Hello,
I am writing a gui application it is supposed to save the position of the
window and upon restart restore the position.
For this I get the position via overriding the on-move method of frame%.
Upon restoring I call (send frame move x y).
The problem is that on my system (linux manjaro xfce gtk) move seems to
treat the position as the outer window position (left-top of the decorated
window).
When move is called and x y is different than what is returned via get-x
and get-y then on-move is called two times the first time with x and y.
The second time with the delta added which corresponds to
outer-window-pos+delta = inner-window-pos.
(send frame move outer-x outer-y) -> (on-move outer-x outer-y) -> (on-move
inner-x inner-y)
The resulting problem is that after every restart the window moves by the
delta because move adds the delta.
To me it seems like on-move should only be called once after a call to move
and move should take inner-xy directly.
That would mean it sets the position of the inner-window-coordinate instead
of setting the outer position.
Here is an example showing the move behaviour:
#lang racket/gui
(define moveframe%
(class frame%
(super-new)
(define/override (on-move x y)
(displayln (format "~a ~a" x y)))))
(define (example)
(define f (new moveframe% [label "move frame"] [width 300] [height 300]))
(define (m msg x y)
(displayln (~a msg " " x " " y ":"))
(send f move x y))
(m "init" 100 100)
(send f show #t)
(sleep/yield 1)
(m "reset" 100 100)
(sleep/yield 1)
;; this depends on the window decoration specific delta which is (1 24)
on my system
(m "stays the same, because x y are already" (send f get-x) (send f
get-y))
(sleep/yield 1)
(m "window decoration delta gets added" (add1 (send f get-x)) (send f
get-y))
(sleep/yield 1)
(m "window decoration delta gets added again" (add1 (send f get-x)) (send
f get-y))
(sleep/yield 1)
(send f show #f))
(module+ main
(example))
;; OUTPUT
;; init 100 100:
;; 100 100
;; 101 124
;; reset 100 100:
;; 100 100
;; 101 124
;; stays the same, because x y are already 101 124:
;; window decoration delta gets added 102 124:
;; 102 124
;; 103 148
;; window decoration delta gets added again 104 148:
;; 104 148
;; 105 172
And here is an ugly workaround I created that calculates the delta between
the outer and inner of the window:
#lang racket
(provide get-delta)
(require racket/gui/base)
(define deltaframe%
(class frame%
(init-field channel)
(super-new [label "get-delta-frame"])
(define ch channel)
(define first-pos #f)
(define/override (on-move x y)
(when ch
(if (not first-pos)
(set! first-pos (list x y))
(begin
(calc-delta ch first-pos (list x y))
(set! ch #f)))))
(define (calc-delta ch first second)
(match-define (list hx hy) first)
(match-define (list vx vy) second)
(define delta (list (- hx vx) (- hy vy)))
(thread
(thunk
(channel-put ch delta)
(send this show #f))))
(send this move 100 100)
(send this show #t)))
(define (get-delta/fetch)
(define ch (make-channel))
(thread
(thunk (new deltaframe% [channel ch])))
(define (loop)
(sync (handle-evt ch (λ (delta) delta))
(handle-evt always-evt (λ (x) (sleep/yield 0) (loop)))))
(loop))
(define delta #f)
(define (get-delta)
(set! delta (get-delta/fetch))
(set! get-delta (λ () delta))
delta)
;; result of get-delta on my system: (list -1 -24)
Does somebody else experience this behaviour?
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