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Toshio Sekiya
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43
gfm/sec4.md
43
gfm/sec4.md
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@ -6,10 +6,10 @@ Up: [Readme.md](../Readme.md), Prev: [Section 3](sec3.md), Next: [Section 5](se
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### GtkLabel
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We made a window and show it on the screen in the previous section.
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Now we go on to the next topic, widgets in the window.
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In the previous section we made a window and displayed it on the screen.
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Now we go on to the next topic, where we add widgets to this window.
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The simplest widget is GtkLabel.
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It is a widget with a string in it.
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It is a widget with text in it.
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~~~C
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1 #include <gtk/gtk.h>
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@ -77,7 +77,7 @@ $ cd misc; diff pr4.c lb1.c
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This tells us:
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- The definition of a variable `lab` is added.
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- The definition of a new variable `lab` is added.
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- The title of the window is changed.
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- A label is created and connected to the window as a child.
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@ -89,20 +89,20 @@ But these two relationships are totally different.
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Don't be confused.
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In the program `lb1.c`, `lab` is a child widget of `win`.
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Child widgets are always located in their parent widget on the screen.
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See the window appeared on the screen.
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The window includes the label.
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See how the window has appeared on the screen.
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The application window includes the label.
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The window `win` doesn't have any parents.
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We call such a window top-level window.
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One application can have two or more top-level windows.
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An application can have more than one top-level window.
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### GtkButton
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Next widget is GtkButton.
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It has a label or icon on it.
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The next widget to introduce is GtkButton.
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It displays a button on the screen with a label or icon on it.
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In this subsection, we will make a button with a label.
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When a button is clicked on, it emits a "clicked" signal.
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The following program shows how to catch the signal and do something.
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When the button is clicked, it emits a "clicked" signal.
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The following program shows how to catch the signal to then do something.
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~~~C
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1 #include <gtk/gtk.h>
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@ -149,16 +149,16 @@ Finally, connects a "clicked" signal of the button to a handler (function) `clic
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So, if `btn` is clicked, the function `click_cb` is invoked.
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The suffix "cb" means "call back".
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Name the program `lb2.c` and save it.
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Name the program `lb2.c` and save it.
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Now compile and run it.
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A window with the button appears.
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Click the button (it is a large button, you can click everywhere in the window), then a string "Clicked." appears on the terminal.
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It shows the handler was invoked by clicking the button.
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It's fairly good for us to make sure that the clicked signal was caught and the handler was invoked.
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It's good that we make sure that the clicked signal was caught and the handler was invoked by using `g_print`.
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However, using g_print is out of harmony with Gtk which is a GUI library.
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So, we will change the handler.
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The following code is `lb3.c`.
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@ -216,17 +216,17 @@ $ cd misc; diff lb2.c lb3.c
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<
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~~~
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The change is:
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The changes are:
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- The function `g_print` in `lb2.c` was deleted and two lines above are inserted instead.
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- The function `g_print` in `lb2.c` was deleted and the two lines above are inserted instead.
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- The label of `btn` is changed from "Click me" to "Quit".
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- The fourth argument of `g_signal_connect` is changed from `NULL` to `win`.
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- The fourth argument of `g_signal_connect` is changed from `NULL` to `win`.
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Most important is the fourth argument of `g_signal_connect`.
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It is described as "data to pass to handler" in the definition of `g_signal_connect` in [GObject API Reference](https://docs.gtk.org/gobject/func.signal_connect.html).
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The most important change is the fourth argument of `g_signal_connect`.
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This argument is described as "data to pass to handler" in the definition of `g_signal_connect` in [GObject API Reference](https://docs.gtk.org/gobject/func.signal_connect.html).
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Therefore, `win` which is a pointer to GtkApplicationWindow is passed to the handler as a second parameter `user_data`.
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Then, the handler cast it to a pointer to GtkWindow and call `gtk_window_destroy` to destroy the top-level window.
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Then, the application quits.
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The handler then casts it to a pointer to GtkWindow and calls `gtk_window_destroy` to destroy the top-level window.
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The application then quits.
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### GtkBox
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@ -327,5 +327,4 @@ Then, these two buttons are appended to the box.
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The handler corresponds to `btn1` toggles its label.
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The handler corresponds to `btn2` destroys the top-level window and the application quits.
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Up: [Readme.md](../Readme.md), Prev: [Section 3](sec3.md), Next: [Section 5](sec5.md)
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62
gfm/sec5.md
62
gfm/sec5.md
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@ -20,16 +20,16 @@ See the sample program `tfv1.c` below.
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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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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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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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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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@ -56,7 +56,6 @@ See the sample program `tfv1.c` below.
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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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46
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~~~
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Look at line 25.
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@ -76,22 +75,23 @@ 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 change is kept in the GtkTextBuffer.
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If you add more characters than the limit of the window, the height of the window extends.
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If the height gets bigger than the height of the display screen, you won't be able to control the size of the window back to the original size.
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It's a problem and it shows that there exists a bug in the program.
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You can solve it by putting a GtkScrolledWindow between the GtkApplicationWindow and GtkTextView.
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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 instance and insert it to the GtkApplicationWindow as a child.
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- insert the GtkTextView to the GtkScrolledWindow as a child.
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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 very little.
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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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@ -111,7 +111,7 @@ $ cd tfv; diff tfv1.c tfv2.c
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> app = gtk_application_new ("com.github.ToshioCP.tfv2", G_APPLICATION_FLAGS_NONE);
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~~~
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Though you can modify the source file by this diff output, It's good for you to show `tfv2.c`.
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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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@ -124,16 +124,16 @@ Though you can modify the source file by this diff output, It's good for you to
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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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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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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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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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@ -163,12 +163,10 @@ Though you can modify the source file by this diff output, It's good for you to
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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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50
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~~~
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Now compile and run it.
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This time the window doesn't extend even if you type a lot of characters.
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It just scrolls.
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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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