nandi/jolt-native · core.jolt

⑂ 5adddc7cbf30ef4d53728c38d1d9260567b3875c

core.jolt · 449 lines · 17.6 KBGDScript3    Blame HistoryRaw
Bring vidya in   1(ns glimmer-vidya.core
"The Vidya/egui backend for glimmer. Requiring this namespace installs it,
after which glimmer's portable reconciler renders hiccup into a GPU window:
  (ns myapp
    (:require [glimmer.ratom :refer [atom]]
              [glimmer.core :as ui]
              [glimmer-vidya.core]))        ; installs this backend
  (defn -main [& _] (ui/run my-app :title \"myapp\"))
egui is an immediate-mode toolkit: it has no widgets to hand a reconciler,
only calls you make every frame. So the widget tree lives one layer down, in
the Rust library, and this namespace is the thin part — it turns glimmer's
create/patch/append/remove into node mutations, runs the frame loop, and
routes the events that come back to the handlers the components declared.
A widget, from the reconciler's point of view, is an integer node handle. It
never looks inside one, which is exactly why an id is enough.
**Handlers do not cross the FFI.** A jolt closure cannot be a callback in a
library painting at 60fps, so identity travels instead: a node reports that
it was clicked, and the handler map here says whose `:on-click` that was."
(:require [glimmer.backend :as b]
          [glimmer-vidya.ffi :as ffi]))
27;; Node id -> the :on-* props that node was last rendered with. Kept here
28;; rather than sent across because a closure has no C representation.
30;; Ids are recycled by the arena, which is safe only because every id is
31;; written here by `create!` before anything can raise an event against it — a
32;; reused id has its predecessor's handlers overwritten in the same breath.
33(defonce ^:private handlers (atom {}))
35;; Work posted from other threads, run on the loop thread at the top of a tick.
36(defonce ^:private pending (atom []))
38;; Set by quit!, read by the loop.
39(defonce ^:private quit-requested (atom false))
41;; --- props -------------------------------------------------------------------
42;; :hbox and :vbox are one node in the library; the tag only implies an
43;; orientation, and an explicit :orientation prop still wins.
44(def ^:private tag-orientation {:hbox "horizontal" :vbox "vertical"})
46(defn- handler-key?
"True for a prop that names an event handler rather than a value."
(let [s (name k)]
  (and (> (count s) 3) (= "on-" (subs s 0 3)))))
52(defn- set-prop!
"Write one prop to a node, in the ABI type that fits its value. nil clears
nothing — the prop was already dropped by the clear that precedes a write —
and an unrecognized value is stringified rather than refused, so a prop this
backend has not learned yet still reaches the library."
[node k v]
(let [key (name k)]
59
    (nil? v)     nil
    (true? v)    (ffi/node-set-bool! node key true)
    (false? v)   (ffi/node-set-bool! node key false)
    (number? v)  (ffi/node-set-num! node key (double v))
    (string? v)  (ffi/node-set-str! node key v)
    (keyword? v) (ffi/node-set-str! node key (name v))
    :else        (ffi/node-set-str! node key (str v)))))
68(defn- write-props!
"Replace a node's props with `props`.
Cleared first, deliberately: a re-render that stops setting `:placeholder`
means the placeholder is gone, and patching in place would leave the old one
behind. It also discards the value the library wrote back when the user typed
in an entry or clicked a checkbutton — which is the point. The component's
state is the truth, and this is the frame where it says so."
[node tag props]
(ffi/node-clear-props! node)
(when-let [orientation (tag-orientation tag)]
  (when-not (contains? props :orientation)
    (ffi/node-set-str! node "orientation" orientation)))
(doseq [[k v] props]
  (when-not (handler-key? k)
    (set-prop! node k v)))
(swap! handlers assoc node
       (reduce (fn [acc [k v]]
                 (if (and (handler-key? k) (fn? v)) (assoc acc k v) acc))
               props))
91(defn- forget-dead-handlers!
"Drop handler entries for nodes the library has freed.
Removing a subtree frees every node under it, and only the library knows
which those were — so rather than mirror the tree here to walk it, the map is
filtered against what still exists. It runs once per removal, over a map the
size of the UI."
(swap! handlers
       (fn [m]
         (reduce (fn [acc [id hs]]
                   (if (ffi/node-exists? id) (assoc acc id hs) acc))
107;; --- the backend operations --------------------------------------------------
108(defn- create!
