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<section id="drag-and-drop">
<h1>Drag and Drop<a class="headerlink" href="#drag-and-drop" title="Permalink to this headline">#</a></h1>
<p>Drag and drop is an essential part of applications that deal with many files,
and very easy to add to an application.</p>
<section id="adding-a-drop-target">
<h2>Adding a drop target<a class="headerlink" href="#adding-a-drop-target" title="Permalink to this headline">#</a></h2>
<p>You will need to create a <code class="docutils literal notranslate"><span class="pre">GtkDropTarget</span></code>, which is an event controller that,
connected to a widget, emits the “drop” signal if the dragged object is dropped
on the widget. To receive the data, connect to that signal.</p>
<p>For this first example, we will setup the program to receive files from another
program, such as Nautilus. Signal connections are included in this snippet for
ease of copy-and-paste.</p>
<div class="sphinx-tabs docutils container">
<div aria-label="Tabbed content" class="closeable" role="tablist"><button aria-controls="panel-0-Qw==" aria-selected="true" class="sphinx-tabs-tab code-tab group-tab" id="tab-0-Qw==" name="Qw==" role="tab" tabindex="0">C</button><button aria-controls="panel-0-UHl0aG9u" aria-selected="false" class="sphinx-tabs-tab code-tab group-tab" id="tab-0-UHl0aG9u" name="UHl0aG9u" role="tab" tabindex="-1">Python</button></div><div aria-labelledby="tab-0-Qw==" class="sphinx-tabs-panel code-tab group-tab" id="panel-0-Qw==" name="Qw==" role="tabpanel" tabindex="0"><div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">GtkDropTarget</span><span class="w"> </span><span class="o">*</span><span class="n">target</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gtk_drop_target_new</span><span class="w"> </span><span class="p">(</span><span class="n">G_TYPE_INVALID</span><span class="p">,</span><span class="w"> </span><span class="n">GDK_ACTION_COPY</span><span class="p">);</span><span class="w"></span>
<span class="n">gtk_drop_target_set_gtypes</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="p">(</span><span class="n">GType</span><span class="p">[</span><span class="mi">1</span><span class="p">])</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">GDK_TYPE_FILE_LIST</span><span class="p">,</span><span class="w"> </span><span class="p">},</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
<span class="n">g_signal_connect</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;drop&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">G_CALLBACK</span><span class="w"> </span><span class="p">(</span><span class="n">on_drop</span><span class="p">),</span><span class="w"> </span><span class="nb">NULL</span><span class="p">);</span><span class="w"></span>
<span class="cm">/* Visually emphasize the user that he is dropping a widget. */</span><span class="w"></span>
<span class="n">g_signal_connect</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;enter&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">G_CALLBACK</span><span class="w"> </span><span class="p">(</span><span class="n">on_enter</span><span class="p">),</span><span class="w"> </span><span class="n">my_window</span><span class="p">);</span><span class="w"></span>
<span class="n">g_signal_connect</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;leave&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">G_CALLBACK</span><span class="w"> </span><span class="p">(</span><span class="n">on_leave</span><span class="p">),</span><span class="w"> </span><span class="n">my_window</span><span class="p">);</span><span class="w"></span>
<span class="n">gtk_widget_add_controller</span><span class="w"> </span><span class="p">(</span><span class="n">GTK_WIDGET</span><span class="w"> </span><span class="p">(</span><span class="n">my_window</span><span class="p">),</span><span class="w"> </span><span class="n">GTK_EVENT_CONTROLLER</span><span class="w"> </span><span class="p">(</span><span class="n">target</span><span class="p">));</span><span class="w"></span>
</pre></div>
</div>
</div><div aria-labelledby="tab-0-UHl0aG9u" class="sphinx-tabs-panel code-tab group-tab" hidden="true" id="panel-0-UHl0aG9u" name="UHl0aG9u" role="tabpanel" tabindex="0"><div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">content</span> <span class="o">=</span> <span class="n">Gdk</span><span class="o">.</span><span class="n">ContentFormats</span><span class="o">.</span><span class="n">new_for_gtype</span><span class="p">(</span><span class="n">Gdk</span><span class="o">.</span><span class="n">FileList</span><span class="p">)</span>
<span class="n">target</span> <span class="o">=</span> <span class="n">Gtk</span><span class="o">.</span><span class="n">DropTarget</span><span class="p">(</span><span class="n">formats</span><span class="o">=</span><span class="n">content</span><span class="p">,</span> <span class="n">actions</span><span class="o">=</span><span class="n">Gdk</span><span class="o">.</span><span class="n">DragAction</span><span class="o">.</span><span class="n">COPY</span><span class="p">)</span>
<span class="n">target</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">&#39;drop&#39;</span><span class="p">,</span> <span class="n">on_drop</span><span class="p">)</span>
<span class="c1"># Visually emphasize the user that he is dropping a widget.</span>
<span class="n">target</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">&#39;enter&#39;</span><span class="p">,</span> <span class="n">on_enter</span><span class="p">)</span>
<span class="n">target</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s1">&#39;leave&#39;</span><span class="p">,</span> <span class="n">on_leave</span><span class="p">)</span>
<span class="c1"># self here is a widget.</span>
<span class="bp">self</span><span class="o">.</span><span class="n">add_controller</span><span class="p">(</span><span class="n">target</span><span class="p">)</span>
</pre></div>
</div>
</div></div>
<p>We have told GTK that this widget is ready to be used for dragging and dropping.
