Event Handling

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=ProPgEventHandling
• Last revised: 2022-06-07

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Handling (querying and processing) keyboard, mouse, and window Events.

Preamble:

Events are basically user actions like key press, clicks, mouse movements, etc., or some occurrence like system generated notifications.

The Event type plus the ScreenEvent function constitute a built-in interface provided by FreeBASIC for accessing events (keyboard, mouse, and window events).

ScreenEvent signals the events so the user can write his own event handlers (which require that he keeps track of the data himself).

By using ScreenEvent, the user can check the events as they are returned by the function.

It is assumed that this function is regularly called to fetch events as they are queued internally by the system.

Event type

The Event type is a pre-defined structure in "fbgfx.bi" (in the FB Namespace for the lang fb dialect only).

When the user calls ScreenEvent passing an instance of Event type, ScreenEvent fills in it with the event data (if an event flag is returned).

Syntax

#include once "fbgfx.bi"
Using FB
Dim variable As Event

"Event" structure

This structure is extracted from "fbgfx.bi".

start GeSHi

Type EVENT Field = 1
    Type As Long
    Union
        Type
            scancode As Long
            ascii As Long
        End Type
        Type
            x As Long
            y As Long
            dx As Long
            dy As Long
        End Type
        button As Long
        z As Long
        w As Long
    End Union
End Type

end GeSHi

• .type field contains the event type ID value corresponding to one of the following symbols defined in "fbgfx.bi":