"glimmer.backend's :create!. Children are appended by the reconciler, not
110
[tag props]
(let [node (ffi/node-new (name tag))]
  (when (zero? node)
    (throw (ex-info "vidya could not allocate a node" {:tag tag})))
  (write-props! node tag props)
116
118(defn- apply-props! [tag node props] (write-props! node tag props))
120(defn- append-child! [_parent-tag parent child]
(ffi/node-append! parent child)
124(defn- remove-child! [_parent-tag parent child]
;; The library frees the subtree; glimmer never mentions it again.
(ffi/node-remove! parent child)
(forget-dead-handlers!)
130(defn- replace-child! [_parent-tag parent old-child new-child]
(ffi/node-replace! parent old-child new-child)
(forget-dead-handlers!)
135(defn- reorder-child! [_parent-tag parent child sibling]
;; nil sibling means "first"; the ABI spells that 0.
(ffi/node-insert-after! parent child (or sibling 0))
140;; --- the UI thread -----------------------------------------------------------
141(defn- schedule
"glimmer.backend's :schedule. Every node call belongs to the thread that
opened the window, so a ratom mutated on an nREPL worker (or any future)
queues its re-render here and the loop performs it on the next tick."
145
(swap! pending conj work)
149(defn- drain!
"Run everything `schedule` queued. compare-and-set! rather than reset!, so
work posted while the queue is being taken is not dropped."
153
  (let [q @pending]
    (when (seq q)
      (if (compare-and-set! pending q [])
        (doseq [f q] (f))
        (recur))))))
160;; --- timers ------------------------------------------------------------------
161;; A spinner or a clock has to change with nothing being pressed. The loop
162;; already wakes every frame, so a timer is a due time and a thunk. Both
163;; entry points are safe to call from another thread, and both run their thunk
164;; ON the loop thread, the only one allowed to touch nodes.
165(defonce ^:private timers (atom {:next-id 0 :entries {}}))
167(defn- now-ms [] (System/currentTimeMillis))
169(defn- add-timer! [ms every? f]
(let [id (:next-id (swap! timers update :next-id inc))]
  (swap! timers assoc-in [:entries id]
         {:due (+ (now-ms) ms) :every (when every? ms) :f f})
173
175(defn after!
"Run `f` on the loop thread in about `ms` milliseconds. Returns an id for
`cancel!`. Resolution is one frame."
[ms f] (add-timer! ms false f))
180(defn every!
"Run `f` on the loop thread about every `ms` milliseconds until cancelled:
  (every! 80 #(swap! tick inc))"
[ms f] (add-timer! ms true f))
186(defn cancel!
"Stop the timer `id`."
[id] (swap! timers update :entries dissoc id) nil)
190(defn cancel-all!
"Stop every timer, so a repeating one does not outlive the UI it animated."
[] (swap! timers assoc :entries {}) nil)
194(defn- pump-timers! []
(let [t (now-ms)
      due (reduce (fn [acc [id e]] (if (<= (:due e) t) (conj acc [id e]) acc))
                  (:entries @timers))]
  (doseq [[id e] due]
    (if-let [period (:every e)]
      (swap! timers assoc-in [:entries id :due] (+ t period))
      (swap! timers update :entries dissoc id))
    ((:f e)))
204
206;; --- events ------------------------------------------------------------------
207(defn- dispatch-events!
"Drain the frame's interactions and call the handlers they belong to.
An event whose node has no handler for it is dropped, which is what makes a
control that ignores its own event still work: the library wrote the new
state into the node, and the next render either confirms it or overwrites it."
214
  (when (ffi/poll-event!)
    (let [node (ffi/event-node)
          kind (ffi/event-name)
          hs (get @handlers node)]
      (case kind
        "click"    (when-let [f (:on-click hs)] (f))
        "toggled"  (when-let [f (:on-toggled hs)] (f))
        ;; The text is read before anything else can overwrite the library's
        ;; one scratch buffer — jolt copies it as it crosses.
        "change"   (when-let [f (:on-change hs)] (f (ffi/event-text)))
        "activate" (when-let [f (:on-activate hs)] (f))
        ;; Ctrl+V on a clipboard with no text on it. What is on it instead is
        ;; the caller's to find out — `clipboard-image-png!` is the only
        ;; question the backend answers about it.
        "paste-empty" (when-let [f (:on-paste-empty hs)] (f))
        nil))
    (recur))))
233;; --- the event loop ----------------------------------------------------------
234(defn- clear-children!
