Fix double-click word selection not extending beyond viewport edges

Add continue_word_upwards_scrollback() and continue_word_downwards_offscreen()
to extend word selection beyond viewport boundaries, mirroring the line
selection fix. Add tests for word selection wrapping into scrollback and
below viewport.

Agent-Logs-Url: https://github.com/kovidgoyal/kitty/sessions/58191e45-d925-4996-b0d5-8b1bd4baa8d5

Co-authored-by: kovidgoyal <1308621+kovidgoyal@users.noreply.github.com>

docs/changelog.rst

@@ -217,7 +217,7 @@ Detailed list of changes
 
 - Fix dragging of splits layout borders sometimes moving in the wrong direction or having no effect (:pull:`9447`)
 
-- Fix triple-click line selection not extending wrapped lines beyond the bottom edge of the viewport
+- Fix triple-click line selection and double-click word selection not extending wrapped lines beyond the edges of the viewport
 
 - Password input in kittens: hide the cursor and display a blinking 🔒 at the end of typed characters to make it visually clear the user is entering a password
 

kitty/screen.c

@@ -5406,6 +5406,36 @@ continue_line_downwards_offscreen(Screen *self, int bottom_line, SelectionBounda
     return num_offscreen;
 }
 
+static index_type
+continue_word_upwards_scrollback(Screen *self, int range_y, index_type *start_x) {
+    index_type num_in_scrollback = 0;
+    Line *line = NULL;
+    while (*start_x == 0 && range_line_is_continued(self, range_y) && (line = checked_range_line(self, range_y - 1))) {
+        if (!is_char_ok_for_word_extension(line, self->columns - 1, false)) break;
+        range_y--;
+        num_in_scrollback++;
+        index_type s = self->columns - 1;
+        while (s > 0 && is_char_ok_for_word_extension(line, s - 1, false)) s--;
+        *start_x = s;
+    }
+    return num_in_scrollback;
+}
+
+static index_type
+continue_word_downwards_offscreen(Screen *self, int range_y, index_type *end_x) {
+    index_type num_offscreen = 0;
+    Line *line = NULL;
+    while (*end_x >= self->columns - 1 && (line = checked_range_line(self, range_y + 1)) && range_line_is_continued(self, range_y + 1)) {
+        if (!is_char_ok_for_word_extension(line, 0, true)) break;
+        range_y++;
+        num_offscreen++;
+        index_type e = 0;
+        while (e < self->columns - 1 && is_char_ok_for_word_extension(line, e + 1, true)) e++;
+        *end_x = e;
+    }
+    return num_offscreen;
+}
+
 static int
 clamp_selection_input_to_multicell(Screen *self, const Selection *s, index_type x, index_type y, bool in_left_half_of_cell) {
     int delta = 0;
@@ -5498,6 +5528,25 @@ do_update_selection(Screen *self, Selection *s, index_type x, index_type y, bool
                 }
                 if (s->adjusting_start || adjust_both_ends) s->start_scrolled_by = self->scrolled_by;
                 if (!s->adjusting_start || adjust_both_ends) s->end_scrolled_by = self->scrolled_by;
+                // extend word into scrollback if needed
+                if (start.y == 0 && self->linebuf == self->main_linebuf &&
+                        (adjust_both_ends || adjusted_boundary_is_before)) {
+                    index_type num_in_scrollback = continue_word_upwards_scrollback(self, 0, &start.x);
+                    if (num_in_scrollback) {
+                        s->start_scrolled_by += num_in_scrollback;
+                        s->start.x = start.x;
+                    }
+                }
+                // extend word below viewport if needed
+                if (end.y >= self->lines - 1 && self->scrolled_by > 0 && self->linebuf == self->main_linebuf &&
+                        (adjust_both_ends || !adjusted_boundary_is_before)) {
+                    int range_bottom = (int)end.y - (int)self->scrolled_by;
+                    index_type num_below_viewport = continue_word_downwards_offscreen(self, range_bottom, &end.x);
+                    if (num_below_viewport) {
+                        s->end_scrolled_by -= num_below_viewport;
+                        s->end.x = end.x;
+                    }
+                }
             } else {
                 *a = s->input_current;
                 if (s->adjusting_start) s->start_scrolled_by = self->scrolled_by; else s->end_scrolled_by = self->scrolled_by;

kitty_tests/mouse.py

@@ -282,6 +282,25 @@ def scroll(x=0, y=0, up=True):
         self.ae(sel(), '678\nABCDE12345')
         s.scroll(100, False)
 
+        # word select for wrapped words in scrollback
+        s.reset()
+        s.draw('abcde12345')
+        s.linefeed(), s.carriage_return()
+        s.draw(('X' * s.columns) * (s.lines-1))
+        multi_click(x=1)
+        self.ae(sel(), 'abcde12345')
+
+        # word select for wrapped words below viewport
+        s.reset()
+        s.scroll(100, False)
+        s.draw(('X' * s.columns) * (s.lines - 1))
+        s.linefeed(), s.carriage_return()
+        s.draw('abcde12345')
+        s.scroll(1, True)
+        multi_click(x=1, y=s.lines - 1)
+        self.ae(sel(), 'abcde12345')
+        s.scroll(100, False)
+
         # Rectangle select
         init()
         press(x=1, y=1, modifiers=GLFW_MOD_ALT | GLFW_MOD_CONTROL)