Fix one-frame latency when a canvas texture feeds a same-frame consumer#1777
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bghgary merged 3 commits intoJul 13, 2026
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Follow-up to BabylonJS/Babylon.js#18506, which fixed the two GUI unicode visualization playgrounds to return Promise<Scene> from createScene (the old revisions fire-and-forget parseFromSnippetAsync / parseFromURLAsync, racing the screenshot), re-saved them as new revisions, and dropped the renderCount: 50 settle-frame workaround on the Babylon.js side. The Native viz runner already awaits the promise returned by createScene, so move to the awaiting revisions and drop the same workaround here: - Load GUI snippet with unicode: #YS93KY#0 -> #YS93KY#1 - Parse GUI json with unicode: #ERVGT5#0 -> #ERVGT5#1 - Remove renderCount: 50 from both (no longer needed now that setup is awaited) Same playground content, so the reference images are unchanged. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Updates Babylon Native’s Playground validation configuration to use the newer GUI Unicode visualization playground revisions that properly return Promise<Scene> from createScene, allowing the native runner to wait for scene setup and removing the need for a frame-settle workaround.
Changes:
- Bump the two GUI Unicode visualization tests to newer playground revisions (
#0→#1). - Remove the
renderCount: 50workaround from those two tests.
CI showed the "Load GUI snippet with unicode" viz test fails without the settle frames: that GUI includes an async color-emoji image load that Babylon Native does not finish within a single frame (the button colors also haven't settled), so the emoji renders broken and the buttons render red. Babylon.js completes it fast enough, which is why #18506 could drop the settle frames there. Retain renderCount on that test; the "Parse GUI json with unicode" test has no image load and passes with the awaiting revision and no settle frames. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
NativeEngine::CopyTexture scheduled the canvas->texture blit on PeekNextViewId(). Once the scene/backbuffer view had already been acquired, that placed the copy on a view id AFTER the view that samples the destination. bgfx processes blits in numeric view-id order, so a fullscreen GUI AdvancedDynamicTexture layer sampled the previous frame's canvas content — a one-frame GUI latency (blank/stale first frame). The viz suite masked this by pinning the GUI unicode tests to large renderCount settle frames. Reserve the blit's view id in Context::Flush, immediately after the canvas draws but before the scene/backbuffer render is recorded, and hand it to the source texture so CopyTexture blits on a view ordered after the canvas Flush yet before the consuming view. Non-canvas copies keep the PeekNextViewId() fallback, preserving BabylonJS#1683's multi-canvas ordering fix. Drop the now-unnecessary renderCount from the two GUI unicode viz tests; with the fix they render correctly on the first frame. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
bghgary
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bkaradzic-microsoft
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Jul 13, 2026
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Context
The two GUI unicode viz tests were pinned to old playground revisions with
renderCount: 50settle frames. BabylonJS/Babylon.js#18506 re-saved them as awaiting#1revisions and dropped the settle frames on the Babylon.js side. Adopting the#1revisions on Native isn't enough to droprenderCount— the settle frames masked a Native rendering bug, independent of #18506.Root cause
updateDynamicTextureflushes a GUIAdvancedDynamicTexture'sNativeCanvas(nanovg), then copies the canvas render target into the ADT texture viaNativeEngine::CopyTexture(abgfx::blit). The fullscreen ADT layer samples that texture during the scene/backbuffer render.CopyTexturescheduled the blit onPeekNextViewId(), which — once the backbuffer view was already acquired — placed the blit on a view id after the view that samples the destination. bgfx runs blits in numeric view-id order, so the layer sampled the previous frame's canvas: a one-frame latency (blank first frame; forParse, red buttons + broken emoji).renderCount: 50just rendered past it.Trace of one ADT frame, before: canvas
view 0-7, backbuffer + layerview 8, blitview 9— blit runs after the layer.Fix
Context::Flushreserves the blit's view id right after the canvas draws (before the scene render is recorded) and hands it to the source texture;CopyTextureuses it. Non-canvas copies keep thePeekNextViewId()fallback (preserves #1683).After: canvas
view 0-7, blitview 8, backbuffer + layerview 9— same-frame. General to Native GUI, not just these two tests.Changes
NativeEngine.cpp,Context.cpp,Canvas.{h,cpp},Texture.h: reserve and thread the blit view id.config.json: adopt#YS93KY#1/#ERVGT5#1, droprenderCountfrom both.Both tests pass at the default
renderCount: 1on Win32 D3D11, including the ASAN sanitizer viz run.[Created by Copilot on behalf of @bghgary]