[RFC 8.3 1/3] Make TUI react to "set style enabled"

[Tom Tromey <tromey@adacore.com>]

When the user toggles "set style enabled", the TUI should react by
redrawing the source window, if necessary.  This patch implements this
behavior.

No test because the TUI is generally not tested.

I was not sure of a clean way to force an update of the window's
contents; see the new tui_redisplay_source for the workaround I used.

gdb/ChangeLog
2019-03-08  Tom Tromey  <tromey@adacore.com>

	* cli/cli-style.c (set_style_enabled): Notify new observable.
	* tui/tui-hooks.c (tui_redisplay_source): New function.
	(tui_attach_detach_observers): Attach or detach
	tui_redisplay_source.
	* observable.h (source_styling_changed): New observable.
	* observable.c: Define source_styling_changed observable.
---
 gdb/ChangeLog       |  9 +++++++++
 gdb/cli/cli-style.c |  2 ++
 gdb/observable.c    |  1 +
 gdb/observable.h    |  4 ++++
 gdb/tui/tui-hooks.c | 14 ++++++++++++++
 5 files changed, 30 insertions(+)

diff --git a/gdb/cli/cli-style.c b/gdb/cli/cli-style.c
index 234cc410dda..729a024c47a 100644
--- a/gdb/cli/cli-style.c
+++ b/gdb/cli/cli-style.c
@@ -21,6 +21,7 @@
 #include "cli/cli-cmds.h"
 #include "cli/cli-style.h"
 #include "source-cache.h"
+#include "observable.h"
 
 /* True if styling is enabled.  */
 
@@ -216,6 +217,7 @@ static void
 set_style_enabled  (const char *args, int from_tty, struct cmd_list_element *c)
 {
   g_source_cache.clear ();
+  gdb::observers::source_styling_changed.notify ();
 }
 
 static void
diff --git a/gdb/observable.c b/gdb/observable.c
index 33112062424..c077b025932 100644
--- a/gdb/observable.c
+++ b/gdb/observable.c
@@ -74,6 +74,7 @@ DEFINE_OBSERVABLE (inferior_call_pre);
 DEFINE_OBSERVABLE (inferior_call_post);
 DEFINE_OBSERVABLE (register_changed);
 DEFINE_OBSERVABLE (user_selected_context_changed);
+DEFINE_OBSERVABLE (source_styling_changed);
 
 } /* namespace observers */
 } /* namespace gdb */
diff --git a/gdb/observable.h b/gdb/observable.h
index 999ecfbc353..edd1fffae0a 100644
--- a/gdb/observable.h
+++ b/gdb/observable.h
@@ -228,6 +228,10 @@ extern observable<struct frame_info *, int> register_changed;
    frame has changed.  */
 extern observable<user_selected_what> user_selected_context_changed;
 
+/* This is notified when the source styling setting has changed and
+   should be reconsulted.  */
+extern observable<> source_styling_changed;
+
 } /* namespace observers */
 
 } /* namespace gdb */
diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index 98c6fd651fa..162d6ef525a 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -204,6 +204,18 @@ tui_normal_stop (struct bpstats *bs, int print_frame)
   tui_refresh_frame_and_register_information (/*registers_too_p=*/1);
 }
 
+/* Observer for source_cache_cleared.  */
+
+static void
+tui_redisplay_source ()
+{
+  if (tui_is_window_visible (SRC_WIN))
+    {
+      /* Force redisplay.  */
+      tui_horizontal_source_scroll (tui_win_list[SRC_WIN], LEFT_SCROLL, 0);
+    }
+}
+
 /* Token associated with observers registered while TUI hooks are
    installed.  */
 static const gdb::observers::token tui_observers_token {};
@@ -239,6 +251,8 @@ tui_attach_detach_observers (bool attach)
 		    tui_normal_stop, attach);
   attach_or_detach (gdb::observers::register_changed,
 		    tui_register_changed, attach);
+  attach_or_detach (gdb::observers::source_styling_changed,
+		    tui_redisplay_source, attach);
 }
 
 /* Install the TUI specific hooks.  */
-- 
2.20.1