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core.clj · 352 lines · 14.2 KBClojure Blame HistoryRaw
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago1(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 10d ago42 [jvui.widgets :as w]
Answer the rest of what a client asks its window 0b92f67 nandi 10d ago43 [jvui.frames :as frames]
44 [jvui.host :as host]))
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago45
46;; --- the retained tree -------------------------------------------------------
47
48(defonce ^:private serial (atom 0))
49
50(defn- create! [tag props]
51 (atom {:tag tag :props props :children [] :key (swap! serial inc)}))
52
53(defn- apply-props! [_tag n props] (swap! n assoc :props props) nil)
54(defn- append-child! [_t parent child] (swap! parent update :children conj child) nil)
55(defn- remove-child! [_t parent child]
56 (swap! parent update :children #(vec (remove #{child} %))) nil)
57(defn- replace-child! [_t parent old new]
58 (swap! parent update :children #(mapv (fn [c] (if (= c old) new c)) %)) nil)
59(defn- reorder-child! [_t parent child sibling]
60 (swap! parent update :children
61 (fn [cs]
62 (let [cs (vec (remove #{child} cs))
63 i (if (nil? sibling) 0 (inc (.indexOf cs sibling)))]
64 (vec (concat (subvec cs 0 i) [child] (subvec cs i))))))
65 nil)
66
67;; --- props -------------------------------------------------------------------
68
69(defn- txt [props] (str (or (:label props) (:text props) "")))
70
71(defn- num [v default] (if (number? v) (double v) default))
72
73(defn- box-opts
74 "The container options shared by every container tag."
75 [props key]
76 (cond-> {:key key
77 :dir (if (= :horizontal (:orientation props)) :horizontal :vertical)}
78 (:spacing props) (assoc :spacing (num (:spacing props) 0.0))
79 (:padding props) (assoc :padding (num (:padding props) 0.0))
80 (:margin props) (assoc :margin (num (:margin props) 0.0))
81 (:expand props) (assoc :expand (:expand props))))
82
83(defn- fire! [n k & args]
84 (when-let [f (get (:props @n) k)] (apply f args)))
85
86;; --- the walk ----------------------------------------------------------------
87
88(def ^:dynamic *record-rects?*
89 "When true, each node keeps the rectangle jvui gave it, under `:rect`.
90
91 Off in a running window, where it would be a `swap!` per node per frame for
92 nobody's benefit. On under `render-once`, so a test can click the centre of
93 a button the way a person would, rather than guessing at a coordinate and
94 re-guessing every time a padding changes."
95 false)
96
97(declare emit!)
98
99(defn- record! [n id]
100 (when *record-rects?* (swap! n assoc :rect (c/rect-of id)))
101 nil)
102
103(defn- emit-children! [n]
104 (fn [_id _rect] (doseq [c (:children @n)] (emit! c))))
105
106(defn- emit!
107 "Render one node, and through it everything below it.
108
109 A widget answers what the person did to it, and that answer is turned back
110 into the callback prop the component registered — which is the whole seam
111 between an immediate-mode toolkit and a retained, callback-shaped one."
112 [n]
113 (let [{:keys [tag props key]} @n
114 s (txt props)]
115 (case tag
116 :page (w/page* (cond-> {:key key}
117 (:max-width props) (assoc :max-width (:max-width props)))
118 (emit-children! n))
119
120 (:card :frame) (w/card* (box-opts props key) (emit-children! n))
121
122 :scroll (w/scroll* (assoc (box-opts props key)
123 :height (num (:height props) 200.0))
124 (emit-children! n))
125
126 :hbox (c/box* (assoc (box-opts props key) :dir :horizontal)
127 (emit-children! n))
128
129 (:vbox :box) (c/box* (box-opts props key) (emit-children! n))
130
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 10d ago131 ;; A live picture: a camera, a call, anything a decoder is filling in
132 ;; between frames. The node carries only the KEY — the pixels never go
133 ;; through the reconciler, because a video frame arrives when the
134 ;; network says so and a props diff at thirty a second would be a
135 ;; re-render per frame per peer.
