Question

I want to create labels that the text in them can be selected for copy/paste. To do this I tried to use entries that are read-only. But I can’t seem to initialize the text value in them. The labels are generated inside a loop and the number of labels and their content is unknown. The code to produce the labels is:

proc test_labels {} {
    toplevel .labels
    # Main Frame
    frame       .labels.main_frame -relief "groove" -bd 2
    pack        .labels.main_frame

    set r 1

    foreach t [list banana apple grapes orange lemon peach] {
        set lbl  [label .labels.main_frame.lbl_$r   -text "fruit $r:"]
        set lbl2 [label .labels.main_frame.val_$r -text $t]

        grid $lbl  -row $r -column 1 -sticky nse
        grid $lbl2 -row $r -column 2 -sticky nsw

        incr r
    }
    set ok_btn [button .labels.main_frame.ok_b -text "OK" -command {prop_menu_ok_button}]
    grid $ok_btn -row [expr $r+2] -column 1 -columnspan 2 -sticky nsew

    grab release .
    grab set .labels
    center_the_toplevel .labels
    bind .labels <Key-Return> {test_labels_ok_button}
}

And it creates the fallowing window:

Then I try to replace the line set lbl2 [label .labels.main_frame.val_$r -text $t] with the lines:

eval "set text_val_$r $t"
eval "set lbl2 [entry .labels.main_frame.val_$r -relief flat -state readonly -textvar text_val_$r]"

But this only creates empty lines:

How can I put default values to entry widgets?

Related to the question How to make the text in a Tk label selectable?

Answer 1

These lines are almost certainly not what you want! (If you’re using eval, you should always ask whether it’s really necessary; from 8.5 onwards, the likely answer is “it’s not necessary”.)

eval "set text_val_$r $t"
eval "set lbl2 [entry   .labels.main_frame.val_$r -relief flat -state readonly -textvar \$\{text_var_$r\}]"

The key problem — apart from the use of eval — is that the -textvariable option takes the name of a variable. Let’s fix that by using an array to hold the values:

set text_val($r) $t
set lbl2 [entry .labels.main_frame.val_$r -relief flat -state readonly \
        -textvariable text_val($r)]

Also, be aware that the text_val array needs to be global (or in a namespace, if you fully qualify the name when giving it to the -textvariable option). This is because it is accessed from places which are outside the scope of any procedure.

Of course, it turns out that if we are keeping values constant then we can avoid using a variable at all and just insert the value manually.

set lbl2 [entry .labels.main_frame.val_$r -relief flat]
$lbl2 insert 0 $t
$lbl2 configure -state readonly

If you’re never changing the value, that will work fine.