sec-gdkevent.html

gtk 开发手册和参考文档。 包括gtk glib gdk等

              <span class="STRUCTNAME">GDK_BUTTON_PRESS</span>&#13;
            </p>
          </li>
          <li>
            <p>
              <span class="STRUCTNAME">
              GDK_3BUTTON_PRESS</span>&#13;
            </p>
          </li>
          <li>
            <p>
              <span class="STRUCTNAME">
              GDK_BUTTON_RELEASE</span>&#13;
            </p>
          </li>
        </ol>
        <p>
          The X server automatically causes a pointer grab when a
          button is pressed, and releases it when it is released.
          This means that the button release event always goes to
          the same window that received the button press event.
          Xlib allows you to change this behavior, but GDK does
          not. (In the Xlib documentation, this automatic grab is
          referred to as a "passive" grab. It's distinct from an
          "active" grab initiated with <tt class="FUNCTION">
          gdk_pointer_grab()</tt>, described in <a href= 
          "sec-gdkcursor.html#SEC-POINTERGRAB">the section called
          <i>Grabbing the Pointer</i></a>.)
        </p>
        <p>
          A button event is defined as follows:
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13;typedef struct _GdkEventButton GdkEventButton;

struct _GdkEventButton
{
  GdkEventType type;
  GdkWindow *window;
  gint8 send_event;
  guint32 time;
  gdouble x;
  gdouble y;
  gdouble pressure;
  gdouble xtilt;
  gdouble ytilt;
  guint state;
  guint button;
  GdkInputSource source;
  guint32 deviceid;
  gdouble x_root, y_root;
};&#13;
</pre>
            </td>
          </tr>
        </table>
        <p>
          Button events are marked with a time stamp (<span class= 
          "STRUCTNAME">time</span>) by the X server. The time is
          given in milliseconds of "server time"; every few weeks
          the integer overflows and timestamps begin again at 0.
          Thus, you should not rely on the value as an absolute
          measure of time; it is intended only to determine
          relative time between events.
        </p>
        <p>
          The mouse pointer's X and Y coordinates (relative to the
          window the event occurred in) are included in <span
          class="STRUCTNAME">GdkEventButton</span>. Keep in mind
          that the pointer may be outside the window (if a pointer
          grab is in effect; see <a href="sec-gdkcursor.html">the
          section called <i>The Mouse Pointer</i></a>). If the
          pointer is outside the window, its coordinates could be
          negative or larger than the window's size. Coordinates
          are given as doubles rather than integers, because some
          input devices such as graphics tablets have sub-pixel
          resolution. For most purposes, you will want to cast the
          doubles to integers. <span class="STRUCTNAME">
          pressure</span>, <span class="STRUCTNAME">xtilt</span>,
          and <span class="STRUCTNAME">ytilt</span> are also
          special features of some input devices; they can be
          ignored almost all the time.
        </p>
        <p>
          The <span class="STRUCTNAME">state</span> member of <span
          class="STRUCTNAME">GdkEventButton</span> indicates which
          modifier keys or mouse buttons were held down an instant
          before the button was pressed. It is a bitfield, with one
          or more of the flags in <a href= 
          "sec-gdkevent.html#TAB-MODMASKS">Table 5</a> set. Since
          the modifiers are read just before the button press, it
          follows that button press events do not have the pressed
          button in <span class="STRUCTNAME">state</span>, but
          button release events do have it.
        </p>
        <p>
          Be careful to check for the presence of certain bit
          masks, rather than the exact value of <span class= 
          "STRUCTNAME">state</span>. That is, prefer this:
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13; if ( (state &amp; GDK_SHIFT_MASK) == GDK_SHIFT_MASK )&#13;
</pre>
            </td>
          </tr>
        </table>
        <p>
          and avoid this:
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13; if ( state == GDK_SHIFT_MASK )&#13;
</pre>
            </td>
          </tr>
        </table>
        <p>
          If you check the exact value of <span class="STRUCTNAME">
          state</span>, your application will mysteriously stop
          working if the user has Num Lock or some other obscure
          modifier turned on.
        </p>
        <div class="TABLE">
          <a name="TAB-MODMASKS"></a>
          <p>
            <b>Table 5. Modifier Masks for Key and Button
            Events</b>
          </p>
          <table border="1" bgcolor="#E0E0E0" cellspacing="0"
          cellpadding="4" class="CALSTABLE">
            <tr>
              <th align="LEFT" valign="TOP">
                Modifier Mask
              </th>
              <th align="LEFT" valign="TOP">
                Meaning
              </th>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_SHIFT_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Shift
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_LOCK_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Caps Lock
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_CONTROL_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Control
