[Tcl-bugs] [ tktoolkit-Patches-2863003 ] Add a virtual event when GM leaves parent without slaves

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Patches item #2863003, was opened at 2009-09-20 20:41
Message generated for change (Comment added) made by egavilan
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Category: 48. Geometry Management
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Emiliano (egavilan)
Assigned to: Chengye Mao (chengyemao)
Summary: Add a virtual event when GM leaves parent without slaves

Initial Comment:
When trying to build a custom scrolledframe one generally resorts to the <Configure> event to catch the resizing of the scrolled frame [usually a frame inside a canvas] to keep scrollbars in sync. The problem with this approach is that, when the last slave is removed from inside the frame, the geometry managers leave the frame size as-is, and the scrolled frame ends scrolling an empty region.
This can be noted in this BWidget example:
==================================================
package require BWidget

set sw [ScrolledWindow .sw]
set sf [ScrollableFrame .sf]
$sw setwidget $sf
set f [$sf getframe]

pack $sw -expand 1 -fill both -padx 10 -pady 10

for {set i 0} {$i <= 20} {incr i} {
	grid \
		[label $f.la$i -text "Label a order $i"] \
		[label $f.lb$i -text "Label b order $i"] \
		[label $f.lc$i -text "Label c order $i"]
}

after 5000 {destroy {*}[winfo children $sf]}
=================================================

A way to note when the GM removes the last slave is to deliver a virtual event to the master.
This patch adds the virtual event, and is intended as a sketch of the final code (the name of the
virtual event, and whether to send additional details or not can be changed)


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>Comment By: Emiliano (egavilan)
Date: 2009-09-20 20:59

Message:
Forgot to mention, patch's code is copied almost literally from the
GenerateModifiedEvent() function in generic/tkText.c

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=312997&aid=2863003&group_id=12997