// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.

#include "precomp.h"
#include "inc/CodepointWidthDetector.hpp"

namespace
{
    // used to store range data in CodepointWidthDetector's internal map
    struct UnicodeRange final
    {
        char32_t lowerBound;
        char32_t upperBound : 31;
        char32_t isAmbiguous : 1;
    };

    static bool operator<(const UnicodeRange& range, const unsigned int searchTerm) noexcept
    {
        return range.upperBound < searchTerm;
    }

    // Generated by Generate-CodepointWidthsFromUCD.ps1 -Pack:True -Full: -NoOverrides:False
    // on 2022-11-15 19:54:23Z from Unicode 15.0.0.
    // 321149 (0x4E67D) codepoints covered.
    // 240 (0xF0) codepoints overridden.
    // Override path: .\src\types\unicode_width_overrides.xml
    static constexpr std::array<UnicodeRange, 297> s_wideAndAmbiguousTable{
        UnicodeRange{ 0xa1, 0xa1, 1 },
        UnicodeRange{ 0xa4, 0xa4, 1 },
        UnicodeRange{ 0xa7, 0xa8, 1 },
        UnicodeRange{ 0xaa, 0xaa, 1 },
        UnicodeRange{ 0xad, 0xae, 1 },
        UnicodeRange{ 0xb0, 0xb4, 1 },
        UnicodeRange{ 0xb6, 0xba, 1 },
        UnicodeRange{ 0xbc, 0xbf, 1 },
        UnicodeRange{ 0xc6, 0xc6, 1 },
        UnicodeRange{ 0xd0, 0xd0, 1 },
        UnicodeRange{ 0xd7, 0xd8, 1 },
        UnicodeRange{ 0xde, 0xe1, 1 },
        UnicodeRange{ 0xe6, 0xe6, 1 },
        UnicodeRange{ 0xe8, 0xea, 1 },
        UnicodeRange{ 0xec, 0xed, 1 },
        UnicodeRange{ 0xf0, 0xf0, 1 },
        UnicodeRange{ 0xf2, 0xf3, 1 },
        UnicodeRange{ 0xf7, 0xfa, 1 },
        UnicodeRange{ 0xfc, 0xfc, 1 },
        UnicodeRange{ 0xfe, 0xfe, 1 },
        UnicodeRange{ 0x101, 0x101, 1 },
        UnicodeRange{ 0x111, 0x111, 1 },
        UnicodeRange{ 0x113, 0x113, 1 },
        UnicodeRange{ 0x11b, 0x11b, 1 },
        UnicodeRange{ 0x126, 0x127, 1 },
        UnicodeRange{ 0x12b, 0x12b, 1 },
        UnicodeRange{ 0x131, 0x133, 1 },
        UnicodeRange{ 0x138, 0x138, 1 },
        UnicodeRange{ 0x13f, 0x142, 1 },
        UnicodeRange{ 0x144, 0x144, 1 },
        UnicodeRange{ 0x148, 0x14b, 1 },
        UnicodeRange{ 0x14d, 0x14d, 1 },
        UnicodeRange{ 0x152, 0x153, 1 },
        UnicodeRange{ 0x166, 0x167, 1 },
        UnicodeRange{ 0x16b, 0x16b, 1 },
        UnicodeRange{ 0x1ce, 0x1ce, 1 },
        UnicodeRange{ 0x1d0, 0x1d0, 1 },
        UnicodeRange{ 0x1d2, 0x1d2, 1 },
        UnicodeRange{ 0x1d4, 0x1d4, 1 },
        UnicodeRange{ 0x1d6, 0x1d6, 1 },
        UnicodeRange{ 0x1d8, 0x1d8, 1 },
        UnicodeRange{ 0x1da, 0x1da, 1 },
        UnicodeRange{ 0x1dc, 0x1dc, 1 },
        UnicodeRange{ 0x251, 0x251, 1 },
        UnicodeRange{ 0x261, 0x261, 1 },
        UnicodeRange{ 0x2c4, 0x2c4, 1 },
