[gnome-builder/wip/gtk4-port] libide/code: fix implicit newline handling

[Christian Hergert <chergert src gnome org>]

commit e6f5423a71fb74c294312c7eb09c2f602c3a86cb
Author: Christian Hergert <chergert redhat com>
Date:   Wed Apr 6 16:17:15 2022 -0700

    libide/code: fix implicit newline handling
    
    This fixes a rather old bug with handling newlines related to change
    monitors and how the implicit-trailing-newline gets applied.
    
    They default to true, so we need to alter the buffer contents when setting
    the property so that things stay in relatively same "shape" as they are
    expected to go to/from disk.

 src/libide/code/ide-buffer.c | 81 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
---
diff --git a/src/libide/code/ide-buffer.c b/src/libide/code/ide-buffer.c
index 4505f24e6..efceb67a7 100644
--- a/src/libide/code/ide-buffer.c
+++ b/src/libide/code/ide-buffer.c
@@ -287,6 +287,7 @@ _ide_buffer_new (IdeBufferManager *buffer_manager,
                        "file", file,
                        "enable-addins", enable_addins,
                        "is-temporary", is_temporary,
+                       "implicit-trailing-newline", FALSE,
                        "style-scheme-name", "Adwaita",
                        NULL);
 }
@@ -343,11 +344,86 @@ ide_buffer_set_state (IdeBuffer      *self,
     }
 }
 
+static void
+ide_buffer_update_implicit_newline (IdeBuffer *self)
+{
+  IdeFileSettings *file_settings;
+  gboolean was_implicit;
+  gboolean now_implicit;
+
+  IDE_ENTRY;
+
+  g_assert (IDE_IS_BUFFER (self));
+  g_assert (!ide_buffer_get_loading (self));
+
+  if (!(file_settings = ide_buffer_get_file_settings (self)))
+    IDE_EXIT;
+
+  /* If the new file-settings object does not match our
+   * current setting for trailing newlines, then we need
+   * to adjust that immediately to ensure our buffer contains
+   * the contents as expected.
+   *
+   * Otherwise, buffer change monitors will not line up with
+   * the the expectation on storage.
+   */
+  was_implicit = gtk_source_buffer_get_implicit_trailing_newline (GTK_SOURCE_BUFFER (self));
+  now_implicit = ide_file_settings_get_insert_trailing_newline (file_settings);
+
+  if (was_implicit != now_implicit)
+    {
+      GtkTextIter iter;
+
+      gtk_source_buffer_set_implicit_trailing_newline (GTK_SOURCE_BUFFER (self), now_implicit);
+
+      if (now_implicit)
+        {
+          gtk_text_buffer_get_end_iter (GTK_TEXT_BUFFER (self), &iter);
+
+          if (gtk_text_iter_starts_line (&iter))
+            {
+              GtkTextIter begin = iter;
+
+              gtk_text_iter_backward_char (&begin);
+
+              if (!gtk_text_iter_equal (&begin, &iter))
+                {
+                  gboolean modified = gtk_text_buffer_get_modified (GTK_TEXT_BUFFER (self));
+
+                  gtk_text_buffer_begin_user_action (GTK_TEXT_BUFFER (self));
+                  gtk_text_buffer_delete (GTK_TEXT_BUFFER (self), &begin, &iter);
+                  gtk_text_buffer_end_user_action (GTK_TEXT_BUFFER (self));
+
+                  if (!modified)
+                    gtk_text_buffer_set_modified (GTK_TEXT_BUFFER (self), modified);
+                }
+            }
+        }
+      else
+        {
+          gboolean modified = gtk_text_buffer_get_modified (GTK_TEXT_BUFFER (self));
+
+          gtk_text_buffer_get_end_iter (GTK_TEXT_BUFFER (self), &iter);
+
+          gtk_text_buffer_begin_user_action (GTK_TEXT_BUFFER (self));
+          gtk_text_buffer_insert (GTK_TEXT_BUFFER (self), &iter, "\n", 1);
+          gtk_text_buffer_end_user_action (GTK_TEXT_BUFFER (self));
+
+          if (!modified)
+            gtk_text_buffer_set_modified (GTK_TEXT_BUFFER (self), modified);
+        }
+    }
+
+  IDE_EXIT;
+}
+
 static void
 ide_buffer_real_loaded (IdeBuffer *self)
 {
   g_assert (IDE_IS_BUFFER (self));
 
+  ide_buffer_update_implicit_newline (self);
+
   if (self->buffer_manager != NULL)
     _ide_buffer_manager_buffer_loaded (self->buffer_manager, self);
 }
@@ -1830,12 +1906,17 @@ ide_buffer_set_file_settings (IdeBuffer       *self,
 {
   g_assert (IDE_IS_MAIN_THREAD ());
   g_assert (IDE_IS_BUFFER (self));
+  g_assert (IDE_IS_FILE_SETTINGS (file_settings));
 
   if (self->file_settings == file_settings)
     return;
 
   ide_clear_and_destroy_object (&self->file_settings);
   self->file_settings = g_object_ref (file_settings);
+
+  if (!ide_buffer_get_loading (self))
+    ide_buffer_update_implicit_newline (self);
+
   g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_FILE_SETTINGS]);
 }