Phase 8C: RioJoy.Tray multi-targets net48 (x64) + net40 (x86, Windows XP)

The XP flavor keeps the full runtime AND the mapping editor (decided:
editor everywhere). Gated per flavor:
- Wallpaper maker + WallpaperCanvas + generation (SkiaSharp) are
  net48-only; the XP coordinator applies the profile's pre-rendered
  wallpaper instead, and WallpaperApplier converts PNG->BMP on net40
  (XP SPI_SETDESKWALLPAPER accepts only BMP).
- Joystick chain: ViGEm branch compiled out on net40 (HID feeder stays,
  ready for RioGamepadXP.sys); the editor button picker offers the full
  96 HID buttons on net40 vs the 11 named Xbox buttons on net48.

Verified: net40/x86 exe boots on Win10; the editor renders offline in a
32-bit host with a Button-50 joystick binding resolving correctly and
live gauges working (screenshot harness).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/RioJoy.Tray/Editor/ProfileEditorForm.cs

@@ -261,9 +261,15 @@ public sealed class ProfileEditorForm : Form
                     _valueCombo.Items.Add(new ValueItem(k.Name, k.Value));
                 break;
             case RioRouteKind.Joystick:
+#if NET40
+                // XP: RioGamepadXP exposes the full 96-button HID layout.
+                for (int btn = 1; btn <= RioJoy.Core.Hid.RioHidReport.ButtonCount; btn++)
+                    _valueCombo.Items.Add(new ValueItem($"Button {btn}", (byte)btn));
+#else
                 // The signed ViGEmBus Xbox 360 pad exposes 11 buttons; show their names.
                 for (int btn = 1; btn <= ViGEmJoystickSink.MappableButtonCount; btn++)
                     _valueCombo.Items.Add(new ValueItem($"Button {btn} ({ViGEmJoystickSink.ButtonNames[btn - 1]})", (byte)btn));
+#endif
                 break;
             case RioRouteKind.Hat:
                 foreach (RioHat h in new[] { RioHat.Up, RioHat.Right, RioHat.Down, RioHat.Left })

src/RioJoy.Tray/RioCoordinator.cs

@@ -5,7 +5,9 @@ using RioJoy.Core.Output;
 using RioJoy.Core.Overlay;
 using RioJoy.Core.Profiles;
 using RioJoy.Core.Serial;
-using RioJoy.Overlay;
+#if !NET40
+using RioJoy.Overlay; // SkiaSharp wallpaper generation — modern flavor only
+#endif
 
 namespace RioJoy.Tray;
 
@@ -149,12 +151,14 @@ public sealed class RioCoordinator : IDisposable
     // feeder, then a no-op when neither driver is present.
     private IJoystickSink CreateJoystickSink(out string note)
     {
+#if !NET40 // ViGEmBus is Win10+; on XP the HID feeder drives RioGamepadXP.sys
         if (ViGEmJoystickSink.TryCreate(out ViGEmJoystickSink? vigem))
         {
             _joystick = vigem;
             note = string.Empty;
             return vigem!;
         }
+#endif
 
         if (HidFeederJoystickSink.TryCreate(out HidFeederJoystickSink? feeder))
         {
@@ -241,6 +245,20 @@ public sealed class RioCoordinator : IDisposable
     /// </summary>
     private void ApplyWallpaper(RioProfile profile)
     {
+#if NET40
+        // XP flavor: no SkiaSharp, so no generation — apply the profile's
+        // pre-rendered wallpaper (authored on a modern machine) if it exists.
+        if (string.IsNullOrWhiteSpace(profile.WallpaperPath) || !File.Exists(profile.WallpaperPath))
+            return;
+        try
+        {
+            WallpaperApplier.Apply(profile.WallpaperPath!);
+        }
+        catch (Exception ex)
+        {
+            SetStatus($"{Status}  [wallpaper: {ex.Message}]");
+        }
+#else
         string? templatePath = _config().OverlayTemplatePath;
         if (string.IsNullOrWhiteSpace(templatePath) || !File.Exists(templatePath))
             return;
@@ -263,6 +281,7 @@ public sealed class RioCoordinator : IDisposable
         {
             SetStatus($"{Status}  [wallpaper: {ex.Message}]");
         }
+#endif
     }
 
     private static string SafeFileName(string name)