"Drop everything under `node`. Removing a child frees it, so this walks the
first slot until there is nothing left rather than iterating an index."
237
238
  (when (pos? (ffi/node-child-count node))
    (ffi/node-remove! node (ffi/node-child-at node 0))
    (recur)))
(forget-dead-handlers!)
Let the window be renamed after it opens   245(defn set-title!
"Rename the open window. `run` names it once at startup; this is for a title
that has something to say later — who is signed in, which document is open,
what a second window of the same app is for.
A no-op before the window exists and after it closes."
251
(ffi/set-title! (str title))
Bring vidya in   255(defn window-width
"The width in points of the window's content area, as the last painted frame
measured it. 0 before the first frame.
This is how a layout asks how much room it has: nothing else here reports a
size, and the window is not resizable from this side either. Read it from a
timer — `every!` — rather than per render, and hold it in a ratom, so that
the components which switch on it re-render only when it actually changes."
(ffi/node-get-num (ffi/tree-root) "window-width"))
266(defn clipboard-image-png!
"Write the picture on the system clipboard to `path` as a PNG. True when
there was one; false for an empty clipboard, text on it, an unwritable path,
or a platform with no clipboard of images (Android).
A paste of a picture reaches no handler of its own — the backend delivers
clipboard text only — so a caller asks for it, from whatever gesture it means
paste by. An `:entry`'s `:on-paste-empty` is that gesture where the reader
expects it: a Ctrl+V the field had no text to answer with."
275
(ffi/clipboard-image-png! path))
278(defn open-url!
"Hand `url` to whatever shows web pages here — xdg-open or `open` on a
desktop, an ACTION_VIEW intent on Android. True when something took it;
false leaves the caller to show the URL and let the reader carry it across.
A sign-in that goes through a browser is the reason this exists: the app
leaves for a page and the page comes back to it."
(ffi/open-url! url))
Catch up with vidya   288(defn pick-image!
"Open the platform's own picture chooser. True when one opened, false where
there is none — a desktop, or an Android activity that does not offer it —
and a false is the caller's cue to browse the filesystem itself.
It does not answer with the picture. The reader is in another screen by then,
so what they chose arrives at `picked-image!`, which the caller polls."
(ffi/pick-image!))
298(defn picked-image!
"Move the picture chosen since the last call to `path`; true when there was
one. The answer is handed over once, so a poll still running does not take
the same picture twice."
302
(ffi/picked-image! path))
Tell a caller how big the window is   305(defn screen-size
"The window's size in points, as `[width height]`. `[0 0]` before the first
frame has been painted.
For laying something out as a share of the window — a row of tiles that
should divide the width between them — where how many there are and how much
gap goes between them is the caller's arithmetic, and not something one
widget can work out from the space it was handed.
Follows the window as it is dragged, so a component that reads it wants to be
re-rendered when it changes: keep it in a ratom rather than asking here at
render time, or the layout will be whatever it was on the first frame."
[(ffi/screen-width) (ffi/screen-height)])
Bring vidya in   320(defn frame-rgba!
"Hand the backend a frame of live pixels under `key`. An `:image` node with
`:feed key` paints the latest one.
`rgba` is a foreign pointer — `width * height * 4` un-premultiplied bytes,
row-major — and is copied before this returns, so whoever owns it may reuse
it immediately. False when the length does not match the dimensions.
This is the source an `:image` `:src` cannot be: a `:src` decodes a file and
caches it by path for the life of the process, which is right for a picture
in a message and wrong for one that is new thirty times a second. Frames
coalesce rather than queue, so a source faster than the window costs nothing.
On the window's thread, like everything else here: a frame produced on a
decoder thread is the caller's to hand across."
[key width height rgba]
(ffi/frame-rgba! key width height rgba))
338(defn frame-drop!
"Forget the feed named `key` and release its texture; true when there was
one. A source that has stopped keeps painting its last frame otherwise."
(ffi/frame-drop! key))
344(defn quit!
"Stop the running loop and close the window."
(reset! quit-requested true)
350(defn- run!
"glimmer.backend's :run. Opens a window, mounts the root component into the
library's root node, and paints until the window closes or `quit!` is called.
Blocks, like every UI main loop.
