Support GUI dialogs and message boxes better on MS-Windows

* src/w32menu.c (TASKDIALOG_COMMON_BUTTON_FLAGS, TASKDIALOG_FLAGS)
(PFTASKDIALOGCALLBACK, TASKDIALOG_BUTTON, TASKDIALOGCONFIG)
(TDN_CREATED, TDM_ENABLE_BUTTON, TDF_ALLOW_DIALOG_CANCELLATION)
(TD_INFORMATION_ICON) [!MINGW_W64]: Define.
(TaskDialogIndirect_Proc): Declare function type.
(TASK_DIALOG_MAX_BUTTONS): New macro.
(task_dialog_callback): New callback function.
(w32_popup_dialog): Add dialog implementation using TaskDialog.
(globals_of_w32menu): Load TaskDialogIndirect from comctl32.dll.
(Bug#20481)

2 files changed, 216 insertions, 5 deletions

diff --git a/src/menu.c b/src/menu.c
index de4d0964e9c..6b4aaef1715 100644
--- a/src/menu.c
+++ b/src/menu.c
@@ -1594,9 +1594,10 @@ for instance using the window manager, then this produces a quit and
       Lisp_Object selection
         = FRAME_TERMINAL (f)->popup_dialog_hook (f, header, contents);
 #ifdef HAVE_NTGUI
-      /* NTGUI supports only simple dialogs with Yes/No choices.  For
-         other dialogs, it returns the symbol 'unsupported--w32-dialog',
-         as a signal for the caller to fall back to the emulation code.  */
+      /* NTGUI on Windows versions before Vista supports only simple
+         dialogs with Yes/No choices.  For other dialogs, it returns the
+         symbol 'unsupported--w32-dialog', as a signal for the caller to
+         fall back to the emulation code.  */
       if (!EQ (selection, Qunsupported__w32_dialog))
 #endif
         return selection;
diff --git a/src/w32menu.c b/src/w32menu.c
index cea4f4892a4..c3d147841b6 100644
--- a/src/w32menu.c
+++ b/src/w32menu.c
@@ -52,6 +52,9 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include "w32common.h"  /* for osinfo_cache */
 
+#include "commctrl.h"
+
+/* This only applies to OS versions prior to Vista.  */
 #undef HAVE_DIALOGS /* TODO: Implement native dialogs.  */
 
 #ifndef TRUE
@@ -77,6 +80,66 @@ typedef int (WINAPI * MessageBoxW_Proc) (
     IN const WCHAR *caption,
     IN UINT type);
 
+#ifndef MINGW_W64
+/* mingw.org's MinGW doesn't have this in its header files.  */
+  typedef int TASKDIALOG_COMMON_BUTTON_FLAGS;
+
+  typedef int TASKDIALOG_FLAGS;
+
+  typedef HRESULT (CALLBACK *PFTASKDIALOGCALLBACK) (
+    HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam, LONG_PTR lpRefData);
+
+  typedef struct _TASKDIALOG_BUTTON {
+    int nButtonID;
+    PCWSTR pszButtonText;
+  } TASKDIALOG_BUTTON;
+
+  typedef struct _TASKDIALOGCONFIG {
+    UINT cbSize;
+    HWND hwndParent;
+    HINSTANCE hInstance;
+    TASKDIALOG_FLAGS dwFlags;
+    TASKDIALOG_COMMON_BUTTON_FLAGS dwCommonButtons;
+    PCWSTR pszWindowTitle;
+    union {
+      HICON hMainIcon;
+      PCWSTR pszMainIcon;
+    } DUMMYUNIONNAME;
+    PCWSTR pszMainInstruction;
+    PCWSTR pszContent;
+    UINT cButtons;
+    const TASKDIALOG_BUTTON *pButtons;
+    int nDefaultButton;
+    UINT cRadioButtons;
+    const TASKDIALOG_BUTTON *pRadioButtons;
+    int nDefaultRadioButton;
+    PCWSTR pszVerificationText;
+    PCWSTR pszExpandedInformation;
+    PCWSTR pszExpandedControlText;
+    PCWSTR pszCollapsedControlText;
+    union {
+      HICON hFooterIcon;
+      PCWSTR pszFooterIcon;
+    } DUMMYUNIONNAME2;
+    PCWSTR pszFooter;
+    PFTASKDIALOGCALLBACK pfCallback;
+    LONG_PTR lpCallbackData;
+    UINT cxWidth;
+  } TASKDIALOGCONFIG;
+
+# define TDN_CREATED 0
+# define TDM_ENABLE_BUTTON (WM_USER+111)
+# define TDF_ALLOW_DIALOG_CANCELLATION 0x8
+# define TD_INFORMATION_ICON MAKEINTRESOURCEW (-3)
+
+#endif
+
+typedef HRESULT (WINAPI *TaskDialogIndirect_Proc) (
+    IN const TASKDIALOGCONFIG *pTaskConfig,
+    OUT int *pnButton,
+    OUT int *pnRadioButton,
+    OUT BOOL *pfVerificationFlagChecked);
+
 #ifdef NTGUI_UNICODE
 GetMenuItemInfoA_Proc get_menu_item_info = GetMenuItemInfoA;
 SetMenuItemInfoA_Proc set_menu_item_info = SetMenuItemInfoA;
@@ -89,6 +152,8 @@ AppendMenuW_Proc unicode_append_menu = NULL;
 MessageBoxW_Proc unicode_message_box = NULL;
 #endif /* NTGUI_UNICODE */
 
