nandi/jolt-native · core.clj

⑂ 32fae8d36cadee8d58ff342979aea79722e69784

core.clj · 328 lines · 13.0 KBClojure    Blame HistoryRaw
Write dvui's shape in jolt, on SDL3, with no shared object  Veronika Winters 1(ns glimmer-jvui.core
"A glimmer backend that renders through [jvui](../../../jvui).
 glimmer owns the reactive core — ratoms, components, the reconciler — and
 knows nothing about any toolkit. glimmer-gtk fills that in with GtkWidgets,
 glimmer-vidya with a Rust node arena painted by egui, glimmer-gfx with a
 software rasterizer it writes itself. This fills it in with jvui, and so is
 the smallest of the four: everything a backend usually has to supply — the
 measuring, the placing, the hit testing, the painting — is already a toolkit
 one directory over.
 What is left is the half an immediate-mode library does not have: a tree to
 hold still between frames. The reconciler needs somewhere to put a widget it
 created and to append a child to, and jvui's widgets draw and return within
 one call. So a node here is an atom of {:tag :props :children :key}, about
 thirty lines of it, and once a frame `emit!` walks that tree and calls the
 jvui widget each node names.
 # The walk is the closure
 glimmer-vidya's README explains why its tree lives in Rust: `ScrollArea` and
 `Frame` take an `FnOnce(&mut Ui)` and keep their begin/end private, so a
 push/pop ABI cannot scroll a page. jvui's containers take a body function
 for the same reason, and here the recursion *is* that function — `emit!` on
 a container passes `emit-children!` as the body, and the nesting takes care
 of itself.
 # Why every node carries a key
 jvui identifies a widget by its parent and its index among its siblings,
 unless it is given a `:key`, which replaces the index. A reconciler reorders
 children; an identity built on the index would hand each widget after the
 moved one the caret, the scroll offset and the drag of whichever widget used
 to sit at its index. So every node gets a serial number at creation and
 passes it as its key, and the identity follows the node rather than its
 position. That is the bug class zvui's README describes from the backend
 side, closed here at the other end."
(:require [glimmer.backend :as b]
          [jvui.app :as app]
          [jvui.core :as c]
          [jvui.theme :as theme]
Give jvui a picture from somewhere else, and a clock   42            [jvui.widgets :as w]
          [jvui.frames :as frames]))
Write dvui's shape in jolt, on SDL3, with no shared object  Veronika Winters 44
45;; --- the retained tree -------------------------------------------------------
47(defonce ^:private serial (atom 0))
49(defn- create! [tag props]
(atom {:tag tag :props props :children [] :key (swap! serial inc)}))
52(defn- apply-props! [_tag n props] (swap! n assoc :props props) nil)
53(defn- append-child! [_t parent child] (swap! parent update :children conj child) nil)
54(defn- remove-child! [_t parent child]
(swap! parent update :children #(vec (remove #{child} %))) nil)
56(defn- replace-child! [_t parent old new]
(swap! parent update :children #(mapv (fn [c] (if (= c old) new c)) %)) nil)
58(defn- reorder-child! [_t parent child sibling]
(swap! parent update :children
       (fn [cs]
         (let [cs (vec (remove #{child} cs))
               i (if (nil? sibling) 0 (inc (.indexOf cs sibling)))]
           (vec (concat (subvec cs 0 i) [child] (subvec cs i))))))
66;; --- props -------------------------------------------------------------------
68(defn- txt [props] (str (or (:label props) (:text props) "")))
70(defn- num [v default] (if (number? v) (double v) default))
72(defn- box-opts
"The container options shared by every container tag."
[props key]
(cond-> {:key key
         :dir (if (= :horizontal (:orientation props)) :horizontal :vertical)}
  (:spacing props) (assoc :spacing (num (:spacing props) 0.0))
  (:padding props) (assoc :padding (num (:padding props) 0.0))
  (:margin props)  (assoc :margin (num (:margin props) 0.0))
  (:expand props)  (assoc :expand (:expand props))))
82(defn- fire! [n k & args]
(when-let [f (get (:props @n) k)] (apply f args)))
85;; --- the walk ----------------------------------------------------------------
87(def ^:dynamic *record-rects?*
"When true, each node keeps the rectangle jvui gave it, under `:rect`.