Options (on top of glimmer's own):
  :title :width :height   the window
  :fps                    frame rate cap (default 60)
  :mode                   :dark (default) or :light
  :font                   path to a TTF/OTF to use for UI text
  :auto-quit-ms           stop after roughly this long — for smoke tests,
                          which have nobody to close the window
The window is closed in a finally, so a handler that throws does not leave a
GPU surface and an event loop behind."
[opts mount-root!]
(let [{:keys [title width height fps mode font auto-quit-ms]
       :or {title "glimmer" width 900 height 640 fps 60}} opts]
  (when-not (ffi/open! width height title)
    (throw (ex-info "vidya could not open a window"
                    {:title title :width width :height height})))
  (reset! quit-requested false)
  (ffi/set-target-fps! fps)
  (ffi/set-mode! (if (= mode :light) ffi/light-mode ffi/dark-mode))
  (when font (ffi/load-font! font))
  (let [started (now-ms)
        root (ffi/tree-root)]
377
      ;; The library's root outlives a run — it is process-wide, not per
      ;; window — so a second `ui/run` in one session (a REPL, a test) would
      ;; otherwise mount its tree alongside the last one's.
      (clear-children! root)
      (mount-root! root :window)
      (reset! b/loop-running? true)
      (loop []
        (drain!)
        (pump-timers!)
        ;; One call paints the whole tree; the events it produced are read
        ;; straight after, while the frame that caused them is still the
        ;; frame the components rendered.
        (ffi/tree-frame!)
        (dispatch-events!)
        (when-not (or @quit-requested
                      (ffi/should-close?)
                      (and auto-quit-ms (>= (- (now-ms) started) auto-quit-ms)))
          (recur)))
      (finally
        (reset! b/loop-running? false)
        (cancel-all!)
        (ffi/close!)
        (reset! handlers {}))))))
402;; --- looking at what was rendered --------------------------------------------
403(defn dump-str
"The rendered tree as hiccup text, read back out of the library.
With no argument, the whole window; with a node handle, that subtree. This is
the tree as it *is* after the reconciler has run, not what a component
returned, so paste it into a bug report and the two can be compared.
Two things to know when reading one. `:hbox` and `:vbox` are one node down
there and both dump as `:box`, with the orientation in the props; and no
`:on-*` appears, because handlers are held on this side and never sent."
([] (dump-str 0))
([node] (ffi/tree-dump node)))
416
"`dump-str`, read back as hiccup data — vectors, keywords and maps — for a
test that wants to assert on a subtree rather than on a string."
([] (dump 0))
([node] (read-string (dump-str node))))
422(defn dump!
"Print `dump-str` to stdout. The one you want from a handler or the REPL."
([] (dump! 0))
([node] (println (dump-str node)) nil))
427;; --- the backend -------------------------------------------------------------
428(def backend
"The Vidya backend map handed to glimmer.backend/register!. See that
namespace for the contract each key satisfies."
{:name           :vidya
 :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!})
441(defn install!
"Make Vidya/egui the backend glimmer renders with. Called on load, so
requiring this namespace is enough; exposed for code that wants to be
explicit, or to switch back after another backend was installed."
(b/register! backend)
449(defonce ^:private installed (do (install!) true))

Bring vidya in cfd3e36 nandi 20d ago	1	(ns glimmer-vidya.core
	2	"The Vidya/egui backend for glimmer. Requiring this namespace installs it,
	3	after which glimmer's portable reconciler renders hiccup into a GPU window:
	4
	5	(ns myapp
	6	(:require [glimmer.ratom :refer [atom]]
	7	[glimmer.core :as ui]
	8	[glimmer-vidya.core])) ; installs this backend
	9
	10	(defn -main [& _] (ui/run my-app :title \"myapp\"))
	11
	12	egui is an immediate-mode toolkit: it has no widgets to hand a reconciler,
	13	only calls you make every frame. So the widget tree lives one layer down, in
	14	the Rust library, and this namespace is the thin part — it turns glimmer's
	15	create/patch/append/remove into node mutations, runs the frame loop, and
	16	routes the events that come back to the handlers the components declared.
	17
	18	A widget, from the reconciler's point of view, is an integer node handle. It
	19	never looks inside one, which is exactly why an id is enough.
	20
	21	Handlers do not cross the FFI. A jolt closure cannot be a callback in a
	22	library painting at 60fps, so identity travels instead: a node reports that
	23	it was clicked, and the handler map here says whose `:on-click` that was."
