Merge current dev and refresh PR #6741 from the 7011 integration

tests/test_editor_composite_double_buffer.py

@@ -0,0 +1,36 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+EDITOR = (ROOT / "static/js/galleryEditor.js").read_text(encoding="utf-8")
+
+
+def test_async_composite_renders_into_a_back_buffer():
+    assert "let _documentBackCanvas = null;" in EDITOR
+    assert "const copyBack = () => {" in EDITOR
+    start = EDITOR.index("  if (asyncComposite) {")
+    end = EDITOR.index("    _asyncCompositeInFlight = job;", start)
+    block = EDITOR[start:end]
+    assert "_documentBackCanvas = document.createElement('canvas');" in block
+    assert "_drawDocumentLayersAsync(back.getContext('2d'), render.isCurrent)" in block
+    assert "_drawDocumentLayers(back.getContext('2d'), render.isCurrent);" in block
+    # The document canvas must only be written by a completed generation, so an
+    # invalidated render can never leave a half-drawn document on screen.
+    assert "_drawDocumentLayersAsync(documentCanvas.getContext('2d')" not in block
+    assert "_drawDocumentLayers(documentCanvas.getContext('2d')" not in block
+    assert block.count("if (!render.isCurrent()) return;") >= 2
+
+
+def test_completed_generation_replaces_the_document_atomically():
+    copy = EDITOR[EDITOR.index("    const copyBack = () => {"):EDITOR.index("    const renderPromise =")]
+    assert "dctx.clearRect(0, 0, documentCanvas.width, documentCanvas.height);" in copy
+    assert "dctx.drawImage(back, 0, 0);" in copy
+    assert "_finishComposite(render, documentCanvas);" in copy
+
+
+def test_direct_drawing_stays_synchronous_for_live_feedback():
+    start = EDITOR.index("  const asyncComposite = _hasRetainedEffects()")
+    end = EDITOR.index(";", EDITOR.index("typeof OffscreenCanvas !== 'undefined'", start))
+    gate = EDITOR[start:end]
+    assert "&& !state.drawing" in gate
+    assert "&& !state.moving" in gate