patch 8.1.1518: crash when setting 'columns' while a popup is visible

Problem:    Crash when setting 'columns' while a popup is visible.
Solution:   Recompute all positions when clearing the screen. (closes #4467)

src/screen.c

@@ -1029,9 +1029,16 @@ may_update_popup_mask(int type)
     win_T	*wp;
     short	*mask;
     int		line, col;
+    int		redraw_all = FALSE;
 
-    if (popup_mask_tab != curtab)
+    // Need to recompute when switching tabs.
+    // Also recompute when the type is CLEAR or NOT_VALID, something basic
+    // (such as the screen size) must have changed.
+    if (popup_mask_tab != curtab || type >= NOT_VALID)
+    {
 	popup_mask_refresh = TRUE;
+	redraw_all = TRUE;
+    }
     if (!popup_mask_refresh)
     {
 	// Check if any buffer has changed.
@@ -1070,7 +1077,8 @@ may_update_popup_mask(int type)
 	popup_visible = TRUE;
 
 	// Recompute the position if the text changed.
-	if (wp->w_popup_last_changedtick != CHANGEDTICK(wp->w_buffer))
+	if (redraw_all
+		|| wp->w_popup_last_changedtick != CHANGEDTICK(wp->w_buffer))
 	    popup_adjust_position(wp);
 
 	// the width and height are for the inside, add the padding and

src/testdir/dumps/Test_popupwin_04a.dump

@@ -0,0 +1,10 @@
+> +0&#ffffff0@11
+|~+0#4040ff13&| @10
+|~| @10
+|~| @6|o+0#0000001#ffd7ff255|t|h|e
+|~+0#4040ff13#ffffff0| @6|r+0#0000001#ffd7ff255| |t|a
+|~+0#4040ff13#ffffff0| @6|b+0#0000001#ffd7ff255| @2
+|~+0#4040ff13#ffffff0| @6|a+0#0000001#ffd7ff255| |c+0#ff404010&|o
+|~+0#4040ff13#ffffff0| @6|m+0#ff404010#ffd7ff255@1|e|n
+|~+0#4040ff13#ffffff0| @6|t+0#ff404010#ffd7ff255| +0#0000001&|l|i
+| +0#0000000#ffffff0@5|0|,|n+0#0000001#ffd7ff255|e| @1

src/testdir/test_popupwin.vim

@@ -41,6 +41,12 @@ func Test_simple_popup()
   call term_sendkeys(buf, ":quit!\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_04', {})
 
+  " set 'columns' to a small value, size must be recomputed
+  call term_sendkeys(buf, ":let cols = &columns\<CR>")
+  call term_sendkeys(buf, ":set columns=12\<CR>")
+  call VerifyScreenDump(buf, 'Test_popupwin_04a', {})
+  call term_sendkeys(buf, ":let &columns = cols\<CR>")
+
   " resize popup, show empty line at bottom
   call term_sendkeys(buf, ":call popup_move(popupwin, {'minwidth': 15, 'maxwidth': 25, 'minheight': 3, 'maxheight': 5})\<CR>")
   call term_sendkeys(buf, ":redraw\<CR>")

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1518,
 /**/
     1517,
 /**/