patch 8.2.1406: popupwindow lacks scrollbar if no "maxheight" is used

Problem:    Popupwindow lacks scrollbar if no "maxheight" is used.
Solution:   Compute the max height depending on the position. (closes #6664)

src/popupwin.c

@@ -1130,6 +1130,7 @@ popup_adjust_position(win_T *wp)
     int		org_leftcol = wp->w_leftcol;
     int		org_leftoff = wp->w_popup_leftoff;
     int		minwidth, minheight;
+    int		maxheight = Rows;
     int		wantline = wp->w_wantline;  // adjusted for textprop
     int		wantcol = wp->w_wantcol;    // adjusted for textprop
     int		use_wantcol = wantcol != 0;
@@ -1277,6 +1278,9 @@ popup_adjust_position(win_T *wp)
     }
 #endif
 
+    if (wp->w_maxheight > 0)
+	maxheight = wp->w_maxheight;
+
     // start at the desired first line
     if (wp->w_firstline > 0)
 	wp->w_topline = wp->w_firstline;
@@ -1353,11 +1357,11 @@ popup_adjust_position(win_T *wp)
 	    ++lnum;
 
 	// do not use the width of lines we're not going to show
-	if (wp->w_maxheight > 0
+	if (maxheight > 0
 		   && (wp->w_firstline >= 0
 			       ? lnum - wp->w_topline
 			       : wp->w_buffer->b_ml.ml_line_count - lnum)
-		       + wrapped >= wp->w_maxheight)
+		       + wrapped >= maxheight)
 	    break;
     }
 
@@ -1449,13 +1453,11 @@ popup_adjust_position(win_T *wp)
 								 + 1 + wrapped;
     if (minheight > 0 && wp->w_height < minheight)
 	wp->w_height = minheight;
-    if (wp->w_maxheight > 0 && wp->w_height > wp->w_maxheight)
-	wp->w_height = wp->w_maxheight;
+    if (maxheight > 0 && wp->w_height > maxheight)
+	wp->w_height = maxheight;
     w_height_before_limit = wp->w_height;
     if (wp->w_height > Rows - wp->w_winrow)
 	wp->w_height = Rows - wp->w_winrow;
-    if (wp->w_height != org_height)
-	win_comp_scroll(wp);
 
     if (center_vert)
     {
@@ -1477,9 +1479,21 @@ popup_adjust_position(win_T *wp)
 	    wp->w_height = wantline - extra_height;
 	}
 	else
+	{
 	    // Not enough space and more space on the other side: make top
 	    // aligned.
 	    wp->w_winrow = (wantline < 0 ? 0 : wantline) + 1;
+	    if (wp->w_winrow + wp->w_height + extra_height >= Rows)
+	    {
+		wp->w_height = Rows - wp->w_winrow - extra_height;
+		if (wp->w_want_scrollbar
+#ifdef FEAT_TERMINAL
+			    && wp->w_buffer->b_term == NULL
+#endif
+			    )
+		    wp->w_has_scrollbar = TRUE;
+	    }
+	}
     }
     else if (wp->w_popup_pos == POPPOS_TOPRIGHT
 		|| wp->w_popup_pos == POPPOS_TOPLEFT)
@@ -1501,11 +1515,15 @@ popup_adjust_position(win_T *wp)
 	else
 	    wp->w_winrow = wantline - 1;
     }
+    // make sure w_window is valid
     if (wp->w_winrow >= Rows)
 	wp->w_winrow = Rows - 1;
     else if (wp->w_winrow < 0)
 	wp->w_winrow = 0;
 
+    if (wp->w_height != org_height)
+	win_comp_scroll(wp);
+
     wp->w_popup_last_changedtick = CHANGEDTICK(wp->w_buffer);
     if (win_valid(wp->w_popup_prop_win))
     {

src/testdir/dumps/Test_popupwin_toohigh_1.dump

@@ -0,0 +1,10 @@
+|1+0&#ffffff0@9| @64
+|2@9| @64
+|3@8>3| @64
+|4@8|╔+0#0000001#ffd7ff255|═@8|╗| +0#0000000#ffffff0@54
+|5@8|║+0#0000001#ffd7ff255|o|n|e| @4| +0#0000000#0000001|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|6@8|║+0#0000001#ffd7ff255|t|w|o| @4| +0#0000000#0000001|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|7@8|║+0#0000001#ffd7ff255|t|h|r|e@1| @2| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|8@8|║+0#0000001#ffd7ff255|f|o|u|r| @3| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|9@8|║+0#0000001#ffd7ff255|f|i|v|e| @3| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+@9|╚+0#0000001#ffd7ff255|═@8|╝| +0#0000000#ffffff0@36|3|,|1|0| @9|T|o|p| 

src/testdir/dumps/Test_popupwin_toohigh_2.dump

@@ -0,0 +1,10 @@
+|1+0&#ffffff0@8|╔+0#0000001#ffd7ff255|═@8|╗| +0#0000000#ffffff0@54
+|2@8|║+0#0000001#ffd7ff255|o|n|e| @4| +0#0000000#0000001|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|3@8|║+0#0000001#ffd7ff255|t|w|o| @4| +0#0000000#0000001|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|4@8|║+0#0000001#ffd7ff255|t|h|r|e@1| @2| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|5@8|║+0#0000001#ffd7ff255|f|o|u|r| @3| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|6@8|║+0#0000001#ffd7ff255|f|i|v|e| @3| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255| +0#0000000#ffffff0@54
+|7@8|╚+0#0000001#ffd7ff255|═@8|╝| +0#0000000#ffffff0@54
+|8@8>8| @64
+|9@9| @64
+|:|c|a|l@1| |S|h|o|w|P|o|p|u|p|(|)| @39|8|,|1|0| @9|T|o|p| 

src/testdir/test_popupwin.vim

@@ -2144,6 +2144,36 @@ func Test_popup_scrollbar()
   call delete('XtestPopupScroll')
 endfunc
 
+func Test_popup_too_high_scrollbar()
+  CheckScreendump
+
+  let lines =<< trim END
+    call setline(1, range(1, 20)->map({i, v -> repeat(v, 10)}))
+    set scrolloff=0
+    func ShowPopup()
+      let winid = popup_atcursor(['one', 'two', 'three', 'four', 'five',
+	    \ 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'twelve'], #{
+	    \ minwidth: 8,
+	    \ border: [],
+	    \ })
+    endfunc
+    normal 3G$
+    call ShowPopup()
+  END
+  call writefile(lines, 'XtestPopupToohigh')
+  let buf = RunVimInTerminal('-S XtestPopupToohigh', #{rows: 10})
+  call VerifyScreenDump(buf, 'Test_popupwin_toohigh_1', {})
+
+  call term_sendkeys(buf, ":call popup_clear()\<CR>")
+  call term_sendkeys(buf, "8G$")
+  call term_sendkeys(buf, ":call ShowPopup()\<CR>")
+  call VerifyScreenDump(buf, 'Test_popupwin_toohigh_2', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XtestPopupToohigh')
+endfunc
+
 func Test_popup_fitting_scrollbar()
   " this was causing a crash, divide by zero
   let winid = popup_create([

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1406,
 /**/
     1405,
 /**/