 Off in a running window, where it would be a `swap!` per node per frame for
 nobody's benefit. On under `render-once`, so a test can click the centre of
 a button the way a person would, rather than guessing at a coordinate and
 re-guessing every time a padding changes."
96(declare emit!)
98(defn- record! [n id]
(when *record-rects?* (swap! n assoc :rect (c/rect-of id)))
102(defn- emit-children! [n]
(fn [_id _rect] (doseq [c (:children @n)] (emit! c))))
105(defn- emit!
"Render one node, and through it everything below it.
 A widget answers what the person did to it, and that answer is turned back
 into the callback prop the component registered — which is the whole seam
 between an immediate-mode toolkit and a retained, callback-shaped one."
(let [{:keys [tag props key]} @n
      s (txt props)]
  (case tag
    :page (w/page* (cond-> {:key key}
                     (:max-width props) (assoc :max-width (:max-width props)))
                   (emit-children! n))
    (:card :frame) (w/card* (box-opts props key) (emit-children! n))
    :scroll (w/scroll* (assoc (box-opts props key)
                              :height (num (:height props) 200.0))
                       (emit-children! n))
    :hbox (c/box* (assoc (box-opts props key) :dir :horizontal)
                  (emit-children! n))
    (:vbox :box) (c/box* (box-opts props key) (emit-children! n))
Give jvui a picture from somewhere else, and a clock   130      ;; A live picture: a camera, a call, anything a decoder is filling in
    ;; between frames. The node carries only the KEY — the pixels never go
    ;; through the reconciler, because a video frame arrives when the
    ;; network says so and a props diff at thirty a second would be a
    ;; re-render per frame per peer.
    :video (w/video (or (:feed props) (:key props) (str key))
                    (cond-> {}
                      (:size props)    (assoc :size (:size props))
                      (:expand props)  (assoc :expand (:expand props))
                      (:gravity props) (assoc :gravity (:gravity props))))
Write dvui's shape in jolt, on SDL3, with no shared object  Veronika Winters 141      :title (w/title s)
    :label (if (:dim props) (w/dim-label s) (w/label s))
    :dim-label (w/dim-label s)
    :button (let [id (c/next-id key)
                  hit? (w/button s {:key key :kind (or (:kind props) :normal)})]
              (record! n id)
              (when hit? (fire! n :on-click)))
    :checkbox (let [was (boolean (:checked props))
                    id (c/next-id key)
                    now (w/checkbox was s {:key key})]
                (record! n id)
                (when (not= now was) (fire! n :on-change now)))
    :slider (let [was (num (:value props) 0.0)
                  id (c/next-id key)
                  now (w/slider was {:key key
                                     :min (num (:min props) 0.0)
                                     :max (num (:max props) 100.0)})]
              ;; == and not not=, because a component holding a long 0 must
              ;; not be told every frame that its slider moved to 0.0
              (record! n id)
              (when-not (== now was) (fire! n :on-change now)))
    (:entry :text-entry)
    (let [was (str (or (:value props) (:text props) ""))
          id (c/next-id key)
          now (w/text-entry was {:key key :placeholder (:placeholder props)})]
      (record! n id)
      (when (not= now was) (fire! n :on-change now)))
    :progress (w/progress (num (:value props) 0.0))
    :separator (w/separator)
    (:spacer :gap) (w/spacer {:size (num (:size props) 8.0)
                              :expand (:expand props :none)})
    ;; An unknown tag is a container rather than an error, so a tree written
    ;; against a richer backend still shows its contents here — the same
    ;; bargain jolt-zvui makes with the tags it does not know.
