Add win32 theming implementation

src/win32_init.c

@@ -151,6 +151,8 @@ static GLFWbool loadLibraries(void)
             _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmEnableBlurBehindWindow");
         _glfw.win32.dwmapi.GetColorizationColor = (PFN_DwmGetColorizationColor)
             _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmGetColorizationColor");
+        _glfw.win32.dwmapi.SetWindowAttribute = (PFN_DwmSetWindowAttribute)
+                _glfwPlatformGetModuleSymbol(_glfw.win32.dwmapi.instance, "DwmSetWindowAttribute");
     }
 
     _glfw.win32.shcore.instance = _glfwPlatformLoadModule("shcore.dll");
@@ -169,6 +171,18 @@ static GLFWbool loadLibraries(void)
             _glfwPlatformGetModuleSymbol(_glfw.win32.ntdll.instance, "RtlVerifyVersionInfo");
     }
 
+    _glfw.win32.uxtheme.instance = _glfwPlatformLoadModule("uxtheme.dll");
+    if (_glfw.win32.uxtheme.instance)
+    {
+        _glfw.win32.uxtheme.ShouldAppsUseDarkMode = (ShouldAppsUseDarkModePtr)_glfwPlatformGetModuleSymbol(_glfw.win32.uxtheme.instance, MAKEINTRESOURCEA(132));
+        _glfw.win32.uxtheme.GetImmersiveColorFromColorSetEx = (GetImmersiveColorFromColorSetExPtr)_glfwPlatformGetModuleSymbol(_glfw.win32.uxtheme.instance, MAKEINTRESOURCEA(95));
+        _glfw.win32.uxtheme.GetImmersiveColorTypeFromName = (GetImmersiveColorTypeFromNamePtr)_glfwPlatformGetModuleSymbol(_glfw.win32.uxtheme.instance, MAKEINTRESOURCEA(96));
+        _glfw.win32.uxtheme.GetImmersiveUserColorSetPreference = (GetImmersiveUserColorSetPreferencePtr)_glfwPlatformGetModuleSymbol(_glfw.win32.uxtheme.instance, MAKEINTRESOURCEA(98));
+
+        _glfw.win32.uxtheme.uxThemeAvailable = _glfw.win32.uxtheme.ShouldAppsUseDarkMode && _glfw.win32.uxtheme.GetImmersiveColorFromColorSetEx && _glfw.win32.uxtheme.GetImmersiveColorTypeFromName && _glfw.win32.uxtheme.GetImmersiveUserColorSetPreference;
+        _glfw.win32.uxtheme.darkTitleAvailable = _glfwIsWindows10BuildOrGreaterWin32(22000);
+    }
+
     return GLFW_TRUE;
 }
 
@@ -739,9 +753,18 @@ void _glfwTerminateWin32(void)
 
 _GLFWtheme* _glfwGetSystemDefaultThemeWin32(void)
 {
-    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
+    _GLFWtheme* theme = &_glfw.theme;
-    return NULL; // TODO: implement
+
+    theme->variation = GLFW_THEME_LIGHT;
+    theme->flags = 0;
+
+    if (_glfw.win32.uxtheme.uxThemeAvailable && _glfw.win32.uxtheme.darkTitleAvailable) {
+        if (_glfw.win32.uxtheme.ShouldAppsUseDarkMode() & 0x1) {
+            theme->variation = GLFW_THEME_DARK;
+        }
+    }
+
+    return theme;
 }
 
 #endif // _GLFW_WIN32
-

src/win32_platform.h

@@ -299,12 +299,15 @@ typedef int (WINAPI * PFN_GetSystemMetricsForDpi)(int,UINT);
 // dwmapi.dll function pointer typedefs
 typedef HRESULT (WINAPI * PFN_DwmIsCompositionEnabled)(BOOL*);
 typedef HRESULT (WINAPI * PFN_DwmFlush)(VOID);
-typedef HRESULT(WINAPI * PFN_DwmEnableBlurBehindWindow)(HWND,const DWM_BLURBEHIND*);
+typedef HRESULT (WINAPI * PFN_DwmEnableBlurBehindWindow)(HWND,const DWM_BLURBEHIND*);
 typedef HRESULT (WINAPI * PFN_DwmGetColorizationColor)(DWORD*,BOOL*);
+typedef HRESULT (WINAPI * PFN_DwmSetWindowAttribute)(HWND,DWORD,LPCVOID,DWORD);
+
 #define DwmIsCompositionEnabled _glfw.win32.dwmapi.IsCompositionEnabled
 #define DwmFlush _glfw.win32.dwmapi.Flush
 #define DwmEnableBlurBehindWindow _glfw.win32.dwmapi.EnableBlurBehindWindow
 #define DwmGetColorizationColor _glfw.win32.dwmapi.GetColorizationColor
+#define DwmSetWindowAttribute _glfw.win32.dwmapi.SetWindowAttribute
 
 // shcore.dll function pointer typedefs
 typedef HRESULT (WINAPI * PFN_SetProcessDpiAwareness)(PROCESS_DPI_AWARENESS);
@@ -366,6 +369,11 @@ typedef VkBool32 (APIENTRY *PFN_vkGetPhysicalDeviceWin32PresentationSupportKHR)(
 #define GLFW_WGL_CONTEXT_STATE          _GLFWcontextWGL wgl;
 #define GLFW_WGL_LIBRARY_CONTEXT_STATE  _GLFWlibraryWGL wgl;
 
