patch 8.1.1548: popup_dialog() is not implemented

Problem:    Popup_dialog() is not implemented.
Solution:   Implement popup_dialog() and popup_filter_yesno().
diff --git a/runtime/doc/popup.txt b/runtime/doc/popup.txt
index 3ee92f2..a9f55be 100644
--- a/runtime/doc/popup.txt
+++ b/runtime/doc/popup.txt
@@ -103,10 +103,10 @@
 - When drawing on top half a double-wide character, display ">" or "<" in the
   incomplete cell.
 - Can the buffer be re-used, to avoid using up lots of buffer numbers?
+- Use a popup window for the "info" item of completion instead of using a
+  preview window.
 - Implement:
-	popup_dialog({text}, {options})
 	popup_filter_menu({id}, {key})
-	popup_filter_yesno({id}, {key})
 	popup_menu({text}, {options})
 	popup_setoptions({id}, {options})
 	flip option
@@ -196,16 +196,23 @@
 
 
 popup_dialog({text}, {options})				*popup_dialog()*
-		{not implemented yet}
 		Just like |popup_create()| but with these default options: >
 			call popup_create({text}, {
 				\ 'pos': 'center',
 				\ 'zindex': 200,
+				\ 'drag': 1,
 				\ 'border': [],
 				\ 'padding': [],
 				\})
 <		Use {options} to change the properties. E.g. add a 'filter'
-		option with value 'popup_filter_yesno'.
+		option with value 'popup_filter_yesno'.  Example: >
+			call popup_create('do you want to quit (Yes/no)?', {
+				\ 'filter': 'popup_filter_yesno',
+				\ 'callback': 'QuitCallback',
+				\ })
+
+<		By default the dialog can be dragged, so that text below it
+		can be read if needed.
 
 
 popup_filter_menu({id}, {key})				*popup_filter_menu()*
@@ -218,12 +225,12 @@
 
 
 popup_filter_yesno({id}, {key})				*popup_filter_yesno()*
-		{not implemented yet}
 		Filter that can be used for a popup. It handles only the keys
 		'y', 'Y' and 'n' or 'N'.  Invokes the "callback" of the
 		popup menu with the 1 for 'y' or 'Y' and zero for 'n' or 'N'
-		as the second argument.  Pressing Esc and CTRL-C works like
-		pressing 'n'.  Other keys are ignored.
+		as the second argument.  Pressing Esc and 'x' works like
+		pressing 'n'.  CTRL-C invokes the callback with -1.  Other
+		keys are ignored.
 
 
 popup_getoptions({id})					*popup_getoptions()*
@@ -301,7 +308,7 @@
 				\ 'minwidth': 20,
 				\ 'time': 3000,
 				\ 'tabpage': -1,
-				\ 'zindex': 200,
+				\ 'zindex': 300,
 				\ 'drag': 1,
 				\ 'highlight': 'WarningMsg',
 				\ 'border': [],
@@ -521,7 +528,7 @@
 is called first.
 
 The filter function is called with two arguments: the ID of the popup and the
-key, e.g.: >
+key as a string, e.g.: >
 	func MyFilter(winid, key)
 	  if a:key == "\<F2>"
 	    " do something
@@ -556,15 +563,14 @@
 
 POPUP CALLBACK						*popup-callback*
 
-A callback that is invoked when the popup closes.  Used by
-|popup_filter_menu()|.
+A callback that is invoked when the popup closes.
 
 The callback is invoked with two arguments: the ID of the popup window and the
 result, which could be an index in the popup lines, or whatever was passed as
 the second argument of `popup_close()`.
 
-If the popup is closed because the cursor moved, the number -1 is passed to
-the callback.
+If the popup is force-closed, e.g. because the cursor moved or CTRL-C was
+pressed, the number -1 is passed to the callback.
 
 ==============================================================================
 3. Examples						*popup-examples*
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 544426f..d371c28 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -815,6 +815,8 @@
     {"popup_clear",	0, 0, f_popup_clear},
     {"popup_close",	1, 2, f_popup_close},
     {"popup_create",	2, 2, f_popup_create},
+    {"popup_dialog",	2, 2, f_popup_dialog},
+    {"popup_filter_yesno", 2, 2, f_popup_filter_yesno},
     {"popup_getoptions", 1, 1, f_popup_getoptions},
     {"popup_getpos",	1, 1, f_popup_getpos},
     {"popup_hide",	1, 1, f_popup_hide},
diff --git a/src/globals.h b/src/globals.h
index 992ce2a..ec42984 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -599,7 +599,8 @@
 EXTERN int	aucmd_win_used INIT(= FALSE);	/* aucmd_win is being used */
 
