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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"><title>Test for modifier keys correctly</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"><link rel="start" href="index.html" title="GTK+ Reference Manual"><link rel="up" href="gtk-migrating-checklist.html" title="Migration Checklist"><link rel="prev" href="checklist-gdkeventexpose-region.html" title="Use GdkEventExpose.region"><link rel="next" href="checklist-named-icons.html" title="Use named icons"><meta name="generator" content="GTK-Doc V1.9 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"><link rel="part" href="gtk.html" title="Part I. GTK+ Overview"><link rel="part" href="gtkbase.html" title="Part II. GTK+ Core Reference"><link rel="part" href="gtkobjects.html" title="Part III. GTK+ Widgets and Objects"><link rel="chapter" href="ch01.html" title="Object Hierarchy"><link rel="chapter" 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class="keycap"><strong>NumLock</strong></span> or <span class="keycap"><strong>CapsLock</strong></span> are activated. </p><p> In a <span class="structname">GdkEventKey</span>, the <em class="structfield"><code>state</code></em> field is a bit mask which indicates the modifier state at the time the key was pressed. Modifiers are keys like <span class="keycap"><strong>Control</strong></span> and <span class="keycap"><strong>NumLock</strong></span>. When implementing a <a class="link" href="GtkWidget.html#GtkWidget-key-press-event"><span class="type">"key-press-event"</span></a> handler, you should use <a class="link" href="gtk-Keyboard-Accelerators.html#gtk-accelerator-get-default-mod-mask"><code class="function">gtk_accelerator_get_default_mod_mask()</code></a> to test against modifier keys. This function returns a bit mask which encompasses all the modifiers which the user may be actively pressing, such as <span class="keycap"><strong>Control</strong></span>, <span class="keycap"><strong>Shift</strong></span>, and <span class="keycap"><strong>Alt</strong></span>, but ignores "innocuous" modifiers such as <span class="keycap"><strong>NumLock</strong></span> and <span class="keycap"><strong>CapsLock</strong></span>. </p><p> Say you want to see if <span class="keycap"><strong>Control</strong></span>+<span class="keycap"><strong>F10</strong></span> was pressed. Doing a simple test like <code class="literal">event->keysym == GDK_F10 && event->state == GDK_CONTROL_MASK</code> is not enough. If <span class="keycap"><strong>CapsLock</strong></span> is pressed, then <em class="structfield"><code>event->state</code></em> will be equal to <code class="literal">GDK_CONTROL_MASK | GDK_LOCK_MASK</code>, and the simple test will fail. By taking the logical-and of <em class="structfield"><code>event->state</code></em> and <a class="link" href="gtk-Keyboard-Accelerators.html#gtk-accelerator-get-default-mod-mask"><code class="function">gtk_accelerator_get_default_mod_mask()</code></a>, you can ignore the modifiers which are not actively pressed by the user at the same time as the base key. </p><p> The following example correctly tests for <span class="keycap"><strong>Control</strong></span>+<span class="keycap"><strong>F10</strong></span> being pressed. </p><a name="default-mod-mask"></a><pre class="programlisting">static gbooleanmy_widget_key_press_event_handler (GtkWidget *widget, GdkEventKey *event){ guint modifiers; modifiers = gtk_accelerator_get_default_mod_mask (); if (event->keysym == GDK_F10 && (event->state & modifiers) == GDK_CONTROL_MASK) { g_print ("Control-F10 was pressed\n"); return TRUE; } return FALSE;} </pre></div></body></html>⌨️ 快捷键说明
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