Markdown
Up: [Readme.md](../Readme.md), Prev: [Section 4](sec4.md), Next: [Section 6](sec6.md)
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# Widgets (2)
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## GtkTextView, GtkTextbuffer and GtkScrolledWindow
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### GtkTextView and GtkTextBuffer
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GtkTextview is a widget for multi-line text editing.
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GtkTextBuffer is a text buffer which is connected to GtkTextView.
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See the sample program `tfv1.c` below.
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~~~C
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1 #include <gtk/gtk.h>
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2
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3 static void
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4 app_activate (GApplication *app, gpointer user_data) {
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5 GtkWidget *win;
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6 GtkWidget *tv;
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7 GtkTextBuffer *tb;
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8 gchar *text;
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9
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10 text =
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11 "Once upon a time, there was an old man who was called Taketori-no-Okina. "
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12 "It is a japanese word that means a man whose work is making bamboo baskets.\n"
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13 "One day, he went into a mountain and found a shining bamboo. "
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14 "\"What a mysterious bamboo it is!,\" he said. "
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15 "He cut it, then there was a small cute baby girl in it. "
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16 "The girl was shining faintly. "
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17 "He thought this baby girl is a gift from Heaven and took her home.\n"
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18 "His wife was surprized at his tale. "
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19 "They were very happy because they had no children. "
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20 ;
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21 win = gtk_application_window_new (GTK_APPLICATION (app));
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22 gtk_window_set_title (GTK_WINDOW (win), "Taketori");
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23 gtk_window_set_default_size (GTK_WINDOW (win), 400, 300);
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24
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25 tv = gtk_text_view_new ();
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26 tb = gtk_text_view_get_buffer (GTK_TEXT_VIEW (tv));
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27 gtk_text_buffer_set_text (tb, text, -1);
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28 gtk_text_view_set_wrap_mode (GTK_TEXT_VIEW (tv), GTK_WRAP_WORD_CHAR);
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29
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30 gtk_window_set_child (GTK_WINDOW (win), tv);
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31
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32 gtk_widget_show (win);
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33 }
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34
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35 int
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36 main (int argc, char **argv) {
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37 GtkApplication *app;
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38 int stat;
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39
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40 app = gtk_application_new ("com.github.ToshioCP.tfv1", G_APPLICATION_FLAGS_NONE);
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41 g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);
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42 stat = g_application_run (G_APPLICATION (app), argc, argv);
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43 g_object_unref (app);
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44 return stat;
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45 }
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~~~
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Look at line 25.
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A GtkTextView instance is created and its pointer is assigned to `tv`.
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When the GtkTextView instance is created, a GtkTextBuffer instance is also created and connected to the GtkTextView automatically.
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"GtkTextBuffer instance" will be referred to simply as "GtkTextBuffer" or "buffer".
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In the next line, the pointer to the buffer is got and assigned to `tb`.
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Then, the text from line 10 to 20 is assigned to the buffer.
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GtkTextView has a wrap mode.
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When it is set to `GTK_WRAP_WORD_CHAR`, text wraps in between words, or if that is not enough, also between graphemes.
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In line 30, `tv` is added to `win` as a child.
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Now compile and run it.
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There's an I-beam pointer in the window.
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You can add or delete any characters on the GtkTextview,
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and your changes are kept in the GtkTextBuffer.
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If you add more characters beyond the limit of the window, the height increases and the window extends.
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If the height gets bigger than the height of the display screen, you won't be
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able to control the size of the window, and change it back to the original size.
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This is a problem and shows that there is a bug in our program.
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This can solve it by adding a GtkScrolledWindow between the GtkApplicationWindow and GtkTextView.
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### GtkScrolledWindow
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What we need to do is:
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- Create a GtkScrolledWindow and insert it as a child of the GtkApplicationWindow; and
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- Insert the GtkTextView widget to the GtkScrolledWindow as a child.
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Modify `tfv1.c` and save it as `tfv2.c`.
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The difference between these two files is small.
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~~~
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$ cd tfv; diff tfv1.c tfv2.c
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5a6
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> GtkWidget *scr;
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24a26,28
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> scr = gtk_scrolled_window_new ();
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> gtk_window_set_child (GTK_WINDOW (win), scr);
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>
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30c34
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< gtk_window_set_child (GTK_WINDOW (win), tv);
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---
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> gtk_scrolled_window_set_child (GTK_SCROLLED_WINDOW (scr), tv);
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40c44
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< app = gtk_application_new ("com.github.ToshioCP.tfv1", G_APPLICATION_FLAGS_NONE);
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---
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> app = gtk_application_new ("com.github.ToshioCP.tfv2", G_APPLICATION_FLAGS_NONE);
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~~~
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Here is the complete code of `tfv2.c`.
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~~~C
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1 #include <gtk/gtk.h>
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2
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3 static void
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4 app_activate (GApplication *app, gpointer user_data) {
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5 GtkWidget *win;
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6 GtkWidget *scr;
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7 GtkWidget *tv;
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8 GtkTextBuffer *tb;
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9 gchar *text;
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10
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11 text =
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12 "Once upon a time, there was an old man who was called Taketori-no-Okina. "
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13 "It is a japanese word that means a man whose work is making bamboo baskets.\n"
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14 "One day, he went into a mountain and found a shining bamboo. "
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15 "\"What a mysterious bamboo it is!,\" he said. "
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16 "He cut it, then there was a small cute baby girl in it. "
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17 "The girl was shining faintly. "
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18 "He thought this baby girl is a gift from Heaven and took her home.\n"
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19 "His wife was surprized at his tale. "
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20 "They were very happy because they had no children. "
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21 ;
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22 win = gtk_application_window_new (GTK_APPLICATION (app));
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23 gtk_window_set_title (GTK_WINDOW (win), "Taketori");
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24 gtk_window_set_default_size (GTK_WINDOW (win), 400, 300);
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25
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26 scr = gtk_scrolled_window_new ();
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27 gtk_window_set_child (GTK_WINDOW (win), scr);
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28
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29 tv = gtk_text_view_new ();
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30 tb = gtk_text_view_get_buffer (GTK_TEXT_VIEW (tv));
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31 gtk_text_buffer_set_text (tb, text, -1);
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32 gtk_text_view_set_wrap_mode (GTK_TEXT_VIEW (tv), GTK_WRAP_WORD_CHAR);
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33
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34 gtk_scrolled_window_set_child (GTK_SCROLLED_WINDOW (scr), tv);
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35
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36 gtk_widget_show (win);
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37 }
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38
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39 int
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40 main (int argc, char **argv) {
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41 GtkApplication *app;
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42 int stat;
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43
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44 app = gtk_application_new ("com.github.ToshioCP.tfv2", G_APPLICATION_FLAGS_NONE);
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45 g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);
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46 stat = g_application_run (G_APPLICATION (app), argc, argv);
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47 g_object_unref (app);
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48 return stat;
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49 }
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~~~
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Compile and run it.
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Notice how this time the window doesn't extend when you type a lot of characters,
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it just scrolls and displays a slider.
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Up: [Readme.md](../Readme.md), Prev: [Section 4](sec4.md), Next: [Section 6](sec6.md)
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