mirror of
https://github.com/ToshioCP/Gtk4-tutorial.git
synced 2024-11-16 19:50:35 +01:00
428 lines
28 KiB
HTML
428 lines
28 KiB
HTML
<!DOCTYPE html>
|
||
<html lang="en">
|
||
<head>
|
||
<meta charset="utf-8" />
|
||
<meta name="generator" content="pandoc" />
|
||
<meta name="viewport" content="width=device-width, initial-scale=1" />
|
||
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">
|
||
<title>GTK 4 tutorial</title>
|
||
<style>
|
||
code{white-space: pre-wrap;}
|
||
span.smallcaps{font-variant: small-caps;}
|
||
span.underline{text-decoration: underline;}
|
||
div.column{display: inline-block; vertical-align: top; width: 50%;}
|
||
div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;}
|
||
ul.task-list{list-style: none;}
|
||
pre{overflow: visible;}
|
||
pre > code.sourceCode { white-space: pre; position: relative; }
|
||
pre > code.sourceCode > span { display: inline-block; line-height: 1.25; }
|
||
pre > code.sourceCode > span:empty { height: 1.2em; }
|
||
code.sourceCode > span { color: inherit; text-decoration: inherit; }
|
||
div.sourceCode { margin: 1em 0; }
|
||
pre.sourceCode { margin: 0; }
|
||
@media screen {
|
||
div.sourceCode { overflow: auto; }
|
||
}
|
||
@media print {
|
||
pre > code.sourceCode { white-space: pre-wrap; }
|
||
pre > code.sourceCode > span { text-indent: -5em; padding-left: 5em; }
|
||
}
|
||
pre.numberSource code
|
||
{ counter-reset: source-line 0; }
|
||
pre.numberSource code > span
|
||
{ position: relative; left: -4em; counter-increment: source-line; }
|
||
pre.numberSource code > span > a:first-child::after
|
||
{ content: counter(source-line);
|
||
position: relative; left: -1em; text-align: right; vertical-align: baseline;
|
||
border: none; display: inline-block;
|
||
-webkit-touch-callout: none; -webkit-user-select: none;
|
||
-khtml-user-select: none; -moz-user-select: none;
|
||
-ms-user-select: none; user-select: none;
|
||
padding: 0 4px; width: 4em;
|
||
color: #aaaaaa;
|
||
}
|
||
pre.numberSource { margin-left: 3em; border-left: 1px solid #aaaaaa; padding-left: 4px; }
|
||
div.sourceCode
|
||
{ }
|
||
@media screen {
|
||
pre > code.sourceCode > span > a:first-child::before { text-decoration: underline; }
|
||
}
|
||
code span.al { color: #ff0000; font-weight: bold; } /* Alert */
|
||
code span.an { color: #60a0b0; font-weight: bold; font-style: italic; } /* Annotation */
|
||
code span.at { color: #7d9029; } /* Attribute */
|
||
code span.bn { color: #40a070; } /* BaseN */
|
||
code span.bu { } /* BuiltIn */
|
||
code span.cf { color: #007020; font-weight: bold; } /* ControlFlow */
|
||
code span.ch { color: #4070a0; } /* Char */
|
||
code span.cn { color: #880000; } /* Constant */
|
||
code span.co { color: #60a0b0; font-style: italic; } /* Comment */
|
||
code span.cv { color: #60a0b0; font-weight: bold; font-style: italic; } /* CommentVar */
|
||
code span.do { color: #ba2121; font-style: italic; } /* Documentation */
|
||
code span.dt { color: #902000; } /* DataType */
|
||
code span.dv { color: #40a070; } /* DecVal */
|
||
code span.er { color: #ff0000; font-weight: bold; } /* Error */
|
||
code span.ex { } /* Extension */
|
||
code span.fl { color: #40a070; } /* Float */
|
||
code span.fu { color: #06287e; } /* Function */
|
||
code span.im { } /* Import */
|
||
code span.in { color: #60a0b0; font-weight: bold; font-style: italic; } /* Information */
|
||
code span.kw { color: #007020; font-weight: bold; } /* Keyword */
|
||
code span.op { color: #666666; } /* Operator */
|
||
code span.ot { color: #007020; } /* Other */
|
||
code span.pp { color: #bc7a00; } /* Preprocessor */
|
||
code span.sc { color: #4070a0; } /* SpecialChar */
|
||
code span.ss { color: #bb6688; } /* SpecialString */
|
||
code span.st { color: #4070a0; } /* String */
|
||
code span.va { color: #19177c; } /* Variable */
|
||
code span.vs { color: #4070a0; } /* VerbatimString */
|
||
code span.wa { color: #60a0b0; font-weight: bold; font-style: italic; } /* Warning */
|
||
