fix: address Copilot review — dual-screen rendering correctness

- Add dualScreenPipelineBuildFailed flag to skip per-frame pipeline retry
  and log spam after a build failure; reset on layout reinstall
- Apply outputFrame normalization heuristic (same as normalizeFrame()) to
  handle Delta skin JSON that stores pixel-space rather than 0-1 coords
- Replace isMetalDualScreenActive checks in skin frame handler with direct
  dualScreenLayout != nil checks for more accurate fallback detection

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: github-actions[bot]

PVUI/Sources/PVUIBase/PVEmulatorVC/PVEmulatorViewController+DualScreen.swift

@@ -544,10 +544,11 @@ extension PVEmulatorViewController {
                 if self.core.coreIdentifier?.contains("emuThree") == true || self.core.coreIdentifier?.contains("3DS") == true {
                     DLOG("🎮 SKIN: Applying dual screen viewport for emuThreeDS: \(combinedRect)")
                     self.applyDualScreenViewportForEmuThree(frame: combinedRect)
-                } else if self.isMetalDualScreenActive {
-                    // Metal dual-screen is actively handling layout via sub-rectangle blits;
-                    // skip applyFrameToGPUView to avoid overriding expandMetalViewToFillParent.
-                    DLOG("🎮 SKIN: Metal dual-screen active, skipping applyFrameToGPUView")
+                } else if (self.gpuViewController as? PVMetalViewController)?.dualScreenLayout != nil {
+                    // Metal dual-screen layout is installed and handling rendering via
+                    // sub-rectangle blits; skip applyFrameToGPUView to avoid overriding
+                    // the view that expandMetalViewToFillParent already sized to full frame.
+                    DLOG("🎮 SKIN: Metal dual-screen layout active, skipping applyFrameToGPUView")
                 } else {
                     DLOG("🎮 SKIN: Applying dual screen viewport (standard): \(combinedRect)")
                     self.applyFrameToGPUView(combinedRect)
@@ -567,7 +568,7 @@ extension PVEmulatorViewController {
                 DLOG("🎮 SKIN: Timeout - only one screen received, applying single frame: \(frame)")
                 if self.core.coreIdentifier?.contains("emuThree") == true || self.core.coreIdentifier?.contains("3DS") == true {
                     self.applyDualScreenViewportForEmuThree(frame: frame)
-                } else if !self.isMetalDualScreenActive {
+                } else if (self.gpuViewController as? PVMetalViewController)?.dualScreenLayout == nil {
                     self.applyFrameToGPUView(frame)
                 }
                 self.currentTargetFrame = frame

PVUI/Sources/PVUIBase/PVEmulatorVC/PVEmulatorViewController+MetalDualScreen.swift

@@ -147,10 +147,24 @@ extension PVEmulatorViewController {
 
             // --- Destination (view-space points) ---
             // Mirror the calculation in currentDualScreenViewportFrame() exactly.
-            let inLayout = CGRect(x: outputFrame.minX * scaledW,
-                                  y: outputFrame.minY * scaledH,
-                                  width:  outputFrame.width  * scaledW,
-                                  height: outputFrame.height * scaledH)
+            // Skin outputFrames are *supposed* to be 0–1 normalised relative to
+            // mappingSize, but some JSON skins store raw pixel coordinates instead.
+            // Apply the same heuristic used by normalizeFrame(): if any component
+            // exceeds 1.0, divide by mappingSize to convert to the 0–1 range first.
+            let normOutput: CGRect
+            if outputFrame.origin.x > 1.0 || outputFrame.origin.y > 1.0 ||
+               outputFrame.size.width > 1.0 || outputFrame.size.height > 1.0 {
+                normOutput = CGRect(x: outputFrame.minX / mappingSize.width,
+                                    y: outputFrame.minY / mappingSize.height,
+                                    width:  outputFrame.width  / mappingSize.width,
+                                    height: outputFrame.height / mappingSize.height)
+            } else {
+                normOutput = outputFrame
+            }
+            let inLayout = CGRect(x: normOutput.minX * scaledW,
+                                  y: normOutput.minY * scaledH,
+                                  width:  normOutput.width  * scaledW,
+                                  height: normOutput.height * scaledH)
             let destRect = CGRect(x: xOff + inLayout.midX - inLayout.width  / 2,
                                   y: yOff + inLayout.midY - inLayout.height / 2,
                                   width:  inLayout.width,
@@ -168,6 +182,8 @@ extension PVEmulatorViewController {
 
