Text Widget List Viewer

 

 

The list widget is a great tool for displaying related information in sets. That is a sample, distributed across rows and columns. To do this the list widget creates cells for each sample and allocated memory to handle its formatting and data. In practice, this means two 'blocks' for each piece of data. The information to display, and how to display it.

This arrangement works fine for large humanly workable amounts of data, perhaps up to 1,500 or more rows. But, what about more, much, much more?

I have a translation data set with source and target language pairs well in excess of 57,000 pairs. The list widget will handle these, but the delay receiving and rendering is far too long. The solution then, is to tweak the text widget to handle similar rows with a row picker. Sounds complicated, but its not. Just a couple of tweaks needed. Put the text widget inside an eventBox and then trap any direct events being passed to it, whilst allowing the scrolledWindow container to get the input it needs.

Why do this? By default the text widget will change the mouse pointer to an edit bar. The eventBox retains use of the

Achieving the latter is the easiest, nothing required. The scrolledWindow takes priority over the eventBox by default. So, turn off the text cursor, and make it invisible and respond to the eventBox mouse button events to change the paragraph colour of the selected block -simples!

 

# !/bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" "$@"

package require Gnocl


# ~~~~~~~~~~~~~~~~~~~~~~~~~~

set txt [gnocl::text -editable 0 -cursorVisible 0]
$txt tag create idx -paragraph orange

set ebox [gnocl::eventBox -child $txt -aboveChild 1]
gnocl::window -child $ebox -setSize 0.2


# add some text to the widget.
for {set i 0} {$i<250} {incr i} {
append buff "$i) Lorem\n"
append buff [gnocl::lorem]\n
}
$txt set $buff
puts [$txt getLineCount]


#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# SET EBOX EVENTS TO SIMULATE LINE SELECTION AND TEXT SCROLLING
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
$ebox configure \
-onButtonRelease {
    %c tag remove start end -tags idx
    %c setCursor [%c getPos]
    %c tag apply lineStart lineEnd -tags idx
} \
-onScroll {
    if { "%D" == "down" } {
        incr ::scrollPos 5
            if { $::scrollPos > [%c getLineCount] } { set ::scrollPos [%c getLineCount]}
        } else {
            incr ::scrollPos -5
            if { $::scrollPos < 0 } { set ::scrollPos 0}
        }
    %c scrollToPosition "$::scrollPos 0"   
}