fix(core): PresentPixels check-before-mutate + docs (v0.30.20)

AGENTS.md

@@ -65,7 +65,7 @@ wgpu (public API — Device, Queue, Buffer, Texture, Pipeline...)
 
 ## Current Version
 
-v0.30.19 | Go 1.25+ | Dependencies: naga v0.17.15, gpucontext v0.21.1, gputypes v0.5.1, goffi v0.6.0, webgpu v0.5.3
+v0.30.20 | Go 1.25+ | Dependencies: naga v0.17.15, gpucontext v0.21.1, gputypes v0.5.1, goffi v0.6.0, webgpu v0.5.3
 
 ## Build & Test
 

CHANGELOG.md

@@ -5,6 +5,23 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.30.20] - 2026-07-14
+
+### Fixed
+
+- **PresentPixels check-before-mutate** — move `hal.PixelPresenter` type assertion
+  before acquired texture discard. Failed `PresentPixels` on GPU backends no longer
+  corrupts surface state. Validate-then-mutate pattern matches Rust wgpu.
+
+### Added
+
+- **DX12 UMA GPU classification** — `CheckFeatureSupport(D3D12_FEATURE_ARCHITECTURE)`
+  replaces DedicatedVideoMemory heuristic for integrated/discrete detection.
+  Matches Rust wgpu pattern exactly. Contributor: @Zeroes1 (#254).
+- **DX12 `CacheCoherentUMA`** — stored for future memory pool optimization
+  (`D3D12_MEMORY_POOL_L0` vs `L1`).
+- **DX12 architecture diagnostic logging** — `hal.Logger().Info("dx12: adapter architecture", ...)`
+
 ## [0.30.19] - 2026-07-12
 
 ### Changed

core/surface.go

@@ -199,6 +199,14 @@ func (s *Surface) PresentPixels(data []byte, width, height uint32, damageRects [
 		return ErrSurfaceNotConfigured
 	}
 
+	// Check backend support BEFORE discarding acquired texture.
+	// GPU backends don't implement PixelPresenter — early return preserves
+	// the acquired texture so the normal render→Present path still works.
+	pp, ok := s.raw.(hal.PixelPresenter)
+	if !ok {
+		return fmt.Errorf("core: PresentPixels not supported on this backend")
+	}
+
 	// Discard stale acquired texture if any — PresentPixels replaces the
 	// entire AcquireTexture→render→Present flow.
 	if s.state == SurfaceStateAcquired && s.acquiredTex != nil {
@@ -207,11 +215,6 @@ func (s *Surface) PresentPixels(data []byte, width, height uint32, damageRects [
 		s.state = SurfaceStateConfigured
 	}
 
-	// Only software backend implements hal.PixelPresenter.
-	pp, ok := s.raw.(hal.PixelPresenter)
-	if !ok {
-		return fmt.Errorf("core: PresentPixels not supported on this backend")
-	}
 	return pp.PresentPixels(data, width, height, damageRects)
 }
 

core/surface_test.go

@@ -696,19 +696,17 @@ func TestPresentPixels_UnsupportedBackend(t *testing.T) {
 	}
 }
 
-func TestPresentPixels_DiscardsAcquiredTexture(t *testing.T) {
-	// After AcquireTexture, PresentPixels should discard the stale texture
-	// and succeed (on a backend that supports it). Since noop doesn't support
-	// PresentPixels, we verify the state transition: acquired → configured,
-	// then the "not supported" error comes from the duck-type check.
+func TestPresentPixels_PreservesAcquiredOnUnsupported(t *testing.T) {
+	// On backends that don't support PixelPresenter (like noop), PresentPixels
+	// should return an error WITHOUT discarding the acquired texture. This
+	// preserves the surface state so the normal render→Present path still works.
 	surface, device, _ := newTestSurface(t)
 	config := testSurfaceConfig()
 
 	if err := surface.Configure(device, config); err != nil {
 		t.Fatalf("Configure: %v", err)
 	}
 
-	// Acquire a texture
 	_, err := surface.AcquireTexture(nil)
 	if err != nil {
 		t.Fatalf("AcquireTexture: %v", err)
@@ -717,21 +715,14 @@ func TestPresentPixels_DiscardsAcquiredTexture(t *testing.T) {
 		t.Fatalf("state = %d, want SurfaceStateAcquired", surface.State())
 	}
 
-	// PresentPixels discards the acquired texture, then fails because noop
-	// doesn't implement the interface.
+	// PresentPixels on noop should fail without side effects.
 	err = surface.PresentPixels([]byte{0, 0, 0, 0}, 1, 1, nil)
 	if err == nil {
 		t.Error("PresentPixels on noop should return error")
 	}
 
-	// State should be Configured (texture was discarded before the duck-type check).
-	if surface.State() != SurfaceStateConfigured {
-		t.Errorf("state after PresentPixels = %d, want SurfaceStateConfigured", surface.State())
-	}
-
-	// Should be able to acquire again (proves discard happened).
-	_, err = surface.AcquireTexture(nil)
-	if err != nil {
-		t.Errorf("AcquireTexture after PresentPixels: %v", err)
+	// State must stay Acquired — texture NOT discarded on unsupported backend.
+	if surface.State() != SurfaceStateAcquired {
+		t.Errorf("state after PresentPixels = %d, want SurfaceStateAcquired", surface.State())
 	}
 }