136 :video (w/video (or (:feed props) (:key props) (str key))
137 (cond-> {}
138 (:size props) (assoc :size (:size props))
139 (:expand props) (assoc :expand (:expand props))
140 (:gravity props) (assoc :gravity (:gravity props))))
141
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago142 :title (w/title s)
143
144 :label (if (:dim props) (w/dim-label s) (w/label s))
145 :dim-label (w/dim-label s)
146
147 :button (let [id (c/next-id key)
148 hit? (w/button s {:key key :kind (or (:kind props) :normal)})]
149 (record! n id)
150 (when hit? (fire! n :on-click)))
151
Take :checkbutton, which is :checkbox under another name 26defff nandi 10d ago152 ;; :checkbutton is the same widget under GTK's name for it, which is
153 ;; what libvidya calls it too — `"checkbutton" | "checkbox"` is one
154 ;; arm of its tag table. frq writes both.
155 (:checkbox :checkbutton) (let [was (boolean (:checked props))
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago156 id (c/next-id key)
157 now (w/checkbox was s {:key key})]
158 (record! n id)
159 (when (not= now was) (fire! n :on-change now)))
160
161 :slider (let [was (num (:value props) 0.0)
162 id (c/next-id key)
163 now (w/slider was {:key key
164 :min (num (:min props) 0.0)
165 :max (num (:max props) 100.0)})]
166 ;; == and not not=, because a component holding a long 0 must
167 ;; not be told every frame that its slider moved to 0.0
168 (record! n id)
169 (when-not (== now was) (fire! n :on-change now)))
170
171 (:entry :text-entry)
172 (let [was (str (or (:value props) (:text props) ""))
173 id (c/next-id key)
174 now (w/text-entry was {:key key :placeholder (:placeholder props)})]
175 (record! n id)
176 (when (not= now was) (fire! n :on-change now)))
177
178 :progress (w/progress (num (:value props) 0.0))
179 :separator (w/separator)
180 (:spacer :gap) (w/spacer {:size (num (:size props) 8.0)
181 :expand (:expand props :none)})
182
183 ;; An unknown tag is a container rather than an error, so a tree written
184 ;; against a richer backend still shows its contents here — the same
185 ;; bargain jolt-zvui makes with the tags it does not know.
186 (c/box* (box-opts props key) (emit-children! n)))))
187
188;; --- the loop ----------------------------------------------------------------
189
190(defonce ^:private pending (atom []))
191
192(defn- schedule! [work] (swap! pending conj work) nil)
193
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 10d ago194;; --- timers -----------------------------------------------------------------
195;; A client needs somewhere to run work that is not a reaction to anything:
196;; frq drives its whole media plane from `(every! 16 pump!)`, and a decoded
197;; frame arrives because a timer asked for it rather than because a person
198;; clicked. There is no other hook of the right shape — a component body runs
199;; when its state changes, which for a video feed is never.
200;;
201;; Run from the same `:before` as the reconciler's queue, and for the same
202;; reason: a callback that patches the tree must not do it mid-walk.
203
204(defonce ^:private timers (atom {}))
205(defonce ^:private next-timer (atom 0))
206
207(defn- now-ms [] (System/currentTimeMillis))
208
209(defn after!
210 "Run `f` once, at least `ms` from now. Answers a handle for `cancel!`."
211 [ms f]
212 (let [id (swap! next-timer inc)]
213 (swap! timers assoc id {:at (+ (now-ms) ms) :every nil :f f})
214 id))
215
216(defn every!
217 "Run `f` every `ms`. Answers a handle for `cancel!`.
218
219 Every `ms` AT MOST, not exactly: it fires on the first frame after the
220 deadline, so a 16ms timer on a 60Hz window runs once a frame and on a
221 slower one runs less often. That is the right failure — a timer that tried
222 to catch up would run twice in a row on a stutter, and for a pump that
223 means two frames decoded and one shown."
224 [ms f]
225 (let [id (swap! next-timer inc)]
226 (swap! timers assoc id {:at (+ (now-ms) ms) :every ms :f f})
227 id))
228
229(defn cancel!
230 "Stop a timer."
231 [id]
232 (swap! timers dissoc id)
233 nil)
234
235(defn- run-timers! []
236 (let [t (now-ms)
237 due (filter (fn [[_ v]] (<= (:at v) t)) @timers)]
238 (doseq [[id {:keys [every f]}] due]
239 (if every
240 (swap! timers assoc-in [id :at] (+ t every))
241 (swap! timers dissoc id))
242 ;; A throwing timer is cancelled rather than allowed to throw every
243 ;; frame for the rest of the session, which is unreadable and stops
244 ;; the ones behind it.
