Add overlay (bezel) support

Draws a user image around or behind the PSP screen, to fill the black bars
on displays whose aspect ratio doesn't match the PSP's (#20325).

- Overlays are PNGs in PSP/OVERLAYS. A plain PNG there just works: it's
  drawn in front of the game, and its transparent hole is found by walking
  from the image center to each edge until a nearly opaque pixel. Existing
  RetroArch overlay images can be dropped in as-is.
- A subfolder with an overlay.ini can define overlays with a Name, Layer
  (Foreground/Background) and an explicit Hole=x,y,w,h.
- "Load overlay image..." in the display layout screen imports any PNG
  (including Android content URIs) into the overlays folder and selects it.
- The overlay is fit to the screen (aspect preserved, centered). The hole is
  mapped with the same scale, and the game is fit into it with the normal
  stretch / integer scale / aspect ratio options. Offset and scale don't
  apply while an overlay with a hole is active. This goes through
  CalculateDisplayOutputRect, so touch mapping and post shaders agree.
- The selection is a per-orientation, per-game DisplayLayout setting.
- Disabled in VR, Cardboard, and with skip buffer effects (except software
  rendering), since the presentation path doesn't run there.

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

UI/DisplayLayoutScreen.cpp

@@ -30,6 +30,10 @@
 #include "Common/System/NativeApp.h"
 #include "Common/VR/PPSSPPVR.h"
 #include "Common/StringUtils.h"
+#include "Common/File/FileUtil.h"
+#include "Common/System/OSD.h"
+#include "Common/System/Request.h"
+#include "Core/Util/PathUtil.h"
 
 #include "Common/Data/Color/RGBAUtil.h"
 #include "Common/Data/Text/I18n.h"
@@ -41,6 +45,7 @@
 #include "Core/System.h"
 #include "GPU/GPUCommon.h"
 #include "GPU/Common/FramebufferManagerCommon.h"
+#include "GPU/Common/Overlay.h"
 #include "GPU/Common/PresentationCommon.h"
 
 static const int leftColumnWidth = 200;
@@ -345,6 +350,54 @@ void DisplayLayoutScreen::CreateViews() {
 	if (!IsVREnabled()) {
 		static const char *bufFilters[] = { "Linear", "Nearest", };
 		leftColumn->Add(new PopupMultiChoice(&config.iDisplayFilter, gr->T("Screen Scaling Filter"), bufFilters, 1, ARRAY_SIZE(bufFilters), I18NCat::GRAPHICS, screenManager()));
+
+		// Overlays (bezels), from PSP/OVERLAYS. Rescanned each time, so new files show up without a restart.
+		ReloadAllOverlayInfo();
+		const std::vector<OverlayInfo> overlays = GetAllOverlayInfo();
+		std::vector<std::string> overlayNames{ std::string(sy->T("Off")) };
+		std::vector<std::string> overlayIds{ "" };
+		bool selectedFound = config.sOverlay.empty();
+		for (const auto &overlay : overlays) {
+			overlayNames.push_back(overlay.name);
+			overlayIds.push_back(overlay.id);
+			if (overlay.id == config.sOverlay)
+				selectedFound = true;
+		}
+		if (!selectedFound) {
+			// Keep showing a selected overlay whose files went missing, so it can be turned off.
+			overlayNames.push_back(config.sOverlay);
+			overlayIds.push_back(config.sOverlay);
+		}
+		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 &) {
+				// The game rect may have moved, which matters for post shaders that run at output resolution.
+				NotifyPostChanges();
+			});
+		}
+
+		// Just pick any PNG: it's copied into the overlays folder and everything is auto-detected.
+		Choice *browseOverlay = leftColumn->Add(new Choice(gr->T("Load overlay image...")));
+		const DeviceOrientation orientation = GetDeviceOrientation();
+		browseOverlay->OnClick.Add([this, orientation](UI::EventParams &) {
+			auto gr = GetI18NCategory(I18NCat::GRAPHICS);
+			const Path savePath = GetSysDirectory(DIRECTORY_CUSTOM_OVERLAYS) / "imported.png";
+			System_BrowseForImage(GetRequesterToken(), gr->T("Load overlay image..."), savePath, [this, orientation, savePath](std::string_view value, int converted) {
+				// If the platform converted the image, it's been saved to savePath already.
+				const Path source = converted == 1 ? savePath : Path(value);
+				std::string id;
+				if (!source.empty() && ImportOverlayImage(source, &id)) {
+					if (converted == 1)
+						File::Delete(savePath);
+					g_Config.GetDisplayLayoutConfig(orientation).sOverlay = id;
+					NotifyPostChanges();
+					RecreateViews();
+				} else if (!value.empty() || converted == 1) {
+					auto gr = GetI18NCategory(I18NCat::GRAPHICS);
+					g_OSD.Show(OSDType::MESSAGE_ERROR, gr->T("Overlay images must be PNG files"));
+				}
+			});
+		});
 	}
 
 	Draw::DrawContext *draw = screenManager()->getDrawContext();