Canvas WASM TI/TI$: use emscripten_get_now for tight loops

Follow-up: advancing ticks60 only in do_sleep_ticks still froze TI in
GOTO-only loops. Read TI/TI$ from elapsed monotonic ms since run start;
keep gfx_video_advance_ticks60 for basic-gfx frame loop only.

Co-authored-by: Chris Garrett <chris@chrisg.com>

Author: cursoragent

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ### Unreleased
 
-- **Canvas WASM `TI` / `TI$`**: **`GfxVideoState.ticks60`** was only advanced in the **Raylib** main loop, so **canvas** builds left **`TI`** / **`TI$`** frozen. **`emscripten_sleep`** in **`do_sleep_ticks`** now advances **`ticks60`** by elapsed milliseconds (60 Hz), shared via **`gfx_video_advance_ticks60`**. **Terminal WASM** (`basic.js`, no **`GFX_VIDEO`**) still uses wall-clock **`time()`** for **`TI`** / **`TI$`** (seconds + `HHMMSS`), not C64 jiffies.
+- **Canvas WASM `TI` / `TI$`**: **`GfxVideoState.ticks60`** was only advanced in the **Raylib** main loop, so **canvas** **`TI`** / **`TI$`** stayed frozen (especially in tight **`GOTO`** loops). **Canvas** now derives 60 Hz jiffies from **`emscripten_get_now()`** since **`basic_load_and_run_gfx`** ( **`gfx_video_advance_ticks60`** still drives **basic-gfx** each frame). **Terminal WASM** (`basic.js`, no **`GFX_VIDEO`**) still uses **`time()`** for **`TI`** / **`TI$`** (seconds + wall-clock `HHMMSS`), not C64 jiffies.
 
 - **WordPress**: New plugin **`wordpress/rgc-basic-tutorial-block`** — Gutenberg block **RGC-BASIC embed** with automatic script/style enqueue, **`copy-web-assets.sh`** to sync **`web/tutorial-embed.js`**, **`vfs-helpers.js`**, and modular WASM into **`assets/`**; optional **Settings → RGC-BASIC Tutorial** base URL.
 

basic.c

@@ -60,6 +60,8 @@
 /* Video state pointer; must precede __EMSCRIPTEN__ key helpers that reference gfx_vs. */
 static GfxVideoState *gfx_vs = NULL;
 #if defined(__EMSCRIPTEN__) && defined(GFX_VIDEO)
+/* Canvas WASM: TI/TI$ from high-res clock (tight GOTO loops have no SLEEP). */
+static double wasm_gfx_ti_epoch_ms;
 /* Canvas WASM: trek.bas-style lines pack many ':' statements; yield inside long PRINT too. */
 static unsigned wasm_gfx_put_budget;
 /* Yield every few execute_statement calls — LET/GOTO/IF on one line skip gfx_put_byte. */
@@ -3180,16 +3182,6 @@ static void do_sleep_ticks(double ticks)
         ms = 1;
     }
     emscripten_sleep(ms);
-#if defined(GFX_VIDEO)
-    /* Canvas WASM has no per-frame loop like Raylib; advance TI/TI$ from real sleep. */
-    if (gfx_vs) {
-        uint32_t add = (uint32_t)((ms * 60 + 500) / 1000);
-        if (add < 1u) {
-            add = 1u;
-        }
-        gfx_video_advance_ticks60(gfx_vs, add);
-    }
-#endif
 }
 #elif defined(_WIN32)
 /* Windows: sleep using Sleep() in milliseconds derived from 60Hz ticks. */
@@ -5548,7 +5540,21 @@ static struct value eval_factor(char **p)
                 int is_str = (len > 0 && namebuf[len - 1] == '$');
 #ifdef GFX_VIDEO
                 if (gfx_vs) {
-                    uint32_t t = gfx_vs->ticks60;
+                    uint32_t t;
+#if defined(__EMSCRIPTEN__)
+                    /* Canvas WASM: no per-frame tick increment; use monotonic ms → 60 Hz jiffies. */
+                    {
+                        double now = emscripten_get_now();
+                        double elapsed_ms = now - wasm_gfx_ti_epoch_ms;
+                        if (elapsed_ms < 0.0) {
+                            elapsed_ms = 0.0;
+                        }
+                        t = (uint32_t)((elapsed_ms * 60.0 / 1000.0) + 0.5);
+                        t %= GFX_TICKS60_WRAP;
+                    }
+#else
+                    t = gfx_vs->ticks60;
+#endif
                     *p = q;
                     if (!is_str) {
                         return make_num((double)t);
@@ -9352,6 +9358,7 @@ EMSCRIPTEN_KEEPALIVE int wasm_gfx_screen_screencode_at(int col, int row)
 
 static void wasm_gfx_set_video(void)
 {
+    wasm_gfx_ti_epoch_ms = emscripten_get_now();
     gfx_sprite_shutdown();
     gfx_video_init(&wasm_gfx_state);
     wasm_gfx_state.charset_lowercase = (uint8_t)(petscii_get_lowercase() ? 1 : 0);