OpenGL uses the diamond exit rule to rasterize lines. If we don't shift
the points down and to the right by 0.5, the line can sometimes miss a
pixel when it shouldn't. The final fragment of a line isn't drawn. By
drawing the lines clockwise, we can avoid a missing pixel in the rectangle.
See section 3.4.1 in the OpenGL 1.5 specification.
Fixes#32279
If the preview is already cached, queue_ressource_preview calls
_thumbnail_done immediately, so preview_waiting is never set to false
again. The progress wheel isn't rendered, because the WaitPreview icons
don't exist. This should probably be Progress.
Fixes#25749
If a scene is instanced in another scene, any changes to the first
triggers _clear_undo_history in EditorNode::set_current_scene, which
increments the version in UndoRedo::clear_history. This results in a
modified status. Passing false to clear_history fixes this issue.
Fixes#25942
Paul Trojahn