Use a curses pad for source and disassembly windows

This changes the TUI source and disassembly windows to use a curses
pad for their text.  This is an important step toward properly
handling non-ASCII characters, because it makes it easy to scroll
horizontally without needing gdb to also understand multi-byte
character boundaries -- this can be wholly delegated to curses.
Horizontal scrolling is probably also faster now, because no
re-rendering is required.

gdb/ChangeLog
2020-09-27  Tom Tromey  <tom@tromey.com>

	* unittests/tui-selftests.c: Update.
	* tui/tui-winsource.h (struct tui_source_window_base)
	<extra_margin, show_line_number, refresh_pad>: New methods.
	<m_max_length, m_pad>: New members.
	(tui_copy_source_line): Update.
	* tui/tui-winsource.c (tui_copy_source_line): Remove line_no,
	first_col, line_width, ndigits parameters.  Add length.
	(tui_source_window_base::show_source_line): Write to pad.  Line
	number now 0-based.
	(tui_source_window_base::refresh_pad): New method.
	(tui_source_window_base::show_source_content): Write to pad.  Call
	refresh_pad.
	(tui_source_window_base::do_scroll_horizontal): Call refresh_pad,
	not refill.
	(tui_source_window_base::update_exec_info): Call
	show_line_number.
	* tui/tui-source.h (struct tui_source_window) <extra_margin>: New
	method.
	<m_digits>: New member.
	* tui/tui-source.c (tui_source_window::set_contents): Set m_digits
	and m_max_length.
	(tui_source_window::show_line_number): New method.
	* tui/tui-io.h (tui_puts): Fix comment.
	* tui/tui-disasm.c (tui_disasm_window::set_contents): Set
	m_max_length.

1 files changed, 11 insertions, 0 deletions

diff --git a/gdb/tui/tui-source.h b/gdb/tui/tui-source.h
index 1df84cf..020f710 100644
--- a/gdb/tui/tui-source.h
+++ b/gdb/tui/tui-source.h
@@ -63,12 +63,23 @@ protected:
   bool set_contents (struct gdbarch *gdbarch,
 		     const struct symtab_and_line &sal) override;
 
+  int extra_margin () const override
+  {
+    return m_digits;
+  }
+
+  void show_line_number (int lineno) const override;
+
 private:
 
   /* Answer whether a particular line number or address is displayed
      in the current source window.  */
   bool line_is_displayed (int line) const;
 
+  /* How many digits to use when formatting the line number.  This
+     includes the trailing space.  */
+  int m_digits;
+
   /* It is the resolved form as returned by symtab_to_fullname.  */
   gdb::unique_xmalloc_ptr<char> m_fullname;
 };