Backends: Win32: Rework to handle certains Windows 8.1/10 features without a manifest. (#4200, #4191)

backends/imgui_impl_win32.cpp

@@ -7,7 +7,7 @@
 //  [X] Platform: Keyboard arrays indexed using VK_* Virtual Key Codes, e.g. ImGui::IsKeyPressed(VK_SPACE).
 //  [X] Platform: Gamepad support. Enabled with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
 
-// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this. 
+// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
 // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
 // Read online: https://github.com/ocornut/imgui/tree/master/docs
@@ -22,7 +22,7 @@
 #include <dwmapi.h>
 
 // Configuration flags to add in your imconfig.h file:
-//#define IMGUI_IMPL_WIN32_DISABLE_GAMEPAD              // Disable gamepad support (this used to be meaningful before <1.81) but we know load XInput dynamically so the option is less relevant now.
+//#define IMGUI_IMPL_WIN32_DISABLE_GAMEPAD              // Disable gamepad support. This was meaningful before <1.81 but we now load XInput dynamically so the option is now less relevant.
 
 // Using XInput for gamepad (will load DLL dynamically)
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
@@ -33,6 +33,7 @@ typedef DWORD (WINAPI *PFN_XInputGetState)(DWORD, XINPUT_STATE*);
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-06-08: Fix ImGui_ImplWin32_EnableDpiAwareness() and ImGui_ImplWin32_GetDpiScaleForMonitor() to handle Windows 8.1/10 features without a manifest (per-monitor DPI, and properly calls SetProcessDpiAwareness() on 8.1).
 //  2021-03-23: Inputs: Clearing keyboard down array when losing focus (WM_KILLFOCUS).
 //  2021-02-18: Added ImGui_ImplWin32_EnableAlphaCompositing(). Non Visual Studio users will need to link with dwmapi.lib (MinGW/gcc: use -ldwmapi).
 //  2021-02-17: Fixed ImGui_ImplWin32_EnableDpiAwareness() attempting to get SetProcessDpiAwareness from shcore.dll on Windows 8 whereas it is only supported on Windows 8.1.
@@ -410,21 +411,30 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARA
 // If you are trying to implement your own backend for your own engine, you may ignore that noise.
 //---------------------------------------------------------------------------------------------------------
 