+static TaskDialogIndirect_Proc task_dialog_indirect;
+
 #ifdef HAVE_DIALOGS
 static Lisp_Object w32_dialog_show (struct frame *, Lisp_Object, Lisp_Object, char **);
 #else
@@ -101,14 +166,155 @@ static int fill_in_menu (HMENU, widget_value *);
 
 void w32_free_menu_strings (HWND);
 
+#define TASK_DIALOG_MAX_BUTTONS 10
+
+static HRESULT CALLBACK
+task_dialog_callback (HWND hwnd, UINT msg, WPARAM wParam,
+                      LPARAM lParam, LONG_PTR callback_data)
+{
+  switch (msg)
+    {
+    case TDN_CREATED:
+      /* Disable all buttons with ID >= 2000  */
+      for (int i = 0; i < TASK_DIALOG_MAX_BUTTONS; i++)
+        SendMessage (hwnd, TDM_ENABLE_BUTTON, 2000 + i, FALSE);
+      break;
+    }
+  return S_OK;
+}
+
 Lisp_Object
 w32_popup_dialog (struct frame *f, Lisp_Object header, Lisp_Object contents)
 {
-
   check_window_system (f);
 
-#ifndef HAVE_DIALOGS
+  if (task_dialog_indirect)
+    {
+      int wide_len;
+
+      CHECK_CONS (contents);
+
+      /* Get the title as an UTF-16 string.  */
+      char *title = SSDATA (ENCODE_UTF_8 (XCAR (contents)));
+      wide_len = (sizeof (WCHAR)
+                  * pMultiByteToWideChar (CP_UTF8, 0, title, -1, NULL, 0));
+      WCHAR *title_w = alloca (wide_len);
+      pMultiByteToWideChar (CP_UTF8, 0, title, -1, title_w, wide_len);
+
+      /* Prepare the arrays with the dialog's buttons and return values.  */
+      TASKDIALOG_BUTTON buttons[TASK_DIALOG_MAX_BUTTONS];
+      Lisp_Object button_values[TASK_DIALOG_MAX_BUTTONS];
+      int button_count = 0;
+      Lisp_Object b = XCDR (contents);
+
+      while (!NILP (b))
+        {
+          if (button_count >= TASK_DIALOG_MAX_BUTTONS)
+            {
+              /* We have too many buttons.  We ignore the rest.  */
+              break;
+            }
+
+          Lisp_Object item = XCAR (b);
+
+          if (CONSP (item))
+            {
+              /* A normal item (text . value)  */
+              Lisp_Object item_name = XCAR (item);
+              Lisp_Object item_value = XCDR (item);
+
+              CHECK_STRING (item_name);
+
+              item_name = ENCODE_UTF_8 (item_name);
+              wide_len = (sizeof (WCHAR)
+                          * pMultiByteToWideChar (CP_UTF8, 0, SSDATA (item_name),
+                                                  -1, NULL, 0));
+              buttons[button_count].pszButtonText = alloca (wide_len);
+              pMultiByteToWideChar (CP_UTF8, 0, SSDATA (item_name), -1,
+                                    (LPWSTR)
+                                    buttons[button_count].pszButtonText,
+                                    wide_len);
+              buttons[button_count].nButtonID = 1000 + button_count;
+              button_values[button_count++] = item_value;
+            }
+          else if (NILP (item))
+            {
+              /* A nil item means to put all following items on the
+                 right.  We ignore this.  */
+            }
+          else if (STRINGP (item))
+            {
+              /* A string item means an unselectable button.  We add a
