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<div class="titlepage"><div><div><h1 class="title">
<a name="chapter-adjustment"></a>Chapter 16. Adjustments</h1></div></div></div>
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<p><b>Table of Contents</b></p>
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<li><span class="section"><a href="chapter-adjustment.html#sec-creating-adjustment">Creating an Adjustment</a></span></li>
<li><span class="section"><a href="sec-adjustments-easy.html">Using Adjustments the Easy Way</a></span></li>
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<p>
<span class="application">gtkmm</span> has various widgets that can be visually adjusted using the mouse or
the keyboard, such as the <code class="classname">Range</code> widgets (described in
the <a class="link" href="chapter-range-widgets.html" title="Chapter 7. Range Widgets">Range Widgets</a> section). There are
also a few widgets that display some adjustable part of a larger area, such as
the <code class="classname">Viewport</code> widget. These widgets have
<code class="classname">Gtk::Adjustment</code> objects that express this common part of
their API.
</p>
<p>
So that applications can react to changes, for instance when a user moves a
scrollbar, <code class="classname">Gtk::Adjustment</code> has a
<code class="literal">value_changed</code> signal. You can then use the
<code class="methodname">get_value()</code> method to discover the new value.
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-creating-adjustment"></a>Creating an Adjustment</h2></div></div></div>
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The <code class="classname">Gtk::Adjustment</code> is created by its
<code class="methodname">create()</code> method which is as follows:
</p>
<pre class="programlisting"><code class="code">Glib::RefPtr<Gtk::Adjustment> Gtk::Adjustment::create(
double value,
double lower,
double upper,
double step_increment = 1,
double page_increment = 10,
double page_size = 0);</code></pre>
<p>
The <em class="parameter"><code>value</code></em> argument is the initial value of the
adjustment, usually corresponding to the topmost or leftmost position of an
adjustable widget. The <em class="parameter"><code>lower</code></em> and
<em class="parameter"><code>upper</code></em> arguments specify the possible range of values
which the adjustment can hold. The
<em class="parameter"><code>step_increment</code></em> argument specifies the smaller of
the two increments by which the user can change the value, while the
<em class="parameter"><code>page_increment</code></em> is the larger one. The
<em class="parameter"><code>page_size</code></em> argument usually corresponds somehow to
the visible area of a panning widget. The <em class="parameter"><code>upper</code></em> argument
is used to represent the bottommost or rightmost coordinate in a panning
widget's child.
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