div.sourceCode { margin: 10px; padding: 16px 10px 8px 10px; border: 2px solid silver; background-color: ghostwhite; overflow-x:scroll}
|
||
pre:not(.sourceCode) { margin: 10px; padding: 16px 10px 8px 10px; border: 2px solid silver; background-color: ghostwhite; overflow-x:scroll}
|
||
table {margin-left: auto; margin-right: auto; border-collapse: collapse; border: 1px solid;}
|
||
th {padding: 2px 6px; border: 1px solid; background-color: ghostwhite;}
|
||
td {padding: 2px 6px; border: 1px solid;}
|
||
img {display: block; margin-left: auto; margin-right: auto;}
|
||
figcaption {text-align: center;}
|
||
</style>
|
||
</head>
|
||
<body style="padding-top: 70px;">
|
||
<div class="container">
|
||
<nav class="navbar fixed-top navbar-expand-lg navbar-dark bg-primary">
|
||
<div class="container-fluid">
|
||
<span class="navbar-brand">Gtk4 tutorial</span>
|
||
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
|
||
<span class="navbar-toggler-icon"></span>
|
||
</button>
|
||
<div class="collapse navbar-collapse" id="navbarSupportedContent">
|
||
<ul class="navbar-nav me-auto mb-2 mb-lg-0">
|
||
<li class="nav-item">
|
||
<a class="nav-link" href="index.html">Home</a>
|
||
</li>
|
||
|
||
<li class="nav-item">
|
||
<a class="nav-link" href="sec2.html">Prev: section2</a>
|
||
</li>
|
||
|
||
<li class="nav-item">
|
||
<a class="nav-link" href="sec4.html">Next: section4</a>
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</nav>
|
||
<h1 id="gtkapplication-and-gtkapplicationwindow">GtkApplication and
|
||
GtkApplicationWindow</h1>
|
||
<h2 id="gtkapplication">GtkApplication</h2>
|
||
<h3 id="gtkapplication-and-g_application_run">GtkApplication and
|
||
g_application_run</h3>
|
||
<p>People write programming code to make an application. What are
|
||
applications? Applications are software that runs using libraries, which
|
||
includes the OS, frameworks and so on. In GTK 4 programming, the
|
||
GtkApplication is a program (or executable) that runs using Gtk
|
||
libraries.</p>
|
||
<p>The basic way to write a GtkApplication is as follows.</p>
|
||
<ul>
|
||
<li>Create a GtkApplication instance.</li>
|
||
<li>Run the application.</li>
|
||
</ul>
|
||
<p>That’s all. Very simple. The following is the C code representing the
|
||
scenario above.</p>
|
||
<div class="sourceCode" id="cb1"><pre
|
||
class="sourceCode numberSource C numberLines"><code class="sourceCode c"><span id="cb1-1"><a href="#cb1-1"></a><span class="pp">#include </span><span class="im"><gtk/gtk.h></span></span>
|
||
<span id="cb1-2"><a href="#cb1-2"></a></span>
|
||
<span id="cb1-3"><a href="#cb1-3"></a><span class="dt">int</span></span>
|
||
<span id="cb1-4"><a href="#cb1-4"></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="cb1-5"><a href="#cb1-5"></a> GtkApplication <span class="op">*</span>app<span class="op">;</span></span>
|
||
<span id="cb1-6"><a href="#cb1-6"></a> <span class="dt">int</span> stat<span class="op">;</span></span>
|
||
<span id="cb1-7"><a href="#cb1-7"></a></span>
|
||
<span id="cb1-8"><a href="#cb1-8"></a> app <span class="op">=</span> gtk_application_new <span class="op">(</span><span class="st">"com.github.ToshioCP.pr1"</span><span class="op">,</span> G_APPLICATION_DEFAULT_FLAGS<span class="op">);</span></span>
|
||
<span id="cb1-9"><a href="#cb1-9"></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="cb1-10"><a href="#cb1-10"></a> g_object_unref <span class="op">(</span>app<span class="op">);</span></span>
|
||
<span id="cb1-11"><a href="#cb1-11"></a> <span class="cf">return</span> stat<span class="op">;</span></span>
|
||
<span id="cb1-12"><a href="#cb1-12"></a><span class="op">}</span></span></code></pre></div>
|
||
<p>The first line says that this program includes the header files of
|
||
the Gtk libraries. The function <code>main</code> is a startup function
|
||
in C language. The variable <code>app</code> is defined as a pointer to
|
||
a GtkApplication instance. The function <code>gtk_application_new</code>
|
||
creates a GtkApplication instance and returns a pointer to the instance.