 #ifdef FEAT_TEXT_PROP
-EXTERN win_T    *first_popupwin;	// first global popup window
+EXTERN win_T    *first_popupwin;		// first global popup window
+EXTERN win_T	*popup_dragwin INIT(= NULL);	// popup window being dragged
 #endif
 
 /*
diff --git a/src/popupwin.c b/src/popupwin.c
index aeed2e7..adbc729 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -201,6 +201,10 @@
 	drag_start_wantcol = wp->w_wincol + 1;
     else
 	drag_start_wantcol = wp->w_wantcol;
+
+    // Stop centering the popup
+    if (wp->w_popup_pos == POPPOS_CENTER)
+	wp->w_popup_pos = POPPOS_TOPLEFT;
 }
 
 /*
@@ -301,7 +305,9 @@
 	wp->w_p_wrap = nr != 0;
     }
 
-    wp->w_popup_drag = dict_get_number(dict, (char_u *)"drag");
+    di = dict_find(dict, (char_u *)"drag", -1);
+    if (di != NULL)
+	wp->w_popup_drag = dict_get_number(dict, (char_u *)"drag");
 
     di = dict_find(dict, (char_u *)"callback", -1);
     if (di != NULL)
@@ -692,13 +698,13 @@
 {
     TYPE_NORMAL,
     TYPE_ATCURSOR,
-    TYPE_NOTIFICATION
+    TYPE_NOTIFICATION,
+    TYPE_DIALOG
 } create_type_T;
 
 /*
  * popup_create({text}, {options})
  * popup_atcursor({text}, {options})
- * When called from f_popup_atcursor() "type" is TYPE_ATCURSOR.
  */
     static void
 popup_create(typval_T *argvars, typval_T *rettv, create_type_T type)
@@ -871,6 +877,20 @@
 		OPT_FREE|OPT_LOCAL, 0);
     }
 
+    if (type == TYPE_DIALOG)
+    {
+	int i;
+
+	wp->w_popup_pos = POPPOS_CENTER;
+	wp->w_zindex = POPUPWIN_DIALOG_ZINDEX;
+	wp->w_popup_drag = 1;
+	for (i = 0; i < 4; ++i)
+	{
+	    wp->w_popup_border[i] = 1;
+	    wp->w_popup_padding[i] = 1;
+	}
+    }
+
     // Deal with options.
     apply_options(wp, buf, argvars[1].vval.v_dict);
 
@@ -913,33 +933,6 @@
 }
 
 /*
- * popup_notification({text}, {options})
- */
-    void
-f_popup_notification(typval_T *argvars, typval_T *rettv)
-{
-    popup_create(argvars, rettv, TYPE_NOTIFICATION);
-}
-
-/*
- * Find the popup window with window-ID "id".
- * If the popup window does not exist NULL is returned.
- * If the window is not a popup window, and error message is given.
- */
-    static win_T *
-find_popup_win(int id)
-{
-    win_T *wp = win_id2wp(id);
-
-    if (wp != NULL && !bt_popup(wp->w_buffer))
-    {
-	semsg(_("E993: window %d is not a popup window"), id);
-	return NULL;
-    }
-    return wp;
-}
-
-/*
  * Invoke the close callback for window "wp" with value "result".
  * Careful: The callback may make "wp" invalid!
  */
@@ -986,6 +979,90 @@
 }
 
 /*
+ * popup_filter_yesno({text}, {options})
+ */
+    void
+f_popup_filter_yesno(typval_T *argvars, typval_T *rettv)
+{
+    int		id = tv_get_number(&argvars[0]);
+    win_T	*wp = win_id2wp(id);
+    char_u	*key = tv_get_string(&argvars[1]);
+    typval_T	res;
+
+    // If the popup has been closed don't consume the key.
+    if (wp == NULL)
+	return;
+
+    // consume all keys until done
+    rettv->vval.v_number = 1;
+
+    if (STRCMP(key, "y") == 0 || STRCMP(key, "Y") == 0)
+	res.vval.v_number = 1;
+    else if (STRCMP(key, "n") == 0 || STRCMP(key, "N") == 0
+	    || STRCMP(key, "x") == 0 || STRCMP(key, "X") == 0
+	    || STRCMP(key, "\x1b") == 0)
+	res.vval.v_number = 0;
+    else
+    {
+	int	c = *key;
+	int	row = mouse_row;
+	int	col = mouse_col;
+
+	if (c == K_SPECIAL && key[1] != NUL)
+	    c = TO_SPECIAL(key[1], key[2]);
+	if (wp->w_popup_drag
+		&& is_mouse_key(c)
+		&& (wp == popup_dragwin
+			      || wp == mouse_find_win(&row, &col, FIND_POPUP)))
+	    // allow for dragging the popup
+	    rettv->vval.v_number = 0;
+
+	// ignore this key
+	return;
+    }
+
+    // Invoke callback
+    res.v_type = VAR_NUMBER;
+    popup_close_and_callback(wp, &res);
+}
+
+/*
+ * popup_dialog({text}, {options})
+ */
+    void
+f_popup_dialog(typval_T *argvars, typval_T *rettv)
+{
+    popup_create(argvars, rettv, TYPE_DIALOG);
+}
+
+/*
+ * popup_notification({text}, {options})
+ */
+    void
+f_popup_notification(typval_T *argvars, typval_T *rettv)
+{
+    popup_create(argvars, rettv, TYPE_NOTIFICATION);
+}
+
+/*
+ * Find the popup window with window-ID "id".
+ * If the popup window does not exist NULL is returned.
+ * If the window is not a popup window, and error message is given.
+ */
+    static win_T *
+find_popup_win(int id)
+{
+    win_T *wp = win_id2wp(id);
+
+    if (wp != NULL && !bt_popup(wp->w_buffer))
+    {
+	semsg(_("E993: window %d is not a popup window"), id);
+	return NULL;
+    }
+    return wp;
+}
+
+/*
  * popup_close({id})
  */
     void
@@ -1299,6 +1376,15 @@
     typval_T	argv[3];
     char_u	buf[NUMBUFLEN];
 
