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Increase metrics cache maximal size

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Increase the maximal size of the breakString cache (to compute where
to break lines) from 512kB to 10MB. This has a big impact of cache
hits on large file like the example in #12297, which is now 99%. On
this example the time taken by breakString decreases from 33.5us to
2.4us.

The string width cache has been increased fro 512kB to 1MB, but this
does not make such a big difference.

Additionally, comments and variable names have been improved.

Related to bug #12297.
This commit is contained in:
Jean-Marc Lasgouttes 2021-10-05 15:52:31 +02:00
parent 5966d4fb8d
commit 572b06d640
1 changed files with 17 additions and 15 deletions
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32
src/frontends/qt/GuiFontMetrics.cpp
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@ -86,25 +86,27 @@ namespace lyx {
namespace frontend {
/*
* Limit (strwidth|breakstr)_cache_ size to 512kB of string data.
* Limit qtextlayout_cache_ size to 500 elements (we do not know the
* size of the QTextLayout objects anyway).
* Note that all these numbers are arbitrary.
* Also, setting size to 0 is tantamount to disabling the cache.
*/
int cache_metrics_width_size = 1 << 19;
int cache_metrics_breakstr_size = 1 << 19;
namespace {
// Maximal size/cost for various caches. See QCache documentation to
// see what cost means.
// Limit strwidth_cache_ total cost to 1MB of string data.
int const strwidth_cache_max_cost = 1024 * 1024;
// Limit breakat_cache_ total cost to 10MB of string data.
// This is useful for documents with very large insets.
int const breakstr_cache_max_cost = 10 * 1024 * 1024;
// Qt 5.x already has its own caching of QTextLayout objects
// but it does not seem to work well on MacOS X.
#if (QT_VERSION < 0x050000) || defined(Q_OS_MAC)
int cache_metrics_qtextlayout_size = 500;
// Limit qtextlayout_cache_ size to 500 elements (we do not know the
// size of the QTextLayout objects anyway).
int const qtextlayout_cache_max_size = 500;
#else
int cache_metrics_qtextlayout_size = 0;
// Disable the cache
int const qtextlayout_cache_max_size = 0;
#endif
namespace {
/**
* Convert a UCS4 character into a QChar.
* This is a hack (it does only make sense for the common part of the UCS4
@ -128,9 +130,9 @@ inline QChar const ucs4_to_qchar(char_type const ucs4)
GuiFontMetrics::GuiFontMetrics(QFont const & font)
: font_(font), metrics_(font, 0),
strwidth_cache_(cache_metrics_width_size),
breakstr_cache_(cache_metrics_breakstr_size),
qtextlayout_cache_(cache_metrics_qtextlayout_size)
strwidth_cache_(strwidth_cache_max_cost),
breakstr_cache_(breakstr_cache_max_cost),
qtextlayout_cache_(qtextlayout_cache_max_size)
{
// Determine italic slope
double const defaultSlope = tan(qDegreesToRadians(19.0));