TextLayoutCache.hxx

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
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 *   Licensed to the Apache Software Foundation (ASF) under one or more
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#pragma once
 
#include <sal/types.h>
#include <rtl/ustring.hxx>
#include <o3tl/hash_combine.hxx>
 
#include <vcl/dllapi.h>
 
#include <unicode/uscript.h>
 
#include <vector>
 
namespace vcl::text
{
struct Run
{
    int32_t nStart;
    int32_t nEnd;
    UScriptCode nCode;
    Run(int32_t nStart_, int32_t nEnd_, UScriptCode nCode_)
        : nStart(nStart_)
        , nEnd(nEnd_)
        , nCode(nCode_)
    {
    }
};
 
class VCL_DLLPUBLIC TextLayoutCache
{
public:
    std::vector<vcl::text::Run> runs;
    TextLayoutCache(sal_Unicode const* pStr, sal_Int32 const nEnd);
    // Creates a cached instance.
    static std::shared_ptr<const vcl::text::TextLayoutCache> Create(OUString const&);
};
 
struct FirstCharsStringHash
{
    size_t operator()(const OUString& str) const
    {
        // Strings passed to GenericSalLayout::CreateTextLayoutCache() may be very long,
        // and computing an entire hash could almost negate the gain of hashing. Hash just first
        // characters, that should be good enough.
        size_t hash
            = rtl_ustr_hashCode_WithLength(str.getStr(), std::min<size_t>(100, str.getLength()));
        o3tl::hash_combine(hash, str.getLength());
        return hash;
    }
};
 
struct FastStringCompareEqual
{
    bool operator()(const OUString& str1, const OUString& str2) const
    {
        // Strings passed to GenericSalLayout::CreateTextLayoutCache() may be very long,
        // and OUString operator == compares backwards and using hard-written code, while
        // memcmp() compares much faster.
        if (str1.getLength() != str2.getLength())
            return false;
        if (str1.getStr() == str2.getStr())
            return true;
        return memcmp(str1.getStr(), str2.getStr(), str1.getLength() * sizeof(str1.getStr()[0]))
               == 0;
    }
};
}
 
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