+typedef BOOL (WINAPI * ShouldAppsUseDarkModePtr)();
+typedef DWORD(WINAPI * GetImmersiveColorFromColorSetExPtr)(UINT,UINT,BOOL,UINT);
+typedef int (WINAPI * GetImmersiveColorTypeFromNamePtr)(const WCHAR*);
+typedef int (WINAPI * GetImmersiveUserColorSetPreferencePtr)(BOOL,BOOL);
+
 
 // WGL-specific per-context data
 //
@@ -487,6 +495,7 @@ typedef struct _GLFWlibraryWin32
         PFN_DwmFlush                    Flush;
         PFN_DwmEnableBlurBehindWindow   EnableBlurBehindWindow;
         PFN_DwmGetColorizationColor     GetColorizationColor;
+        PFN_DwmSetWindowAttribute       SetWindowAttribute;
     } dwmapi;
 
     struct {
@@ -499,6 +508,16 @@ typedef struct _GLFWlibraryWin32
         HINSTANCE                       instance;
         PFN_RtlVerifyVersionInfo        RtlVerifyVersionInfo_;
     } ntdll;
+
+    struct {
+        HINSTANCE                              instance;
+        GLFWbool                               uxThemeAvailable;
+        GLFWbool                               darkTitleAvailable;
+        ShouldAppsUseDarkModePtr               ShouldAppsUseDarkMode;
+        GetImmersiveColorFromColorSetExPtr     GetImmersiveColorFromColorSetEx;
+        GetImmersiveColorTypeFromNamePtr       GetImmersiveColorTypeFromName;
+        GetImmersiveUserColorSetPreferencePtr  GetImmersiveUserColorSetPreference;
+    } uxtheme;
 } _GLFWlibraryWin32;
 
 // Win32-specific per-monitor data

src/win32_window.c

@@ -37,6 +37,21 @@
 #include <windowsx.h>
 #include <shellapi.h>
 
+// Ref: https://docs.microsoft.com/windows/win32/api/dwmapi/ne-dwmapi-dwmwindowattribute
+#ifndef DWMWA_USE_IMMERSIVE_DARK_MODE
+#define DWMWA_USE_IMMERSIVE_DARK_MODE 20
+#endif
+
+static void applySystemTheme(HWND handle) {
+    if (_glfw.win32.uxtheme.uxThemeAvailable && _glfw.win32.uxtheme.darkTitleAvailable) {
+        GLFWbool value = _glfw.win32.uxtheme.ShouldAppsUseDarkMode() & 0x1;
+        DwmSetWindowAttribute(handle,
+                              DWMWA_USE_IMMERSIVE_DARK_MODE,
+                              &value,
+                              sizeof(value));
+    }
+}
+
 // Returns the window style for the specified window
 //
 static DWORD getWindowStyle(const _GLFWwindow* window)
@@ -1146,6 +1161,13 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM l
             return 0;
         }
 
+        case WM_THEMECHANGED:
+        case WM_SETTINGCHANGE: {
+            if (window->theme.variation == GLFW_THEME_DEFAULT) {
+                applySystemTheme(window->win32.handle);
+            }
+        } break;
+
         case WM_GETDPISCALEDSIZE:
         {
             if (window->win32.scaleToMonitor)
@@ -1436,6 +1458,10 @@ static int createNativeWindow(_GLFWwindow* window,
 
     _glfwGetWindowSizeWin32(window, &window->win32.width, &window->win32.height);
 
+    if (window->theme.variation == GLFW_THEME_DEFAULT) {
+        applySystemTheme(window->win32.handle);
+    }
+
     return GLFW_TRUE;
 }
 
@@ -2375,13 +2401,32 @@ const char* _glfwGetClipboardStringWin32(void)
 
 void _glfwSetThemeWin32(_GLFWwindow* window, _GLFWtheme* theme)
 {
-    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
+    if (!theme || theme->variation == GLFW_THEME_DEFAULT)
+    {
+        applySystemTheme(window->win32.handle);
+        return;
+    }
+
+    GLFWbool darkMode = theme->variation == GLFW_THEME_DARK;
+
+    DwmSetWindowAttribute(window->win32.handle,
+                          DWMWA_USE_IMMERSIVE_DARK_MODE,
+                          &darkMode,
+                          sizeof(darkMode));
 }
 
 _GLFWtheme* _glfwGetThemeWin32(_GLFWwindow* window)
 {
-    _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
+    _GLFWtheme* theme = &window->theme;
-    return NULL; // TODO: implement
+
+    theme->variation = GLFW_THEME_LIGHT;
+    theme->flags = 0;
+
+    if (_glfw.win32.uxtheme.uxThemeAvailable && _glfw.win32.uxtheme.darkTitleAvailable) {
+        theme->variation = GLFW_THEME_DARK;
+    }
+
+    return theme;
 }
 
 EGLenum _glfwGetEGLPlatformWin32(EGLint** attribs)
@@ -2512,4 +2557,3 @@ GLFWAPI HWND glfwGetWin32Window(GLFWwindow* handle)
 }
 
 #endif // _GLFW_WIN32
-