patch 8.2.1108: mouse left-right scroll is not supported in terminal window

Problem:    Mouse left-right scroll is not supported in terminal window.
Solution:   Implement mouse codes 6 and 7. (Trygve Aaberge, closes #6363)

src/testdir/mouse.vim

@@ -169,4 +169,20 @@ func MouseWheelDown(row, col)
   call feedkeys(MouseWheelDownCode(a:row, a:col), 'Lx!')
 endfunc
 
+func MouseWheelLeftCode(row, col)
+  return TerminalEscapeCode(0x42, a:row, a:col, 'M')
+endfunc
+
+func MouseWheelLeft(row, col)
+  call feedkeys(MouseWheelLeftCode(a:row, a:col), 'Lx!')
+endfunc
+
+func MouseWheelRightCode(row, col)
+  return TerminalEscapeCode(0x43, a:row, a:col, 'M')
+endfunc
+
+func MouseWheelRight(row, col)
+  call feedkeys(MouseWheelRightCode(a:row, a:col), 'Lx!')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/testdir/test_termcodes.vim

@@ -194,9 +194,10 @@ func Test_1xterm_mouse_wheel()
   new
   let save_mouse = &mouse
   let save_term = &term
+  let save_wrap = &wrap
   let save_ttymouse = &ttymouse
-  set mouse=a term=xterm
-  call setline(1, range(1, 100))
+  set mouse=a term=xterm nowrap
+  call setline(1, range(100000000000000, 100000000000100))
 
   for ttymouse_val in g:Ttymouse_values
     let msg = 'ttymouse=' .. ttymouse_val
@@ -220,10 +221,31 @@ func Test_1xterm_mouse_wheel()
     call MouseWheelUp(1, 1)
     call assert_equal(1, line('w0'), msg)
     call assert_equal([0, 7, 1, 0], getpos('.'), msg)
+
+    if has('gui')
+      " Horizontal wheel scrolling currently only works when vim is
+      " compiled with gui enabled.
+      call MouseWheelRight(1, 1)
+      call assert_equal(7, 1 + virtcol(".") - wincol(), msg)
+      call assert_equal([0, 7, 7, 0], getpos('.'), msg)
+
+      call MouseWheelRight(1, 1)
+      call assert_equal(13, 1 + virtcol(".") - wincol(), msg)
+      call assert_equal([0, 7, 13, 0], getpos('.'), msg)
+
+      call MouseWheelLeft(1, 1)
+      call assert_equal(7, 1 + virtcol(".") - wincol(), msg)
+      call assert_equal([0, 7, 13, 0], getpos('.'), msg)
+
+      call MouseWheelLeft(1, 1)
+      call assert_equal(1, 1 + virtcol(".") - wincol(), msg)
+      call assert_equal([0, 7, 13, 0], getpos('.'), msg)
+    endif
   endfor
 
   let &mouse = save_mouse
   let &term = save_term
+  let &wrap = save_wrap
   let &ttymouse = save_ttymouse
   bwipe!
 endfunc