|
||
The GtkApplication instance is a C structure data in which the
|
||
information about the application is stored. The meaning of the
|
||
arguments will be explained later. The function
|
||
<code>g_application_run</code> runs an application that the instance
|
||
defined. (We often say that the function runs <code>app</code>.
|
||
Actually, <code>app</code> is not an application but a pointer to the
|
||
instance of the application. However, it is simple and short, and
|
||
probably no confusion occurs.)</p>
|
||
<p>Here I used the word <code>instance</code>. Instance, class and
|
||
object are terminologies in Object Oriented Programming. I use these
|
||
words in the same way. But, I will often use “object” instead of
|
||
“instance” in this tutorial. That means “object” and “instance” is the
|
||
same. Object is a bit ambiguous word. In a broad sense, object has wider
|
||
meaning than instance. So, readers should be careful of the contexts to
|
||
find the meaning of “object”. In many cases, object and instance are the
|
||
same.</p>
|
||
<p>To compile this, the following command needs to be run. The string
|
||
<code>pr1.c</code> is the filename of the C source code above.</p>
|
||
<pre><code>$ gcc `pkg-config --cflags gtk4` pr1.c `pkg-config --libs gtk4`</code></pre>
|
||
<p>The C compiler gcc generates an executable file, <code>a.out</code>.
|
||
Let’s run it.</p>
|
||
<pre><code>$ ./a.out
|
||
|
||
(a.out:13533): GLib-GIO-WARNING **: 15:30:17.449: Your application does not implement
|
||
g_application_activate() and has no handlers connected to the "activate" signal.
|
||
It should do one of these.
|
||
$</code></pre>
|
||
<p>Oh, it just produces an error message. This error message means that
|
||
the GtkApplication object ran, without a doubt. Now, let’s think about
|
||
what this message means.</p>
|
||
<h3 id="signal">signal</h3>
|
||
<p>The message tells us that:</p>
|
||
<ol type="1">
|
||
<li>The application GtkApplication doesn’t implement
|
||
<code>g_application_activate()</code>,</li>
|
||
<li>It has no handlers connected to the “activate” signal, and</li>
|
||
<li>You will need to solve at least one of these.</li>
|
||
</ol>
|
||
<p>These two causes of the error are related to signals. So, I will
|
||
explain that to you first.</p>
|
||
<p>A signal is emitted when something happens. For example, a window is
|
||
created, a window is destroyed and so on. The signal “activate” is
|
||
emitted when the application is activated. (Activated is a bit different
|
||
from started, but you can think the both are almost same so far.) If the
|
||
signal is connected to a function, which is called a signal handler or
|
||
simply handler, then the function is invoked when the signal emits.</p>
|
||
<p>The flow is like this:</p>
|
||
<ol type="1">
|
||
<li>Something happens.</li>
|
||
<li>If it’s related to a certain signal, then the signal is
|
||
emitted.</li>
|
||
<li>If the signal has been connected to a handler in advance, then the
|
||
handler is invoked.</li>
|
||
</ol>
|
||
<p>Signals are defined in objects. For example, the “activate” signal
|
||
belongs to the GApplication object, which is a parent object of
|
||
GtkApplication object.</p>
|
||
<p>The GApplication object is a child object of the GObject object.