245 (try (f)
246 (catch Exception e
247 (swap! timers dissoc id)
248 (println "glimmer-jvui: timer failed, cancelled:" (ex-message e)))))))
249
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago250(defn- drain-pending! []
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 10d ago251 (run-timers!)
Write dvui's shape in jolt, on SDL3, with no shared object 109c7e4 Veronika Winters 10d ago252 (let [[ws] (reset-vals! pending [])]
253 (doseq [w ws] (w))))
254
255(defn- run!
256 "glimmer.backend's :run. Creates the root page, mounts into it, then hands the
257 loop to jvui.
258
259 The reconciler's queued work is drained by jvui's `:before` hook rather than
260 inside the walk: a re-render patches the tree, and patching a tree while it
261 is being walked is how a frame ends up half old and half new."
262 [opts mount-root!]
263 (let [{:keys [title width height max-width theme frames auto-quit-ms shot]
264 :or {title "glimmer" width 720 height 520}} opts
265 root (create! :page (cond-> {} max-width (assoc :max-width max-width)))]
266 (mount-root! root :page)
267 (reset! b/loop-running? true)
268 (try
269 (app/run! (fn [] (emit! root))
270 {:title title :width width :height height
271 :theme (or theme theme/dark)
272 :before drain-pending!
273 :frames frames :auto-quit-ms auto-quit-ms :shot shot})
274 (finally (reset! b/loop-running? false)))))
275
276;; --- registration ------------------------------------------------------------
277
278(def backend
279 {:name :jvui
280 :create! create! :apply-props! apply-props!
281 :append-child! append-child! :remove-child! remove-child!
282 :replace-child! replace-child! :reorder-child! reorder-child!
283 :schedule schedule! :run run!})
284
285(b/register! backend)
286
287;; --- headless driving, for tests ---------------------------------------------
288
289(defn root-node
290 "A bare root page, for mounting into without a window."
291 [] (create! :page {}))
292
293(defn render-once
294 "Walk `root` through jvui with no window, no font and no display.
295
296 `cx` is a `jvui.core/context`; `evs` the events that frame. Answers the
297 context, whose `:data` is every rectangle the walk placed — which is enough
298 for a test to assert about a layout and to click on it."
299 ([root cx] (render-once root cx []))
300 ([root cx evs]
301 (drain-pending!)
302 (swap! cx assoc :events evs)
303 (swap! cx c/apply-input evs)
304 (binding [*record-rects?* true]
305 (c/frame! cx (fn [] (emit! root))))
306 cx))
Give jvui a picture from somewhere else, and a clock 32fae8d nandi 10d ago307
308;; --- feeds ------------------------------------------------------------------
309;; The same three calls glimmer-vidya exposes, so a client that paints a call
310;; does not care which backend is under it. They are not part of the
311;; reconciler and deliberately so: pixels arrive between frames, and the tree
312;; only ever holds the key.
313
314(defn frame-rgba!
315 "Hand feed `key` a new picture: `w` by `h` RGBA at FOREIGN pointer `px`.
316
317 The pointer is read during this call and not kept, so a caller may reuse
318 or free it immediately afterwards — which is what a decoder handing out a
319 borrowed buffer needs."
320 [key w h px]
321 (frames/put! key w h px))
322
323(defn frame-drop!
324 "Forget a feed and release its texture — someone left, or turned a camera
325 off."
326 [key]
327 (frames/drop! key))
328
329(defn feed-keys
330 "Every feed with a picture."
331 []
332 (frames/keys*))
Answer the rest of what a client asks its window 0b92f67 nandi 10d ago333
334;; --- the platform -----------------------------------------------------------
335;; The rest of what glimmer-vidya answers, so a client can ask its backend
336;; about the window it is in without knowing which backend that is. Thin on
337;; purpose: every one of these is jvui.host, and the indirection exists so
338;; the client requires one namespace rather than two.
339
340(def set-title! host/set-title!)
341(def window-width host/window-width)
342(def screen-size host/screen-size)
343(def quit! host/quit!)
344(def open-url! host/open-url!)
345(def clipboard-image-png! host/clipboard-image-png!)
346
347;; False and nil on a desktop, which is the right answer rather than a gap:
348;; the chooser exists so a phone can hand back a grant for one picture, and
349;; a caller reads the false and offers a file browser instead. glimmer-vidya
350;; says the same thing here.
351(def pick-image! host/pick-image!)
352(def picked-image! host/picked-image!)