Method FindPlatformMonitorForRect

imgui_tiny_app/imgui/imgui.cpp:17557–17586

Search for the monitor with the largest intersection area with the given rectangle We generally try to avoid searching loops but the monitor count should be very small here FIXME-OPT: We could test the last monitor used for that viewport first, and early

// We generally try to avoid searching loops but the monitor count should be very small here
// FIXME-OPT: We could test the last monitor used for that viewport first, and early
static int ImGui::FindPlatformMonitorForRect(const ImRect& rect)
{
    ImGuiContext& g = *GImGui;

    const int monitor_count = g.PlatformIO.Monitors.Size;
    if (monitor_count <= 1)
        return monitor_count - 1;

    // Use a minimum threshold of 1.0f so a zero-sized rect won't false positive, and will still find the correct monitor given its position.
    // This is necessary for tooltips which always resize down to zero at first.
    const float surface_threshold = ImMax(rect.GetWidth() * rect.GetHeight() * 0.5f, 1.0f);
    int best_monitor_n = 0; // Default to the first monitor as fallback
    float best_monitor_surface = 0.001f;

    for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size && best_monitor_surface < surface_threshold; monitor_n++)
    {
        const ImGuiPlatformMonitor& monitor = g.PlatformIO.Monitors[monitor_n];
        const ImRect monitor_rect = ImRect(monitor.MainPos, monitor.MainPos + monitor.MainSize);
        if (monitor_rect.Contains(rect))
            return monitor_n;
        ImRect overlapping_rect = rect;
        overlapping_rect.ClipWithFull(monitor_rect);
        float overlapping_surface = overlapping_rect.GetWidth() * overlapping_rect.GetHeight();
        if (overlapping_surface < best_monitor_surface)
            continue;
        best_monitor_surface = overlapping_surface;
        best_monitor_n = monitor_n;
    }
    return best_monitor_n;
}

// Update monitor from viewport rectangle (we'll use this info to clamp windows and save windows lost in a removed monitor)
static void ImGui::UpdateViewportPlatformMonitor(ImGuiViewportP* viewport)