[gtkmm/wip/dboles/make_managed-4: 1/2] demo/demowindow: Use C++17 [[fallthrough]] attrib.

[Daniel Boles <dboles src gnome org>]

commit 13d39e93ea2d27045a6bf520949c262115f05c23
Author: Daniel Boles <dboles src gmail com>
Date:   Fri Oct 12 21:18:11 2018 +0100

    demo/demowindow: Use C++17 [[fallthrough]] attrib.
    
    Flip the if/else case so that the /* Fall through */ comment comes
    before the next case label, which would suppress a warning from
    -Wimplicit-fallthrough and looks clearer anyway - and then replace said
    comment with the standard C++17 [[fallthrough]] attribute intended to
    assuage compiler diagnostics in cases like this, as we use C++17 now.

 demos/gtk-demo/demowindow.cc | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)
---
diff --git a/demos/gtk-demo/demowindow.cc b/demos/gtk-demo/demowindow.cc
index d7e99ae0..809f0e65 100644
--- a/demos/gtk-demo/demowindow.cc
+++ b/demos/gtk-demo/demowindow.cc
@@ -361,20 +361,12 @@ void DemoWindow::load_file(const std::string& filename)
          while (isspace (*p))
            p++;
 
-          if (*p)
-          {
-            p = lines[i];
-            state++;
-            /* Fall through */
-            // TODO: Replace with [[fallthrough]] annotation (to case 3)
-            // when we ue C++17.
-            /* Reading program body */
-            start = refBufferSource->insert(start, p);
-            start = refBufferSource->insert(start, "\n");
+          if (!*p)
             break;
-          }
-         else
-           break;
+
+          p = lines[i];
+          state++;
+          [[fallthrough]];
 
        case 3:
          /* Reading program body */