If you drag a file from your file manager, it will show the drag and drop icon.
Next, we have to retrieve the data.</p>
<div class="sphinx-tabs docutils container">
<div aria-label="Tabbed content" class="closeable" role="tablist"><button aria-controls="panel-1-Qw==" aria-selected="true" class="sphinx-tabs-tab code-tab group-tab" id="tab-1-Qw==" name="Qw==" role="tab" tabindex="0">C</button><button aria-controls="panel-1-UHl0aG9u" aria-selected="false" class="sphinx-tabs-tab code-tab group-tab" id="tab-1-UHl0aG9u" name="UHl0aG9u" role="tab" tabindex="-1">Python</button></div><div aria-labelledby="tab-1-Qw==" class="sphinx-tabs-panel code-tab group-tab" id="panel-1-Qw==" name="Qw==" role="tabpanel" tabindex="0"><div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="k">static</span><span class="w"> </span><span class="n">gboolean</span><span class="w"></span>
<span class="nf">on_drop</span><span class="w"> </span><span class="p">(</span><span class="n">GtkDropTarget</span><span class="w"> </span><span class="o">*</span><span class="n">target</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">GValue</span><span class="w"> </span><span class="o">*</span><span class="n">value</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">y</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">gpointer</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"></span>
<span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="cm">/* GdkFileList is a boxed value so we use the boxed API. */</span><span class="w"></span>
<span class="w"> </span><span class="n">GdkFileList</span><span class="w"> </span><span class="o">*</span><span class="n">file_list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">g_value_get_boxed</span><span class="w"> </span><span class="p">(</span><span class="n">value</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">GSList</span><span class="w"> </span><span class="o">*</span><span class="n">list</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gdk_file_list_get_files</span><span class="w"> </span><span class="p">(</span><span class="n">file_list</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="cm">/* Loop through the files and print their names. */</span><span class="w"></span>
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">GSList</span><span class="w"> </span><span class="o">*</span><span class="n">l</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">list</span><span class="p">;</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="nb">NULL</span><span class="p">;</span><span class="w"> </span><span class="n">l</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">l</span><span class="o">-&gt;</span><span class="n">next</span><span class="p">)</span><span class="w"></span>
<span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">GFile</span><span class="o">*</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">l</span><span class="o">-&gt;</span><span class="n">data</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="n">g_print</span><span class="w"> </span><span class="p">(</span><span class="s">&quot;%s</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">g_file_get_path</span><span class="w"> </span><span class="p">(</span><span class="n">file</span><span class="p">));</span><span class="w"></span>
<span class="w"> </span><span class="p">}</span><span class="w"></span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">TRUE</span><span class="p">;</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>
</div>
</div><div aria-labelledby="tab-1-UHl0aG9u" class="sphinx-tabs-panel code-tab group-tab" hidden="true" id="panel-1-UHl0aG9u" name="UHl0aG9u" role="tabpanel" tabindex="0"><div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">on_drop</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">drop_target</span><span class="p">,</span> <span class="n">value</span><span class="p">:</span> <span class="n">Gdk</span><span class="o">.</span><span class="n">FileList</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">user_data</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="n">files</span><span class="p">:</span> <span class="n">List</span><span class="p">[</span><span class="n">Gio</span><span class="o">.</span><span class="n">File</span><span class="p">]</span> <span class="o">=</span> <span class="n">value</span><span class="o">.</span><span class="n">get_files</span><span class="p">()</span>
<span class="c1"># Loop through the files and print their names.</span>
<span class="k">for</span> <span class="n">file</span> <span class="ow">in</span> <span class="n">files</span><span class="p">:</span>
<span class="nb">print</span><span class="p">(</span><span class="n">file</span><span class="o">.</span><span class="n">get_path</span><span class="p">())</span>
</pre></div>
</div>
</div></div>
<p>For the visual emphasis, these callbacks add and remove CSS classes to a widget, which