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOD1_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Mod1 (often Meta or Alt)
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOD2_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Mod2
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOD3_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Mod3
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOD4_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Mod4
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOD5_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Mod5
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON1_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Button 1
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON2_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Button 2
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON3_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Button 3
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON4_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Button 4
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON5_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Button 5
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_RELEASE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Key releases
              </td>
            </tr>
          </table>
        </div>
        <p>
          The <span class="STRUCTNAME">button</span> member of
          <span class="STRUCTNAME">GdkEventButton</span> indicates
          which button triggered the event (i.e., the button which
          was pressed or released). Buttons are numbered from one
          to five; most of the time, button one is the left button,
          button two is the middle button, and button three is the
          right button. Left-handed users might reverse these.
          Button four and five events are generated by some scroll
          wheel mice when you spin the scroll wheel; GTK+ attempts
          to send capture these events and move nearby scroll bars.
          You should probably ignore any events you receive for
          buttons four or five.
        </p>
        <p>
          The three standard mouse buttons have conventional
          meanings in Gnome. Button one is used for selection, drag
          and drop, and operating widgets: the most common tasks.
          Button three typically activates a pop-up menu. Button
          two is traditionally used to move objects, such as the
          panel. Sometimes button one moves objects also; for
          example, desktop icons can be moved with either button
          one or two. It is a good idea to be consistent with other
          applications whenever possible.
        </p>
        <p>
          The <span class="STRUCTNAME">source</span> and <span
          class="STRUCTNAME">deviceid</span> members are used to
          determine which device triggered the event; the user may
          have a graphics tablet and a mouse connected
          simultaneously, for example. You can ignore these fields
          unless you are writing an application that can take
          advantage of non-mouse devices.
        </p>
        <p>
          The last two members of <span class="STRUCTNAME">
          GdkEventButton</span>, <span class="STRUCTNAME">
          x_root</span> and <span class="STRUCTNAME">y_root</span>,
          are the <span class="STRUCTNAME">x</span> and <span
          class="STRUCTNAME">y</span> coordinates translated to be
          relative to the root window rather than the window
          receiving the event. You can use these as "absolute"
          coordinates to compare events from two different windows.
        </p>
      </div>
      <div class="SECT2">
        <h2 class="SECT2">
          <a name="Z120">Keyboard Events</a>
        </h2>
        <p>
          There are only two types of key event: <span class= 
          "STRUCTNAME">GDK_KEY_PRESS</span> and <span class= 
          "STRUCTNAME">GDK_KEY_RELEASE</span>. Some hardware does
          not generate key release events; you should not write
          code that depends on <span class="STRUCTNAME">
          GDK_KEY_RELEASE</span> events, though your code should
          respond sanely if one is received.
        </p>
        <p>
          Here are the contents of a key event:
        </p>
        <table border="0" bgcolor="#E0E0E0" width="100%">
          <tr>
            <td>
<pre class="PROGRAMLISTING">
&#13;typedef struct _GdkEventKey GdkEventKey;

struct _GdkEventKey
{
  GdkEventType type;
  GdkWindow *window;
  gint8 send_event;
  guint32 time;
  guint state;
  guint keyval;
  gint length;
  gchar *string;
};&#13;
</pre>
            </td>
          </tr>
        </table>
        <p>
          The first three members are the standard members from
          <span class="STRUCTNAME">GdkEventAny</span>; the <span
          class="STRUCTNAME">time</span> and <span class=
          "STRUCTNAME">state</span> members are identical to those
          found in <span class="STRUCTNAME">GdkEventButton</span>.
        </p>
        <p>
          <span class="STRUCTNAME">keyval</span> contains a <i
          class="FIRSTTERM">keysym</i>. The X server keeps a global
          translation table which converts combinations of physical
          keys and modifiers to keysyms. For example, the ke