-// Implement some of the functions and types normally declared in recent Windows SDK.
-#if !defined(_versionhelpers_H_INCLUDED_) && !defined(_INC_VERSIONHELPERS)
-static BOOL IsWindowsVersionOrGreater(WORD major, WORD minor, WORD sp)
+// Perform our own check with RtlVerifyVersionInfo() instead of using functions from <VersionHelpers.h> as they
+// require a manifest to be functional for checks above 8.1. See https://github.com/ocornut/imgui/issues/4200
+static BOOL _IsWindowsVersionOrGreater(WORD major, WORD minor, WORD)
 {
-    OSVERSIONINFOEXW osvi = { sizeof(osvi), major, minor, 0, 0, { 0 }, sp, 0, 0, 0, 0 };
-    DWORD mask = VER_MAJORVERSION | VER_MINORVERSION | VER_SERVICEPACKMAJOR;
-    ULONGLONG cond = ::VerSetConditionMask(0, VER_MAJORVERSION, VER_GREATER_EQUAL);
-    cond = ::VerSetConditionMask(cond, VER_MINORVERSION, VER_GREATER_EQUAL);
-    cond = ::VerSetConditionMask(cond, VER_SERVICEPACKMAJOR, VER_GREATER_EQUAL);
-    return ::VerifyVersionInfoW(&osvi, mask, cond);
+    typedef LONG(WINAPI* PFN_RtlVerifyVersionInfo)(OSVERSIONINFOEXW*, ULONG, ULONGLONG);
+    static PFN_RtlVerifyVersionInfo RtlVerifyVersionInfoFn = NULL;
+	if (RtlVerifyVersionInfoFn == NULL)
+		if (HMODULE ntdllModule = ::GetModuleHandleA("ntdll.dll"))
+			RtlVerifyVersionInfoFn = (PFN_RtlVerifyVersionInfo)GetProcAddress(ntdllModule, "RtlVerifyVersionInfo");
+
+	RTL_OSVERSIONINFOEXW versionInfo = { };
+	ULONGLONG conditionMask = 0;
+	versionInfo.dwOSVersionInfoSize = sizeof(RTL_OSVERSIONINFOEXW);
+	versionInfo.dwMajorVersion = major;
+	versionInfo.dwMinorVersion = minor;
+	VER_SET_CONDITION(conditionMask, VER_MAJORVERSION, VER_GREATER_EQUAL);
+	VER_SET_CONDITION(conditionMask, VER_MINORVERSION, VER_GREATER_EQUAL);
+	return (RtlVerifyVersionInfoFn(&versionInfo, VER_MAJORVERSION | VER_MINORVERSION, conditionMask) == 0) ? TRUE : FALSE;
 }
-#define IsWindowsVistaOrGreater()   IsWindowsVersionOrGreater(HIBYTE(0x0600), LOBYTE(0x0600), 0) // _WIN32_WINNT_VISTA
-#define IsWindows8OrGreater()       IsWindowsVersionOrGreater(HIBYTE(0x0602), LOBYTE(0x0602), 0) // _WIN32_WINNT_WIN8
-#define IsWindows8Point1OrGreater() IsWindowsVersionOrGreater(HIBYTE(0x0603), LOBYTE(0x0603), 0) // _WIN32_WINNT_WINBLUE
-#endif
+
+#define _IsWindowsVistaOrGreater()   _IsWindowsVersionOrGreater(HIBYTE(0x0600), LOBYTE(0x0600), 0) // _WIN32_WINNT_VISTA
+#define _IsWindows8OrGreater()       _IsWindowsVersionOrGreater(HIBYTE(0x0602), LOBYTE(0x0602), 0) // _WIN32_WINNT_WIN8
+#define _IsWindows8Point1OrGreater() _IsWindowsVersionOrGreater(HIBYTE(0x0603), LOBYTE(0x0603), 0) // _WIN32_WINNT_WINBLUE
+#define _IsWindows10OrGreater()      _IsWindowsVersionOrGreater(HIBYTE(0x0A00), LOBYTE(0x0A00), 0) // _WIN32_WINNT_WINTHRESHOLD / _WIN32_WINNT_WIN10
 
