Use measured desktop cells for MXP image sizing

CHANGELOG.md

@@ -46,6 +46,10 @@ and a release's notes are its section. The procedure is in [`docs/RELEASING.md`]
 
 ### Fixed
 
+- Desktop MXP images use the measured font cell dimensions when sizing pictures, instead of assuming an 8×16 cell.
+  This avoids stretching pictures when the selected font has a different shape. Explicit server-specified cell boxes
+  stay unchanged, and terminal hosts without measured cells keep their existing sizing.
+
 - Quitting the terminal client turns off the terminal's focus reporting again, so the shell no longer receives
   `ESC [ I` / `ESC [ O` when you switch windows afterwards.
 - Servers now hear this client's name. Over TTYPE (MTTS) it introduced itself as `UNKNOWN`, because its own

src/SharpMUTerm.Avalonia/TerminalView.cs

@@ -59,6 +59,7 @@ public TerminalView(AvaloniaConsoleDriver driver, SKColor foreground, SKColor ba
         _lineHeight = lineHeight;
         _renderer = new CellRenderer(new CellFonts(fontPoints, family, lineHeight), foreground, background);
         _driver.Pointer.CellHeightMeasured = CellSize.Height;
+        _driver.Pointer.ImageCellSizeMeasured = new ImageCellSize(CellSize.Width, CellSize.Height);
         Focusable = true;
         ClipToBounds = true;
         Cursor = new Cursor(StandardCursorType.Ibeam);
@@ -302,6 +303,7 @@ private void Rescale(double scale)
             _renderer.DefaultForeground,
             _renderer.DefaultBackground);
         _driver.Pointer.CellHeightMeasured = CellSize.Height;
+        _driver.Pointer.ImageCellSizeMeasured = new ImageCellSize(CellSize.Width, CellSize.Height);
         Repainted?.Invoke();
     }
 

src/SharpMUTerm.Avalonia/WindowPointer.cs

@@ -91,6 +91,16 @@ internal int WindowColumnsMeasured
 
     int? IPointerPresenter.WindowColumns => WindowColumnsMeasured is > 0 and var columns ? columns : null;
 
+    private ImageCellSize? _imageCellSize;
+
+    internal ImageCellSize? ImageCellSizeMeasured
+    {
+        get => Volatile.Read(ref _imageCellSize);
+        set => Volatile.Write(ref _imageCellSize, value);
+    }
+
+    ImageCellSize? IPointerPresenter.ImageCellSize => ImageCellSizeMeasured;
+
     private double _cellHeight;
 
     /// <summary>

src/SharpMUTerm.Tui/InlineImageHost.cs

@@ -125,7 +125,8 @@ public bool Load(
         int availableColumns,
         Func<IGraphicsProtocol?> kitty,
         Action<int, IReadOnlyList<string>> deliver,
-        int maxRows = InlineImageLayout.MaxRows)
+        int maxRows = InlineImageLayout.MaxRows,
+        ImageCellSize? cellSize = null)
     {
         ArgumentNullException.ThrowIfNull(requests);
         ArgumentNullException.ThrowIfNull(kitty);
@@ -156,7 +157,7 @@ presentation is not (InlineImagePresentation.Kitty or InlineImagePresentation.Ha
                 for (var i = 0; i < requests.Count; i++)
                 {
                     var index = i;
-                    var rows = await RowsForAsync(requests[index], presentation, availableColumns, maxRows, kitty).ConfigureAwait(false);
+                    var rows = await RowsForAsync(requests[index], presentation, availableColumns, maxRows, kitty, cellSize).ConfigureAwait(false);
                     if (rows is not null && !_cts.IsCancellationRequested)
                     {
                         _onUi(() => deliver(index, rows));
@@ -191,16 +192,17 @@ presentation is not (InlineImagePresentation.Kitty or InlineImagePresentation.Ha
         InlineImagePresentation presentation,
         int availableColumns,
         int maxRows,
-        Func<IGraphicsProtocol?> kitty)
+        Func<IGraphicsProtocol?> kitty,
+        ImageCellSize? cellSize)
     {
-        var key = $"{presentation}|{availableColumns}|{maxRows}|{request.Width}|{request.Height}|{request.Url}";
+        var key = $"{presentation}|{availableColumns}|{maxRows}|{cellSize}|{request.Width}|{request.Height}|{request.Url}";
         if (Cached(key) is { } hit)
         {
             return hit;
         }
 
