Method NavProcessItem

src/imgui/imgui.cpp:13084–13158

We get there when either NavId == id, or when g.NavAnyRequest is set (which is updated by NavUpdateAnyRequestFlag above) This is called after LastItemData is set, but NextItemData is also still valid.

// We get there when either NavId == id, or when g.NavAnyRequest is set (which is updated by NavUpdateAnyRequestFlag above)
// This is called after LastItemData is set, but NextItemData is also still valid.
static void ImGui::NavProcessItem()
{
    ImGuiContext& g = *GImGui;
    ImGuiWindow* window = g.CurrentWindow;
    const ImGuiID id = g.LastItemData.ID;
    const ImGuiItemFlags item_flags = g.LastItemData.ItemFlags;

    // When inside a container that isn't scrollable with Left<>Right, clip NavRect accordingly (#2221, #8816)
    ImRect nav_bb = g.LastItemData.NavRect;
    if (window->DC.NavIsScrollPushableX == false)
    {
        nav_bb.Min.x = ImClamp(nav_bb.Min.x, window->ClipRect.Min.x, window->ClipRect.Max.x);
        nav_bb.Max.x = ImClamp(nav_bb.Max.x, window->ClipRect.Min.x, window->ClipRect.Max.x);
    }

    // Process Init Request
    if (g.NavInitRequest && g.NavLayer == window->DC.NavLayerCurrent && (item_flags & ImGuiItemFlags_Disabled) == 0)
    {
        // Even if 'ImGuiItemFlags_NoNavDefaultFocus' is on (typically collapse/close button) we record the first ResultId so they can be used as a fallback
        const bool candidate_for_nav_default_focus = (item_flags & ImGuiItemFlags_NoNavDefaultFocus) == 0;
        if (candidate_for_nav_default_focus || g.NavInitResult.ID == 0)
        {
            NavApplyItemToResult(&g.NavInitResult);
        }
        if (candidate_for_nav_default_focus)
        {
            g.NavInitRequest = false; // Found a match, clear request
            NavUpdateAnyRequestFlag();
        }
    }

    // Process Move Request (scoring for navigation)
    // FIXME-NAV: Consider policy for double scoring (scoring from NavScoringRect + scoring from a rect wrapped according to current wrapping policy)
    if (g.NavMoveScoringItems && (item_flags & ImGuiItemFlags_Disabled) == 0)
    {
        if ((g.NavMoveFlags & ImGuiNavMoveFlags_FocusApi) || (window->Flags & ImGuiWindowFlags_NoNavInputs) == 0)
        {
            const bool is_tabbing = (g.NavMoveFlags & ImGuiNavMoveFlags_IsTabbing) != 0;
            if (is_tabbing)
            {
                NavProcessItemForTabbingRequest(id, item_flags, g.NavMoveFlags);
            }
            else if (g.NavId != id || (g.NavMoveFlags & ImGuiNavMoveFlags_AllowCurrentNavId))
            {
                ImGuiNavItemData* result = (window == g.NavWindow) ? &g.NavMoveResultLocal : &g.NavMoveResultOther;
                if (NavScoreItem(result, nav_bb))
                    NavApplyItemToResult(result);

                // Features like PageUp/PageDown need to maintain a separate score for the visible set of items.
                const float VISIBLE_RATIO = 0.70f;
                if ((g.NavMoveFlags & ImGuiNavMoveFlags_AlsoScoreVisibleSet) && window->ClipRect.Overlaps(nav_bb))
                    if (ImClamp(nav_bb.Max.y, window->ClipRect.Min.y, window->ClipRect.Max.y) - ImClamp(nav_bb.Min.y, window->ClipRect.Min.y, window->ClipRect.Max.y) >= (nav_bb.Max.y - nav_bb.Min.y) * VISIBLE_RATIO)
                        if (NavScoreItem(&g.NavMoveResultLocalVisible, nav_bb))
                            NavApplyItemToResult(&g.NavMoveResultLocalVisible);
            }
        }
    }