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<concept id="GUID-EF7FF39E-929F-4767-B475-5D582D37BB32" xml:lang="en"><title>Window

server events</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Window server events are an important part of the application framework.

They allow applications to receive information regarding key presses, pointer

activities, application switches, and focus transitions. </p>

<p>Every application has at least a <xref href="GUID-FD2CDEB8-0784-4BE5-A775-170F57D71BBC.dita">UI

controller</xref>, which is the root for all other controls owned by the application.

When an event occurs under the window server, the window server passes the

event to the UI controller and possible other controls, depending on the event

and the architecture of your application.</p>

<p>For more information on the window server, see <xref href="GUID-0C4B86B5-530A-5839-86C1-46E7ABE281E0.dita">Introduction

to the window server</xref>.</p>

<p>The framework provides different functions to handle each type of event

separately. You must implement these functions for the events to be handled

by your application.</p>

<p> All the window server event types are defined in the <parmname>w32std.h</parmname> header,

and are as follows:</p>

<codeblock id="GUID-2F04E088-73B0-4006-903D-4651223E0434" xml:space="preserve">enum TEventCode 

    { 

    EEventNull, 

    EEventKey, 

    EEventKeyUp, 

    EEventKeyDown, 

    EEventModifiersChanged, 

    EEventPointer, 

    EEventPointerEnter, 

    EEventPointerExit, 

    EEventPointerBufferReady, 

    EEventDragDrop, 

    EEventFocusLost, 

    EEventFocusGained, 

    EEventSwitchOn, 

    EEventWindowGroupsChanged, 

    EEventErrorMessage, 

    EEventMessageReady, 

    EEventMarkInvalid, 

    EEventSwitchOff, 

    EEventKeySwitchOff, 

    EEventScreenDeviceChanged, 

    EEventFocusGroupChanged, 

    EEventCaseOpened, 

    EEventCaseClosed, 

    EEventWindowGroupListChanged, 

    EEventWindowVisibilityChanged, 

    EEventKeyRepeat=100, 

    EEventDirectScreenAccessBegin = 200, 

    EEventDirectScreenAccessEnd, 

    EEventHeartbeatTimerStateChange, 

    EEventUser = 1000, 

    }; 

</codeblock>

<p>The following window server events have a special function:</p>