logger.cpp

#include <imgui.h>

struct AppLog
{
    ImGuiTextBuffer     Buf;
    ImGuiTextFilter     Filter;
    ImVector<int>       LineOffsets;        // Index to lines offset
    bool                ScrollToBottom;

    void    Clear()     { Buf.clear(); LineOffsets.clear(); }

    void    AddLog(const char* fmt, ...)
    {
        int old_size = Buf.size();
        va_list args;
        va_start(args, fmt);
        Buf.appendv(fmt, args);
        va_end(args);
        for (int new_size = Buf.size(); old_size < new_size; old_size++)
            if (Buf[old_size] == '\n')
                LineOffsets.push_back(old_size);
        ScrollToBottom = true;
    }

    void    Draw(const char* title, bool* p_open = NULL)
    {
        ImGui::SetNextWindowSize(ImVec2(500,400), ImGuiSetCond_FirstUseEver);
        ImGui::Begin(title);
        if (ImGui::Button("Clear")) Clear();
        ImGui::SameLine();
        bool copy = ImGui::Button("Copy");
        ImGui::SameLine();
        Filter.Draw("Filter", -100.0f);
        ImGui::Separator();
        ImGui::BeginChild("scrolling", ImVec2(0,0), false, ImGuiWindowFlags_HorizontalScrollbar);
        if (copy) ImGui::LogToClipboard();

        if (Filter.IsActive())
        {
            const char* buf_begin = Buf.begin();
            const char* line = buf_begin;
            for (int line_no = 0; line != NULL; line_no++)
            {
                const char* line_end = (line_no < LineOffsets.Size) ? buf_begin + LineOffsets[line_no] : NULL;
                if (Filter.PassFilter(line, line_end))
                    ImGui::TextUnformatted(line, line_end);
                line = line_end && line_end[1] ? line_end + 1 : NULL;
            }
        }
        else
        {
            ImGui::TextUnformatted(Buf.begin());
        }

        if (ScrollToBottom)
            ImGui::SetScrollHere(1.0f);
        ScrollToBottom = false;
        ImGui::EndChild();
        ImGui::End();
    }
};