works fine but resizing the window causes things to scale in very very strange ways

src/win32_init.c

@@ -370,7 +370,6 @@ static LRESULT CALLBACK helperWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LP
 //
 static GLFWbool createHelperWindow(void)
 {
-    MSG msg;
     WNDCLASSEXW wc = { sizeof(wc) };
 
     wc.style         = CS_OWNDC;
@@ -421,11 +420,7 @@ static GLFWbool createHelperWindow(void)
                                         DEVICE_NOTIFY_WINDOW_HANDLE);
     }
 
-    while (PeekMessageW(&msg, _glfw.win32.helperWindowHandle, 0, 0, PM_REMOVE))
+    SwitchToFiber(_glfw.win32.messageFiber);
-    {
-        TranslateMessage(&msg);
-        DispatchMessageW(&msg);
-    }
 
    return GLFW_TRUE;
 }
@@ -583,6 +578,41 @@ BOOL _glfwIsWindowsVersionOrGreaterWin32(WORD major, WORD minor, WORD sp)
     return RtlVerifyVersionInfo(&osvi, mask, cond) == 0;
 }
 
+// Windows message dispatch fiber
+void CALLBACK messageFiberProc(LPVOID lpFiberParameter)
+{
+    MSG msg;
+    _GLFWwindow* window;
+    (void)lpFiberParameter;
+
+    for (;;)
+    {
+        while (PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE))
+        {
+            if (msg.message == WM_QUIT)
+            {
+                // NOTE: While GLFW does not itself post WM_QUIT, other processes
+                //       may post it to this one, for example Task Manager
+                // HACK: Treat WM_QUIT as a close on all windows
+
+                window = _glfw.windowListHead;
+                while (window)
+                {
+                    _glfwInputWindowCloseRequest(window);
+                    window = window->next;
+                }
+            }
+            else
+            {
+                TranslateMessage(&msg);
+                DispatchMessageW(&msg);
+            }
+        }
+
+        SwitchToFiber(_glfw.win32.mainFiber);
+    }
+}
+
 // Checks whether we are on at least the specified build of Windows 10
 //
 BOOL _glfwIsWindows10BuildOrGreaterWin32(WORD build)
@@ -695,6 +725,14 @@ int _glfwInitWin32(void)
     else if (IsWindowsVistaOrGreater())
         SetProcessDPIAware();
 
+    _glfw.win32.mainFiber = ConvertThreadToFiber(NULL);
+    if (!_glfw.win32.mainFiber)
+        return GLFW_FALSE;
+
+    _glfw.win32.messageFiber = CreateFiber(0, &messageFiberProc, NULL);
+    if (!_glfw.win32.messageFiber)
+        return GLFW_FALSE;
+
     if (!createHelperWindow())
         return GLFW_FALSE;
 
@@ -717,6 +755,9 @@ void _glfwTerminateWin32(void)
     if (_glfw.win32.mainWindowClass)
         UnregisterClassW(MAKEINTATOM(_glfw.win32.mainWindowClass), _glfw.win32.instance);
     
+    DeleteFiber(_glfw.win32.messageFiber);
+    ConvertFiberToThread();
+
     _glfw_free(_glfw.win32.clipboardString);
     _glfw_free(_glfw.win32.rawInput);
 

src/win32_platform.h

@@ -433,6 +433,11 @@ typedef struct _GLFWwindowWin32
     int                 lastCursorPosX, lastCursorPosY;
     // The last received high surrogate when decoding pairs of UTF-16 messages
     WCHAR               highSurrogate;
+
+    // If user pressed mouse button on window title bar
+    UINT                ncMouseButton;
+    LPARAM              ncMousePos;
+
 } _GLFWwindowWin32;
 
 // Win32-specific global data
@@ -458,6 +463,8 @@ typedef struct _GLFWlibraryWin32
     RAWINPUT*           rawInput;
     int                 rawInputSize;
     UINT                mouseTrailSize;
+    LPVOID              messageFiber;
+    LPVOID              mainFiber;
     // The cursor handle to use to hide the cursor (NULL or a transparent cursor)
     HCURSOR             blankCursor;
 

src/win32_window.c

@@ -854,12 +854,46 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM l
 
             return 0;
         }
+        case WM_NCLBUTTONDOWN:
+        {
+            if (wParam == HTCAPTION)
+            {
+                window->win32.ncMouseButton = uMsg;
+                window->win32.ncMousePos = lParam;
+                return 0;
+            }
+            break;
+        }
+
+        case WM_NCMOUSEMOVE:
+        {
+            if (window->win32.ncMouseButton)
+            {
+                if (GET_X_LPARAM(window->win32.ncMousePos) != GET_X_LPARAM(lParam) ||
+                    GET_Y_LPARAM(window->win32.ncMousePos) != GET_Y_LPARAM(lParam))
+                {
+                    DefWindowProcW(hWnd, window->win32.ncMouseButton, HTCAPTION, window->win32.ncMousePos);
+                    window->win32.ncMouseButton = 0;
+                }
+            }
+            break;
+        }
 
         case WM_MOUSEMOVE:
         {
             const int x = GET_X_LPARAM(lParam);
             const int y = GET_Y_LPARAM(lParam);
 
+            if (window->win32.ncMouseButton)
+            {
+                if (GET_X_LPARAM(window->win32.ncMousePos) != x ||
+                    GET_Y_LPARAM(window->win32.ncMousePos) != y)
+                {
+                    DefWindowProcW(hWnd, window->win32.ncMouseButton, HTCAPTION, window->win32.ncMousePos);
+                    window->win32.ncMouseButton = 0;
+                }
+            }
+
             if (!window->win32.cursorTracked)
             {
                 TRACKMOUSEEVENT tme;
@@ -1000,7 +1034,7 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM l
                 enableCursor(window);
             else if (window->cursorMode == GLFW_CURSOR_CAPTURED)
                 releaseCursor();
-
+            SetTimer(hWnd, 1, 1, NULL);
             break;
         }
 
@@ -1016,9 +1050,18 @@ static LRESULT CALLBACK windowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM l
                 disableCursor(window);
             else if (window->cursorMode == GLFW_CURSOR_CAPTURED)
                 captureCursor(window);
+            KillTimer(hWnd, 1);
 
             break;
         }
+        case WM_TIMER:
+        {
+            if (wParam == 1)
+            {
+                SwitchToFiber(_glfw.win32.mainFiber);
+            }
+            break;
+        }
 
         case WM_SIZE:
         {
@@ -2104,27 +2147,7 @@ void _glfwPollEventsWin32(void)
     HWND handle;
     _GLFWwindow* window;
 
-    while (PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE))
+    SwitchToFiber(_glfw.win32.messageFiber);
-    {
-        if (msg.message == WM_QUIT)
-        {
-            // NOTE: While GLFW does not itself post WM_QUIT, other processes
-            //       may post it to this one, for example Task Manager
-            // HACK: Treat WM_QUIT as a close on all windows
-
-            window = _glfw.windowListHead;
-            while (window)
-            {
-                _glfwInputWindowCloseRequest(window);
-                window = window->next;
-            }
-        }
-        else
-        {
-            TranslateMessage(&msg);
-            DispatchMessageW(&msg);
-        }
-    }
 
     // HACK: Release modifier keys that the system did not emit KEYUP for
     // NOTE: Shift keys on Windows tend to "stick" when both are pressed as