2 /* This file is part of
3 * ======================================================
5 * LyX, The Document Processor
6 * Copyright 1995 Matthias Ettrich
7 * Copyright 1995-2000 The LyX Team
9 * This file is Copyright 2000
12 * ====================================================== */
31 // This is only the very first implemetation and use of the TextCache,
32 // operations on it needs to be put into a class or a namespace, that part
33 // is _NOT_ finished so don't bother to come with too many comments on it
34 // (unless you have some nice ideas on where/how to do it)
36 // I think we need a global TextCache that is common for all BufferViews,
37 // also the BufferList needs access to the TextCache. Please tell if you
40 // Q. What are we caching?
41 // A. We are caching the screen representations (LyXText) of the
42 // documents (Buffer,LyXParagraph) for specific BufferView widths.
44 // A. It is not really needed, but it speeds things up a lot
45 // when you have more than one document loaded at once since a total
46 // rebreak (reformatting) need not be done when switching between
47 // documents. When the cache is in function a document only needs to be
48 // formatted upon loading and when the with of the BufferView changes.
49 // Later it will also be unneccessary to reformat when having two
50 // BufferViews of equal width with the same document, a simple copy
51 // of the LyXText structure will do.
52 // Invariant for the TextCache:
53 // - The buffer of the text in the TextCache _must_ exists
55 // - For a text in the TextCache there _must not_ be an equivalent
56 // text in any BufferView. (same buffer and width).
57 // Among others this mean:
58 // - When a document is closed all trace of it must be removed from
61 // I believe there are only three possible scenarios where the two first
62 // are also covered by the third.
63 // - The simplest scenario is what we have now, a single
66 // Nothing to do with the TextCache is done when opening a file.
68 // We switch from buffer A to buffer B.
69 // * A's text is cached in TextCache.
70 // * We make a search for a text in TextCache that fits B
71 // (same buffer and same width).
72 // o Horizontal resize
73 // If the BufferView's width (LyXView) is horizontally changed all
74 // the entries in the TextCache are deleted. (This causes
75 // reformat of all loaded documents when next viewed)
77 // When a buffer is closed we don't have to do anything, because
78 // to close a single buffer it is required to only exist in the
79 // BufferView and not in the TextCache. Upon LFUN_QUIT we
80 // don't really care since everything is deleted anyway.
81 // - The next scenario is when we have several BufferViews (in one or
82 // more LyXViews) of equal width.
84 // Nothing to do with the TextCache is done when opening a file.
86 // We switch from buffer A to buffer B.
87 // * If A is in another Bufferview we do not put it into TextCache.
88 // else we put A into TextCache.
89 // * If B is viewed in another BufferView we make a copy of its
90 // text and use that, else we search in TextCache for a match.
91 // (same buffer same width)
92 // o Horizontal resize
93 // If the BufferView's width (LyXView) is horisontaly changed all
94 // the entries in the TextCache is deleted. (This causes
95 // reformat of all loaded documents when next viewed)
97 // - The last scenario should cover both the previous ones, this time
98 // we have several BufferViews (in one or more LyXViews) with no
99 // limitations on width. (And if you wonder why the two other
100 // senarios are needed... I used them to get to this one.)
102 // Nothing to do with the TextCache is done when opening a file.
104 // We switch from buffer A to buffer B.
105 // o Horisontal rezize
108 /** This class is used to cache generated LyXText's.
109 The LyXText's is used by the BufferView to visualize the contents
110 of a buffer and its paragraphs. Instead of deleting the LyXText when
111 we switch from one document to another we cache it here so that when
112 we switch back we do not have to reformat. This makes switching very
113 fast at the expense of a bit higher memory usage.
118 typedef vector<LyXText*> Cache;
120 typedef LyXText * value_type;
122 /** Returns a pointer to a LyXText that fits the provided buffer
123 and width. Of there is no match 0 is returned. */
124 LyXText * findFit(Buffer * b, unsigned short p);
125 /** Lists all the LyXText's currently in the cache.
126 Uses msg as header for the list. */
127 void show(ostream & o, string const & msg);
128 /// Gives info on a single LyXText (buffer and width)
129 static void show(ostream & o, LyXText *);
130 /** Adds a LyXText to the cache iff its buffer is
131 present in bufferlist. */
133 /** Clears the cache. Deletes all LyXText's and releases
134 the allocated memory. */
136 /// Removes all LyXText's that has buffer b from the TextCache
137 void removeAllWithBuffer(Buffer * b);
144 extern TextCache textcache;