[PATCH v14 1/2] uxtheme: Add ShouldSystemUseDarkMode.

[Helix Graziani]

From: Helix Graziani

---
 dlls/uxtheme/system.c       | 17 +++++++++++++++++
 dlls/uxtheme/tests/system.c | 34 ++++++++++++++++++++++++++++++++++
 dlls/uxtheme/uxtheme.spec   |  1 +
 3 files changed, 52 insertions(+)

diff --git a/dlls/uxtheme/system.c b/dlls/uxtheme/system.c
index 25f495d29f3..156051406e3 100644
--- a/dlls/uxtheme/system.c
+++ b/dlls/uxtheme/system.c
@@ -1256,3 +1256,20 @@ BOOL WINAPI ThemeHooksRemove(void)
     UnregisterUserApiHook();
     return TRUE;
 }
+
+/**********************************************************************
+ *      ShouldSystemUseDarkMode                           (UXTHEME.138)
+ *
+ * RETURNS
+ *     Whether or not the system should use dark mode.
+ */
+BOOL WINAPI ShouldSystemUseDarkMode(void)
+{
+    DWORD light_theme = TRUE, light_theme_size = sizeof(light_theme);
+
+    RegGetValueW(HKEY_CURRENT_USER,
+                 L"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize",
+                 L"SystemUsesLightTheme", RRF_RT_REG_DWORD, NULL, &light_theme, &light_theme_size);
+
+    return !light_theme;
+}
diff --git a/dlls/uxtheme/tests/system.c b/dlls/uxtheme/tests/system.c
index 2e769625dab..b7f11e044be 100644
--- a/dlls/uxtheme/tests/system.c
+++ b/dlls/uxtheme/tests/system.c
@@ -48,6 +48,7 @@ static HDC (WINAPI *pGetBufferedPaintTargetDC)(HPAINTBUFFER);
 static HRESULT (WINAPI *pGetBufferedPaintTargetRect)(HPAINTBUFFER, RECT *);
 static HRESULT (WINAPI *pGetThemeIntList)(HTHEME, int, int, int, INTLIST *);
 static HRESULT (WINAPI *pGetThemeTransitionDuration)(HTHEME, int, int, int, int, DWORD *);
+static BOOL (WINAPI *pShouldSystemUseDarkMode)(void);

static LONG (WINAPI *pDisplayConfigGetDeviceInfo)(DISPLAYCONFIG_DEVICE_INFO_HEADER *);
 static LONG (WINAPI *pDisplayConfigSetDeviceInfo)(DISPLAYCONFIG_DEVICE_INFO_HEADER *);
@@ -2597,6 +2598,38 @@ static void test_theme(void)
     DestroyWindow(hwnd);
 }

+static void test_ShouldSystemUseDarkMode(void)
+{
+    DWORD light_theme, light_theme_size = sizeof(light_theme), last_error;
+    BOOL result;
+    LSTATUS ls;
+
+    pShouldSystemUseDarkMode = (void *)GetProcAddress(GetModuleHandleA("uxtheme.dll"),
+                                                      MAKEINTRESOURCEA(138));
+    if (!pShouldSystemUseDarkMode)
+    {
+        win_skip("ShouldSystemUseDarkMode() is unavailable.\n");
+        return;
+    }
+
+    ls = RegGetValueW(HKEY_CURRENT_USER,
+                      L"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize",
+                      L"SystemUsesLightTheme", RRF_RT_REG_DWORD, NULL, &light_theme, &light_theme_size);
+    if (ls == ERROR_FILE_NOT_FOUND)
+    {
+        light_theme = 1;
+        ls = 0;
+    }
+    ok(ls == 0, "RegGetValue failed: %ld.\n", ls);
+
+    /* Call ShouldSystemUseDarkMode() and check for errors */
+    SetLastError(0xdeadbeef);
+    result = pShouldSystemUseDarkMode();
+    last_error = GetLastError();
+    ok(last_error == 0xdeadbeef, "ShouldSystemUseDarkMode set last error: %ld.\n", last_error);
+    ok(result == !light_theme, "Expected value %d, got %d.\n", !light_theme, result);
+}
+
 START_TEST(system)
 {
     ULONG_PTR ctx_cookie;
@@ -2622,6 +2655,7 @@ START_TEST(system)
     test_DrawThemeBackgroundEx();
     test_GetThemeBackgroundRegion();
     test_theme();
+    test_ShouldSystemUseDarkMode();

if (load_v6_module(&ctx_cookie, &ctx))
     {
diff --git a/dlls/uxtheme/uxtheme.spec b/dlls/uxtheme/uxtheme.spec
index c60254b677d..a5bfb88c49a 100644
--- a/dlls/uxtheme/uxtheme.spec
+++ b/dlls/uxtheme/uxtheme.spec
@@ -42,6 +42,7 @@
 61 stdcall OpenThemeDataEx(ptr wstr long)
 62 stub -noname ServerClearStockObjects
 63 stub -noname MarkSelection
+138 stdcall -noname ShouldSystemUseDarkMode()

# Standard functions
 @ stdcall BeginBufferedAnimation(ptr ptr ptr long ptr ptr ptr ptr)