         var source = await SourceFor(request.Url).ConfigureAwait(false);
-        var picture = source is null ? null : Fit(source, request, availableColumns, maxRows);
+        var picture = source is null ? null : Fit(source, request, availableColumns, maxRows, cellSize);
         if (picture is null)
         {
             return null;
@@ -358,7 +360,8 @@ internal int SourcesHeld
         byte[] bytes,
         InlineImageRequest request,
         int availableColumns,
-        int maxRows = InlineImageLayout.MaxRows)
+        int maxRows = InlineImageLayout.MaxRows,
+        ImageCellSize? cellSize = null)
     {
         PixelBuffer source;
         try
@@ -370,17 +373,18 @@ internal int SourcesHeld
             return null;
         }
 
-        return Fit(source, request, availableColumns, maxRows);
+        return Fit(source, request, availableColumns, maxRows, cellSize);
     }
 
     /// <summary>Sizes a decoded picture to its cell box, keeping the pixels either presentation needs.</summary>
     internal static DecodedPicture? Fit(
         PixelBuffer source,
         InlineImageRequest request,
         int availableColumns,
-        int maxRows = InlineImageLayout.MaxRows)
+        int maxRows = InlineImageLayout.MaxRows,
+        ImageCellSize? cellSize = null)
     {
-        var box = InlineImageLayout.Fit(source.Width, source.Height, request.Width, request.Height, availableColumns, maxRows);
+        var box = InlineImageLayout.Fit(source.Width, source.Height, request.Width, request.Height, availableColumns, maxRows, cellSize);
         if (box.Columns <= 0 || box.Rows <= 0)
         {
             return null;

src/SharpMUTerm.Tui/InlineImageLayout.cs

@@ -7,10 +7,11 @@ namespace SharpMUTerm.Tui;
 /// the world's <c>W=</c>/<c>H=</c> hints, then the room there is. Pure, so the sizing is testable
 /// without a terminal.
 /// <para>
-/// A cell is taken to be <see cref="CellPixelWidth"/> × <see cref="CellPixelHeight"/> pixels. The
+/// Desktop hosts supply measured logical-pixel cells. Without those, a cell is taken to be
+/// <see cref="CellPixelWidth"/> × <see cref="CellPixelHeight"/> pixels. The
 /// client cannot ask the terminal (the framework owns the input stream a <c>CSI 16 t</c> reply would
-/// arrive on), and the 1:2 ratio is the one thing that matters: it is what keeps a square picture
-/// square under both Kitty and half-blocks, which carry one pixel across and two down per cell.
+/// arrive on), so those hosts retain the established 1:2 fallback. Desktop sizing uses the measured
+/// aspect ratio instead; the final box is rounded to whole cells.
 /// </para>
 /// </summary>
 internal static class InlineImageLayout
@@ -38,19 +39,22 @@ public static WebImageLayout.CellBox Fit(
         ImageExtent? width,
         ImageExtent? height,
         int availableColumns,
-        int maxRows = MaxRows)
+        int maxRows = MaxRows,
+        ImageCellSize? cellSize = null)
     {
         if (pixelWidth <= 0 || pixelHeight <= 0 || availableColumns <= 0 || maxRows <= 0)
         {
             return new WebImageLayout.CellBox(0, 0);
         }
 
-        double columns = Math.Ceiling(pixelWidth / (double)CellPixelWidth);
-        double rows = Math.Ceiling(pixelHeight / (double)CellPixelHeight);
-        var aspect = rows / columns;
+        var cw = cellSize?.Width is > 0 and var measuredWidth && double.IsFinite(measuredWidth) ? measuredWidth : CellPixelWidth;
+        var ch = cellSize?.Height is > 0 and var measuredHeight && double.IsFinite(measuredHeight) ? measuredHeight : CellPixelHeight;
+        double columns = Math.Ceiling(pixelWidth / cw);
+        double rows = Math.Ceiling(pixelHeight / ch);
+        var aspect = cellSize is null ? rows / columns : (pixelHeight / ch) / (pixelWidth / cw);
 