results in a thin line drawn around the interior of the widget (highlighting).</p>
<div class="sphinx-tabs docutils container">
<div aria-label="Tabbed content" class="closeable" role="tablist"><button aria-controls="panel-2-Qw==" aria-selected="true" class="sphinx-tabs-tab code-tab group-tab" id="tab-2-Qw==" name="Qw==" role="tab" tabindex="0">C</button><button aria-controls="panel-2-UHl0aG9u" aria-selected="false" class="sphinx-tabs-tab code-tab group-tab" id="tab-2-UHl0aG9u" name="UHl0aG9u" role="tab" tabindex="-1">Python</button></div><div aria-labelledby="tab-2-Qw==" class="sphinx-tabs-panel code-tab group-tab" id="panel-2-Qw==" name="Qw==" role="tabpanel" tabindex="0"><div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="cm">/* Style the widget when a dragged object enters into its area. */</span><span class="w"></span>
<span class="k">static</span><span class="w"> </span><span class="n">GdkDragAction</span><span class="w"></span>
<span class="nf">on_enter</span><span class="w"> </span><span class="p">(</span><span class="n">GtkDropTarget</span><span class="w"> </span><span class="o">*</span><span class="n">target</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">y</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">gpointer</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"></span>
<span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">gtk_widget_add_css_class</span><span class="w"> </span><span class="p">(</span><span class="n">GTK_WIDGET</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="p">),</span><span class="w"> </span><span class="s">&quot;drop_hover&quot;</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="cm">/* Tell the callee to continue. */</span><span class="w"></span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">GDK_ACTION_COPY</span><span class="p">;</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
<span class="cm">/* Remove the style class added by on_enter. */</span><span class="w"></span>
<span class="k">static</span><span class="w"> </span><span class="kt">void</span><span class="w"></span>
<span class="nf">on_leave</span><span class="w"> </span><span class="p">(</span><span class="n">GtkDropTarget</span><span class="w"> </span><span class="o">*</span><span class="n">target</span><span class="p">,</span><span class="w"></span>
<span class="w"> </span><span class="n">gpointer</span><span class="w"> </span><span class="n">data</span><span class="p">)</span><span class="w"></span>
<span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">gtk_widget_remove_css_class</span><span class="w"> </span><span class="p">(</span><span class="n">GTK_WIDGET</span><span class="w"> </span><span class="p">(</span><span class="n">data</span><span class="p">),</span><span class="w"> </span><span class="s">&quot;drop_hover&quot;</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>
</div>
</div><div aria-labelledby="tab-2-UHl0aG9u" class="sphinx-tabs-panel code-tab group-tab" hidden="true" id="panel-2-UHl0aG9u" name="UHl0aG9u" role="tabpanel" tabindex="0"><div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># Style the widget when a dragged object enters into its area.</span>
<span class="k">def</span> <span class="nf">on_enter</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">drop_target</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">add_css_class</span><span class="p">(</span><span class="s1">&#39;drop_hover&#39;</span><span class="p">)</span>
<span class="c1"># Tell the callee to continue</span>
<span class="k">return</span> <span class="n">Gdk</span><span class="o">.</span><span class="n">DragAction</span><span class="o">.</span><span class="n">COPY</span>
<span class="c1"># Remove the style class added by on_enter.</span>
<span class="k">def</span> <span class="nf">on_leave</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">drop_target</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">remove_css_class</span><span class="p">(</span><span class="s1">&#39;drop_hover&#39;</span><span class="p">)</span>
</pre></div>
</div>
</div></div>
<p>It is possible to use any type supported by the GObject type system for drag and drop
operations within the same application, including complex types.</p>
<p>If you want to support drag and drop of complex types across applications, you will
have to use the <a class="reference external" href="https://docs.gtk.org/gdk4/class.ContentSerializer.html">GdkContentSerializer</a>
and <a class="reference external" href="https://docs.gtk.org/gdk4/class.ContentDeserializer.html">GdkContentDeserializer</a> API.</p>
</section>
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<li><a class="reference internal" href="#">Drag and Drop</a><ul>
<li><a class="reference internal" href="#adding-a-drop-target">Adding a drop target</a></li>
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