        UnicodeRange{ 0x2c7, 0x2c7, 1 },
        UnicodeRange{ 0x2c9, 0x2cb, 1 },
        UnicodeRange{ 0x2cd, 0x2cd, 1 },
        UnicodeRange{ 0x2d0, 0x2d0, 1 },
        UnicodeRange{ 0x2d8, 0x2db, 1 },
        UnicodeRange{ 0x2dd, 0x2dd, 1 },
        UnicodeRange{ 0x2df, 0x2df, 1 },
        UnicodeRange{ 0x300, 0x36f, 1 },
        UnicodeRange{ 0x391, 0x3a1, 1 },
        UnicodeRange{ 0x3a3, 0x3a9, 1 },
        UnicodeRange{ 0x3b1, 0x3c1, 1 },
        UnicodeRange{ 0x3c3, 0x3c9, 1 },
        UnicodeRange{ 0x401, 0x401, 1 },
        UnicodeRange{ 0x410, 0x44f, 1 },
        UnicodeRange{ 0x451, 0x451, 1 },
        UnicodeRange{ 0x1100, 0x115f, 0 },
        UnicodeRange{ 0x2010, 0x2010, 1 },
        UnicodeRange{ 0x2013, 0x2016, 1 },
        UnicodeRange{ 0x2018, 0x2019, 1 },
        UnicodeRange{ 0x201c, 0x201d, 1 },
        UnicodeRange{ 0x2020, 0x2022, 1 },
        UnicodeRange{ 0x2024, 0x2027, 1 },
        UnicodeRange{ 0x2030, 0x2030, 1 },
        UnicodeRange{ 0x2032, 0x2033, 1 },
        UnicodeRange{ 0x2035, 0x2035, 1 },
        UnicodeRange{ 0x203b, 0x203b, 1 },
        UnicodeRange{ 0x203e, 0x203e, 1 },
        UnicodeRange{ 0x2074, 0x2074, 1 },
        UnicodeRange{ 0x207f, 0x207f, 1 },
        UnicodeRange{ 0x2081, 0x2084, 1 },
        UnicodeRange{ 0x20ac, 0x20ac, 1 },
        UnicodeRange{ 0x2103, 0x2103, 1 },
        UnicodeRange{ 0x2105, 0x2105, 1 },
        UnicodeRange{ 0x2109, 0x2109, 1 },
        UnicodeRange{ 0x2113, 0x2113, 1 },
        UnicodeRange{ 0x2116, 0x2116, 1 },
        UnicodeRange{ 0x2121, 0x2122, 1 },
        UnicodeRange{ 0x2126, 0x2126, 1 },
        UnicodeRange{ 0x212b, 0x212b, 1 },
        UnicodeRange{ 0x2153, 0x2154, 1 },
        UnicodeRange{ 0x215b, 0x215e, 1 },
        UnicodeRange{ 0x2160, 0x216b, 1 },
        UnicodeRange{ 0x2170, 0x2179, 1 },
        UnicodeRange{ 0x2189, 0x2189, 1 },
        UnicodeRange{ 0x2190, 0x2199, 1 },
        UnicodeRange{ 0x21b8, 0x21b9, 1 },
        UnicodeRange{ 0x21d2, 0x21d2, 1 },
        UnicodeRange{ 0x21d4, 0x21d4, 1 },
        UnicodeRange{ 0x21e7, 0x21e7, 1 },
        UnicodeRange{ 0x2200, 0x2200, 1 },
        UnicodeRange{ 0x2202, 0x2203, 1 },
        UnicodeRange{ 0x2207, 0x2208, 1 },
        UnicodeRange{ 0x220b, 0x220b, 1 },
        UnicodeRange{ 0x220f, 0x220f, 1 },
        UnicodeRange{ 0x2211, 0x2211, 1 },
        UnicodeRange{ 0x2215, 0x2215, 1 },
        UnicodeRange{ 0x221a, 0x221a, 1 },
        UnicodeRange{ 0x221d, 0x2220, 1 },
        UnicodeRange{ 0x2223, 0x2223, 1 },
        UnicodeRange{ 0x2225, 0x2225, 1 },
        UnicodeRange{ 0x2227, 0x222c, 1 },
        UnicodeRange{ 0x222e, 0x222e, 1 },
        UnicodeRange{ 0x2234, 0x2237, 1 },
        UnicodeRange{ 0x223c, 0x223d, 1 },
