terminal: Fix mouse coordinates issue (#12158)

Offsets of window were not taken into account when sending mouse
coordinates to the terminal. Therefore, when nu or rnu is set, the mouse
coordinates sent to the terminal were not correct. Change it to send the
correct coordinates by subtract window offset from col.

src/nvim/terminal.c

@@ -992,8 +992,9 @@ static void mouse_action(Terminal *term, int button, int row, int col,
 static bool send_mouse_event(Terminal *term, int c)
 {
   int row = mouse_row, col = mouse_col, grid = mouse_grid;
+  int offset;
   win_T *mouse_win = mouse_find_win(&grid, &row, &col);
-  if (mouse_win == NULL) {
+  if (mouse_win == NULL || (offset = win_col_off(mouse_win)) > col) {
     goto end;
   }
 
@@ -1015,7 +1016,7 @@ static bool send_mouse_event(Terminal *term, int c)
       default: return false;
     }
 
-    mouse_action(term, button, row, col, drag, 0);
+    mouse_action(term, button, row, col - offset, drag, 0);
     size_t len = vterm_output_read(term->vt, term->textbuf,
                                    sizeof(term->textbuf));
     terminal_send(term, term->textbuf, (size_t)len);

test/functional/terminal/mouse_spec.lua

@@ -87,6 +87,36 @@ describe(':terminal mouse', function()
           {3:-- TERMINAL --}                                    |
         ]])
       end)
+
+      it('will forward mouse clicks to the program with the correct even if set nu', function()
+        if helpers.pending_win32(pending) then return end
+        nvim('command', 'set number')
+        -- When the display area such as a number is clicked, it returns to the
+        -- normal mode.
+        feed('<LeftMouse><3,0>')
+        eq('n', eval('mode()'))
+        screen:expect([[
+          {7: 11 }^line28                                        |
+          {7: 12 }line29                                        |
+          {7: 13 }line30                                        |
+          {7: 14 }mouse enabled                                 |
+          {7: 15 }rows: 6, cols: 46                             |
+          {7: 16 }{2: }                                             |
+                                                            |
+        ]])
+        -- If click on the coordinate (0,1) of the region of the terminal
+        -- (i.e. the coordinate (4,1) of vim), 'CSI !"' is sent to the terminal.
+        feed('i<LeftMouse><4,1>')
+        screen:expect([[
+          {7: 11 }line28                                        |
+          {7: 12 }line29                                        |
+          {7: 13 }line30                                        |
+          {7: 14 }mouse enabled                                 |
+          {7: 15 }rows: 6, cols: 46                             |
+          {7: 16 } !"{1: }                                          |
+          {3:-- TERMINAL --}                                    |
+        ]])
+      end)
     end)
 
     describe('with a split window and other buffer', function()
@@ -148,7 +178,7 @@ describe(':terminal mouse', function()
       end)
 
       it('wont lose focus if another window is scrolled', function()
-        feed('<ScrollWheelUp><0,0><ScrollWheelUp><0,0>')
+        feed('<ScrollWheelUp><4,0><ScrollWheelUp><4,0>')
         screen:expect([[
           {7: 21 }line                 │line30                  |
           {7: 22 }line                 │rows: 5, cols: 25       |
@@ -158,7 +188,7 @@ describe(':terminal mouse', function()
           ==========                ==========              |
           {3:-- TERMINAL --}                                    |
         ]])
-        feed('<S-ScrollWheelDown><0,0>')
+        feed('<S-ScrollWheelDown><4,0>')
         screen:expect([[
           {7: 26 }line                 │line30                  |
           {7: 27 }line                 │rows: 5, cols: 25       |