mmd-pdf/Controls/Viewer/PdfViewer.PageSelection.cs

using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Text.Json;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using Docnet.Core;
using Docnet.Core.Models;
using Microsoft.Win32;
using PdfSharpCore.Drawing;
using PdfSharpCore.Pdf;
using PdfSharpCore.Pdf.IO;
using MmdPdf.Services;
using PdfPigDoc = UglyToad.PdfPig.PdfDocument;

namespace MmdPdf.Controls
{
    // Moved from Shell/PageSelection.cs; the namespace and class line are the only changes. Window
    // members spelled bare here resolve through PdfViewer.Bridge.cs.
    public partial class PdfViewer
    {
        // ============================================================
        // Page selection handler
        // ============================================================

        private void PageList_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
        {
            // Same speed knob as the document viewport (WheelScrollFactor in Zoom.cs).
            Host?.ScrollSidebar(this, -e.Delta * (48.0 / 120.0) * Controls.PdfViewer.WheelScrollFactor);
            e.Handled = true;
        }

        private void PageJumpBox_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key != Key.Enter || _doc is null) return;
            e.Handled = true;
            if (int.TryParse(Host?.PageJumpText, out int pg))
            {
                int idx = Math.Max(0, Math.Min(_doc.PageCount - 1, pg - 1));
                RecordNavJump();   // Alt+Left retraces the typed jump
                _currentPage = idx;
            }
            else
            {
                // Restore current page number if input was invalid
                if (Host != null) Host.PageJumpText = (_currentPage + 1).ToString();
            }
            Keyboard.ClearFocus();
        }

        private void PageJumpBox_GotFocus(object sender, RoutedEventArgs e)
        {
            Host?.SelectAllPageJumpText();
        }

        /// <summary>Set by SyncCurrentPageTo (and only it) around its programmatic SelectedIndex
        /// write, so the scroll-driven sync does not re-enter the render path through the window's
        /// XAML-bound handler. Replaces the old detach/attach of a cached delegate, which never
        /// worked: the list's real subscription is the WINDOW stub, so the -= removed nothing and
        /// the += accumulated direct subscriptions (2026-08-01).</summary>
        private bool _syncingPageList;

        private void PageList_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (_syncingPageList) return;   // programmatic sync, not a user selection
            // The sidebar page list is WINDOW chrome - there is one of it, and BOTH panes attach
            // their own handler to it. It describes the focused pane only, so the other pane has
            // to sit this out. Scrolling a pane calls SyncCurrentPageTo, which detaches its OWN
            // handler before setting SelectedIndex to avoid re-entering the render path; the other
            // pane's handler stayed attached and navigated that pane to the page you had just
            // scrolled to in this one, which is why scrolling pane A scrolled pane B.
            if (Host != null && !Host.IsViewerFocused(this)) return;

            // Mirror the sidebar into the view's own current page. Set
            // BEFORE the >= 0 guard on purpose - clearing the list (tab close, document close)
            // drops SelectedIndex to -1 and that has to be mirrored too, or a closed document
            // leaves a stale page number behind. Assigns _view.CurrentPage directly rather than
            // going through _currentPage, whose setter would write back into PageList and re-enter
            // this handler.
            State.CurrentPage = (sender as ListBox)?.SelectedIndex ?? -1;

            if (_currentPage >= 0)
            {
                CommitActiveTextBox();
                ClearSelection();
                ClearTextSelection();
                Host?.EnsureSidebarPageVisible(this, _currentPage);
                if (_viewMode == ViewMode.Continuous)
                {
                    if (Host != null) Host.PageJumpText = (_currentPage + 1).ToString();
                    ScrollContinuousToPage(_currentPage);
                    return;
                }
                if (_viewMode == ViewMode.Grid)
                {
                    // Grid is a stable overview: selecting a page highlights it but must NOT
                    // re-anchor the grid. It still needs an initial render (open / first display)
                    // when no tiles exist yet; later selections only update the highlight.
                    if (Host != null) Host.PageJumpText = (_currentPage + 1).ToString();
                    // Keep the statusbar counter honest even when the clicked tile is already in
                    // view (BringIntoView then scrolls nothing, so the scroll-sync never fires).
                    SetStatus(string.Format(Loc("Str_PageOf"), _currentPage + 1, _doc!.PageCount) + $" - {DisplayZoomPct():F0}%");
                    if (_pageContentPanel.Children.Count <= 1)
                    {
                        PagePreviewPanel.ScrollToTop();
                        PagePreviewPanel.ScrollToHorizontalOffset(0);
                        RenderPage(0);   // grid primary is always page 0
                        // Default the grid to a clean 3-columns-across fit. Deferred to Loaded so the
                        // viewport width is valid (it can still be 0 mid-open, which would fall back
                        // to a carried-over zoom and show a single large page).
                        Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Loaded,
                            (Action)(() => SetZoom(GridZoomForN(Math.Min(_doc?.PageCount ?? 1, 3)))));
                    }
                    else if (_currentPage < _pageContentPanel.Children.Count
                             && _pageContentPanel.Children[_currentPage] is FrameworkElement gridTile)
                    {
                        // Scroll the chosen page's tile into view (BringIntoView accounts for the zoom transform).
                        gridTile.BringIntoView();
                    }
                    return;
                }
                // Clicking either page of the spread that's already shown (or re-selecting the
                // current single page) renders the exact same pixels, so skip the re-render and its
                // flash - just move the page number. SpreadStart, NOT a local % 2: this was the
                // fourth pairing site and the one #193's book layout missed - its stale (0,1)
                // pairing matched the rendered cover and swallowed the render of spread (1,2).
                int targetPrimary = _currentPage;
                if (_viewMode == ViewMode.TwoPage) targetPrimary = SpreadStart(targetPrimary);
                if (targetPrimary == _renderedPrimaryPage && Math.Abs(_zoomLevel - _lastRenderZoom) < 0.0001)
                {
                    if (Host != null) Host.PageJumpText = (_currentPage + 1).ToString();
                    return;
                }
                PagePreviewPanel.ScrollToTop();
                PagePreviewPanel.ScrollToHorizontalOffset(0);
                RenderPage(_currentPage);
                ApplyZoom();
                // Update page jump box
                if (Host != null) Host.PageJumpText = (_currentPage + 1).ToString();
                // Re-highlight search results on this page if a search is active
                if (_searchBar is not null && _searchBar.Visibility == Visibility.Visible
                    && Search.HasResults)
                    HighlightSearchResultsOnCurrentPage();
            }
        }

        private void ShortcutHelp_Click(object sender, RoutedEventArgs e)
        {
            if (ShortcutOverlay.Visibility == Visibility.Visible) FadeOverlayOut(ShortcutOverlay);
            else ShowShortcutsOverlayExclusive();
        }

        private void ShortcutOverlay_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            // Click on the dim backdrop closes the overlay.
            FadeOverlayOut(ShortcutOverlay);
        }

        private void ShortcutOverlayCard_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            // Stop the click from bubbling up to the backdrop handler.
            e.Handled = true;
        }

        private void ShortcutOverlayClose_Click(object sender, RoutedEventArgs e)
        {
            FadeOverlayOut(ShortcutOverlay);
        }

        private void Hyperlink_RequestNavigate(object sender, System.Windows.Navigation.RequestNavigateEventArgs e)
        {
            Process.Start(new ProcessStartInfo(e.Uri.AbsoluteUri) { UseShellExecute = true });
            e.Handled = true;
        }

    }

}