        UnicodeRange{ 0x2248, 0x2248, 1 },
        UnicodeRange{ 0x224c, 0x224c, 1 },
        UnicodeRange{ 0x2252, 0x2252, 1 },
        UnicodeRange{ 0x2260, 0x2261, 1 },
        UnicodeRange{ 0x2264, 0x2267, 1 },
        UnicodeRange{ 0x226a, 0x226b, 1 },
        UnicodeRange{ 0x226e, 0x226f, 1 },
        UnicodeRange{ 0x2282, 0x2283, 1 },
        UnicodeRange{ 0x2286, 0x2287, 1 },
        UnicodeRange{ 0x2295, 0x2295, 1 },
        UnicodeRange{ 0x2299, 0x2299, 1 },
        UnicodeRange{ 0x22a5, 0x22a5, 1 },
        UnicodeRange{ 0x22bf, 0x22bf, 1 },
        UnicodeRange{ 0x2312, 0x2312, 1 },
        UnicodeRange{ 0x231a, 0x231b, 0 },
        UnicodeRange{ 0x2329, 0x232a, 0 },
        UnicodeRange{ 0x23e9, 0x23ec, 0 },
        UnicodeRange{ 0x23f0, 0x23f0, 0 },
        UnicodeRange{ 0x23f3, 0x23f3, 0 },
        UnicodeRange{ 0x2460, 0x24e9, 1 },
        UnicodeRange{ 0x24eb, 0x24ff, 1 },
        UnicodeRange{ 0x25a0, 0x25a1, 1 },
        UnicodeRange{ 0x25a3, 0x25a9, 1 },
        UnicodeRange{ 0x25b2, 0x25b3, 1 },
        UnicodeRange{ 0x25b6, 0x25b7, 1 },
        UnicodeRange{ 0x25bc, 0x25bd, 1 },
        UnicodeRange{ 0x25c0, 0x25c1, 1 },
        UnicodeRange{ 0x25c6, 0x25c8, 1 },
        UnicodeRange{ 0x25cb, 0x25cb, 1 },
        UnicodeRange{ 0x25ce, 0x25d1, 1 },
        UnicodeRange{ 0x25e2, 0x25e5, 1 },
        UnicodeRange{ 0x25ef, 0x25ef, 1 },
        UnicodeRange{ 0x25fd, 0x25fe, 0 },
        UnicodeRange{ 0x2605, 0x2606, 1 },
        UnicodeRange{ 0x2609, 0x2609, 1 },
        UnicodeRange{ 0x260e, 0x260f, 1 },
        UnicodeRange{ 0x2614, 0x2615, 0 },
        UnicodeRange{ 0x261c, 0x261c, 1 },
        UnicodeRange{ 0x261e, 0x261e, 1 },
        UnicodeRange{ 0x2640, 0x2640, 1 },
        UnicodeRange{ 0x2642, 0x2642, 1 },
        UnicodeRange{ 0x2648, 0x2653, 0 },
        UnicodeRange{ 0x2660, 0x2661, 1 },
        UnicodeRange{ 0x2663, 0x2665, 1 },
        UnicodeRange{ 0x2667, 0x266a, 1 },
        UnicodeRange{ 0x266c, 0x266d, 1 },
        UnicodeRange{ 0x266f, 0x266f, 1 },
        UnicodeRange{ 0x267f, 0x267f, 0 },
        UnicodeRange{ 0x2693, 0x2693, 0 },
        UnicodeRange{ 0x269e, 0x269f, 1 },
        UnicodeRange{ 0x26a1, 0x26a1, 0 },
        UnicodeRange{ 0x26aa, 0x26ab, 0 },
        UnicodeRange{ 0x26bd, 0x26be, 0 },
        UnicodeRange{ 0x26bf, 0x26bf, 1 },
        UnicodeRange{ 0x26c4, 0x26c5, 0 },
        UnicodeRange{ 0x26c6, 0x26cd, 1 },
        UnicodeRange{ 0x26ce, 0x26ce, 0 },
        UnicodeRange{ 0x26cf, 0x26d3, 1 },
        UnicodeRange{ 0x26d4, 0x26d4, 0 },
        UnicodeRange{ 0x26d5, 0x26e1, 1 },
        UnicodeRange{ 0x26e3, 0x26e3, 1 },
        UnicodeRange{ 0x26e8, 0x26e9, 1 },
        UnicodeRange{ 0x26ea, 0x26ea, 0 },
        UnicodeRange{ 0x26eb, 0x26f1, 1 },