 #ifndef DPI_ENUMS_DECLARED
 typedef enum { PROCESS_DPI_UNAWARE = 0, PROCESS_SYSTEM_DPI_AWARE = 1, PROCESS_PER_MONITOR_DPI_AWARE = 2 } PROCESS_DPI_AWARENESS;
@@ -444,7 +454,7 @@ typedef DPI_AWARENESS_CONTEXT(WINAPI* PFN_SetThreadDpiAwarenessContext)(DPI_AWAR
 // Helper function to enable DPI awareness without setting up a manifest
 void ImGui_ImplWin32_EnableDpiAwareness()
 {
-    // if (IsWindows10OrGreater()) // This needs a manifest to succeed. Instead we try to grab the function pointer!
+    if (_IsWindows10OrGreater())
     {
         static HINSTANCE user32_dll = ::LoadLibraryA("user32.dll"); // Reference counted per-process
         if (PFN_SetThreadDpiAwarenessContext SetThreadDpiAwarenessContextFn = (PFN_SetThreadDpiAwarenessContext)::GetProcAddress(user32_dll, "SetThreadDpiAwarenessContext"))
@@ -453,7 +463,7 @@ void ImGui_ImplWin32_EnableDpiAwareness()
             return;
         }
     }
-    if (IsWindows8Point1OrGreater())
+    if (_IsWindows8Point1OrGreater())
     {
         static HINSTANCE shcore_dll = ::LoadLibraryA("shcore.dll"); // Reference counted per-process
         if (PFN_SetProcessDpiAwareness SetProcessDpiAwarenessFn = (PFN_SetProcessDpiAwareness)::GetProcAddress(shcore_dll, "SetProcessDpiAwareness"))
@@ -474,23 +484,26 @@ void ImGui_ImplWin32_EnableDpiAwareness()
 float ImGui_ImplWin32_GetDpiScaleForMonitor(void* monitor)
 {
     UINT xdpi = 96, ydpi = 96;
-    static BOOL bIsWindows8Point1OrGreater = IsWindows8Point1OrGreater();
-    if (bIsWindows8Point1OrGreater)
+    if (_IsWindows8Point1OrGreater())
     {
-        static HINSTANCE shcore_dll = ::LoadLibraryA("shcore.dll"); // Reference counted per-process
-        if (PFN_GetDpiForMonitor GetDpiForMonitorFn = (PFN_GetDpiForMonitor)::GetProcAddress(shcore_dll, "GetDpiForMonitor"))
-            GetDpiForMonitorFn((HMONITOR)monitor, MDT_EFFECTIVE_DPI, &xdpi, &ydpi);
+		static HINSTANCE shcore_dll = ::LoadLibraryA("shcore.dll"); // Reference counted per-process
+		static PFN_GetDpiForMonitor GetDpiForMonitorFn = NULL;
+		if (GetDpiForMonitorFn == NULL && shcore_dll != NULL)
+            GetDpiForMonitorFn = (PFN_GetDpiForMonitor)::GetProcAddress(shcore_dll, "GetDpiForMonitor");
+		if (GetDpiForMonitorFn != NULL)
+		{
+			GetDpiForMonitorFn((HMONITOR)monitor, MDT_EFFECTIVE_DPI, &xdpi, &ydpi);
+            IM_ASSERT(xdpi == ydpi); // Please contact me if you hit this assert!
+			return xdpi / 96.0f;
+		}
     }
 #ifndef NOGDI
-    else
-    {
-        const HDC dc = ::GetDC(NULL);
-        xdpi = ::GetDeviceCaps(dc, LOGPIXELSX);
-        ydpi = ::GetDeviceCaps(dc, LOGPIXELSY);
-        ::ReleaseDC(NULL, dc);
-    }
-#endif
+    const HDC dc = ::GetDC(NULL);
+    xdpi = ::GetDeviceCaps(dc, LOGPIXELSX);
+    ydpi = ::GetDeviceCaps(dc, LOGPIXELSY);
     IM_ASSERT(xdpi == ydpi); // Please contact me if you hit this assert!
+    ::ReleaseDC(NULL, dc);
+#endif
     return xdpi / 96.0f;
 }
 
@@ -513,7 +526,7 @@ float ImGui_ImplWin32_GetDpiScaleForHwnd(void* hwnd)
 // (the Dwm* functions are Vista era functions but we are borrowing logic from GLFW)
 void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd)
 {
-    if (!IsWindowsVistaOrGreater())
+    if (!_IsWindowsVistaOrGreater())
         return;
 
     BOOL composition;
@@ -522,7 +535,7 @@ void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd)
 
     BOOL opaque;
     DWORD color;
-    if (IsWindows8OrGreater() || (SUCCEEDED(::DwmGetColorizationColor(&color, &opaque)) && !opaque))
+    if (_IsWindows8OrGreater() || (SUCCEEDED(::DwmGetColorizationColor(&color, &opaque)) && !opaque))
     {
         HRGN region = ::CreateRectRgn(0, 0, -1, -1);
         DWM_BLURBEHIND bb = {};

docs/CHANGELOG.txt

@@ -47,6 +47,9 @@ Other Changes:
 - Demo: Fixed requirement in 1.83 to link with imgui_demo.cpp if IMGUI_DISABLE_METRICS_WINDOW is not set. (#4171)
   Normally the right way to disable compiling the demo is to set IMGUI_DISABLE_DEMO_WINDOWS, but we want to avoid
   implying that the file is required.
+- Backends: Win32: Rework to handle certains Windows 8.1/10 features without a manifest. (#4200, #4191)
+  - ImGui_ImplWin32_GetDpiScaleForMonitor() will handle per-monitor DPI on Windows 10 without a manifest.
+  - ImGui_ImplWin32_EnableDpiAwareness() will call SetProcessDpiAwareness() fallback on Windows 8.1 without a manifest.
 - Backends: OpenGL3: Handle GL_CLIP_ORIGIN on <4.5 contexts if "GL_ARB_clip_control" extension is detected. (#4170, #3998)
 - Examples: Updated all .vcxproj to VS2015 (toolset v140) to facilitate usage with vcpkg.
 - Examples: SDL2: Accomodate for vcpkg install having headers in SDL2/SDL.h vs SDL.h.