	24	(:require [glimmer.backend :as b]
	25	[glimmer-vidya.ffi :as ffi]))
	26
	27	;; Node id -> the :on-* props that node was last rendered with. Kept here
	28	;; rather than sent across because a closure has no C representation.
	29	;;
	30	;; Ids are recycled by the arena, which is safe only because every id is
	31	;; written here by `create!` before anything can raise an event against it — a
	32	;; reused id has its predecessor's handlers overwritten in the same breath.
	33	(defonce ^:private handlers (atom {}))
	34
	35	;; Work posted from other threads, run on the loop thread at the top of a tick.
	36	(defonce ^:private pending (atom []))
	37
	38	;; Set by quit!, read by the loop.
	39	(defonce ^:private quit-requested (atom false))
	40
	41	;; --- props -------------------------------------------------------------------
	42	;; :hbox and :vbox are one node in the library; the tag only implies an
	43	;; orientation, and an explicit :orientation prop still wins.
	44	(def ^:private tag-orientation {:hbox "horizontal" :vbox "vertical"})
	45
	46	(defn- handler-key?
	47	"True for a prop that names an event handler rather than a value."
	48	[k]
	49	(let [s (name k)]
	50	(and (> (count s) 3) (= "on-" (subs s 0 3)))))
	51
	52	(defn- set-prop!
	53	"Write one prop to a node, in the ABI type that fits its value. nil clears
	54	nothing — the prop was already dropped by the clear that precedes a write —
	55	and an unrecognized value is stringified rather than refused, so a prop this
	56	backend has not learned yet still reaches the library."
	57	[node k v]
	58	(let [key (name k)]
	59	(cond
	60	(nil? v) nil
	61	(true? v) (ffi/node-set-bool! node key true)
	62	(false? v) (ffi/node-set-bool! node key false)
	63	(number? v) (ffi/node-set-num! node key (double v))
	64	(string? v) (ffi/node-set-str! node key v)
65	(keyword? v) (ffi/node-set-str! node key (name v))
66	:else (ffi/node-set-str! node key (str v)))))
67
68	(defn- write-props!
69	"Replace a node's props with `props`.
70
71	Cleared first, deliberately: a re-render that stops setting `:placeholder`
72	means the placeholder is gone, and patching in place would leave the old one
73	behind. It also discards the value the library wrote back when the user typed
74	in an entry or clicked a checkbutton — which is the point. The component's
75	state is the truth, and this is the frame where it says so."
76	[node tag props]
77	(ffi/node-clear-props! node)
78	(when-let [orientation (tag-orientation tag)]
79	(when-not (contains? props :orientation)
80	(ffi/node-set-str! node "orientation" orientation)))
81	(doseq [[k v] props]
82	(when-not (handler-key? k)
83	(set-prop! node k v)))
84	(swap! handlers assoc node
85	(reduce (fn [acc [k v]]
86	(if (and (handler-key? k) (fn? v)) (assoc acc k v) acc))
87	{}
88	props))
89	nil)
90
91	(defn- forget-dead-handlers!
92	"Drop handler entries for nodes the library has freed.
93
94	Removing a subtree frees every node under it, and only the library knows
95	which those were — so rather than mirror the tree here to walk it, the map is
96	filtered against what still exists. It runs once per removal, over a map the
97	size of the UI."
98	[]
99	(swap! handlers
100	(fn [m]
101	(reduce (fn [acc [id hs]]
102	(if (ffi/node-exists? id) (assoc acc id hs) acc))
103	{}
104	m)))
105	nil)
106
107	;; --- the backend operations --------------------------------------------------
108	(defn- create!
109	"glimmer.backend's :create!. Children are appended by the reconciler, not
110	here."
111	[tag props]
112	(let [node (ffi/node-new (name tag))]
113	(when (zero? node)
114	(throw (ex-info "vidya could not allocate a node" {:tag tag})))
115	(write-props! node tag props)
116	node))
117
118	(defn- apply-props! [tag node props] (write-props! node tag props))
119
120	(defn- append-child! [_parent-tag parent child]
121	(ffi/node-append! parent child)
122	nil)
123
124	(defn- remove-child! [_parent-tag parent child]
125	;; The library frees the subtree; glimmer never mentions it again.
126	(ffi/node-remove! parent child)
127	(forget-dead-handlers!)
128	nil)
129
130	(defn- replace-child! [_parent-tag parent old-child new-child]
131	(ffi/node-replace! parent old-child new-child)
132	(forget-dead-handlers!)
