nandi/jolt-native · 99fabc1

⑂ 99fabc1

Answer screen-size with numbers before there is a window

A client asks this while it is starting. frq computes its layout from
(long (second (screen-size))) on its first tick, which runs before the
window opens, so nil was a NullPointerException in the caller rather than
a small first frame -- found by running frq against this backend, not by
reading it.

window-width already answered 0 for the same reason. A layout computed
against zero for one frame is a layout nobody saw; the value is right on
the next tick.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nandi committed 2026-09-10T05:59:17-07:00 Browse files

99fabc1 parent: c7dc288

modified jvui/src/jvui/host.clj +12 -2 Viewed

@@ -59,9 +59,19 @@
59	59	(or (first (window-size)) 0))
60	60
61	61	(defn screen-size
62		- "[w h] of the display this window is on, or nil with no window."
	62	+ "[w h] of the display this window is on. [0 0] before there is one.
	63	+
	64	+ NUMBERS, not nil, and that is the whole point of the zero. A client asks
	65	+ this while it is starting — frq computes its layout from
	66	+ `(long (second (screen-size)))` on the first tick, which is before the
	67	+ window opens — and nil there is a NullPointerException in the caller
	68	+ rather than a small first frame. `window-width` already answers 0 for the
	69	+ same reason; this matches it.
	70	+
	71	+ The value is right on the next tick, and a layout computed against zero
	72	+ for one frame is a layout nobody saw."
63	73	[]
64		- (when-let [w @win] (sdl/display-bounds w)))
	74	+ (or (when-let [w @win] (sdl/display-bounds w)) [0 0]))
65	75
66	76	;; --- the world outside -------------------------------------------------------
67	77

    (or (first (window-size)) 0))
  (defn screen-size
--  "[w h] of the display this window is on, or nil with no window."
++  "[w h] of the display this window is on. [0 0] before there is one.
++
++  NUMBERS, not nil, and that is the whole point of the zero. A client asks
++  this while it is starting — frq computes its layout from
++  `(long (second (screen-size)))` on the first tick, which is before the
++  window opens — and nil there is a NullPointerException in the caller
++  rather than a small first frame. `window-width` already answers 0 for the
++  same reason; this matches it.
++
++  The value is right on the next tick, and a layout computed against zero
++  for one frame is a layout nobody saw."
    []
--  (when-let [w @win] (sdl/display-bounds w)))
++  (or (when-let [w @win] (sdl/display-bounds w)) [0 0]))
  ;; --- the world outside -------------------------------------------------------

modified jvui/test/jvui/host_check.clj +4 -1 Viewed

@@ -15,7 +15,10 @@
15	15	ck! (fn [n ok?] (swap! out conj [n (boolean ok?)]))
16	16	seen (atom 0)]
17	17	;; Before any window: everything must answer harmlessly rather than throw.
18		- (ck! "no window: screen-size is nil" (nil? (host/screen-size)))
	18	+ ;; Numbers and not nil: a client that asks before the window is open
	19	+ ;; does arithmetic on the answer. frq does exactly that on its first
	20	+ ;; tick, and nil there was a NullPointerException in the caller.
	21	+ (ck! "no window: screen-size is [0 0]" (= [0 0] (host/screen-size)))
19	22	(ck! "no window: window-width is 0" (zero? (host/window-width)))
20	23	(ck! "no window: set-title! is quiet" (nil? (host/set-title! "x")))
21	24	(ck! "no window: no clipboard picture" (false? (host/clipboard-image-png! "/tmp/nope.png")))

          ck! (fn [n ok?] (swap! out conj [n (boolean ok?)]))
          seen (atom 0)]
      ;; Before any window: everything must answer harmlessly rather than throw.
--    (ck! "no window: screen-size is nil"   (nil? (host/screen-size)))
++    ;; Numbers and not nil: a client that asks before the window is open
++    ;; does arithmetic on the answer. frq does exactly that on its first
++    ;; tick, and nil there was a NullPointerException in the caller.
++    (ck! "no window: screen-size is [0 0]" (= [0 0] (host/screen-size)))
      (ck! "no window: window-width is 0"    (zero? (host/window-width)))
      (ck! "no window: set-title! is quiet"  (nil? (host/set-title! "x")))
      (ck! "no window: no clipboard picture" (false? (host/clipboard-image-png! "/tmp/nope.png")))