vim-patch:8.2.3095: with 'virtualedit' set to "block" block selection is wrong

Problem:    With 'virtualedit' set to "block" block selection is wrong after
            using "$".  (Marco Trosi)
Solution:   Compute the longest selected line. (closes vim/vim#8495)
b17ab86e7b

src/nvim/screen.c

@@ -1222,12 +1222,33 @@ static void win_update(win_T *wp, Providers *providers)
         }
 
         getvcols(wp, &VIsual, &curwin->w_cursor, &fromc, &toc);
-        curwin->w_ve_flags = save_ve_flags;
         toc++;
+        curwin->w_ve_flags = save_ve_flags;
         // Highlight to the end of the line, unless 'virtualedit' has
         // "block".
-        if (curwin->w_curswant == MAXCOL && !(get_ve_flags() & VE_BLOCK)) {
+        if (curwin->w_curswant == MAXCOL) {
-          toc = MAXCOL;
+          if (get_ve_flags() & VE_BLOCK) {
+            pos_T pos;
+            int cursor_above = curwin->w_cursor.lnum < VIsual.lnum;
+
+            // Need to find the longest line.
+            toc = 0;
+            pos.coladd = 0;
+            for (pos.lnum = curwin->w_cursor.lnum;
+                 cursor_above ? pos.lnum <= VIsual.lnum : pos.lnum >= VIsual.lnum;
+                 pos.lnum += cursor_above ? 1 : -1) {
+              colnr_T t;
+
+              pos.col = STRLEN(ml_get_buf(wp->w_buffer, pos.lnum, false));
+              getvvcol(wp, &pos, NULL, NULL, &t);
+              if (toc < t) {
+                toc = t;
+              }
+            }
+            toc++;
+          } else {
+            toc = MAXCOL;
+          }
         }
 
         if (fromc != wp->w_old_cursor_fcol

src/nvim/testdir/test_visual.vim

@@ -1124,6 +1124,9 @@ func Test_visual_block_with_virtualedit()
   call term_sendkeys(buf, "\<C-V>gg$")
   call VerifyScreenDump(buf, 'Test_visual_block_with_virtualedit', {})
 
+  call term_sendkeys(buf, "\<Esc>gg\<C-V>G$")
+  call VerifyScreenDump(buf, 'Test_visual_block_with_virtualedit2', {})
+
   " clean up
   call term_sendkeys(buf, "\<Esc>")
   call StopVimInTerminal(buf)

test/functional/legacy/visual_mode_spec.lua

@@ -1,5 +1,3 @@
--- Test visual line mode selection redraw after scrolling
-
 local helpers = require('test.functional.helpers')(after_each)
 
 local Screen = require('test.functional.ui.screen')
@@ -10,6 +8,7 @@ local feed_command = helpers.feed_command
 local funcs = helpers.funcs
 local meths = helpers.meths
 local eq = helpers.eq
+local exec = helpers.exec
 
 describe('visual line mode', function()
   local screen
@@ -40,3 +39,44 @@ describe('visual line mode', function()
     ]])
   end)
 end)
+
+describe('visual block mode', function()
+  it('shows selection correctly with virtualedit=block', function()
+    clear()
+    local screen = Screen.new(30, 7)
+    screen:set_default_attr_ids({
+      [1] = {bold = true},  -- ModeMsg
+      [2] = {background = Screen.colors.LightGrey},  -- Visual
+      [3] = {foreground = Screen.colors.Blue, bold = true}  -- NonText
+    })
+    screen:attach()
+
+    exec([[
+      call setline(1, ['aaaaaa', 'bbbb', 'cc'])
+      set virtualedit=block
+      normal G
+    ]])
+
+    feed('<C-V>gg$')
+    screen:expect([[
+      {2:aaaaaa}^                        |
+      {2:bbbb   }                       |
+      {2:cc     }                       |
+      {3:~                             }|
+      {3:~                             }|
+      {3:~                             }|
+      {1:-- VISUAL BLOCK --}            |
+    ]])
+
+    feed('<Esc>gg<C-V>G$')
+    screen:expect([[
+      {2:aaaaaa }                       |
+      {2:bbbb   }                       |
+      {2:cc}^ {2:    }                       |
+      {3:~                             }|
+      {3:~                             }|
+      {3:~                             }|
+      {1:-- VISUAL BLOCK --}            |
+    ]])
+  end)
+end)