    (c/box* (box-opts props key) (emit-children! n)))))
184;; --- the loop ----------------------------------------------------------------
186(defonce ^:private pending (atom []))
188(defn- schedule! [work] (swap! pending conj work) nil)
Give jvui a picture from somewhere else, and a clock   190;; --- timers -----------------------------------------------------------------
191;; A client needs somewhere to run work that is not a reaction to anything:
192;; frq drives its whole media plane from `(every! 16 pump!)`, and a decoded
193;; frame arrives because a timer asked for it rather than because a person
194;; clicked. There is no other hook of the right shape — a component body runs
195;; when its state changes, which for a video feed is never.
197;; Run from the same `:before` as the reconciler's queue, and for the same
198;; reason: a callback that patches the tree must not do it mid-walk.
200(defonce ^:private timers (atom {}))
201(defonce ^:private next-timer (atom 0))
203(defn- now-ms [] (System/currentTimeMillis))
205(defn after!
"Run `f` once, at least `ms` from now. Answers a handle for `cancel!`."
207
(let [id (swap! next-timer inc)]
  (swap! timers assoc id {:at (+ (now-ms) ms) :every nil :f f})
210
212(defn every!
"Run `f` every `ms`. Answers a handle for `cancel!`.
Every `ms` AT MOST, not exactly: it fires on the first frame after the
deadline, so a 16ms timer on a 60Hz window runs once a frame and on a
slower one runs less often. That is the right failure — a timer that tried
to catch up would run twice in a row on a stutter, and for a pump that
means two frames decoded and one shown."
220
(let [id (swap! next-timer inc)]
  (swap! timers assoc id {:at (+ (now-ms) ms) :every ms :f f})
223
225(defn cancel!
"Stop a timer."
(swap! timers dissoc id)
231(defn- run-timers! []
(let [t (now-ms)
      due (filter (fn [[_ v]] (<= (:at v) t)) @timers)]
  (doseq [[id {:keys [every f]}] due]
    (if every
      (swap! timers assoc-in [id :at] (+ t every))
      (swap! timers dissoc id))
    ;; A throwing timer is cancelled rather than allowed to throw every
    ;; frame for the rest of the session, which is unreadable and stops
    ;; the ones behind it.
    (try (f)
         (catch Exception e
           (swap! timers dissoc id)
           (println "glimmer-jvui: timer failed, cancelled:" (ex-message e)))))))
Write dvui's shape in jolt, on SDL3, with no shared object  Veronika Winters 246(defn- drain-pending! []
Give jvui a picture from somewhere else, and a clock   247  (run-timers!)
Write dvui's shape in jolt, on SDL3, with no shared object  Veronika Winters 248  (let [[ws] (reset-vals! pending [])]
  (doseq [w ws] (w))))
251(defn- run!
"glimmer.backend's :run. Creates the root page, mounts into it, then hands the
 loop to jvui.
 The reconciler's queued work is drained by jvui's `:before` hook rather than
 inside the walk: a re-render patches the tree, and patching a tree while it
 is being walked is how a frame ends up half old and half new."
[opts mount-root!]
(let [{:keys [title width height max-width theme frames auto-quit-ms shot]
       :or {title "glimmer" width 720 height 520}} opts
      root (create! :page (cond-> {} max-width (assoc :max-width max-width)))]
  (mount-root! root :page)
  (reset! b/loop-running? true)
264
    (app/run! (fn [] (emit! root))
              {:title title :width width :height height
               :theme (or theme theme/dark)
               :before drain-pending!
               :frames frames :auto-quit-ms auto-quit-ms :shot shot})
    (finally (reset! b/loop-running? false)))))
272;; --- registration ------------------------------------------------------------
274(def backend
{:name :jvui
 :create! create!               :apply-props!   apply-props!
 :append-child! append-child!   :remove-child!  remove-child!
 :replace-child! replace-child! :reorder-child! reorder-child!
 :schedule schedule!            :run            run!})
281(b/register! backend)
283;; --- headless driving, for tests ---------------------------------------------
285(defn root-node
"A bare root page, for mounting into without a window."