        UnicodeRange{ 0x26f2, 0x26f3, 0 },
        UnicodeRange{ 0x26f4, 0x26f4, 1 },
        UnicodeRange{ 0x26f5, 0x26f5, 0 },
        UnicodeRange{ 0x26f6, 0x26f9, 1 },
        UnicodeRange{ 0x26fa, 0x26fa, 0 },
        UnicodeRange{ 0x26fb, 0x26fc, 1 },
        UnicodeRange{ 0x26fd, 0x26fd, 0 },
        UnicodeRange{ 0x26fe, 0x26ff, 1 },
        UnicodeRange{ 0x2705, 0x2705, 0 },
        UnicodeRange{ 0x270a, 0x270b, 0 },
        UnicodeRange{ 0x2728, 0x2728, 0 },
        UnicodeRange{ 0x273d, 0x273d, 1 },
        UnicodeRange{ 0x274c, 0x274c, 0 },
        UnicodeRange{ 0x274e, 0x274e, 0 },
        UnicodeRange{ 0x2753, 0x2755, 0 },
        UnicodeRange{ 0x2757, 0x2757, 0 },
        UnicodeRange{ 0x2776, 0x277f, 1 },
        UnicodeRange{ 0x2795, 0x2797, 0 },
        UnicodeRange{ 0x27b0, 0x27b0, 0 },
        UnicodeRange{ 0x27bf, 0x27bf, 0 },
        UnicodeRange{ 0x2b1b, 0x2b1c, 0 },
        UnicodeRange{ 0x2b50, 0x2b50, 0 },
        UnicodeRange{ 0x2b55, 0x2b55, 0 },
        UnicodeRange{ 0x2b56, 0x2b59, 1 },
        UnicodeRange{ 0x2e80, 0x2e99, 0 },
        UnicodeRange{ 0x2e9b, 0x2ef3, 0 },
        UnicodeRange{ 0x2f00, 0x2fd5, 0 },
        UnicodeRange{ 0x2ff0, 0x2ffb, 0 },
        UnicodeRange{ 0x3000, 0x303e, 0 },
        UnicodeRange{ 0x3041, 0x3096, 0 },
        UnicodeRange{ 0x3099, 0x30ff, 0 },
        UnicodeRange{ 0x3105, 0x312f, 0 },
        UnicodeRange{ 0x3131, 0x318e, 0 },
        UnicodeRange{ 0x3190, 0x31e3, 0 },
        UnicodeRange{ 0x31f0, 0x321e, 0 },
        UnicodeRange{ 0x3220, 0x3247, 0 },
        UnicodeRange{ 0x3248, 0x324f, 1 },
        UnicodeRange{ 0x3250, 0x4dbf, 0 },
        UnicodeRange{ 0x4e00, 0xa48c, 0 },
        UnicodeRange{ 0xa490, 0xa4c6, 0 },
        UnicodeRange{ 0xa960, 0xa97c, 0 },
        UnicodeRange{ 0xac00, 0xd7a3, 0 },
        UnicodeRange{ 0xe000, 0xf8ff, 1 },
        UnicodeRange{ 0xf900, 0xfaff, 0 },
        UnicodeRange{ 0xfe00, 0xfe0f, 1 },
        UnicodeRange{ 0xfe10, 0xfe19, 0 },
        UnicodeRange{ 0xfe30, 0xfe52, 0 },
        UnicodeRange{ 0xfe54, 0xfe66, 0 },
        UnicodeRange{ 0xfe68, 0xfe6b, 0 },
        UnicodeRange{ 0xff01, 0xff60, 0 },
        UnicodeRange{ 0xffe0, 0xffe6, 0 },
        UnicodeRange{ 0xfffd, 0xfffd, 1 },
        UnicodeRange{ 0x16fe0, 0x16fe4, 0 },
        UnicodeRange{ 0x16ff0, 0x16ff1, 0 },
        UnicodeRange{ 0x17000, 0x187f7, 0 },
        UnicodeRange{ 0x18800, 0x18cd5, 0 },
        UnicodeRange{ 0x18d00, 0x18d08, 0 },
        UnicodeRange{ 0x1aff0, 0x1aff3, 0 },
        UnicodeRange{ 0x1aff5, 0x1affb, 0 },
        UnicodeRange{ 0x1affd, 0x1affe, 0 },
        UnicodeRange{ 0x1b000, 0x1b122, 0 },
        UnicodeRange{ 0x1b132, 0x1b132, 0 },
        UnicodeRange{ 0x1b150, 0x1b152, 0 },
