Add x86 build support for 32-bit WPF targets

- Add x86 CMake preset (build-x86 directory, x86-windows triplet)
- Add x86 to release pipeline matrix (msvc_arch: amd64_x86)
- Add managed WPF assembly build step to CI and release pipelines
- Include WPF TAP DLL and managed assembly in release packages
- Show clear error when 64-bit lvt.exe encounters 32-bit WPF target:
  'WPF target is 32-bit (WoW64) - run lvt-x86.exe instead'
- Remove x86 cross-compile hacks from CMakeLists.txt - each arch
  is built as a separate CMake configuration instead

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: asklar

.github/workflows/ci.yml

@@ -26,6 +26,9 @@ jobs:
       - name: Configure
         run: cmake --preset default
 
+      - name: Build managed WPF assembly
+        run: dotnet build src/tap_wpf/LvtWpfTap.csproj -c Release
+
       - name: Build
         run: cmake --build build
 
@@ -50,3 +53,5 @@ jobs:
           path: |
             build/lvt.exe
             build/lvt_tap_x64.dll
+            build/lvt_wpf_tap_x64.dll
+            build/LvtWpfTap.dll

.github/workflows/release.yml

@@ -25,6 +25,10 @@ jobs:
             msvc_arch: x64
             preset: default
             build_dir: build
+          - arch: x86
+            msvc_arch: amd64_x86
+            preset: x86
+            build_dir: build-x86
           - arch: arm64
             msvc_arch: amd64_arm64
             preset: arm64
@@ -48,6 +52,9 @@ jobs:
       - name: Configure
         run: cmake --preset ${{ matrix.preset }} -DCMAKE_BUILD_TYPE=Release
 
+      - name: Build managed WPF assembly
+        run: dotnet build src/tap_wpf/LvtWpfTap.csproj -c Release
+
       - name: Build
         run: cmake --build ${{ matrix.build_dir }}
 
@@ -64,6 +71,12 @@ jobs:
           New-Item -ItemType Directory -Path release -Force
           Copy-Item ${{ matrix.build_dir }}\lvt.exe release\
           Copy-Item ${{ matrix.build_dir }}\lvt_tap_${{ matrix.arch }}.dll release\
+          if (Test-Path ${{ matrix.build_dir }}\lvt_wpf_tap_${{ matrix.arch }}.dll) {
+            Copy-Item ${{ matrix.build_dir }}\lvt_wpf_tap_${{ matrix.arch }}.dll release\
+          }
+          if (Test-Path ${{ matrix.build_dir }}\LvtWpfTap.dll) {
+            Copy-Item ${{ matrix.build_dir }}\LvtWpfTap.dll release\
+          }
           New-Item -ItemType Directory -Path release\skills\lvt -Force
           Copy-Item .github\skills\lvt\SKILL.md release\skills\lvt\
           Compress-Archive -Path release\* -DestinationPath lvt-${{ env.RELEASE_TAG }}-${{ matrix.arch }}.zip

CMakeLists.txt

@@ -44,6 +44,8 @@ target_compile_definitions(lvt PRIVATE
 # Determine TAP DLL architecture suffix from vcpkg triplet
 if(VCPKG_TARGET_TRIPLET MATCHES "arm64")
     set(TAP_ARCH_SUFFIX "arm64")
+elseif(VCPKG_TARGET_TRIPLET MATCHES "x86")
+    set(TAP_ARCH_SUFFIX "x86")
 else()
     set(TAP_ARCH_SUFFIX "x64")
 endif()
@@ -82,13 +84,12 @@ set_target_properties(lvt_wpf_tap PROPERTIES
 )
 