[] (create! :page {}))
289(defn render-once
"Walk `root` through jvui with no window, no font and no display.
 `cx` is a `jvui.core/context`; `evs` the events that frame. Answers the
 context, whose `:data` is every rectangle the walk placed — which is enough
 for a test to assert about a layout and to click on it."
([root cx] (render-once root cx []))
([root cx evs]
 (drain-pending!)
 (swap! cx assoc :events evs)
 (swap! cx c/apply-input evs)
 (binding [*record-rects?* true]
   (c/frame! cx (fn [] (emit! root))))
Give jvui a picture from somewhere else, and a clock   303
304;; --- feeds ------------------------------------------------------------------
305;; The same three calls glimmer-vidya exposes, so a client that paints a call
306;; does not care which backend is under it. They are not part of the
307;; reconciler and deliberately so: pixels arrive between frames, and the tree
308;; only ever holds the key.
310(defn frame-rgba!
"Hand feed `key` a new picture: `w` by `h` RGBA at FOREIGN pointer `px`.
The pointer is read during this call and not kept, so a caller may reuse
or free it immediately afterwards — which is what a decoder handing out a
borrowed buffer needs."
[key w h px]
(frames/put! key w h px))
319(defn frame-drop!
"Forget a feed and release its texture — someone left, or turned a camera
(frames/drop! key))
325(defn feed-keys
"Every feed with a picture."
(frames/keys*))

Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago	1	(ns glimmer-jvui.core
	2	"A glimmer backend that renders through [jvui](../../../jvui).
	3
	4	glimmer owns the reactive core — ratoms, components, the reconciler — and
	5	knows nothing about any toolkit. glimmer-gtk fills that in with GtkWidgets,
	6	glimmer-vidya with a Rust node arena painted by egui, glimmer-gfx with a
	7	software rasterizer it writes itself. This fills it in with jvui, and so is
	8	the smallest of the four: everything a backend usually has to supply — the
	9	measuring, the placing, the hit testing, the painting — is already a toolkit
	10	one directory over.
	11
	12	What is left is the half an immediate-mode library does not have: a tree to
	13	hold still between frames. The reconciler needs somewhere to put a widget it
	14	created and to append a child to, and jvui's widgets draw and return within
	15	one call. So a node here is an atom of {:tag :props :children :key}, about
	16	thirty lines of it, and once a frame `emit!` walks that tree and calls the
	17	jvui widget each node names.
	18
	19	# The walk is the closure
	20
	21	glimmer-vidya's README explains why its tree lives in Rust: `ScrollArea` and
	22	`Frame` take an `FnOnce(&mut Ui)` and keep their begin/end private, so a
	23	push/pop ABI cannot scroll a page. jvui's containers take a body function
	24	for the same reason, and here the recursion is that function — `emit!` on
	25	a container passes `emit-children!` as the body, and the nesting takes care
	26	of itself.
	27
	28	# Why every node carries a key
	29
	30	jvui identifies a widget by its parent and its index among its siblings,
	31	unless it is given a `:key`, which replaces the index. A reconciler reorders
	32	children; an identity built on the index would hand each widget after the
	33	moved one the caret, the scroll offset and the drag of whichever widget used
	34	to sit at its index. So every node gets a serial number at creation and
	35	passes it as its key, and the identity follows the node rather than its
	36	position. That is the bug class zvui's README describes from the backend
	37	side, closed here at the other end."
