Function InputTextFilterCharacter

src/external/imgui/imgui_widgets.cpp:3918–4017

Return false to discard a character.

// Return false to discard a character.
static bool InputTextFilterCharacter(ImGuiContext* ctx, unsigned int* p_char, ImGuiInputTextFlags flags, ImGuiInputTextCallback callback, void* user_data, ImGuiInputSource input_source)
{
    IM_ASSERT(input_source == ImGuiInputSource_Keyboard || input_source == ImGuiInputSource_Clipboard);
    unsigned int c = *p_char;

    // Filter non-printable (NB: isprint is unreliable! see #2467)
    bool apply_named_filters = true;
    if (c < 0x20)
    {
        bool pass = false;
        pass |= (c == '\n' && (flags & ImGuiInputTextFlags_Multiline)); // Note that an Enter KEY will emit \r and be ignored (we poll for KEY in InputText() code)
        pass |= (c == '\t' && (flags & ImGuiInputTextFlags_AllowTabInput));
        if (!pass)
            return false;
        apply_named_filters = false; // Override named filters below so newline and tabs can still be inserted.
    }

    if (input_source != ImGuiInputSource_Clipboard)
    {
        // We ignore Ascii representation of delete (emitted from Backspace on OSX, see #2578, #2817)
        if (c == 127)
            return false;

        // Filter private Unicode range. GLFW on OSX seems to send private characters for special keys like arrow keys (FIXME)
        if (c >= 0xE000 && c <= 0xF8FF)
            return false;
    }

    // Filter Unicode ranges we are not handling in this build
    if (c > IM_UNICODE_CODEPOINT_MAX)
        return false;

    // Generic named filters
    if (apply_named_filters && (flags & (ImGuiInputTextFlags_CharsDecimal | ImGuiInputTextFlags_CharsHexadecimal | ImGuiInputTextFlags_CharsUppercase | ImGuiInputTextFlags_CharsNoBlank | ImGuiInputTextFlags_CharsScientific)))
    {
        // The libc allows overriding locale, with e.g. 'setlocale(LC_NUMERIC, "de_DE.UTF-8");' which affect the output/input of printf/scanf to use e.g. ',' instead of '.'.
        // The standard mandate that programs starts in the "C" locale where the decimal point is '.'.
        // We don't really intend to provide widespread support for it, but out of empathy for people stuck with using odd API, we support the bare minimum aka overriding the decimal point.
        // Change the default decimal_point with:
        //   ImGui::GetIO()->PlatformLocaleDecimalPoint = *localeconv()->decimal_point;
        // Users of non-default decimal point (in particular ',') may be affected by word-selection logic (is_word_boundary_from_right/is_word_boundary_from_left) functions.
        ImGuiContext& g = *ctx;
        const unsigned c_decimal_point = (unsigned int)g.IO.PlatformLocaleDecimalPoint;
        if (flags & (ImGuiInputTextFlags_CharsDecimal | ImGuiInputTextFlags_CharsScientific))
            if (c == '.' || c == ',')
                c = c_decimal_point;

        // Full-width -> half-width conversion for numeric fields (https://en.wikipedia.org/wiki/Halfwidth_and_Fullwidth_Forms_(Unicode_block)
        // While this is mostly convenient, this has the side-effect for uninformed users accidentally inputting full-width characters that they may
        // scratch their head as to why it works in numerical fields vs in generic text fields it would require support in the font.
        if (flags & (ImGuiInputTextFlags_CharsDecimal | ImGuiInputTextFlags_CharsScientific | ImGuiInputTextFlags_CharsHexadecimal))
            if (c >= 0xFF01 && c <= 0xFF5E)
                c = c - 0xFF01 + 0x21;

        // Allow 0-9 . - + * /
        if (flags & ImGuiInputTextFlags_CharsDecimal)
            if (!(c >= '0' && c <= '9') && (c != c_decimal_point) && (c != '-') && (c != '+') && (c != '*') && (c != '/'))
                return false;