|
||
GObject is the top object in the hierarchy of all the objects.</p>
|
||
<pre><code>GObject -- GApplication -- GtkApplication
|
||
<---parent --->child</code></pre>
|
||
<p>A child object inherits signals, functions, properties and so on from
|
||
its parent object. So, GtkApplication also has the “activate”
|
||
signal.</p>
|
||
<p>Now we can solve the problem in <code>pr1.c</code>. We need to
|
||
connect the “activate” signal to a handler. We use a function
|
||
<code>g_signal_connect</code> which connects a signal to a handler.</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> gpointer <span class="op">*</span>user_data<span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb5-5"><a href="#cb5-5"></a> g_print <span class="op">(</span><span class="st">"GtkApplication is activated.</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">int</span></span>
|
||
<span id="cb5-9"><a href="#cb5-9"></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="cb5-10"><a href="#cb5-10"></a> GtkApplication <span class="op">*</span>app<span class="op">;</span></span>
|
||
<span id="cb5-11"><a href="#cb5-11"></a> <span class="dt">int</span> stat<span class="op">;</span></span>
|
||
<span id="cb5-12"><a href="#cb5-12"></a></span>
|
||
<span id="cb5-13"><a href="#cb5-13"></a> app <span class="op">=</span> gtk_application_new <span class="op">(</span><span class="st">"com.github.ToshioCP.pr2"</span><span class="op">,</span> G_APPLICATION_DEFAULT_FLAGS<span class="op">);</span></span>
|
||
<span id="cb5-14"><a href="#cb5-14"></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="cb5-15"><a href="#cb5-15"></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="cb5-16"><a href="#cb5-16"></a> g_object_unref <span class="op">(</span>app<span class="op">);</span></span>
|
||
<span id="cb5-17"><a href="#cb5-17"></a> <span class="cf">return</span> stat<span class="op">;</span></span>
|
||
<span id="cb5-18"><a href="#cb5-18"></a><span class="op">}</span></span></code></pre></div>
|
||
<p>First, we define the handler <code>app_activate</code> which simply
|
||
displays a message. The function <code>g_print</code> is defined in GLib
|
||
and it’s like a printf in the C standard library. In the function
|
||
<code>main</code>, we add <code>g_signal_connect</code> before
|
||
<code>g_application_run</code>. The function
|
||
<code>g_signal_connect</code> has four arguments.</p>
|
||
<ol type="1">
|
||
<li>An instance to which the signal belongs.</li>
|
||
<li>The name of the signal.</li>
|
||
<li>A handler function (also called callback), which needs to be casted
|
||
by <code>G_CALLBACK</code>.</li>
|
||
<li>Data to pass to the handler. If no data is necessary, NULL should be
|
||
given.</li>
|
||
</ol>
|
||
<p>It is described in the <a
|
||
href="https://docs.gtk.org/gobject/func.signal_connect.html">GObject API
|
||
Reference</a>. Correctly, <code>g_signal_connect</code> is a macro (not
|
||
a C function).</p>
|
||
<div class="sourceCode" id="cb6"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="pp">#define g_signal_connect (</span></span>
|
||
<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a> instance<span class="op">,</span></span>
|
||
<span id="cb6-3"><a href="#cb6-3" aria-hidden="true" tabindex="-1"></a> detailed_signal<span class="op">,</span></span>
|
||
<span id="cb6-4"><a href="#cb6-4" aria-hidden="true" tabindex="-1"></a> c_handler<span class="op">,</span></span>
|
||
<span id="cb6-5"><a href="#cb6-5" aria-hidden="true" tabindex="-1"></a> data</span>
|
||
<span id="cb6-6"><a href="#cb6-6" aria-hidden="true" tabindex="-1"></a><span class="op">)</span></span></code></pre></div>
|
||
<p>You can find the description of each signal in the API reference
|
||
manual. For example, “activate” signal is in <a
|
||
href="https://docs.gtk.org/gio/signal.Application.activate.html">GApplication
|
||
section</a> in the GIO API Reference.</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="dt">void</span></span>
|
||
<span id="cb7-2"><a href="#cb7-2" aria-hidden="true" tabindex="-1"></a>activate <span class="op">(</span></span>
|
||
<span id="cb7-3"><a href="#cb7-3" aria-hidden="true" tabindex="-1"></a> GApplication<span class="op">*</span> self<span class="op">,</span></span>
|
||
<span id="cb7-4"><a href="#cb7-4" aria-hidden="true" tabindex="-1"></a> gpointer user_data</span>
|
||
<span id="cb7-5"><a href="#cb7-5" aria-hidden="true" tabindex="-1"></a><span class="op">)</span></span></code></pre></div>
|
||
<p>This is a declaration of the “activate” signal handler. You can use
|
||
any name instead of “activate” in the declaration above. The parameters
|
||
are:</p>
|
||
<ul>
|
||
<li>self is an instance to which the signal belongs.</li>
|
||
<li>user_data is a data defined in the fourth argument of the
|
||
<code>g_signal_connect</code> function. If it is NULL, then you can
|
||
ignore and left out the second parameter.</li>
|
||
</ul>
|
||
<p>API reference manual is very important. You should see and understand
|
||
it.</p>
|
||
<p>Let’s compile the source file above (<code>pr2.c</code>) and run
|
||
it.</p>
|
||
<pre><code>$ gcc `pkg-config --cflags gtk4` pr2.c `pkg-config --libs gtk4`
|
||
$ ./a.out
|
||
GtkApplication is activated.