	38	(:require [glimmer.backend :as b]
	39	[jvui.app :as app]
	40	[jvui.core :as c]
	41	[jvui.theme :as theme]
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 9d ago	42	[jvui.widgets :as w]
	43	[jvui.frames :as frames]))
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago	44
	45	;; --- the retained tree -------------------------------------------------------
	46
	47	(defonce ^:private serial (atom 0))
	48
	49	(defn- create! [tag props]
	50	(atom {:tag tag :props props :children [] :key (swap! serial inc)}))
	51
	52	(defn- apply-props! [_tag n props] (swap! n assoc :props props) nil)
	53	(defn- append-child! [_t parent child] (swap! parent update :children conj child) nil)
	54	(defn- remove-child! [_t parent child]
	55	(swap! parent update :children #(vec (remove #{child} %))) nil)
	56	(defn- replace-child! [_t parent old new]
	57	(swap! parent update :children #(mapv (fn [c] (if (= c old) new c)) %)) nil)
	58	(defn- reorder-child! [_t parent child sibling]
	59	(swap! parent update :children
	60	(fn [cs]
	61	(let [cs (vec (remove #{child} cs))
	62	i (if (nil? sibling) 0 (inc (.indexOf cs sibling)))]
	63	(vec (concat (subvec cs 0 i) [child] (subvec cs i))))))
	64	nil)
	65
	66	;; --- props -------------------------------------------------------------------
	67
	68	(defn- txt [props] (str (or (:label props) (:text props) "")))
	69
	70	(defn- num [v default] (if (number? v) (double v) default))
	71
	72	(defn- box-opts
	73	"The container options shared by every container tag."
	74	[props key]
	75	(cond-> {:key key
	76	:dir (if (= :horizontal (:orientation props)) :horizontal :vertical)}
	77	(:spacing props) (assoc :spacing (num (:spacing props) 0.0))
	78	(:padding props) (assoc :padding (num (:padding props) 0.0))
	79	(:margin props) (assoc :margin (num (:margin props) 0.0))
	80	(:expand props) (assoc :expand (:expand props))))
	81
	82	(defn- fire! [n k & args]
	83	(when-let [f (get (:props @n) k)] (apply f args)))
	84
	85	;; --- the walk ----------------------------------------------------------------
	86
	87	(def ^:dynamic record-rects?
	88	"When true, each node keeps the rectangle jvui gave it, under `:rect`.
	89
	90	Off in a running window, where it would be a `swap!` per node per frame for
	91	nobody's benefit. On under `render-once`, so a test can click the centre of
	92	a button the way a person would, rather than guessing at a coordinate and
	93	re-guessing every time a padding changes."
	94	false)
	95
	96	(declare emit!)
	97
	98	(defn- record! [n id]
	99	(when record-rects? (swap! n assoc :rect (c/rect-of id)))
	100	nil)
	101
	102	(defn- emit-children! [n]
	103	(fn [_id _rect] (doseq [c (:children @n)] (emit! c))))
	104
	105	(defn- emit!
	106	"Render one node, and through it everything below it.
	107
108	A widget answers what the person did to it, and that answer is turned back
109	into the callback prop the component registered — which is the whole seam
110	between an immediate-mode toolkit and a retained, callback-shaped one."
111	[n]
112	(let [{:keys [tag props key]} @n
113	s (txt props)]
114	(case tag
115	:page (w/page* (cond-> {:key key}
116	(:max-width props) (assoc :max-width (:max-width props)))
117	(emit-children! n))
118
119	(:card :frame) (w/card* (box-opts props key) (emit-children! n))
120
121	:scroll (w/scroll* (assoc (box-opts props key)
122	:height (num (:height props) 200.0))
123	(emit-children! n))
124
125	:hbox (c/box* (assoc (box-opts props key) :dir :horizontal)
126	(emit-children! n))
127
128	(:vbox :box) (c/box* (box-opts props key) (emit-children! n))
129
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 9d ago	130	;; A live picture: a camera, a call, anything a decoder is filling in
	131	;; between frames. The node carries only the KEY — the pixels never go
	132	;; through the reconciler, because a video frame arrives when the
	133	;; network says so and a props diff at thirty a second would be a
	134	;; re-render per frame per peer.