+    // Emergency exit: CTRL-C closes the popup.
+    if (c == Ctrl_C)
+    {
+	rettv.v_type = VAR_NUMBER;
+	rettv.vval.v_number = -1;
+	popup_close_and_callback(wp, &rettv);
+	return 1;
+    }
+
     argv[0].v_type = VAR_NUMBER;
     argv[0].vval.v_number = (varnumber_T)wp->w_id;
 
@@ -1310,6 +1396,7 @@
 
     argv[2].v_type = VAR_UNKNOWN;
 
+    // NOTE: The callback might close the popup, thus make "wp" invalid.
     call_callback(&wp->w_filter_cb, -1,
 			    &rettv, 2, argv, NULL, 0L, 0L, &dummy, TRUE, NULL);
     res = tv_get_number(&rettv);
@@ -1326,7 +1413,7 @@
 popup_do_filter(int c)
 {
     int		res = FALSE;
-    win_T   *wp;
+    win_T	*wp;
 
     popup_reset_handled();
 
diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index cde0cae..6e93791 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -8,6 +8,8 @@
 void f_popup_clear(typval_T *argvars, typval_T *rettv);
 void f_popup_create(typval_T *argvars, typval_T *rettv);
 void f_popup_atcursor(typval_T *argvars, typval_T *rettv);
+void f_popup_filter_yesno(typval_T *argvars, typval_T *rettv);
+void f_popup_dialog(typval_T *argvars, typval_T *rettv);
 void f_popup_notification(typval_T *argvars, typval_T *rettv);
 void f_popup_close(typval_T *argvars, typval_T *rettv);
 void f_popup_hide(typval_T *argvars, typval_T *rettv);
diff --git a/src/structs.h b/src/structs.h
index 5925927..09158a0 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1998,7 +1998,8 @@
 
 # define POPUPWIN_DEFAULT_ZINDEX	 50
 # define POPUPMENU_ZINDEX		100
-# define POPUPWIN_NOTIFICATION_ZINDEX   200
+# define POPUPWIN_DIALOG_ZINDEX		200
+# define POPUPWIN_NOTIFICATION_ZINDEX   300
 #endif
 
 /*
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index a3f2046..f7a319c 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -870,6 +870,36 @@
   call popup_clear()
 endfunc
 
+func ShowDialog(key, result)
+  let s:cb_res = 999
+  let winid = popup_dialog('do you want to quit (Yes/no)?', {
+	  \ 'filter': 'popup_filter_yesno',
+	  \ 'callback': 'QuitCallback',
+	  \ })
+  redraw
+  call feedkeys(a:key, "xt")
+  call assert_equal(winid, s:cb_winid)
+  call assert_equal(a:result, s:cb_res)
+endfunc
+
+func Test_popup_dialog()
+  func QuitCallback(id, res)
+    let s:cb_winid = a:id
+    let s:cb_res = a:res
+  endfunc
+
+  let winid = ShowDialog("y", 1)
+  let winid = ShowDialog("Y", 1)
+  let winid = ShowDialog("n", 0)
+  let winid = ShowDialog("N", 0)
+  let winid = ShowDialog("x", 0)
+  let winid = ShowDialog("X", 0)
+  let winid = ShowDialog("\<Esc>", 0)
+  let winid = ShowDialog("\<C-C>", -1)
+
+  delfunc QuitCallback
+endfunc
+
 func Test_popup_close_callback()
   func PopupDone(id, result)
     let g:result = a:result
diff --git a/src/version.c b/src/version.c
index 113fb97..9d45703 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1548,
+/**/
     1547,
 /**/
     1546,