activate
This function requests @proposal to be activated by the #GtkSourceCompletionProvider.
What the provider does to activate the proposal is specific to that provider. Many providers may choose to insert a #GtkSourceSnippet with edit points the user may cycle through.
See also: class@Snippet, class@SnippetChunk, method@View.push_snippet
Parameters
context
a #GtkSourceCompletionContext
proposal
a #GtkSourceCompletionProposal