133	nil)
134
135	(defn- reorder-child! [_parent-tag parent child sibling]
136	;; nil sibling means "first"; the ABI spells that 0.
137	(ffi/node-insert-after! parent child (or sibling 0))
138	nil)
139
140	;; --- the UI thread -----------------------------------------------------------
141	(defn- schedule
142	"glimmer.backend's :schedule. Every node call belongs to the thread that
143	opened the window, so a ratom mutated on an nREPL worker (or any future)
144	queues its re-render here and the loop performs it on the next tick."
145	[work]
146	(swap! pending conj work)
147	nil)
148
149	(defn- drain!
150	"Run everything `schedule` queued. compare-and-set! rather than reset!, so
151	work posted while the queue is being taken is not dropped."
152	[]
153	(loop []
154	(let [q @pending]
155	(when (seq q)
156	(if (compare-and-set! pending q [])
157	(doseq [f q] (f))
158	(recur))))))
159
160	;; --- timers ------------------------------------------------------------------
161	;; A spinner or a clock has to change with nothing being pressed. The loop
162	;; already wakes every frame, so a timer is a due time and a thunk. Both
163	;; entry points are safe to call from another thread, and both run their thunk
164	;; ON the loop thread, the only one allowed to touch nodes.
165	(defonce ^:private timers (atom {:next-id 0 :entries {}}))
166
167	(defn- now-ms [] (System/currentTimeMillis))
168
169	(defn- add-timer! [ms every? f]
170	(let [id (:next-id (swap! timers update :next-id inc))]
171	(swap! timers assoc-in [:entries id]
172	{:due (+ (now-ms) ms) :every (when every? ms) :f f})
173	id))
174
175	(defn after!
176	"Run `f` on the loop thread in about `ms` milliseconds. Returns an id for
177	`cancel!`. Resolution is one frame."
178	[ms f] (add-timer! ms false f))
179
180	(defn every!
181	"Run `f` on the loop thread about every `ms` milliseconds until cancelled:
182
183	(every! 80 #(swap! tick inc))"
184	[ms f] (add-timer! ms true f))
185
186	(defn cancel!
187	"Stop the timer `id`."
188	[id] (swap! timers update :entries dissoc id) nil)
189
190	(defn cancel-all!
191	"Stop every timer, so a repeating one does not outlive the UI it animated."
192	[] (swap! timers assoc :entries {}) nil)
193
194	(defn- pump-timers! []
195	(let [t (now-ms)
196	due (reduce (fn [acc [id e]] (if (<= (:due e) t) (conj acc [id e]) acc))
197	[]
198	(:entries @timers))]
199	(doseq [[id e] due]
200	(if-let [period (:every e)]
201	(swap! timers assoc-in [:entries id :due] (+ t period))
202	(swap! timers update :entries dissoc id))
203	((:f e)))
204	nil))
205
206	;; --- events ------------------------------------------------------------------
207	(defn- dispatch-events!
208	"Drain the frame's interactions and call the handlers they belong to.
209
210	An event whose node has no handler for it is dropped, which is what makes a
211	control that ignores its own event still work: the library wrote the new
212	state into the node, and the next render either confirms it or overwrites it."
213	[]
214	(loop []
215	(when (ffi/poll-event!)
216	(let [node (ffi/event-node)
217	kind (ffi/event-name)
218	hs (get @handlers node)]
219	(case kind
220	"click" (when-let [f (:on-click hs)] (f))
221	"toggled" (when-let [f (:on-toggled hs)] (f))
222	;; The text is read before anything else can overwrite the library's
223	;; one scratch buffer — jolt copies it as it crosses.
224	"change" (when-let [f (:on-change hs)] (f (ffi/event-text)))
225	"activate" (when-let [f (:on-activate hs)] (f))
226	;; Ctrl+V on a clipboard with no text on it. What is on it instead is
227	;; the caller's to find out — `clipboard-image-png!` is the only
228	;; question the backend answers about it.
229	"paste-empty" (when-let [f (:on-paste-empty hs)] (f))
230	nil))
231	(recur))))
232
233	;; --- the event loop ----------------------------------------------------------
234	(defn- clear-children!
235	"Drop everything under `node`. Removing a child frees it, so this walks the
236	first slot until there is nothing left rather than iterating an index."
237	[node]
238	(loop []
239	(when (pos? (ffi/node-child-count node))
240	(ffi/node-remove! node (ffi/node-child-at node 0))
241	(recur)))
242	(forget-dead-handlers!)