-        var hintedColumns = Columns(width, availableColumns);
-        var hintedRows = Rows(height, maxRows);
+        var hintedColumns = Columns(width, availableColumns, cw);
+        var hintedRows = Rows(height, maxRows, ch);
         if (hintedColumns is { } c && hintedRows is { } r)
         {
             columns = c;
@@ -73,19 +77,22 @@ public static WebImageLayout.CellBox Fit(
             Math.Clamp((int)Math.Round(rows * scale, MidpointRounding.AwayFromZero), 1, maxRows));
     }
 
-    private static double? Columns(ImageExtent? extent, int available) => extent switch
+    private static double? Columns(ImageExtent? extent, int available, double cellWidth) => extent switch
     {
-        { Unit: ImageExtentUnit.Pixels } e => Math.Ceiling(e.Value / (double)CellPixelWidth),
+        { Unit: ImageExtentUnit.Pixels } e => Math.Ceiling(e.Value / cellWidth),
         { Unit: ImageExtentUnit.Characters } e => e.Value,
         { Unit: ImageExtentUnit.Percent } e => Math.Max(1, available * e.Value / 100.0),
         _ => null,
     };
 
-    private static double? Rows(ImageExtent? extent, int maxRows) => extent switch
+    private static double? Rows(ImageExtent? extent, int maxRows, double cellHeight) => extent switch
     {
-        { Unit: ImageExtentUnit.Pixels } e => Math.Ceiling(e.Value / (double)CellPixelHeight),
+        { Unit: ImageExtentUnit.Pixels } e => Math.Ceiling(e.Value / cellHeight),
         { Unit: ImageExtentUnit.Characters } e => e.Value,
         { Unit: ImageExtentUnit.Percent } e => Math.Max(1, maxRows * e.Value / 100.0),
         _ => null,
     };
 }
+
+/// <summary>One display cell in logical pixels; null metrics use the terminal fallback.</summary>
+internal sealed record ImageCellSize(double Width, double Height);

src/SharpMUTerm.Tui/Pointer/PointerTarget.cs

@@ -109,6 +109,9 @@ public bool SameAs(PaneScrollbar other) =>
 /// </summary>
 internal interface IPointerPresenter
 {
+    /// <summary>Measured cell size in logical pixels, or null for terminal hosts with unknown metrics.</summary>
+    ImageCellSize? ImageCellSize => null;
+
     /// <summary>The pointer moved onto something else. <see cref="PointerTarget.Nothing"/> when it left everything.</summary>
     void Hover(PointerTarget target);
 

src/SharpMUTerm.Tui/SharpMUTermApp.cs

@@ -4703,7 +4703,8 @@ private void AppendSessionLine(string windowId, StyledLine line, string stamp)
                 presentation,
                 Math.Min(InlineImageColumns(windowId), edges?.Columns ?? int.MaxValue),
                 Kitty,
-                (index, rows) => PlaceInlinePicture(windowId, anchor, shown, index, rows));
+                (index, rows) => PlaceInlinePicture(windowId, anchor, shown, index, rows),
+                cellSize: _pointer?.ImageCellSize);
         }
 
         foreach (var (picture, request, interaction, columns, rows) in reserved)
@@ -4714,7 +4715,8 @@ private void AppendSessionLine(string windowId, StyledLine line, string stamp)
                 columns,
                 Kitty,
                 (_, drawn) => DrawReservedPicture(windowId, picture, Linked(drawn, interaction)),
-                rows);
+                rows,
+                _pointer?.ImageCellSize);
         }
     }
 

tests/SharpMUTerm.Avalonia.Tests/BundledFontTests.cs

@@ -1,3 +1,6 @@
+using SharpMUTerm.Tui;
+using SkiaSharp;
+
 namespace SharpMUTerm.Avalonia.Tests;
 