	135	:video (w/video (or (:feed props) (:key props) (str key))
	136	(cond-> {}
	137	(:size props) (assoc :size (:size props))
	138	(:expand props) (assoc :expand (:expand props))
	139	(:gravity props) (assoc :gravity (:gravity props))))
	140
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago	141	:title (w/title s)
	142
	143	:label (if (:dim props) (w/dim-label s) (w/label s))
	144	:dim-label (w/dim-label s)
	145
	146	:button (let [id (c/next-id key)
	147	hit? (w/button s {:key key :kind (or (:kind props) :normal)})]
	148	(record! n id)
	149	(when hit? (fire! n :on-click)))
	150
	151	:checkbox (let [was (boolean (:checked props))
	152	id (c/next-id key)
	153	now (w/checkbox was s {:key key})]
	154	(record! n id)
	155	(when (not= now was) (fire! n :on-change now)))
	156
	157	:slider (let [was (num (:value props) 0.0)
	158	id (c/next-id key)
	159	now (w/slider was {:key key
	160	:min (num (:min props) 0.0)
	161	:max (num (:max props) 100.0)})]
	162	;; == and not not=, because a component holding a long 0 must
	163	;; not be told every frame that its slider moved to 0.0
	164	(record! n id)
	165	(when-not (== now was) (fire! n :on-change now)))
	166
	167	(:entry :text-entry)
	168	(let [was (str (or (:value props) (:text props) ""))
	169	id (c/next-id key)
	170	now (w/text-entry was {:key key :placeholder (:placeholder props)})]
	171	(record! n id)
	172	(when (not= now was) (fire! n :on-change now)))
	173
	174	:progress (w/progress (num (:value props) 0.0))
	175	:separator (w/separator)
	176	(:spacer :gap) (w/spacer {:size (num (:size props) 8.0)
	177	:expand (:expand props :none)})
	178
	179	;; An unknown tag is a container rather than an error, so a tree written
	180	;; against a richer backend still shows its contents here — the same
	181	;; bargain jolt-zvui makes with the tags it does not know.
	182	(c/box* (box-opts props key) (emit-children! n)))))
	183
	184	;; --- the loop ----------------------------------------------------------------
	185
	186	(defonce ^:private pending (atom []))
	187
	188	(defn- schedule! [work] (swap! pending conj work) nil)
	189
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 9d ago	190	;; --- timers -----------------------------------------------------------------
	191	;; A client needs somewhere to run work that is not a reaction to anything:
	192	;; frq drives its whole media plane from `(every! 16 pump!)`, and a decoded
	193	;; frame arrives because a timer asked for it rather than because a person
	194	;; clicked. There is no other hook of the right shape — a component body runs
	195	;; when its state changes, which for a video feed is never.
	196	;;
	197	;; Run from the same `:before` as the reconciler's queue, and for the same
	198	;; reason: a callback that patches the tree must not do it mid-walk.
	199
	200	(defonce ^:private timers (atom {}))
	201	(defonce ^:private next-timer (atom 0))
	202
	203	(defn- now-ms [] (System/currentTimeMillis))
	204
	205	(defn after!
	206	"Run `f` once, at least `ms` from now. Answers a handle for `cancel!`."
	207	[ms f]
	208	(let [id (swap! next-timer inc)]
	209	(swap! timers assoc id {:at (+ (now-ms) ms) :every nil :f f})
	210	id))
	211
	212	(defn every!
	213	"Run `f` every `ms`. Answers a handle for `cancel!`.
	214
	215	Every `ms` AT MOST, not exactly: it fires on the first frame after the
	216	deadline, so a 16ms timer on a 60Hz window runs once a frame and on a
	217	slower one runs less often. That is the right failure — a timer that tried
	218	to catch up would run twice in a row on a stutter, and for a pump that
	219	means two frames decoded and one shown."
	220	[ms f]
	221	(let [id (swap! next-timer inc)]
	222	(swap! timers assoc id {:at (+ (now-ms) ms) :every ms :f f})
	223	id))
	224
	225	(defn cancel!
	226	"Stop a timer."