|
||
$</code></pre>
|
||
<p>OK, well done. However, you may have noticed that it’s painful to
|
||
type such a long line to compile. It is a good idea to use shell script
|
||
to solve this problem. Make a text file which contains the following
|
||
line.</p>
|
||
<pre><code>gcc `pkg-config --cflags gtk4` $1.c `pkg-config --libs gtk4`</code></pre>
|
||
<p>Then, save it under the directory $HOME/bin, which is usually
|
||
/home/(username)/bin. (If your user name is James, then the directory is
|
||
/home/james/bin). And turn on the execute bit of the file. If the
|
||
filename is <code>comp</code>, do like this:</p>
|
||
<pre><code>$ chmod 755 $HOME/bin/comp
|
||
$ ls -log $HOME/bin
|
||
... ... ...
|
||
-rwxr-xr-x 1 62 May 23 08:21 comp
|
||
... ... ...</code></pre>
|
||
<p>If this is the first time that you make a $HOME/bin directory and
|
||
save a file in it, then you need to logout and login again.</p>
|
||
<pre><code>$ comp pr2
|
||
$ ./a.out
|
||
GtkApplication is activated.
|
||
$</code></pre>
|
||
<h2 id="gtkwindow-and-gtkapplicationwindow">GtkWindow and
|
||
GtkApplicationWindow</h2>
|
||
<h3 id="gtkwindow">GtkWindow</h3>
|
||
<p>A message “GtkApplication is activated.” was printed out in the
|
||
previous subsection. It was good in terms of a test of GtkApplication.
|
||
However, it is insufficient because Gtk is a framework for graphical
|
||
user interface (GUI). Now we go ahead with adding a window into this
|
||
program. What we need to do is:</p>
|
||
<ol type="1">
|
||
<li>Create a GtkWindow.</li>
|
||
<li>Connect it to GtkApplication.</li>
|
||
<li>Show the window.</li>
|
||
</ol>
|
||
<p>Now rewrite the function <code>app_activate</code>.</p>
|
||
<h4 id="create-a-gtkwindow">Create a GtkWindow</h4>
|
||
<div class="sourceCode" id="cb12"><pre
|
||
class="sourceCode numberSource C numberLines"><code class="sourceCode c"><span id="cb12-1"><a href="#cb12-1"></a><span class="dt">static</span> <span class="dt">void</span></span>
|
||
<span id="cb12-2"><a href="#cb12-2"></a>app_activate <span class="op">(</span>GApplication <span class="op">*</span>app<span class="op">,</span> gpointer user_data<span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb12-3"><a href="#cb12-3"></a> GtkWidget <span class="op">*</span>win<span class="op">;</span></span>
|
||
<span id="cb12-4"><a href="#cb12-4"></a></span>
|
||
<span id="cb12-5"><a href="#cb12-5"></a> win <span class="op">=</span> gtk_window_new <span class="op">();</span></span>
|
||
<span id="cb12-6"><a href="#cb12-6"></a> gtk_window_set_application <span class="op">(</span>GTK_WINDOW <span class="op">(</span>win<span class="op">),</span> GTK_APPLICATION <span class="op">(</span>app<span class="op">));</span></span>
|
||
<span id="cb12-7"><a href="#cb12-7"></a> gtk_window_present <span class="op">(</span>GTK_WINDOW <span class="op">(</span>win<span class="op">));</span></span>
|
||
<span id="cb12-8"><a href="#cb12-8"></a><span class="op">}</span></span></code></pre></div>
|
||
<p>Widget is an abstract concept that includes all the GUI interfaces
|
||
such as windows, dialogs, buttons, multi-line text, containers and so
|
||
on. And GtkWidget is a base object from which all the GUI objects
|
||
derive.</p>
|
||
<pre><code>parent <-----> child
|
||
GtkWidget -- GtkWindow</code></pre>
|
||
<p>GtkWindow includes GtkWidget at the top of its object.</p>
|
||
<figure>
|
||
<img src="image/window_widget.png" alt="GtkWindow and GtkWidget" />
|
||
