Overlay: follow display offset/scale, avoid needless reloads

- Apply the display layout's scale and offset to the overlay itself instead
  of always centering it, so moving/resizing the display in Display Layout
  moves the overlay with the game inside it, and the portrait default
  (screen high up) is respected.
- Rescanning overlays (done whenever the display layout screen recreates its
  views, e.g. after closing the picker popup) no longer unloads the active
  overlay unless its definition changed.
- Re-picking the current overlay no longer posts GPU config change
  notifications, which caused an audio glitch with a game running behind.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QGBg32EFPsTXjAFu7dnTcz

GPU/Common/Overlay.cpp

@@ -172,7 +172,19 @@ void ReloadAllOverlayInfo() {
 	std::lock_guard<std::mutex> guard(g_overlayLock);
 	ScanOverlays(&g_overlayInfo);
 	g_overlayInfoLoaded = true;
-	UnloadActiveLocked();
+
+	// Keep the loaded overlay if its definition didn't change, so that rescanning (which the
+	// display layout screen does every time its views are recreated) doesn't cause a reload.
+	if (!g_activeId.empty()) {
+		auto iter = std::find_if(g_overlayInfo.begin(), g_overlayInfo.end(), [](const OverlayInfo &info) { return info.id == g_activeId; });
+		const bool unchanged = iter != g_overlayInfo.end() && !g_activeFailed &&
+			iter->imagePath == g_activeInfo.imagePath && iter->layer == g_activeInfo.layer &&
+			iter->holeFromIni == g_activeInfo.holeFromIni && iter->holeX == g_activeInfo.holeX &&
+			iter->holeY == g_activeInfo.holeY && iter->holeW == g_activeInfo.holeW && iter->holeH == g_activeInfo.holeH;
+		if (!unchanged) {
+			UnloadActiveLocked();
+		}
+	}
 }
 
 std::vector<OverlayInfo> GetAllOverlayInfo() {
@@ -216,6 +228,7 @@ bool ImportOverlayImage(const Path &source, std::string *id) {
 		return false;
 	}
 	INFO_LOG(Log::G3D, "Imported overlay %s as %s", source.c_str(), filename.c_str());
+	// The file name is new, so this can't affect the loaded overlay.
 	ReloadAllOverlayInfo();
 	*id = filename;
 	return true;
@@ -305,12 +318,15 @@ bool GetOverlayLayout(const DisplayLayoutConfig &config, float frameX, float fra
 	const float imgW = (float)g_activeImage->width;
 	const float imgH = (float)g_activeImage->height;
 
-	// Fit the overlay to the frame, keeping the aspect ratio, centered.
-	const float scale = std::min(frameW / imgW, frameH / imgH);
+	// Fit the overlay to the frame, keeping the aspect ratio. Then apply the display layout's scale
+	// and offset to the overlay, the same way they'd apply to the game without one, so moving and
+	// resizing the display moves the overlay (with the game inside it). This also keeps the portrait
+	// default of having the screen high up.
+	const float scale = std::min(frameW / imgW, frameH / imgH) * config.fDisplayScale;
 	layout->overlayW = imgW * scale;
 	layout->overlayH = imgH * scale;
-	layout->overlayX = frameX + (frameW - layout->overlayW) * 0.5f;
-	layout->overlayY = frameY + (frameH - layout->overlayH) * 0.5f;
+	layout->overlayX = frameX + frameW * config.fDisplayOffsetX - layout->overlayW * 0.5f;
+	layout->overlayY = frameY + frameH * config.fDisplayOffsetY - layout->overlayH * 0.5f;
 
 	layout->layer = g_activeInfo.layer;
 	layout->hasHole = g_activeHasHole;

GPU/Common/Overlay.h

@@ -33,10 +33,11 @@
 //      Layer=Foreground        ; or Background (drawn behind the game)
 //      Hole=0,0,640,362        ; optional, in image pixels. Auto-detected if missing.
 //
-// Placement: the overlay is fit to the screen (aspect preserved, centered). The hole is mapped
-// to the screen with the same scale and offset, and the PSP screen is then fit into the hole
-// using the normal display layout options (stretch, integer scale, aspect ratio).
-// The display offset and scale options are ignored while an overlay with a hole is active.
+// Placement: the overlay is fit to the screen (aspect preserved), then the display layout's scale
+// and offset are applied to it, like they normally are to the game. So moving or resizing the
+// display moves the overlay, and the portrait default (screen high up) works. The hole is mapped
+// with the same scale and offset, and the PSP screen is fit into the hole using the remaining
+// display options (stretch, integer scale, aspect ratio).
 
 #pragma once
 
@@ -86,7 +87,7 @@ struct OverlayLayout {
 	uint32_t generation = 0;
 };
 
-// Rescans the overlays folder. Also unloads the active overlay, so it gets reloaded from disk.
+// Rescans the overlays folder. The loaded overlay is kept unless its definition changed or it's gone.
 void ReloadAllOverlayInfo();
 std::vector<OverlayInfo> GetAllOverlayInfo();
 

GPU/Common/PresentationCommon.cpp

@@ -108,8 +108,8 @@ void CalculateDisplayOutputRect(const DisplayLayoutConfig &config, FRect *rc, fl
 
 	float scale = config.fDisplayScale;
 
-	// With an overlay that has a hole, the overlay is fit to the screen and the game is fit into
-	// the hole instead. The offset and scale options don't apply then, the overlay decides those.
+	// With an overlay that has a hole, the game is fit into the hole instead. The offset and scale
+	// options were already applied to the overlay itself, see GetOverlayLayout.
 	FRect frame = screenFrame;
 	OverlayLayout overlay;
 	const bool inOverlayHole = GetOverlayLayout(config, screenFrame.x, screenFrame.y, screenFrame.w, screenFrame.h, &overlay) && overlay.hasHole;

UI/DisplayLayoutScreen.cpp

@@ -370,7 +370,11 @@ void DisplayLayoutScreen::CreateViews() {
 		}
 		if (overlayIds.size() > 1) {
 			auto overlayChoice = leftColumn->Add(new PopupMultiChoiceDynamic(&config.sOverlay, gr->T("Overlay"), overlayNames, I18NCat::NONE, screenManager(), &overlayIds));
-			overlayChoice->OnChoice.Add([](UI::EventParams &) {
+			overlayChoice->OnChoice.Add([](UI::EventParams &e) {
+				// e.b is set if the value actually changed. Re-picking the current one shouldn't
+				// cause a reload, since that glitches the audio of a game running in the background.
+				if (!e.b)
+					return;
 				// The game rect may have moved, which matters for post shaders that run at output resolution.
 				NotifyPostChanges();
 			});