Volume One: Xlib Programming Manual - Niksula

Figure 9−5. Correct forms fill−in result using a synchronous key grab
To summarize, the solution to this form of type−ahead problem is to use GrabModeSync as the keyboard_mode
argument of the passive grab on the Tab key. Then call XAllowEvents() in response the arrival of the Tab key event
that signals the change in windows. This synchronizes the change of keyboard focus from one window to another and
assures that the events go to the intended window.
9.5 Keyboard Preferences
Xlib provides routines to control beep pitch and volume, key click, Shift−Lock mode, mouse acceleration, keyboard lights
and keyboard auto−repeat. Not all servers will actually be able to control all of these parameters.
There are five routines that deal with the keyboard and pointer preferences. XGetKeyboardControl() and
XChangeKeyboardControl() are the primary routines for getting or setting all these preferences at once.
XAutoRepeatOff() and XAutoRepeatOn() set the global keyboard auto−repeat status but are not able to control
the auto−repeat of individual keys as XChangeKeyboardControl() can.
9.5.1 Setting Keyboard Preferences
XChangeKeyboardControl() uses the standard X method of changing internal structure members. The values
argument to XChangeKeyboardControl() specifies the structure containing the desired values; the value_mask
argument specifies which members in the structure specified in values should replace the current settings. See the
reference page for XChangeKeyboardControl() in Volume Two, Xlib Reference Manual, for a list of the mask
symbols.
Example 9−13 shows the XKeyboardControl() structure.
Example 9−13. The XKeyboardControl() structure
typedef struct {
int key_click_percent;
int bell_percent;
int bell_pitch;
int bell_duration;
int led;
int led_mode; /* LedModeOn or LedModeOff */
int key;
int auto_repeat_mode; /* AutoRepeatModeOff, AutoRepeatModeOn,
* AutoRepeatModeDefault */
} XKeyboardControl;
The following list describes each member of the XKeyboardControl() structure:
• key_click_percent sets the volume for key clicks between 0 (off) and 100 (loud), inclusive.
• bell_percent sets the base volume for the bell (or beep) between 0 (off) and 100 (loud), inclusive.
• bell_pitch sets the pitch (specified in Hz) of the bell.