 # Build managed WPF tree walker assembly and copy to output
-# Run dotnet build separately; the managed DLL must be pre-built before running lvt
-# with WPF targets. Use: dotnet build src/tap_wpf/LvtWpfTap.csproj -c Release -o build
+# Pre-build with: dotnet build src/tap_wpf/LvtWpfTap.csproj -c Release
 add_custom_command(TARGET lvt_wpf_tap POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E copy_if_different
-        "${CMAKE_SOURCE_DIR}/src/tap_wpf/bin/x64/Release/LvtWpfTap.dll"
+        "${CMAKE_SOURCE_DIR}/src/tap_wpf/bin/$<IF:$<STREQUAL:${TAP_ARCH_SUFFIX},x86>,x86,x64>/Release/LvtWpfTap.dll"
         "$<TARGET_FILE_DIR:lvt>/LvtWpfTap.dll"
-    COMMENT "Copying managed WPF tree walker assembly (pre-build with: dotnet build src/tap_wpf/LvtWpfTap.csproj -c Release)"
+    COMMENT "Copying managed WPF tree walker assembly"
 )
 
 # --- Tests ---

CMakePresets.json

@@ -17,6 +17,22 @@
         "VCPKG_TARGET_TRIPLET": "x64-windows"
       }
     },
+    {
+      "name": "x86",
+      "displayName": "x86",
+      "generator": "Ninja",
+      "architecture": {
+        "value": "x86",
+        "strategy": "external"
+      },
+      "binaryDir": "${sourceDir}/build-x86",
+      "toolchainFile": "$env{VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake",
+      "cacheVariables": {
+        "CMAKE_C_COMPILER": "cl.exe",
+        "CMAKE_CXX_COMPILER": "cl.exe",
+        "VCPKG_TARGET_TRIPLET": "x86-windows"
+      }
+    },
     {
       "name": "arm64",
       "displayName": "ARM64",
@@ -39,6 +55,10 @@
       "name": "default",
       "configurePreset": "default"
     },
+    {
+      "name": "x86",
+      "configurePreset": "x86"
+    },
     {
       "name": "arm64",
       "configurePreset": "arm64"

src/providers/wpf_inject.cpp

@@ -158,30 +158,23 @@ static bool inject_dll(DWORD pid, const std::wstring& dllPath) {
 }
 
 bool inject_and_collect_wpf_tree(Element& root, HWND /*hwnd*/, DWORD pid) {
-    // Check target process bitness matches ours — can't inject x64 DLL into x86 process
-    auto targetArch = detect_process_architecture(pid);
-    auto hostArch = get_host_architecture();
-    if (targetArch != hostArch) {
-        if (g_debug)
-            fprintf(stderr, "lvt: WPF target is %s but lvt is %s, skipping injection\n",
-                    architecture_name(targetArch), architecture_name(hostArch));
-        return false;
-    }
-
-    // Also check for WoW64 (32-bit on 64-bit) which detect_process_architecture may miss
+    // Check target process bitness matches ours
     wil::unique_handle proc(OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, FALSE, pid));
     if (proc) {
         BOOL isWow64 = FALSE;
         if (IsWow64Process(proc.get(), &isWow64) && isWow64) {
-            if (g_debug)
-                fprintf(stderr, "lvt: WPF target is 32-bit (WoW64), skipping injection\n");
+#if defined(_M_X64) || defined(_M_ARM64)
+            fprintf(stderr,
+                "lvt: WPF target is 32-bit (WoW64) - run lvt-x86.exe instead\n");
             return false;
+#endif
         }
     }
 
     std::wstring exeDir = get_exe_dir();
     const wchar_t* tapSuffix = (get_host_architecture() == Architecture::arm64)
-        ? L"\\lvt_wpf_tap_arm64.dll" : L"\\lvt_wpf_tap_x64.dll";
+        ? L"\\lvt_wpf_tap_arm64.dll" : (sizeof(void*) == 4)
+        ? L"\\lvt_wpf_tap_x86.dll" : L"\\lvt_wpf_tap_x64.dll";
     std::wstring tapDll = exeDir + tapSuffix;
 
     if (GetFileAttributesW(tapDll.c_str()) == INVALID_FILE_ATTRIBUTES) {