Function ShowExampleAppLongText

src/external/imgui/imgui_demo.cpp:7587–7643

Demonstrate/test rendering huge amount of text, and the incidence of clipping.

// Demonstrate/test rendering huge amount of text, and the incidence of clipping.
static void ShowExampleAppLongText(bool* p_open)
{
    ImGui::SetNextWindowSize(ImVec2(520, 600), ImGuiCond_FirstUseEver);
    if (!ImGui::Begin("Example: Long text display", p_open))
    {
        ImGui::End();
        return;
    }
    IMGUI_DEMO_MARKER("Examples/Long text display");

    static int test_type = 0;
    static ImGuiTextBuffer log;
    static int lines = 0;
    ImGui::Text("Printing unusually long amount of text.");
    ImGui::Combo("Test type", &test_type,
        "Single call to TextUnformatted()\0"
        "Multiple calls to Text(), clipped\0"
        "Multiple calls to Text(), not clipped (slow)\0");
    ImGui::Text("Buffer contents: %d lines, %d bytes", lines, log.size());
    if (ImGui::Button("Clear")) { log.clear(); lines = 0; }
    ImGui::SameLine();
    if (ImGui::Button("Add 1000 lines"))
    {
        for (int i = 0; i < 1000; i++)
            log.appendf("%i The quick brown fox jumps over the lazy dog\n", lines + i);
        lines += 1000;
    }
    ImGui::BeginChild("Log");
    switch (test_type)
    {
    case 0:
        // Single call to TextUnformatted() with a big buffer
        ImGui::TextUnformatted(log.begin(), log.end());
        break;
    case 1:
        {
            // Multiple calls to Text(), manually coarsely clipped - demonstrate how to use the ImGuiListClipper helper.
            ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
            ImGuiListClipper clipper;
            clipper.Begin(lines);
            while (clipper.Step())
                for (int i = clipper.DisplayStart; i < clipper.DisplayEnd; i++)
                    ImGui::Text("%i The quick brown fox jumps over the lazy dog", i);
            ImGui::PopStyleVar();
            break;
        }
    case 2:
        // Multiple calls to Text(), not clipped (slow)
        ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
        for (int i = 0; i < lines; i++)
            ImGui::Text("%i The quick brown fox jumps over the lazy dog", i);
        ImGui::PopStyleVar();
        break;
    }
    ImGui::EndChild();
    ImGui::End();
}