TIP 84: Add control for mouse movement filtering

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by Aug 21.
Author:         Jyrki Alakuijala <Jyrki.Alakuijala@iki.fi>
Author:         Jeff Hobbs <JeffH@ActiveState.com>
State:          Final
Type:           Project
Vote:           Done
Created:        26-Feb-2002
Post-History:   
Tcl-Version:    8.4

Abstract

When the mouse is moved, the Tcl/Tk system eats most of the mouse movement events and only the last movement event when Tcl/Tk is not busy is stored in the event queue. I would like to obtain all the movement events from the X-server or the Windows UI.

Rationale

I have an artistic drawing program where I need to track mouse as accurately as possible. At the moment I poll the XQueryPointer() in the busy loops to create (pseudo)events in the C-side of the code to compensate for the missing events, but (of course) this does not work in Windows.

I would like to have an option for the widget system or for the window control so that a window (or, alternatively all the windows) could receive all the movement events instead of only the last buffered one.

This has been a problem for me since 1995 and has - at many times - caused me to consider changing the widget system.

Implementation

    int Tk_CollapseMotionEvents(Display *display, int collapse)

A reference implementation is SF Tk patch 564642, which adds a flag to the TkDisplay that specifies whether motions events should be collapsed or not. The default is the current behavior of collapsing these events.

Copyright

This document has been placed in the public domain.

History