Layout does not automatically adjust. What can I do?

Questions & Answers
1

Hi,

I've got following code (as a spike):

(require racket/gui)

(define win (new frame% [label "Hi there!"]))
(define grid-group (new group-box-panel% [label "My group"] [parent win] [horiz-margin 10] [vert-margin 10]))

(define g1 (new horizontal-pane% [parent grid-group]))
(define g1-1 (new horizontal-pane% [alignment '(left center)] [parent g1] [min-width 200]))
(define g1-2 (new horizontal-pane% [alignment '(left center)] [parent g1] [min-width 300]))
(define g1-3 (new horizontal-pane% [alignment '(center center)] [parent g1] [min-width 100]))

(define btn1 (new button% [parent g1-1] [label "Button 1"]
                  [callback (lambda (b e)
                              (send lbl1 set-label "New label")
                              ;(send g1 reflow-container)
                              ;(send g1-3 container-flow-modified)
                              )]))
(define gg1 (new gauge%  [parent g1-2] [stretchable-width #t] [label "gauge 1"] [range 100]))
(define lbl1 (new message% [parent g1-3] [label "This is lbl 1 and long"]))

(define g2 (new horizontal-pane% [parent grid-group]))
(define g2-1 (new horizontal-pane% [alignment '(left center)] [parent g2] [min-width 200]))
(define g2-2 (new horizontal-pane% [alignment '(left center)] [parent g2] [min-width 300]))
(define g2-3 (new horizontal-pane% [alignment '(center center)] [parent g2] [min-width 100]))

(define btn2 (new button% [parent g2-1] [label "Btn 2"]))
(define g2-lbl (new message% [parent g2-2] [label "This is something else then a gauge"]))
(define lbl2 (new message% [parent g2-3] [label "This is lbl 2"]))

(define g3 (new horizontal-pane% [parent grid-group]))
(define g3-1 (new horizontal-pane% [alignment '(left center)] [parent g3] [min-width 200]))
(define g3-2 (new horizontal-pane% [alignment '(left center)] [parent g3] [min-width 300]))
(define g3-3 (new horizontal-pane% [alignment '(center center)] [parent g3] [min-width 100]))

(define btn3 (new button% [parent g3-1] [label "Btn 3"]
                  [callback (lambda (b e) (send lbl3 set-label "Longer label now"))]))
(define g3-lbl (new message% [parent g3-2] [label "This is something else then a gauge, another message"]))
(define lbl3 (new message% [parent g3-3] [label "short"]))

(send win show #t)

It results in the following window:

afbeelding
afbeelding646×184 11 KB

As can be seen, the labels on the right are centered. This is as expected.
Now, when I push 'Button 1', the label on the right will change to "New label".

afbeelding
afbeelding646×184 10.7 KB

What happens here? The label is not centered anymore, while the horizontal alignment of the containing horizontal-pane% is 'center.

When I push 'Btn3', the short label is changed to "Longer label now". And that looks like this:

afbeelding
afbeelding646×184 11.3 KB

So, the "Longer label..." is displayed, but not centered.

What am I missing here?

Thanks in advance for your answers.

2

Replying to myself. Apparently there is an option 'auto-resize' for message%. This already helps a lot. But is there a generic solution, also applicable for other widgets?

E.g. check-box%.