        UnicodeRange{ 0x1b155, 0x1b155, 0 },
        UnicodeRange{ 0x1b164, 0x1b167, 0 },
        UnicodeRange{ 0x1b170, 0x1b2fb, 0 },
        UnicodeRange{ 0x1f004, 0x1f004, 0 },
        UnicodeRange{ 0x1f0cf, 0x1f0cf, 0 },
        UnicodeRange{ 0x1f100, 0x1f10a, 1 },
        UnicodeRange{ 0x1f110, 0x1f12d, 1 },
        UnicodeRange{ 0x1f130, 0x1f169, 1 },
        UnicodeRange{ 0x1f170, 0x1f18d, 1 },
        UnicodeRange{ 0x1f18e, 0x1f18e, 0 },
        UnicodeRange{ 0x1f18f, 0x1f190, 1 },
        UnicodeRange{ 0x1f191, 0x1f19a, 0 },
        UnicodeRange{ 0x1f19b, 0x1f1ac, 1 },
        UnicodeRange{ 0x1f1e6, 0x1f202, 0 },
        UnicodeRange{ 0x1f210, 0x1f23b, 0 },
        UnicodeRange{ 0x1f240, 0x1f248, 0 },
        UnicodeRange{ 0x1f250, 0x1f251, 0 },
        UnicodeRange{ 0x1f260, 0x1f265, 0 },
        UnicodeRange{ 0x1f300, 0x1f320, 0 },
        UnicodeRange{ 0x1f32d, 0x1f335, 0 },
        UnicodeRange{ 0x1f337, 0x1f37c, 0 },
        UnicodeRange{ 0x1f37e, 0x1f393, 0 },
        UnicodeRange{ 0x1f3a0, 0x1f3ca, 0 },
        UnicodeRange{ 0x1f3cf, 0x1f3d3, 0 },
        UnicodeRange{ 0x1f3e0, 0x1f3f0, 0 },
        UnicodeRange{ 0x1f3f4, 0x1f3f4, 0 },
        UnicodeRange{ 0x1f3f8, 0x1f43e, 0 },
        UnicodeRange{ 0x1f440, 0x1f440, 0 },
        UnicodeRange{ 0x1f442, 0x1f4fc, 0 },
        UnicodeRange{ 0x1f4ff, 0x1f53d, 0 },
        UnicodeRange{ 0x1f54b, 0x1f54e, 0 },
        UnicodeRange{ 0x1f550, 0x1f567, 0 },
        UnicodeRange{ 0x1f57a, 0x1f57a, 0 },
        UnicodeRange{ 0x1f595, 0x1f596, 0 },
        UnicodeRange{ 0x1f5a4, 0x1f5a4, 0 },
        UnicodeRange{ 0x1f5fb, 0x1f64f, 0 },
        UnicodeRange{ 0x1f680, 0x1f6c5, 0 },
        UnicodeRange{ 0x1f6cc, 0x1f6cc, 0 },
        UnicodeRange{ 0x1f6d0, 0x1f6d2, 0 },
        UnicodeRange{ 0x1f6d5, 0x1f6d7, 0 },
        UnicodeRange{ 0x1f6dc, 0x1f6df, 0 },
        UnicodeRange{ 0x1f6eb, 0x1f6ec, 0 },
        UnicodeRange{ 0x1f6f4, 0x1f6fc, 0 },
        UnicodeRange{ 0x1f7e0, 0x1f7eb, 0 },
        UnicodeRange{ 0x1f7f0, 0x1f7f0, 0 },
        UnicodeRange{ 0x1f90c, 0x1f93a, 0 },
        UnicodeRange{ 0x1f93c, 0x1f945, 0 },
        UnicodeRange{ 0x1f947, 0x1f9ff, 0 },
        UnicodeRange{ 0x1fa70, 0x1fa7c, 0 },
        UnicodeRange{ 0x1fa80, 0x1fa88, 0 },
        UnicodeRange{ 0x1fa90, 0x1fabd, 0 },
        UnicodeRange{ 0x1fabf, 0x1fac5, 0 },
        UnicodeRange{ 0x1face, 0x1fadb, 0 },
        UnicodeRange{ 0x1fae0, 0x1fae8, 0 },
        UnicodeRange{ 0x1faf0, 0x1faf8, 0 },
        UnicodeRange{ 0x20000, 0x2fffd, 0 },
        UnicodeRange{ 0x30000, 0x3fffd, 0 },
        UnicodeRange{ 0xe0100, 0xe01ef, 1 },
        UnicodeRange{ 0xf0000, 0xffffd, 1 },
        UnicodeRange{ 0x100000, 0x10fffd, 1 },
    };
}

