Prawn::Document::Snapshot

    # File lib/prawn/document/snapshot.rb, line 22
22:       def rollback
23:         raise RollbackTransaction
24:       end

    # File lib/prawn/document/snapshot.rb, line 34
34:       def transaction
35:         snap = take_snapshot
36:         yield
37:         true
38:       rescue RollbackTransaction
39:         restore_snapshot(snap)
40:         false
41:       end

    # File lib/prawn/document/snapshot.rb, line 62
62:       def restore_snapshot(shot)
63:         page = state.page
64:         # Because these objects are referenced by identifier from the Pages
65:         # dictionary, we can't just restore them over the current refs in
66:         # page_content and current_page. We have to restore them over the old
67:         # ones.
68:         page.content = shot[:page_content].identifier
69:         page.content.replace shot[:page_content]
70: 
71:         page.dictionary = shot[:current_page].identifier
72:         page.dictionary.replace shot[:current_page]
73:         page.dictionary.data[:Contents] = page.content
74: 
75:         self.page_number = shot[:page_number]
76: 
77:         state.store.pages.data[:Kids] = shot[:page_kids].map{|id| state.store[id]}
78:         state.store.pages.data[:Count] = shot[:page_kids].size
79: 
80:         if shot[:dests]
81:           names.data[:Dests] = shot[:dests] 
82:         end
83:       end

    # File lib/prawn/document/snapshot.rb, line 48
48:       def take_snapshot
49:         # current_page holds a ref to the Pages dictionary which grows
50:         # monotonically as data is added to the document, so we share that
51:         # between the old and new copies.
52:         {:page_content    => state.page.content.deep_copy,
53:          :current_page    => state.page.dictionary.deep_copy(share=[:Parent]),
54:          :page_number     => page_number,
55:          :page_kids       => state.store.pages.data[:Kids].map{|kid| kid.identifier},
56:          :dests           => names? && 
57:                              Marshal.load(Marshal.dump(names.data[:Dests]))}
58:       end