cmake-gui: Honor installDir from configure presets

The GUI ignored a preset's installDir, so CMAKE_INSTALL_PREFIX fell back
to the platform default instead of the value the command line uses. This
fixes that by reading installDir in QCMake::properties(), and while we're
there, it applies toolchainFile after the cacheVariables loop so both
override a same-named entry.

Fixes: #27804

Source/QtDialog/QCMake.cxx

@@ -470,6 +470,14 @@ QCMakePropertyList QCMake::properties() const
     auto const& p =
       this->CMakePresetsGraph.ConfigurePresets.at(presetName).Expanded;
     if (p) {
+      for (auto const& v : p->CacheVariables) {
+        if (!v.second) {
+          continue;
+        }
+        auto prop = cache_to_property(v);
+        add_to_property_list(ret, std::move(prop));
+      }
+      // Dedicated fields override same-named cacheVariables, so apply last.
       if (!p->ToolchainFile.empty()) {
         using CacheVariable = cmCMakePresetsGraph::CacheVariable;
         CacheVariable var{ "FILEPATH", p->ToolchainFile };
@@ -479,11 +487,13 @@ QCMakePropertyList QCMake::properties() const
         auto prop = cache_to_property(value);
         add_to_property_list(ret, std::move(prop));
       }
-      for (auto const& v : p->CacheVariables) {
-        if (!v.second) {
-          continue;
-        }
-        auto prop = cache_to_property(v);
+      if (!p->InstallDir.empty()) {
+        using CacheVariable = cmCMakePresetsGraph::CacheVariable;
+        CacheVariable var{ "PATH", p->InstallDir };
+        std::pair<std::string, cm::optional<CacheVariable>> value = {
+          "CMAKE_INSTALL_PREFIX", var
+        };
+        auto prop = cache_to_property(value);
         add_to_property_list(ret, std::move(prop));
       }
     }

Tests/CMakeGUI/CMakeGUITest.cmake

@@ -176,6 +176,11 @@ run_cmake_gui_test(presetArg:presetConfigExists
     -S "${CMakeGUITest_BINARY_DIR}/presetArg-presetConfigExists/src"
     "--preset=ninja"
   )
+run_cmake_gui_test(presetArg:installDir
+  ARGS
+    -S "${CMakeGUITest_BINARY_DIR}/presetArg-installDir/src/"
+    "--preset=installDir"
+  )
 run_cmake_gui_test(presetArg:noExist
   ARGS
     -S "${CMakeGUITest_BINARY_DIR}/presetArg-noExist/src"

Tests/CMakeGUI/CMakeGUITest.cxx

@@ -353,6 +353,33 @@ void CMakeGUITest::presetArg_data()
     << CMakeGUITest_BINARY_DIR "/presetArg-presetConfigExists/src"
     << CMakeGUITest_BINARY_DIR "/presetArg-presetConfigExists/src/build"
     << makePresetProperties("presetArg-presetConfigExists");
+  QCMakePropertyList installDirProperties{
+    QCMakeProperty{
+      /*Key=*/"CMAKE_INSTALL_PREFIX",
+      /*Value=*/
+      QString::fromLocal8Bit(CMakeGUITest_BINARY_DIR
+                             "/presetArg-installDir/src/install"),
+      /*Strings=*/{},
+      /*Help=*/"",
+      /*Type=*/QCMakeProperty::PATH,
+      /*Advanced=*/false,
+    },
+    QCMakeProperty{
+      /*Key=*/"CMAKE_TOOLCHAIN_FILE",
+      /*Value=*/
+      QString::fromLocal8Bit(CMakeGUITest_BINARY_DIR
+                             "/presetArg-installDir/src/toolchain.cmake"),
+      /*Strings=*/{},
+      /*Help=*/"",
+      /*Type=*/QCMakeProperty::FILEPATH,
+      /*Advanced=*/false,
+    },
+  };
+  QTest::newRow("installDir")
+    << WindowSetupHelper{} << "installDir"
+    << CMakeGUITest_BINARY_DIR "/presetArg-installDir/src"
+    << CMakeGUITest_BINARY_DIR "/presetArg-installDir/src/build"
+    << installDirProperties;
   QTest::newRow("noExist") << WindowSetupHelper{} << QString{}
                            << CMakeGUITest_BINARY_DIR "/presetArg-noExist/src"
                            << "" << QCMakePropertyList{};

Tests/CMakeGUI/presetArg-installDir/CMakePresets.json.in

@@ -0,0 +1,22 @@
+{
+  "version": 3,
+  "configurePresets": [
+    {
+      "name": "installDir",
+      "generator": "Ninja",
+      "binaryDir": "${sourceDir}/build",
+      "installDir": "${sourceDir}/install",
+      "toolchainFile": "${sourceDir}/toolchain.cmake",
+      "cacheVariables": {
+        "CMAKE_INSTALL_PREFIX": {
+          "type": "PATH",
+          "value": "${sourceDir}/bad_install"
+        },
+        "CMAKE_TOOLCHAIN_FILE": {
+          "type": "FILEPATH",
+          "value": "${sourceDir}/bad_toolchain.cmake"
+        }
+      }
+    }
+  ]
+}