<figcaption aria-hidden="true">GtkWindow and GtkWidget</figcaption>
|
||
</figure>
|
||
<p>The function <code>gtk_window_new</code> is defined as follows.</p>
|
||
<div class="sourceCode" id="cb14"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb14-1"><a href="#cb14-1" aria-hidden="true" tabindex="-1"></a>GtkWidget <span class="op">*</span></span>
|
||
<span id="cb14-2"><a href="#cb14-2" aria-hidden="true" tabindex="-1"></a>gtk_window_new <span class="op">(</span><span class="dt">void</span><span class="op">);</span></span></code></pre></div>
|
||
<p>By this definition, it returns a pointer to GtkWidget, not GtkWindow.
|
||
It actually creates a new GtkWindow instance (not GtkWidget) but returns
|
||
a pointer to GtkWidget. However,the pointer points the GtkWidget and at
|
||
the same time it also points GtkWindow that contains GtkWidget in
|
||
it.</p>
|
||
<p>If you want to use <code>win</code> as a pointer to a GtkWindow type
|
||
instance, you need to cast it.</p>
|
||
<div class="sourceCode" id="cb15"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb15-1"><a href="#cb15-1" aria-hidden="true" tabindex="-1"></a><span class="op">(</span>GtkWindow <span class="op">*)</span> win</span></code></pre></div>
|
||
<p>It works, but isn’t usually used. Instead, <code>GTK_WINDOW</code>
|
||
macro is used.</p>
|
||
<div class="sourceCode" id="cb16"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb16-1"><a href="#cb16-1" aria-hidden="true" tabindex="-1"></a>GTK_WINDOW <span class="op">(</span>win<span class="op">)</span></span></code></pre></div>
|
||
<p>The macro is recommended because it does not only cast but also check
|
||
the type.</p>
|
||
<h4 id="connect-it-to-gtkapplication.">Connect it to
|
||
GtkApplication.</h4>
|
||
<p>The function <code>gtk_window_set_application</code> is used to
|
||
connect GtkWindow to GtkApplication.</p>
|
||
<div class="sourceCode" id="cb17"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb17-1"><a href="#cb17-1" aria-hidden="true" tabindex="-1"></a>gtk_window_set_application <span class="op">(</span>GTK_WINDOW <span class="op">(</span>win<span class="op">),</span> GTK_APPLICATION <span class="op">(</span>app<span class="op">));</span></span></code></pre></div>
|
||
<p>You need to cast <code>win</code> to GtkWindow and <code>app</code>
|
||
to GtkApplication with <code>GTK_WINDOW</code> and
|
||
<code>GTK_APPLICATION</code> macro.</p>
|
||
<p>GtkApplication continues to run until the related window is
|
||
destroyed. If you didn’t connect GtkWindow and GtkApplication,
|
||
GtkApplication destroys itself immediately. Because no window is
|
||
connected to GtkApplication, GtkApplication doesn’t need to wait
|
||
anything. As it destroys itself, the GtkWindow is also destroyed.</p>
|
||
<h4 id="show-the-window.">Show the window.</h4>
|
||
<p>The function <code>gtk_window_present</code> presents the window to a
|
||
user (shows it to the user).</p>
|
||
<p>GTK 4 changes the default widget visibility to on, so every widget
|
||
doesn’t need to change it to on. But, there’s an exception. Top level
|
||
window (this term will be explained later) isn’t visible when it is
|
||
created. So you need to use the function above to show the window.</p>
|
||
<p>You can use <code>gtk_widget_set_visible (win, true)</code> instead
|
||
of <code>gtk_window_present</code>. But the behavior of these two is
|
||
different. Suppose there are two windows win1 and win2 on the screen and
|
||
