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, 30 insertions, 11 deletions

diff --git a/gdb/tui/tui-winsource.h b/gdb/tui/tui-winsource.h
index ba9c0fd..5fc6a6d 100644
--- a/gdb/tui/tui-winsource.h
+++ b/gdb/tui/tui-winsource.h
@@ -107,6 +107,20 @@ protected:
   virtual bool set_contents (struct gdbarch *gdbarch,
 			     const struct symtab_and_line &sal) = 0;
 
+  /* Return the number of extra margin characters needed by this
+     instance.  */
+  virtual int extra_margin () const
+  {
+    return 0;
+  }
+
+  /* Display the line number in the window margin.  OFFSET indicates
+     which line to display; it is 0-based, with 0 meaning the line at
+     the top of the window.  */
+  virtual void show_line_number (int offset) const
+  {
+  }
+
   /* Redraw the complete line of a source or disassembly window.  */
   void show_source_line (int lineno);
 
@@ -119,6 +133,9 @@ protected:
 
   std::vector<tui_source_element> m_content;
 
+  /* Length of longest line to be displayed.  */
+  int m_max_length;
+
 public:
 
   /* Refill the source window's source cache and update it.  If this
@@ -162,11 +179,17 @@ private:
 
   void show_source_content ();
 
+  /* Re-display the pad in the window.  */
+  void refresh_pad ();
+
   /* Called when the user "set style enabled" setting is changed.  */
   void style_changed ();
 
   /* A token used to register and unregister an observer.  */
   gdb::observers::token m_observable;
+
+  /* Pad used to display fixme mumble  */
+  std::unique_ptr<WINDOW, curses_deleter> m_pad;
 };
 
 
@@ -264,19 +287,15 @@ extern void tui_display_main (void);
 extern void tui_update_source_windows_with_addr (struct gdbarch *, CORE_ADDR);
 extern void tui_update_source_windows_with_line (struct symtab_and_line sal);
 
-/* Extract some source text from PTR.  LINE_NO is the line number.  If
-   it is positive, it is printed at the start of the line.  FIRST_COL
-   is the first column to extract, and LINE_WIDTH is the number of
-   characters to display.  NDIGITS is used to format the line number
-   (if it is positive).  If NDIGITS is greater than 0, then that many
-   digits are used; otherwise the line number is formatted with 6
-   digits and the text is aligned to the next tab stop.  Returns a
-   string holding the desired text.  PTR is updated to point to the
-   start of the next line.  */
+/* Extract some source text from PTR.  Returns a string holding the
+   desired text.  PTR is updated to point to the start of the next
+   line.  If LENGTH is non-NULL, then the length of the line is stored
+   there.  Escape sequences are not counted against the length.
+   Actually an approximation is used -- each byte of a multi-byte
+   sequence counts as a character here.  */
 
 extern std::string tui_copy_source_line (const char **ptr,
-					 int line_no, int first_col,
-					 int line_width, int ndigits);
+					 int *length = nullptr);
 
 /* Constant definitions. */
 #define SCROLL_THRESHOLD 2	/* Threshold for lazy scroll.  */