[win] Add hkey::delete_value() function

Author: dacap

base/win/registry.cpp

@@ -1,5 +1,5 @@
 // LAF Base Library
-// Copyright (c) 2023 Igara Studio S.A.
+// Copyright (c) 2023-2025 Igara Studio S.A.
 // Copyright (c) 2017 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -215,6 +215,16 @@ void hkey::dword(const std::string& name, const DWORD value)
     throw Win32Exception("Error setting registry value");
 }
 
+void hkey::delete_value(const std::string& name)
+{
+  if (!m_hkey)
+    return;
+
+  LONG result = RegDeleteValueW(m_hkey, from_utf8(name).c_str());
+  if (result != ERROR_SUCCESS)
+    throw Win32Exception("Error deleting registry value");
+}
+
 void hkey::delete_tree(const std::string& subkey)
 {
   if (!m_hkey)

base/win/registry.h

@@ -1,5 +1,5 @@
 // LAF Base Library
-// Copyright (c) 2021-2023 Igara Studio S.A.
+// Copyright (c) 2021-2025 Igara Studio S.A.
 // Copyright (c) 2017 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -37,6 +37,7 @@ class hkey {
   ~hkey();
 
   hkey& operator=(hkey&& key);
+  operator bool() const { return (m_hkey != nullptr); }
 
   HKEY handle() const { return m_hkey; }
 
@@ -52,6 +53,8 @@ class hkey {
   DWORD dword(const std::string& name);
   void dword(const std::string& name, const DWORD value);
 
+  void delete_value(const std::string& name);
+
   // Deletes keys in the given subkey, if subkey == "", all children
   // keys are deleted but this hkey isn't (the root is kept).
   void delete_tree(const std::string& subkey);

base/win/registry_tests.cpp

@@ -1,5 +1,5 @@
 // LAF Base Library
-// Copyright (c) 2024 Igara Studio S.A.
+// Copyright (c) 2024-2025 Igara Studio S.A.
 // Copyright (c) 2017 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -33,8 +33,8 @@ TEST(Registry, OpenKey)
 TEST(Registry, CreateKey)
 {
   try {
-    hkey k = hkey::current_user();
-    k = k.create("Software\\Classes\\.laf-base-test-extension");
+    hkey hkcu = hkey::current_user();
+    hkey k = hkcu.create("Software\\Classes\\.laf-base-test-extension");
     k.string("", "testing");
     k.string("A", "value A");
     k.string("B", "value B");
@@ -49,7 +49,46 @@ TEST(Registry, CreateKey)
     // We cannot use k.delete_tree("") because it does delete the
     // whole tree, but leaves the root key untouched.
 
-    hkey::current_user().delete_tree("Software\\Classes\\.laf-base-test-extension");
+    hkcu.delete_tree("Software\\Classes\\.laf-base-test-extension");
+  }
+  catch (Win32Exception& ex) {
+    printf("Win32Exception: %s\nError Code: %d\n", ex.what(), ex.errorCode());
+    throw;
+  }
+  catch (const std::exception& ex) {
+    printf("std::exception: %s\n", ex.what());
+    throw;
+  }
+}
+
+TEST(Registry, DeleteValue)
+{
+  try {
+    hkey hkcu = hkey::current_user();
+    hkey k = hkcu.create("Software\\Classes\\.laf-base-test-delete-value");
+    k.string("A", "value A");
+    k.string("B", "");
+    k.dword("C", 2);
+
+    EXPECT_TRUE(k.exists("A"));
+    EXPECT_TRUE(k.exists("B"));
+    EXPECT_TRUE(k.exists("C"));
+    EXPECT_EQ("value A", k.string("A"));
+    EXPECT_EQ("", k.string("B"));
+    EXPECT_EQ(2, k.dword("C"));
+
+    k.delete_value("A");
+    k.delete_value("B");
+    k.delete_value("C");
+
+    EXPECT_FALSE(k.exists("A"));
+    EXPECT_FALSE(k.exists("B"));
+    EXPECT_FALSE(k.exists("C"));
+    EXPECT_EQ("", k.string("A"));
+    EXPECT_EQ("", k.string("B"));
+    EXPECT_EQ(0, k.dword("C"));
+
+    hkcu.delete_tree("Software\\Classes\\.laf-base-test-delete-value");
   }
   catch (Win32Exception& ex) {
     printf("Win32Exception: %s\nError Code: %d\n", ex.what(), ex.errorCode());