 /// <summary>
@@ -6,6 +9,23 @@ namespace SharpMUTerm.Avalonia.Tests;
 /// </summary>
 public class BundledFontTests
 {
+    [Test]
+    public async Task ImageSizingUsesTheViewsMeasuredCellsAfterScaling()
+    {
+        var measurements = await TerminalViewTests.Session.Dispatch(() =>
+        {
+            var driver = new AvaloniaConsoleDriver(80, 24);
+            var view = new TerminalView(driver, SKColors.White, SKColors.Black, 16, null, WindowOptions.DefaultLineHeight);
+            var first = ((IPointerPresenter)driver.Pointer).ImageCellSize;
+            var initial = new ImageCellSize(view.CellExtent.Width, view.CellExtent.Height);
+            view.PrepareScale(1.5);
+            return (first, initial, current: ((IPointerPresenter)driver.Pointer).ImageCellSize,
+                expected: new ImageCellSize(view.CellExtent.Width, view.CellExtent.Height));
+        }, CancellationToken.None);
+        await Assert.That(measurements.first).IsEqualTo(measurements.initial);
+        await Assert.That(measurements.current).IsEqualTo(measurements.expected);
+    }
+
     [Test]
     public async Task TheBundledFacesAreInTheBuild()
     {

tests/SharpMUTerm.Tui.Tests/InlineImageCacheTests.cs

@@ -36,6 +36,23 @@ private static async Task<List<IReadOnlyList<string>>> Show(InlineImageHost host
         return drawn;
     }
 
+    [Test]
+    public async Task NewCellMetricsResizeRowsWithoutRefetching()
+    {
+        var count = new Counting();
+        using var host = new InlineImageHost(count.Fetch(Task.FromResult<byte[]?>(TestImages.RgbaPng(240, 240))), run => run());
+        var request = Room with { Width = new ImageExtent(24, ImageExtentUnit.Characters) };
+        var drawn = new List<IReadOnlyList<string>>();
+        foreach (var cell in new[] { new ImageCellSize(10, 20), new ImageCellSize(10, 24) })
+        {
+            host.Load([request], InlineImagePresentation.HalfBlock, 100, () => null, (_, rows) => drawn.Add(rows), cellSize: cell);
+            await host.Pending;
+        }
+        await Assert.That(count.Fetches).IsEqualTo(1);
+        await Assert.That(drawn[0].Count).IsEqualTo(12);
+        await Assert.That(drawn[1].Count).IsEqualTo(10);
+    }
+
     [Test]
     public async Task APictureShownAtAnotherWidthIsNotFetchedAgain()
     {

tests/SharpMUTerm.Tui.Tests/MxpImageTests.cs

@@ -66,6 +66,37 @@ public async Task BothHintsStretch()
         await Assert.That(box).IsEqualTo(new WebImageLayout.CellBox(40, 2));
     }
 
+    [Test]
+    public async Task MeasuredCellsKeepOneHintPhysicallySquare()
+    {
+        var box = InlineImageLayout.Fit(160, 160, new ImageExtent(24, ImageExtentUnit.Characters), null, 100,
+            cellSize: new ImageCellSize(10, 24));
+        await Assert.That(box).IsEqualTo(new WebImageLayout.CellBox(24, 10));
+    }
+
+    [Test]
+    public async Task MeasuredPixelHintsUseActualCells()
+    {
+        var box = InlineImageLayout.Fit(160, 160, new ImageExtent(120, ImageExtentUnit.Pixels),
+            new ImageExtent(120, ImageExtentUnit.Pixels), 100, cellSize: new ImageCellSize(10, 24));
+        await Assert.That(box).IsEqualTo(new WebImageLayout.CellBox(12, 5));
+    }
+
+    [Test]
+    public async Task ExplicitCellBoxRemainsTheServersGeometry()
+    {
+        var box = InlineImageLayout.Fit(160, 160, new ImageExtent(24, ImageExtentUnit.Characters),
+            new ImageExtent(12, ImageExtentUnit.Characters), 100, cellSize: new ImageCellSize(10, 24));
+        await Assert.That(box).IsEqualTo(new WebImageLayout.CellBox(24, 12));
+    }
+
+    [Test]
+    public async Task InvalidMeasuredCellsKeepTerminalFallback()
+    {
+        var box = InlineImageLayout.Fit(160, 160, null, null, 100, cellSize: new ImageCellSize(double.NaN, 0));
+        await Assert.That(box).IsEqualTo(new WebImageLayout.CellBox(20, 10));
+    }
+
     // ---- Rows ---------------------------------------------------------------------------------
 
     /// <summary>