+               button, and then need to disable it on the callback.  We
+               use ids based on 2000 to mark these buttons.  */
+              Lisp_Object item_name = ENCODE_UTF_8 (item);
+              wide_len = (sizeof (WCHAR)
+                          * pMultiByteToWideChar (CP_UTF8, 0,
+                                                  SSDATA (item_name),
+                                                  -1, NULL, 0));
+              buttons[button_count].pszButtonText = alloca (wide_len);
+              pMultiByteToWideChar (CP_UTF8, 0, SSDATA (item_name), -1,
+                                    (LPWSTR)
+                                    buttons[button_count].pszButtonText,
+                                    wide_len);
+              buttons[button_count].nButtonID = 2000 + button_count;
+              button_values[button_count++] = Qnil;
+            }
+          else
+            {
+              error ("Incorrect dialog button specification");
+              return Qnil;
+            }
+
+          b = XCDR (b);
+        }
+
+      int pressed_button = 0;
 
+      TASKDIALOGCONFIG config = { 0 };
+      config.hwndParent = FRAME_W32_WINDOW (f);
+      config.cbSize = sizeof (config);
+      config.hInstance = hinst;
+      config.dwFlags = TDF_ALLOW_DIALOG_CANCELLATION;
+      config.pfCallback = task_dialog_callback;
+      config.pszWindowTitle = L"Question";
+      if (!NILP (header))
+        {
+          config.pszWindowTitle = L"Information";
+          config.pszMainIcon = TD_INFORMATION_ICON;
+        }
+
+      config.pszMainInstruction = title_w;
+      config.pButtons = buttons;
+      config.cButtons = button_count;
+
+      if (!SUCCEEDED (task_dialog_indirect (&config, &pressed_button,
+                                            NULL, NULL)))
+        quit ();
+
+      int button_index;
+      switch (pressed_button)
+        {
+        case IDOK:
+          /* This can only happen if no buttons were provided.  The OK
+             button is automatically added by TaskDialogIndirect in that
+             case.  */
+          return Qt;
+        case IDCANCEL:
+          /* The user closed the dialog without using the buttons.  */
+          return quit ();
+        default:
+          /* One of the specified buttons.  */
+          button_index = pressed_button - 1000;
+          if (button_index >= 0 && button_index < button_count)
+            return button_values[button_index];
+          return quit ();
+        }
+    }
+
+  /* If we get here, TaskDialog is not supported.  Use MessageBox/Menu.  */
+
+#ifndef HAVE_DIALOGS
   /* Handle simple Yes/No choices as MessageBox popups.  */
   if (is_simple_dialog (contents))
     return simple_dialog_show (f, contents, header);
@@ -1618,6 +1824,10 @@ syms_of_w32menu (void)
 void
 globals_of_w32menu (void)
 {
+  HMODULE comctrl32 = GetModuleHandle ("comctl32.dll");
+  task_dialog_indirect = (TaskDialogIndirect_Proc)
+    get_proc_addr (comctrl32, "TaskDialogIndirect");
+
 #ifndef NTGUI_UNICODE
   /* See if Get/SetMenuItemInfo functions are available.  */
   HMODULE user32 = GetModuleHandle ("user32.dll");