src/RioJoy.Tray/RioJoy.Tray.csproj

@@ -2,9 +2,12 @@
 
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
-    <TargetFramework>net48</TargetFramework>
+    <!-- net48 = Windows 10/11 (x64, full app incl. wallpaper maker/SkiaSharp).
+         net40 = Windows XP SP3 (x86): full runtime + mapping editor; wallpaper
+         GENERATION is excluded (SkiaSharp has no XP support) — XP applies
+         pre-rendered wallpapers only. See docs/PLAN.md §Phase 8. -->
+    <TargetFrameworks>net48;net40</TargetFrameworks>
     <Platforms>x64</Platforms>
-    <PlatformTarget>x64</PlatformTarget>
     <Nullable>enable</Nullable>
     <UseWindowsForms>true</UseWindowsForms>
     <ImplicitUsings>enable</ImplicitUsings>
@@ -12,12 +15,29 @@
     <ApplicationManifest>app.manifest</ApplicationManifest>
   </PropertyGroup>
 
-  <ItemGroup>
-    <ProjectReference Include="..\RioJoy.Core\RioJoy.Core.csproj" />
-    <ProjectReference Include="..\RioJoy.Overlay\RioJoy.Overlay.csproj" />
+  <PropertyGroup Condition="'$(TargetFramework)' == 'net48'">
+    <PlatformTarget>x64</PlatformTarget>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(TargetFramework)' == 'net40'">
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+    <!-- net40 has no System.Net.Http assembly for the implicit global using. -->
+    <Using Remove="System.Net.Http" />
+    <!-- Wallpaper maker needs the SkiaSharp renderer (RioJoy.Overlay) — modern only. -->
+    <Compile Remove="Editor\WallpaperMakerForm.cs" />
+    <Compile Remove="Editor\WallpaperCanvas.cs" />
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\RioJoy.Core\RioJoy.Core.csproj" />
+    <ProjectReference Include="..\RioJoy.Overlay\RioJoy.Overlay.csproj" Condition="'$(TargetFramework)' == 'net48'" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" PrivateAssets="all" />
     <PackageReference Include="PolySharp" Version="1.14.1">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>

src/RioJoy.Tray/TrayApplicationContext.cs

@@ -74,10 +74,12 @@ internal sealed class TrayApplicationContext : ApplicationContext
         RebuildEditMenu(editMenu);
         menu.Items.Add(editMenu);
 
+#if !NET40 // wallpaper maker needs SkiaSharp — modern flavor only (XP applies pre-rendered)
         var wallpaperMenu = new ToolStripMenuItem("Wallpaper maker");
         wallpaperMenu.DropDownOpening += (_, _) => RebuildWallpaperMenu(wallpaperMenu);
         RebuildWallpaperMenu(wallpaperMenu);
         menu.Items.Add(wallpaperMenu);
+#endif
 
         menu.Items.Add("Import .ini…", null, (_, _) => ImportIniProfiles());
 
@@ -155,6 +157,7 @@ internal sealed class TrayApplicationContext : ApplicationContext
         editMenu.DropDownItems.Add(new ToolStripMenuItem("New profile…", null, (_, _) => OpenEditor(NewProfile())));
     }
 
+#if !NET40
     // Rebuild the "Wallpaper maker" submenu: one entry per profile.
     private void RebuildWallpaperMenu(ToolStripMenuItem wallpaperMenu)
     {
@@ -205,6 +208,7 @@ internal sealed class TrayApplicationContext : ApplicationContext
                 "RIOJoy", MessageBoxButtons.OK, MessageBoxIcon.Warning);
         }
     }
+#endif
 
     // Create, register and persist a fresh empty profile with a unique name.
     private RioProfile NewProfile()

src/RioJoy.Tray/WallpaperApplier.cs

@@ -30,6 +30,22 @@ public static class WallpaperApplier
         if (!File.Exists(full))
             throw new FileNotFoundException("Wallpaper image not found.", full);
 
+#if NET40
+        // Windows XP's SPI_SETDESKWALLPAPER accepts only BMP. Wallpapers are
+        // authored as PNG on a modern machine, so convert beside the source on
+        // apply (idempotent: reuses an up-to-date .bmp).
+        if (!full.EndsWith(".bmp", StringComparison.OrdinalIgnoreCase))
+        {
+            string bmp = Path.ChangeExtension(full, ".bmp");
+            if (!File.Exists(bmp) || File.GetLastWriteTimeUtc(bmp) < File.GetLastWriteTimeUtc(full))
+            {
+                using var image = System.Drawing.Image.FromFile(full);
+                image.Save(bmp, System.Drawing.Imaging.ImageFormat.Bmp);
+            }
+            full = bmp;
+        }
+#endif
+
         return SystemParametersInfo(
             SPI_SETDESKWALLPAPER, 0, full, SPIF_UPDATEINIFILE | SPIF_SENDCHANGE);
     }