243	nil)
244
Let the window be renamed after it opens 5adddc7 nandi 20d ago	245	(defn set-title!
	246	"Rename the open window. `run` names it once at startup; this is for a title
	247	that has something to say later — who is signed in, which document is open,
	248	what a second window of the same app is for.
	249
	250	A no-op before the window exists and after it closes."
	251	[title]
	252	(ffi/set-title! (str title))
	253	nil)
	254
Bring vidya in cfd3e36 nandi 20d ago	255	(defn window-width
	256	"The width in points of the window's content area, as the last painted frame
	257	measured it. 0 before the first frame.
	258
	259	This is how a layout asks how much room it has: nothing else here reports a
	260	size, and the window is not resizable from this side either. Read it from a
	261	timer — `every!` — rather than per render, and hold it in a ratom, so that
	262	the components which switch on it re-render only when it actually changes."
	263	[]
	264	(ffi/node-get-num (ffi/tree-root) "window-width"))
	265
	266	(defn clipboard-image-png!
	267	"Write the picture on the system clipboard to `path` as a PNG. True when
	268	there was one; false for an empty clipboard, text on it, an unwritable path,
	269	or a platform with no clipboard of images (Android).
	270
	271	A paste of a picture reaches no handler of its own — the backend delivers
	272	clipboard text only — so a caller asks for it, from whatever gesture it means
	273	paste by. An `:entry`'s `:on-paste-empty` is that gesture where the reader
	274	expects it: a Ctrl+V the field had no text to answer with."
	275	[path]
	276	(ffi/clipboard-image-png! path))
	277
	278	(defn open-url!
	279	"Hand `url` to whatever shows web pages here — xdg-open or `open` on a
	280	desktop, an ACTION_VIEW intent on Android. True when something took it;
	281	false leaves the caller to show the URL and let the reader carry it across.
	282
	283	A sign-in that goes through a browser is the reason this exists: the app
	284	leaves for a page and the page comes back to it."
	285	[url]
	286	(ffi/open-url! url))
	287
Catch up with vidya c90f8af nandi 20d ago	288	(defn pick-image!
	289	"Open the platform's own picture chooser. True when one opened, false where
	290	there is none — a desktop, or an Android activity that does not offer it —
	291	and a false is the caller's cue to browse the filesystem itself.
	292
	293	It does not answer with the picture. The reader is in another screen by then,
	294	so what they chose arrives at `picked-image!`, which the caller polls."
	295	[]
	296	(ffi/pick-image!))
	297
	298	(defn picked-image!
	299	"Move the picture chosen since the last call to `path`; true when there was
	300	one. The answer is handed over once, so a poll still running does not take
	301	the same picture twice."
	302	[path]
	303	(ffi/picked-image! path))
	304
Tell a caller how big the window is 42dabb0 nandi 20d ago	305	(defn screen-size
	306	"The window's size in points, as `[width height]`. `[0 0]` before the first
	307	frame has been painted.
	308
	309	For laying something out as a share of the window — a row of tiles that
	310	should divide the width between them — where how many there are and how much
	311	gap goes between them is the caller's arithmetic, and not something one
	312	widget can work out from the space it was handed.
	313
	314	Follows the window as it is dragged, so a component that reads it wants to be
	315	re-rendered when it changes: keep it in a ratom rather than asking here at
	316	render time, or the layout will be whatever it was on the first frame."
	317	[]
	318	[(ffi/screen-width) (ffi/screen-height)])
	319
Bring vidya in cfd3e36 nandi 20d ago	320	(defn frame-rgba!
	321	"Hand the backend a frame of live pixels under `key`. An `:image` node with
	322	`:feed key` paints the latest one.
	323
	324	`rgba` is a foreign pointer — `width * height * 4` un-premultiplied bytes,
	325	row-major — and is copied before this returns, so whoever owns it may reuse
	326	it immediately. False when the length does not match the dimensions.
	327
	328	This is the source an `:image` `:src` cannot be: a `:src` decodes a file and
	329	caches it by path for the life of the process, which is right for a picture
	330	in a message and wrong for one that is new thirty times a second. Frames
	331	coalesce rather than queue, so a source faster than the window costs nothing.
	332
	333	On the window's thread, like everything else here: a frame produced on a
	334	decoder thread is the caller's to hand across."
	335	[key width height rgba]
	336	(ffi/frame-rgba! key width height rgba))
	337
	338	(defn frame-drop!