         ILOG("dual-screen metal: installing layout with \(renderInfos.count) screens")
         metalVC.dualScreenLayout = renderInfos
+        // Reset failure flag so the pipeline gets another build attempt on new layout.
+        metalVC.dualScreenPipelineBuildFailed = false
         isMetalDualScreenActive = true
 
         // Expand the Metal view to fill the parent so both screen quads are visible.

PVUI/Sources/PVUIBase/PVGLViewController/PVMetalViewController+DualScreen.swift

@@ -98,11 +98,14 @@ extension PVMetalViewController {
     // MARK: Pipeline setup
 
     /// Compiles and caches the dual-screen blit pipeline.
-    /// Safe to call multiple times; no-ops when the pipeline already exists.
+    /// Safe to call multiple times; no-ops when the pipeline already exists or after a build failure.
     func buildDualScreenBlitPipelineIfNeeded() {
         guard dualScreenBlitPipeline == nil else { return }
+        // Skip retry after a failure to avoid per-frame shader compilation attempts.
+        guard !dualScreenPipelineBuildFailed else { return }
         guard let device = device else {
             ELOG("dual-screen: cannot build pipeline – Metal device is nil")
+            dualScreenPipelineBuildFailed = true
             return
         }
 
@@ -111,12 +114,14 @@ extension PVMetalViewController {
             library = try device.makeLibrary(source: Self.dualScreenShaderSource, options: nil)
         } catch {
             ELOG("dual-screen: shader compile error: \(error)")
+            dualScreenPipelineBuildFailed = true
             return
         }
 
         guard let vertFn = library.makeFunction(name: "dual_screen_vs"),
               let fragFn = library.makeFunction(name: "dual_screen_ps") else {
             ELOG("dual-screen: shader functions missing from compiled library")
+            dualScreenPipelineBuildFailed = true
             return
         }
 
@@ -130,6 +135,7 @@ extension PVMetalViewController {
             ILOG("dual-screen: render pipeline ready")
         } catch {
             ELOG("dual-screen: pipeline creation failed: \(error)")
+            dualScreenPipelineBuildFailed = true
         }
     }
 

PVUI/Sources/PVUIBase/PVGLViewController/PVMetalViewController.swift

@@ -243,6 +243,10 @@ class PVMetalViewController : PVGPUViewController, PVRenderDelegate, MTKViewDele
     /// Built lazily the first time it is needed.
     var dualScreenBlitPipeline: MTLRenderPipelineState? = nil
 
+    /// Set to `true` after a failed attempt to build `dualScreenBlitPipeline` so
+    /// subsequent frames skip the (expensive) retry and log the error only once.
+    var dualScreenPipelineBuildFailed: Bool = false
+
     /// Controls whether VSync is enabled (synchronizes rendering with display refresh rate)
     public var vsyncEnabled: Bool = true
 
@@ -2468,7 +2472,10 @@ class PVMetalViewController : PVGPUViewController, PVRenderDelegate, MTKViewDele
             // renderDualScreenLayout produced no output (empty layout or pipeline
             // failure) — fall through to the standard fullscreen blit below to
             // avoid presenting a black frame.
-            WLOG("dual-screen: renderDualScreenLayout produced no output, falling back to standard blit")
+            if !dualScreenPipelineBuildFailed {
+                WLOG("dual-screen: renderDualScreenLayout produced no output, falling back to standard blit")
+                dualScreenPipelineBuildFailed = true
+            }
         }
 
         /// Local scope so `endEncoding` runs before `present`/`commit` (function-scoped `defer` would run too late and trip Metal debug `encoding in progress`).