internal/glfwwin: remove GetProp and SetProp

GetProp and SetProp forced a risky usage of pointers.

internal/glfwwin/api_windows.go

@@ -799,7 +799,6 @@ var (
 	procGetLayeredWindowAttributes    = user32.NewProc("GetLayeredWindowAttributes")
 	procGetMessageTime                = user32.NewProc("GetMessageTime")
 	procGetMonitorInfoW               = user32.NewProc("GetMonitorInfoW")
-	procGetPropW                      = user32.NewProc("GetPropW")
 	procGetRawInputData               = user32.NewProc("GetRawInputData")
 	procGetSystemMetrics              = user32.NewProc("GetSystemMetrics")
 	procGetSystemMetricsForDpi        = user32.NewProc("GetSystemMetricsForDpi")
@@ -835,7 +834,6 @@ var (
 	procSetLayeredWindowAttributes    = user32.NewProc("procSetLayeredWindowAttributes")
 	procSetProcessDPIAware            = user32.NewProc("SetProcessDPIAware")
 	procSetProcessDpiAwarenessContext = user32.NewProc("SetProcessDpiAwarenessContext")
-	procSetPropW                      = user32.NewProc("SetPropW")
 	procSetWindowLongW                = user32.NewProc("SetWindowLongW")
 	procSetWindowPlacement            = user32.NewProc("SetWindowPlacement")
 	procSetWindowPos                  = user32.NewProc("SetWindowPos")
@@ -1358,22 +1356,6 @@ func _GetDpiForMonitor(hmonitor _HMONITOR, dpiType _MONITOR_DPI_TYPE) (dpiX, dpi
 	return dpiX, dpiY, nil
 }
 
-func _GetPropW(hWnd windows.HWND, str string) windows.Handle {
-	var lpString *uint16
-	if str != "" {
-		var err error
-		lpString, err = windows.UTF16PtrFromString(str)
-		if err != nil {
-			panic("glfwwin: str must not include a NUL character")
-		}
-	}
-
-	r, _, _ := procGetPropW.Call(uintptr(hWnd), uintptr(unsafe.Pointer(lpString)))
-	runtime.KeepAlive(lpString)
-
-	return windows.Handle(r)
-}
-
 func _GetRawInputData(hRawInput _HRAWINPUT, uiCommand uint32, pData unsafe.Pointer, pcbSize *uint32) (uint32, error) {
 	r, _, e := procGetRawInputData.Call(uintptr(hRawInput), uintptr(uiCommand), uintptr(pData), uintptr(unsafe.Pointer(pcbSize)), unsafe.Sizeof(_RAWINPUTHEADER{}))
 	if uint32(r) == (1<<32)-1 {
@@ -1691,25 +1673,6 @@ func _SetProcessDpiAwarenessContext_Available() bool {
 	return procSetProcessDpiAwarenessContext.Find() == nil
 }
 
-func _SetPropW(hWnd windows.HWND, str string, hData windows.Handle) error {
-	var lpString *uint16
-	if str != "" {
-		var err error
-		lpString, err = windows.UTF16PtrFromString(str)
-		if err != nil {
-			panic("glfwwin: str must not include a NUL character")
-		}
-	}
-
-	r, _, e := procSetPropW.Call(uintptr(hWnd), uintptr(unsafe.Pointer(lpString)), uintptr(hData))
-	runtime.KeepAlive(lpString)
-
-	if int32(r) == 0 {
-		return fmt.Errorf("glfwwin: SetPropW failed: %w", e)
-	}
-	return nil
-}
-
 func _SetThreadExecutionState(esFlags _EXECUTION_STATE) _EXECUTION_STATE {
 	r, _, _ := procSetThreadExecutionState.Call(uintptr(esFlags))
 	return _EXECUTION_STATE(r)

internal/glfwwin/win32window_windows.go

@@ -580,7 +580,7 @@ func (w *Window) maximizeWindowManually() error {
 }
 
 func windowProc(hWnd windows.HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) uintptr /*_LRESULT*/ {
-	window := (*Window)(unsafe.Pointer(_GetPropW(hWnd, "GLFW")))
+	window := handleToWindow[hWnd]
 	if window == nil {
 		// This is the message handling for the hidden helper window
 		// and for a regular window during its initial creation
@@ -1180,6 +1180,8 @@ func windowProc(hWnd windows.HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM)
 
 var windowProcPtr = windows.NewCallbackCDecl(windowProc)
 
+var handleToWindow = map[windows.HWND]*Window{}
+
 func (w *Window) createNativeWindow(wndconfig *wndconfig, fbconfig *fbconfig) error {
 	style := w.getWindowStyle()
 	exStyle := w.getWindowExStyle()
@@ -1225,9 +1227,7 @@ func (w *Window) createNativeWindow(wndconfig *wndconfig, fbconfig *fbconfig) er
 	}
 	w.win32.handle = h
 
-	if err := _SetPropW(w.win32.handle, "GLFW", windows.Handle(unsafe.Pointer(w))); err != nil {
+	handleToWindow[w.win32.handle] = w
-		return err
-	}
 
 	if _IsWindows7OrGreater() {
 		if err := _ChangeWindowMessageFilterEx(w.win32.handle, _WM_DROPFILES, _MSGFLT_ALLOW, nil); err != nil {
@@ -1432,6 +1432,7 @@ func (w *Window) platformDestroyWindow() error {
 		if err := _DestroyWindow(w.win32.handle); err != nil {
 			return err
 		}
+		delete(handleToWindow, w.win32.handle)
 		w.win32.handle = 0
 	}
 
@@ -1998,7 +1999,7 @@ func platformPollEvents() error {
 	//       because they change the input focus
 	// NOTE: The other half of this is in the WM_*KEY* handler in windowProc
 	if handle := _GetActiveWindow(); handle != 0 {
-		if window := (*Window)(unsafe.Pointer(_GetPropW(handle, "GLFW"))); window != nil {
+		if window := handleToWindow[handle]; window != nil {
 			keys := [...]struct {
 				VK  int
 				Key Key