	227	[id]
	228	(swap! timers dissoc id)
	229	nil)
	230
	231	(defn- run-timers! []
	232	(let [t (now-ms)
	233	due (filter (fn [[_ v]] (<= (:at v) t)) @timers)]
	234	(doseq [[id {:keys [every f]}] due]
	235	(if every
	236	(swap! timers assoc-in [id :at] (+ t every))
	237	(swap! timers dissoc id))
	238	;; A throwing timer is cancelled rather than allowed to throw every
	239	;; frame for the rest of the session, which is unreadable and stops
	240	;; the ones behind it.
	241	(try (f)
	242	(catch Exception e
	243	(swap! timers dissoc id)
	244	(println "glimmer-jvui: timer failed, cancelled:" (ex-message e)))))))
	245
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago	246	(defn- drain-pending! []
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 9d ago	247	(run-timers!)
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago	248	(let [[ws] (reset-vals! pending [])]
	249	(doseq [w ws] (w))))
	250
	251	(defn- run!
	252	"glimmer.backend's :run. Creates the root page, mounts into it, then hands the
	253	loop to jvui.
	254
	255	The reconciler's queued work is drained by jvui's `:before` hook rather than
	256	inside the walk: a re-render patches the tree, and patching a tree while it
	257	is being walked is how a frame ends up half old and half new."
	258	[opts mount-root!]
	259	(let [{:keys [title width height max-width theme frames auto-quit-ms shot]
	260	:or {title "glimmer" width 720 height 520}} opts
	261	root (create! :page (cond-> {} max-width (assoc :max-width max-width)))]
	262	(mount-root! root :page)
	263	(reset! b/loop-running? true)
	264	(try
	265	(app/run! (fn [] (emit! root))
	266	{:title title :width width :height height
	267	:theme (or theme theme/dark)
	268	:before drain-pending!
	269	:frames frames :auto-quit-ms auto-quit-ms :shot shot})
	270	(finally (reset! b/loop-running? false)))))
	271
	272	;; --- registration ------------------------------------------------------------
	273
	274	(def backend
	275	{:name :jvui
	276	:create! create! :apply-props! apply-props!
	277	:append-child! append-child! :remove-child! remove-child!
	278	:replace-child! replace-child! :reorder-child! reorder-child!
	279	:schedule schedule! :run run!})
	280
	281	(b/register! backend)
	282
	283	;; --- headless driving, for tests ---------------------------------------------
	284
	285	(defn root-node
	286	"A bare root page, for mounting into without a window."
	287	[] (create! :page {}))
	288
	289	(defn render-once
	290	"Walk `root` through jvui with no window, no font and no display.
	291
	292	`cx` is a `jvui.core/context`; `evs` the events that frame. Answers the
	293	context, whose `:data` is every rectangle the walk placed — which is enough
	294	for a test to assert about a layout and to click on it."
	295	([root cx] (render-once root cx []))
	296	([root cx evs]
	297	(drain-pending!)
	298	(swap! cx assoc :events evs)
	299	(swap! cx c/apply-input evs)
	300	(binding [record-rects? true]
	301	(c/frame! cx (fn [] (emit! root))))
	302	cx))
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 9d ago	303
	304	;; --- feeds ------------------------------------------------------------------
	305	;; The same three calls glimmer-vidya exposes, so a client that paints a call
	306	;; does not care which backend is under it. They are not part of the
	307	;; reconciler and deliberately so: pixels arrive between frames, and the tree
	308	;; only ever holds the key.
	309
	310	(defn frame-rgba!
	311	"Hand feed `key` a new picture: `w` by `h` RGBA at FOREIGN pointer `px`.
	312
	313	The pointer is read during this call and not kept, so a caller may reuse
	314	or free it immediately afterwards — which is what a decoder handing out a
	315	borrowed buffer needs."
	316	[key w h px]
	317	(frames/put! key w h px))
	318
	319	(defn frame-drop!
	320	"Forget a feed and release its texture — someone left, or turned a camera
	321	off."
	322	[key]
	323	(frames/drop! key))
	324
	325	(defn feed-keys
	326	"Every feed with a picture."
	327	[]
	328	(frames/keys*))