// Routine Description:
// - returns the width type of codepoint as fast as we can by using quick lookup table and fallback cache.
// Arguments:
// - glyph - the utf16 encoded codepoint to search for
// Return Value:
// - the width type of the codepoint
CodepointWidth CodepointWidthDetector::GetWidth(const std::wstring_view& glyph) noexcept
{
    char32_t codepoint = 0;

    switch (glyph.size())
    {
    case 1:
        codepoint = til::at(glyph, 0);
        break;
    case 2:
        codepoint = (til::at(glyph, 0) & 0x3FF) << 10;
        codepoint |= til::at(glyph, 1) & 0x3FF;
        codepoint += 0x10000;
        break;
    default:
        codepoint = 0;
        break;
    }

    if (codepoint < 0x80)
    {
        return CodepointWidth::Narrow;
    }

    // The return value of _lookupGlyphWidth coincides with the enum value of CodepointWidth
    // on purpose to allow for this easy conversion to happen. Optimally, we should probably
    // remove CodepointWidth altogether to allow for zero-width joiners and other characters.
    static_assert(WI_EnumValue(CodepointWidth::Narrow) == 1);
    static_assert(WI_EnumValue(CodepointWidth::Wide) == 2);
    return static_cast<CodepointWidth>(_lookupGlyphWidth(codepoint, glyph));
}

// Routine Description:
// - checks if codepoint is wide. will attempt to fallback as much possible until an answer is determined
// Arguments:
// - glyph - the utf16 encoded codepoint to check width of
// Return Value:
// - true if codepoint is wide
bool CodepointWidthDetector::IsWide(const std::wstring_view& glyph) noexcept
{
    return GetWidth(glyph) == CodepointWidth::Wide;
}

// GetWidth's slow-path for non-ASCII characters. Returns the number of columns the codepoint takes up in the terminal.
uint8_t CodepointWidthDetector::_lookupGlyphWidth(const char32_t codepoint, const std::wstring_view& glyph) noexcept
{
#pragma warning(suppress : 26447) // The function is declared 'noexcept' but calls function 'lower_bound<...>()' which may throw exceptions (f.6).
    const auto it = std::lower_bound(s_wideAndAmbiguousTable.begin(), s_wideAndAmbiguousTable.end(), codepoint);
    uint8_t width = 1;

    if (it != s_wideAndAmbiguousTable.end() && codepoint >= it->lowerBound && codepoint <= it->upperBound)
    {
        width = 2;
        if (it->isAmbiguous)
        {
            width = _checkFallbackViaCache(codepoint, glyph);
        }
    }

    return width;
}

// Call the function specified via SetFallbackMethod() to turn CodepointWidth::Ambiguous into Narrow/Wide.
// Caches the results in _fallbackCache. This is _lookupGlyphWidth's even-slower-path.
uint8_t CodepointWidthDetector::_checkFallbackViaCache(const char32_t codepoint, const std::wstring_view& glyph) noexcept
try
{
    // Ambiguous glyphs are considered narrow by default. See microsoft/terminal#2066 for more info.
    if (!_pfnFallbackMethod)
    {
        return 1;
    }

    if (const auto it = _fallbackCache.find(codepoint); it != _fallbackCache.end())
    {
        return it->second;
    }

    const uint8_t width = _pfnFallbackMethod(glyph) ? 2 : 1;
    _fallbackCache.insert_or_assign(codepoint, width);
    return width;
}
catch (...)
{
    LOG_CAUGHT_EXCEPTION();
    return 1;
}

// Method Description:
// - Sets a function that should be used as the fallback mechanism for
//      determining a particular glyph's width, should the glyph be an ambiguous
//      width.
//   A Terminal could hook in a Renderer's IsGlyphWideByFont method as the
//      fallback to ask the renderer for the glyph's width (for example).
// Arguments:
// - pfnFallback - the function to use as the fallback method.
// Return Value:
// - <none>
void CodepointWidthDetector::SetFallbackMethod(std::function<bool(const std::wstring_view&)> pfnFallback) noexcept
{
    _pfnFallbackMethod = std::move(pfnFallback);
}

// Method Description:
// - Resets the internal ambiguous character width cache mechanism
//   since it will be different when the font changes and we should
//   re-query the new font for that information.
// Arguments:
// - <none>
// Return Value:
// - <none>
void CodepointWidthDetector::NotifyFontChanged() noexcept
{
#pragma warning(suppress : 26447) // The function is declared 'noexcept' but calls function 'clear()' which may throw exceptions (f.6).
    _fallbackCache.clear();
}
