Only move the cursor a line down on resize if the cursor line was split

kitty/data-types.h

@@ -331,6 +331,7 @@ void line_set_char(Line *, unsigned int , uint32_t , unsigned int , Cursor *);
 void line_right_shift(Line *, unsigned int , unsigned int );
 void line_add_combining_char(Line *, uint32_t , unsigned int );
 index_type line_as_ansi(Line *self, Py_UCS4 *buf, index_type buflen);
+unsigned int line_length(Line *self);
 
 void linebuf_init_line(LineBuf *, index_type);
 void linebuf_clear(LineBuf *, char_type ch);

kitty/line-buf.c

@@ -432,7 +432,8 @@ copy_old(LineBuf *self, PyObject *y) {
 
 #include "rewrap.h"
 
-void linebuf_rewrap(LineBuf *self, LineBuf *other, int *cursor_y_out, HistoryBuf *historybuf) {
+void 
+linebuf_rewrap(LineBuf *self, LineBuf *other, int *cursor_y_out, HistoryBuf *historybuf) {
     index_type first, i;
     bool is_empty = true;
 

kitty/line.c

@@ -24,7 +24,16 @@ dealloc(Line* self) {
     Py_TYPE(self)->tp_free((PyObject*)self);
 }
 
-PyObject* line_text_at(char_type ch, combining_type cc) {
+unsigned int
+line_length(Line *self) {
+    for (int i = self->xnum - 1; i >= 0; i++) {
+        if ((self->chars[i] & CHAR_MASK) != 32) return i + 1;
+    }
+    return 0;
+}
+
+PyObject* 
+line_text_at(char_type ch, combining_type cc) {
     PyObject *ans;
     if (cc == 0) {
         ans = PyUnicode_New(1, ch);

kitty/screen.c

@@ -108,7 +108,17 @@ screen_resize(Screen *self, unsigned int lines, unsigned int columns) {
     LineBuf *n = realloc_lb(self->main_linebuf, lines, columns, &cursor_y, self->historybuf);
     if (n == NULL) return false;
     Py_CLEAR(self->main_linebuf); self->main_linebuf = n;
-    if (is_main) self->cursor->y = MAX(0, cursor_y);
+    bool index_after_resize = false;
+    if (is_main) {
+        linebuf_init_line(self->main_linebuf, self->cursor->y);
+        if (is_x_shrink && (self->main_linebuf->continued_map[self->cursor->y] || line_length(self->main_linebuf->line) > columns)) {
+            // If the client is in line drawing mode, it will redraw the cursor
+            // line, this can cause rendering artifacts, so ensure that the
+            // cursor is on a new line
+            index_after_resize = true;
+        }
+        self->cursor->y = MAX(0, cursor_y);
+    }
     cursor_y = -1;
     n = realloc_lb(self->alt_linebuf, lines, columns, &cursor_y, NULL);
     if (n == NULL) return false;
@@ -129,6 +139,7 @@ screen_resize(Screen *self, unsigned int lines, unsigned int columns) {
     init_tabstops(self->main_tabstops, self->columns);
     init_tabstops(self->alt_tabstops, self->columns);
     tracker_update_screen(self->change_tracker);
+    if (index_after_resize) screen_index(self);
 
     return true;
 }

kitty/window.py

@@ -65,10 +65,6 @@ class Window:
     def set_geometry(self, new_geometry):
         if self.needs_layout or new_geometry.xnum != self.screen.columns or new_geometry.ynum != self.screen.lines:
             self.screen.resize(new_geometry.ynum, new_geometry.xnum)
-            if self.screen.cursor.y > 0:
-                # We move the cursor once line down to prevent the shell from
-                # overwriting the contents of the last line
-                self.screen.index()
             self.child.resize_pty(self.screen.columns, self.screen.lines)
             self.char_grid.resize(new_geometry)
             self.needs_layout = False

kitty_tests/screen.py

@@ -243,14 +243,14 @@ class TestScreen(BaseTest):
         s.resize(5, 1)
         self.ae(str(s.line(0)), '4')
         hb = s.historybuf
-        for i in range(s.lines):
-            self.ae(str(hb.line(i)), '3')
-        self.ae(str(hb.line(5)), '2')
+        for i in range(hb.ynum):
+            self.ae(str(hb.line(i)), '4' if i == 0 else '3')
         s = self.create_screen(scrollback=6)
         s.draw(''.join([str(i) * s.columns for i in range(s.lines*2)]))
         self.ae(str(s.line(4)), '9'*5)
         s.resize(5, 2)
-        self.ae(str(s.line(4)), '9 ')
+        self.ae(str(s.line(3)), '9 ')
+        self.ae(str(s.line(4)), '  ')
 
     def test_tab_stops(self):
         # Taken from vttest/main.c