[PATCH v4 1/1] uxtheme: Add ShouldSystemUseDarkMode.

[Helix Graziani]

From: Helix Graziani

---
 dlls/uxtheme/system.c       | 18 ++++++++++++++++++
 dlls/uxtheme/tests/system.c | 25 +++++++++++++++++++++++++
 dlls/uxtheme/uxtheme.spec   |  1 +
 3 files changed, 44 insertions(+)

diff --git a/dlls/uxtheme/system.c b/dlls/uxtheme/system.c
index 25f495d29f3..00642eb18ad 100644
--- a/dlls/uxtheme/system.c
+++ b/dlls/uxtheme/system.c
@@ -1256,3 +1256,21 @@ BOOL WINAPI ThemeHooksRemove(void)
     UnregisterUserApiHook();
     return TRUE;
 }
+
+/**********************************************************************
+ *      ShouldSystemUseDarkMode                           (UXTHEME.138)
+ *
+ * RETURNS
+ *     whether or not the system should use dark mode
+ */
+BOOL WINAPI ShouldSystemUseDarkMode(void)
+{
+    HKEY hk = HKEY_CURRENT_USER;
+    DWORD systemUsesLightTheme;
+
+    if (RegGetValueA(hk, "Software\Microsoft\Windows\CurrentVersion\Themes\Personalize",
+                     "AppsUseLightTheme", RRF_RT_REG_DWORD, NULL, &systemUsesLightTheme, NULL))
+        systemUsesLightTheme = TRUE; /* when there is no theme selected, it is light */
+
+    return !systemUsesLightTheme;
+}
diff --git a/dlls/uxtheme/tests/system.c b/dlls/uxtheme/tests/system.c
index 2e769625dab..5f340a17e6f 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 +2598,29 @@ static void test_theme(void)
     DestroyWindow(hwnd);
 }

+static void test_ShouldUseDarkMode(void)
+{
+    HKEY hk = HKEY_CURRENT_USER;
+    DWORD systemUsesLightTheme;
+    LRESULT lr;
+
+    pShouldSystemUseDarkMode = (void *)GetProcAddress(GetModuleHandleA("uxtheme.dll"), 
+                                                      MAKEINTRESOURCEA(138));
+    if (!pShouldSystemUseDarkMode)
+    {
+        skip("ShouldSystemUseDarkMode was not found.\n");
+        return;
+    }
+
+    lr = RegGetValueA(hk, "Software\Microsoft\Windows\CurrentVersion\Themes\Personalize", 
+                      "AppsUseLightTheme", RRF_RT_REG_DWORD, NULL, &systemUsesLightTheme, NULL);
+    ok(lr == 0 || lr == ERROR_FILE_NOT_FOUND, "RegGetValueA failed.\n");
+
+    if (lr == ERROR_FILE_NOT_FOUND) systemUsesLightTheme = 1;
+
+    ok(pShouldSystemUseDarkMode() == !systemUsesLightTheme, "Expected registry key to match api.\n");
+}
+
 START_TEST(system)
 {
     ULONG_PTR ctx_cookie;
@@ -2622,6 +2646,7 @@ START_TEST(system)
     test_DrawThemeBackgroundEx();
     test_GetThemeBackgroundRegion();
     test_theme();
+    test_ShouldUseDarkMode();

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)