win1 is behind win2. Both windows are visible. The function
|
||
<code>gtk_widget_set_visible (win1, true)</code> does nothing because
|
||
win1 is already visible. So, win1 is still behind win2. The other
|
||
function <code>gtk_window_present (win1)</code> moves win1 to the top of
|
||
the stack of the windows. Therefore, if you want to present the window,
|
||
you should use <code>gtk_window_present</code>.</p>
|
||
<p>Two functions <code>gtk_widget_show</code> and
|
||
<code>gtk_widget_hide</code> is deprecated since GTK 4.10. You should
|
||
use <code>gtk_widget_set_visible</code> instead.</p>
|
||
<p>Save the program as <code>pr3.c</code>, then compile and run it.</p>
|
||
<pre><code>$ comp pr3
|
||
$ ./a.out</code></pre>
|
||
<p>A small window appears.</p>
|
||
<figure>
|
||
<img src="image/screenshot_pr3.png" alt="Screenshot of the window" />
|
||
<figcaption aria-hidden="true">Screenshot of the window</figcaption>
|
||
</figure>
|
||
<p>Click on the close button then the window disappears and the program
|
||
finishes.</p>
|
||
<h3 id="gtkapplicationwindow">GtkApplicationWindow</h3>
|
||
<p>GtkApplicationWindow is a child object of GtkWindow. It has some
|
||
extra feature for better integration with GtkApplication. It is
|
||
recommended to use it as the top-level window of the application instead
|
||
of GtkWindow.</p>
|
||
<p>Now rewrite the program and use GtkApplicationWindow.</p>
|
||
<div class="sourceCode" id="cb19"><pre
|
||
class="sourceCode numberSource C numberLines"><code class="sourceCode c"><span id="cb19-1"><a href="#cb19-1"></a><span class="dt">static</span> <span class="dt">void</span></span>
|
||
<span id="cb19-2"><a href="#cb19-2"></a>app_activate <span class="op">(</span>GApplication <span class="op">*</span>app<span class="op">,</span> gpointer user_data<span class="op">)</span> <span class="op">{</span></span>
|
||
<span id="cb19-3"><a href="#cb19-3"></a> GtkWidget <span class="op">*</span>win<span class="op">;</span></span>
|
||
<span id="cb19-4"><a href="#cb19-4"></a></span>
|
||
<span id="cb19-5"><a href="#cb19-5"></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="cb19-6"><a href="#cb19-6"></a> gtk_window_set_title <span class="op">(</span>GTK_WINDOW <span class="op">(</span>win<span class="op">),</span> <span class="st">"pr4"</span><span class="op">);</span></span>
|
||
<span id="cb19-7"><a href="#cb19-7"></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="cb19-8"><a href="#cb19-8"></a> gtk_window_present <span class="op">(</span>GTK_WINDOW <span class="op">(</span>win<span class="op">));</span></span>
|
||
<span id="cb19-9"><a href="#cb19-9"></a><span class="op">}</span></span></code></pre></div>
|
||
<p>When you create GtkApplicationWindow, you need to give GtkApplication
|
||
instance as an argument. Then it automatically connect these two
|
||
instances. So you don’t need to call
|
||
<code>gtk_window_set_application</code> any more.</p>
|
||
<p>The program sets the title and the default size of the window.
|
||
Compile it and run <code>a.out</code>, then you will see a bigger window
|
||
with its title “pr4”.</p>
|
||
<figure>
|
||
<img src="image/screenshot_pr4.png" alt="Screenshot of the window" />
|
||
<figcaption aria-hidden="true">Screenshot of the window</figcaption>
|
||
</figure>
|
||
</div>
|
||
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-MrcW6ZMFYlzcLA8Nl+NtUVF0sA7MsXsP1UyJoMp4YLEuNSfAP+JcXn/tWtIaxVXM" crossorigin="anonymous"></script>
|
||
</body>
|
||
</html>
|