	339	"Forget the feed named `key` and release its texture; true when there was
	340	one. A source that has stopped keeps painting its last frame otherwise."
	341	[key]
	342	(ffi/frame-drop! key))
	343
	344	(defn quit!
	345	"Stop the running loop and close the window."
	346	[]
	347	(reset! quit-requested true)
	348	nil)
	349
	350	(defn- run!
	351	"glimmer.backend's :run. Opens a window, mounts the root component into the
	352	library's root node, and paints until the window closes or `quit!` is called.
	353	Blocks, like every UI main loop.
	354
	355	Options (on top of glimmer's own):
	356	:title :width :height the window
	357	:fps frame rate cap (default 60)
	358	:mode :dark (default) or :light
	359	:font path to a TTF/OTF to use for UI text
	360	:auto-quit-ms stop after roughly this long — for smoke tests,
	361	which have nobody to close the window
	362
	363	The window is closed in a finally, so a handler that throws does not leave a
	364	GPU surface and an event loop behind."
	365	[opts mount-root!]
	366	(let [{:keys [title width height fps mode font auto-quit-ms]
	367	:or {title "glimmer" width 900 height 640 fps 60}} opts]
	368	(when-not (ffi/open! width height title)
	369	(throw (ex-info "vidya could not open a window"
	370	{:title title :width width :height height})))
	371	(reset! quit-requested false)
	372	(ffi/set-target-fps! fps)
	373	(ffi/set-mode! (if (= mode :light) ffi/light-mode ffi/dark-mode))
	374	(when font (ffi/load-font! font))
	375	(let [started (now-ms)
	376	root (ffi/tree-root)]
	377	(try
	378	;; The library's root outlives a run — it is process-wide, not per
	379	;; window — so a second `ui/run` in one session (a REPL, a test) would
	380	;; otherwise mount its tree alongside the last one's.
	381	(clear-children! root)
	382	(mount-root! root :window)
	383	(reset! b/loop-running? true)
384	(loop []
385	(drain!)
386	(pump-timers!)
387	;; One call paints the whole tree; the events it produced are read
388	;; straight after, while the frame that caused them is still the
389	;; frame the components rendered.
390	(ffi/tree-frame!)
391	(dispatch-events!)
392	(when-not (or @quit-requested
393	(ffi/should-close?)
394	(and auto-quit-ms (>= (- (now-ms) started) auto-quit-ms)))
395	(recur)))
396	(finally
397	(reset! b/loop-running? false)
398	(cancel-all!)
399	(ffi/close!)
400	(reset! handlers {}))))))
401
402	;; --- looking at what was rendered --------------------------------------------
403	(defn dump-str
404	"The rendered tree as hiccup text, read back out of the library.
405
406	With no argument, the whole window; with a node handle, that subtree. This is
407	the tree as it is after the reconciler has run, not what a component
408	returned, so paste it into a bug report and the two can be compared.
409
410	Two things to know when reading one. `:hbox` and `:vbox` are one node down
411	there and both dump as `:box`, with the orientation in the props; and no
412	`:on-*` appears, because handlers are held on this side and never sent."
413	([] (dump-str 0))
414	([node] (ffi/tree-dump node)))
415
416	(defn dump
417	"`dump-str`, read back as hiccup data — vectors, keywords and maps — for a
418	test that wants to assert on a subtree rather than on a string."
419	([] (dump 0))
420	([node] (read-string (dump-str node))))
421
422	(defn dump!
423	"Print `dump-str` to stdout. The one you want from a handler or the REPL."
424	([] (dump! 0))
425	([node] (println (dump-str node)) nil))
426
427	;; --- the backend -------------------------------------------------------------
428	(def backend
429	"The Vidya backend map handed to glimmer.backend/register!. See that
430	namespace for the contract each key satisfies."
431	{:name :vidya
432	:create! create!
433	:apply-props! apply-props!
434	:append-child! append-child!
435	:remove-child! remove-child!
436	:replace-child! replace-child!
437	:reorder-child! reorder-child!
438	:schedule schedule
439	:run run!})
440
441	(defn install!
442	"Make Vidya/egui the backend glimmer renders with. Called on load, so
443	requiring this namespace is enough; exposed for code that wants to be
444	explicit, or to switch back after another backend was installed."
445	[]
446	(b/register! backend)
447	nil)
448
449	(defonce ^:private installed (do (install!) true))