CMake: Prevent WiX installations over existing NSIS installations

Use a custom action to look for Uninstall.exe in the user
selected installation prefix.

Its presence indicates a previous NSIS installation.
Inform the user and request manual resolution of the issue.

3 files changed, 60 insertions, 0 deletions

diff --git a/Utilities/Release/WiX/CustomAction/CMakeLists.txt b/Utilities/Release/WiX/CustomAction/CMakeLists.txt
new file mode 100644
index 0000000..7efd01e
--- /dev/null
+++ b/Utilities/Release/WiX/CustomAction/CMakeLists.txt
@@ -0,0 +1,13 @@
+foreach(CONFIG DEBUG MINSIZEREL RELEASE RELWITHDEBINFO)
+  string(REPLACE "/MD" "/MT"
+    "CMAKE_CXX_FLAGS_${CONFIG}"
+    "${CMAKE_CXX_FLAGS_${CONFIG}}"
+  )
+endforeach()
+
+add_library(CMakeWiXCustomActions MODULE
+  detect_nsis_overwrite.cpp
+  exports.def
+)
+
+target_link_libraries(CMakeWiXCustomActions PRIVATE msi)
diff --git a/Utilities/Release/WiX/CustomAction/detect_nsis_overwrite.cpp b/Utilities/Release/WiX/CustomAction/detect_nsis_overwrite.cpp
new file mode 100644
index 0000000..dad1ae5
--- /dev/null
+++ b/Utilities/Release/WiX/CustomAction/detect_nsis_overwrite.cpp
@@ -0,0 +1,45 @@
+#include <windows.h>
+#include <msi.h>
+#include <msiquery.h>
+
+#include <string>
+#include <vector>
+
+std::wstring get_property(MSIHANDLE msi_handle, std::wstring const& name)
+{
+  DWORD size = 0;
+
+  UINT status = MsiGetPropertyW(msi_handle, name.c_str(), L"", &size);
+
+  if(status == ERROR_MORE_DATA)
+    {
+    std::vector<wchar_t> buffer(size + 1);
+    MsiGetPropertyW(msi_handle, name.c_str(), &buffer[0], &size);
+    return std::wstring(&buffer[0]);
+    }
+  else
+    {
+    return std::wstring();
+    }
+}
+
+void set_property(MSIHANDLE msi_handle,
+  std::wstring const& name, std::wstring const& value)
+{
+  MsiSetPropertyW(msi_handle, name.c_str(), value.c_str());
+}
+
+extern "C" UINT __stdcall DetectNsisOverwrite(MSIHANDLE msi_handle)
+{
+  std::wstring install_root = get_property(msi_handle, L"INSTALL_ROOT");
+
+  std::wstring uninstall_exe = install_root + L"\\uninstall.exe";
+
+  bool uninstall_exe_exists =
+      GetFileAttributesW(uninstall_exe.c_str()) != INVALID_FILE_ATTRIBUTES;
+
+  set_property(msi_handle, L"CMAKE_NSIS_OVERWRITE_DETECTED",
+    uninstall_exe_exists ? L"1" : L"0");
+
+  return ERROR_SUCCESS;
+}
diff --git a/Utilities/Release/WiX/CustomAction/exports.def b/Utilities/Release/WiX/CustomAction/exports.def
new file mode 100644
index 0000000..0e448b2
--- /dev/null
+++ b/Utilities/Release/WiX/CustomAction/exports.def
@@ -0,0 +1,2 @@
+EXPORTS
+	DetectNsisOverwrite=DetectNsisOverwrite