patch 9.0.0898: with 'smoothscroll' cursor is one screen line too far down

Problem:    With 'smoothscroll' cursor is one screen line too far down. (Ernie
            Rael)
Solution:   Add a test that currently has the wrong result so that a fix can
            be made. (issue #11436)

src/testdir/dumps/Test_smooth_long_showbreak_1.dump

@@ -0,0 +1,6 @@
+>w+0&#ffffff0|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| 
+|++0#4040ff13&@2| |o+0#0000000&|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x
+|++0#4040ff13&@2| |t+0#0000000&| |i|n| |o|n|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o
+|++0#4040ff13&@2| |n+0#0000000&|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n
+|++0#4040ff13&@2| |e+0#0000000&| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n|e| @4
+@22|1|,|1| @10|A|l@1| 

src/testdir/dumps/Test_smooth_long_showbreak_2.dump

@@ -0,0 +1,6 @@
+|++0#4040ff13#ffffff0@2| |o+0#0000000&|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x
+|++0#4040ff13&@2| >t+0#0000000&| |i|n| |o|n|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o
+|++0#4040ff13&@2| |n+0#0000000&|e| |l|i|n|e| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n
+|++0#4040ff13&@2| |e+0#0000000&| |w|i|t|h| |l|o|t|s| |o|f| |t|e|x|t| |i|n| |o|n|e| |l|i|n|e| @4
+|~+0#4040ff13&| @38
+| +0#0000000&@21|1|,|7@1|-|8|5| @6|A|l@1| 

src/testdir/test_scroll_opt.vim

@@ -308,6 +308,29 @@ func Test_smoothscroll_one_long_line()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_smoothscroll_long_line_showbreak()
+  CheckScreendump
+
+  let lines =<< trim END
+      vim9script
+      # a line that spans four screen lines
+      setline(1, 'with lots of text in one line '->repeat(6))
+      set smoothscroll scrolloff=0 showbreak=+++\ 
+  END
+  call writefile(lines, 'XSmoothLongShowbreak', 'D')
+  let buf = RunVimInTerminal('-S XSmoothLongShowbreak', #{rows: 6, cols: 40})
+  call VerifyScreenDump(buf, 'Test_smooth_long_showbreak_1', {})
+  
+  " FIXME: this currently has the cursor in screen line 2, should be one up.
+  call term_sendkeys(buf, "\<C-E>")
+  call VerifyScreenDump(buf, 'Test_smooth_long_showbreak_2', {})
+
+  call term_sendkeys(buf, "0")
+  call VerifyScreenDump(buf, 'Test_smooth_long_showbreak_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " Test that if the current cursor is on a smooth scrolled line, we correctly
 " reposition it. Also check that we don't miscalculate the values by checking
 " the consistency between wincol() and col('.') as they are calculated

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    898,
 /**/
     897,
 /**/