patch 8.1.1945: popup window "firstline" cannot be reset

Problem:    Popup window "firstline" cannot be reset.
Solution:   Allow for setting "firstline" to zero.  Fix that the text jumps to
            the top when using win_execute(). (closes #4876)

src/popupwin.c

@@ -610,8 +610,8 @@ apply_general_options(win_T *wp, dict_T *dict)
     di = dict_find(dict, (char_u *)"firstline", -1);
     if (di != NULL)
 	wp->w_firstline = dict_get_number(dict, (char_u *)"firstline");
-    if (wp->w_firstline < 1)
+    if (wp->w_firstline < 0)
-	wp->w_firstline = 1;
+	wp->w_firstline = 0;
 
     di = dict_find(dict, (char_u *)"scrollbar", -1);
     if (di != NULL)
@@ -3192,8 +3192,17 @@ update_popups(void (*win_update)(win_T *wp))
 
 	// Draw the popup text, unless it's off screen.
 	if (wp->w_winrow < screen_Rows && wp->w_wincol < screen_Columns)
+	{
 	    win_update(wp);
 
+	    // move the cursor into the visible lines, otherwise executing
+	    // commands with win_execute() may cause the text to jump.
+	    if (wp->w_cursor.lnum < wp->w_topline)
+		wp->w_cursor.lnum = wp->w_topline;
+	    else if (wp->w_cursor.lnum >= wp->w_botline)
+		wp->w_cursor.lnum = wp->w_botline - 1;
+	}
+
 	wp->w_winrow -= top_off;
 	wp->w_wincol -= left_extra;
 

src/testdir/dumps/Test_popupwin_scroll_5.dump

@@ -1,10 +1,10 @@
 >1+0&#ffffff0| @73
 |2| @73
 |3| @73
-|4| @31|o+0#0000001#ffd7ff255|n|e| @4| +0#0000000#4040ff13| +0&#ffffff0@32
+|4| @31|f+0#0000001#ffd7ff255|o|u|r| @3| +0#0000000#ff404010| +0&#ffffff0@32
-|5| @31|t+0#0000001#ffd7ff255|w|o| @4| +0#0000000#4040ff13| +0&#ffffff0@32
+|5| @31|f+0#0000001#ffd7ff255|i|v|e| @3| +0#0000000#4040ff13| +0&#ffffff0@32
-|6| @31|t+0#0000001#ffd7ff255|h|r|e@1| @2| +0#0000000#ff404010| +0&#ffffff0@32
+|6| @31|s+0#0000001#ffd7ff255|i|x| @4| +0#0000000#4040ff13| +0&#ffffff0@32
-|7| @31|f+0#0000001#ffd7ff255|o|u|r| @3| +0#0000000#ff404010| +0&#ffffff0@32
+|7| @31|s+0#0000001#ffd7ff255|e|v|e|n| @2| +0#0000000#ff404010| +0&#ffffff0@32
 |8| @73
 |9| @73
 |:|c|a|l@1| |S|c|r|o|l@1|U|p|(|)| @40|1|,|1| @10|T|o|p| 

src/testdir/dumps/Test_popupwin_scroll_6.dump

@@ -1,10 +1,10 @@
 >1+0&#ffffff0| @73
 |2| @73
 |3| @73
-|4| @31|t+0#0000001#ffd7ff255|h|r|e@1| @2| +0#0000000#ff404010| +0&#ffffff0@32
+|4| @31|s+0#0000001#ffd7ff255|i|x| @4| +0#0000000#ff404010| +0&#ffffff0@32
-|5| @31|f+0#0000001#ffd7ff255|o|u|r| @3| +0#0000000#4040ff13| +0&#ffffff0@32
+|5| @31|s+0#0000001#ffd7ff255|e|v|e|n| @2| +0#0000000#ff404010| +0&#ffffff0@32
-|6| @31|f+0#0000001#ffd7ff255|i|v|e| @3| +0#0000000#4040ff13| +0&#ffffff0@32
+|6| @31|e+0#0000001#ffd7ff255|i|g|h|t| @2| +0#0000000#4040ff13| +0&#ffffff0@32
-|7| @31|s+0#0000001#ffd7ff255|i|x| @4| +0#0000000#ff404010| +0&#ffffff0@32
+|7| @31|n+0#0000001#ffd7ff255|i|n|e| @3| +0#0000000#4040ff13| +0&#ffffff0@32
 |8| @73
 |9| @73
 |:|c|a|l@1| |S|c|r|o|l@1|D|o|w|n|(|)| @38|1|,|1| @10|T|o|p| 

src/testdir/test_popupwin.vim

@@ -333,6 +333,36 @@ func Test_popup_firstline()
   call assert_equal(3, popup_getoptions(winid).firstline)
   call popup_setoptions(winid, #{firstline: 1})
   call assert_equal(1, popup_getoptions(winid).firstline)
+  call popup_close(winid)
+
+  let winid = popup_create(['xxx']->repeat(50), #{
+	\ maxheight: 3,
+	\ firstline: 11,
+	\ })
+  redraw
+  call assert_equal(11, popup_getoptions(winid).firstline)
+  call assert_equal(11, popup_getpos(winid).firstline)
+
+  " Normal command changes what is displayed but not "firstline"
+  call win_execute(winid, "normal! \<c-y>")
+  call assert_equal(11, popup_getoptions(winid).firstline)
+  call assert_equal(10, popup_getpos(winid).firstline)
+
+  " Making some property change applies "firstline" again
+  call popup_setoptions(winid, #{line: 4})
+  call assert_equal(11, popup_getoptions(winid).firstline)
+  call assert_equal(11, popup_getpos(winid).firstline)
+
+  " Remove "firstline" property and scroll
+  call popup_setoptions(winid, #{firstline: 0})
+  call win_execute(winid, "normal! \<c-y>")
+  call assert_equal(0, popup_getoptions(winid).firstline)
+  call assert_equal(10, popup_getpos(winid).firstline)
+
+  " Making some property change has no side effect
+  call popup_setoptions(winid, #{line: 3})
+  call assert_equal(0, popup_getoptions(winid).firstline)
+  call assert_equal(10, popup_getpos(winid).firstline)
 
   call popup_close(winid)
 endfunc
@@ -1678,7 +1708,7 @@ func Test_popup_scrollbar()
   call term_sendkeys(buf, ":\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_scroll_4', {})
 
-  call term_sendkeys(buf, ":call popup_setoptions(winid, #{scrollbarhighlight: 'ScrollBar', thumbhighlight: 'ScrollThumb'})\<CR>")
+  call term_sendkeys(buf, ":call popup_setoptions(winid, #{scrollbarhighlight: 'ScrollBar', thumbhighlight: 'ScrollThumb', firstline: 5})\<CR>")
   call term_sendkeys(buf, ":call ScrollUp()\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_scroll_5', {})
 

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1945,
 /**/
     1944,
 /**/