Update AddNewLine to insert post-scaling glyph height on empty line

This one required a bit more work as CSS usually takes the "glyph scale"
of the font specified in the `font-family` as far as my manual testing went.

I think it should be fine to create a `GetFont` method returning
`IGlyphStore`s for that purpose, as it's also required in visual testing
to visualise the baseline position in a sprite text.

osu.Framework/IO/Stores/FontStore.cs

@@ -130,6 +130,26 @@ public override void RemoveStore(IResourceStore<TextureUpload> store)
             base.RemoveStore(store);
         }
 
+        /// <summary>
+        /// Searches for a <see cref="IGlyphStore"/> with the specified name.
+        /// </summary>
+        /// <param name="name">The font name.</param>
+        public IGlyphStore GetFont(string name)
+        {
+            var found = glyphStores.Find(g => g.FontName == name);
+
+            if (found == null)
+            {
+                foreach (var store in nestedFontStores)
+                {
+                    if ((found = store.GetFont(name)) != null)
+                        break;
+                }
+            }
+
+            return found;
+        }
+
         public new Texture Get(string name)
         {
             var found = base.Get(name, WrapMode.None, WrapMode.None);

osu.Framework/Text/ITexturedGlyphLookupStore.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Threading.Tasks;
+using osu.Framework.IO.Stores;
 
 namespace osu.Framework.Text
 {
@@ -22,5 +23,11 @@ public interface ITexturedGlyphLookupStore
         /// <param name="character">The character to retrieve.</param>
         /// <returns>The character glyph.</returns>
         Task<ITexturedCharacterGlyph> GetAsync(string fontName, char character);
+
+        /// <summary>
+        /// Searches for a <see cref="IGlyphStore"/> with the specified name.
+        /// </summary>
+        /// <param name="name">The font name.</param>
+        IGlyphStore GetFont(string name);
     }
 }

osu.Framework/Text/TextBuilder.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using JetBrains.Annotations;
 using osu.Framework.Caching;
 using osu.Framework.Graphics.Primitives;
 using osu.Framework.Graphics.Sprites;
@@ -36,6 +37,12 @@ public class TextBuilder : IHasLineBaseHeight
         private readonly Vector2 spacing;
         private readonly float maxWidth;
 
+        /// <summary>
+        /// The <see cref="IGlyphStore"/> of the font specified in the <see cref="FontUsage"/>.
+        /// </summary>
+        [CanBeNull]
+        private readonly IGlyphStore fontGlyphStore;
+
         private Vector2 currentPos;
         private float currentLineHeight;
         private float? currentLineBase;
@@ -81,6 +88,8 @@ public TextBuilder(ITexturedGlyphLookupStore store, FontUsage font, float maxWid
             this.spacing = spacing;
             this.maxWidth = maxWidth;
 
+            fontGlyphStore = store.GetFont(font.FontName);
+
             Characters = characterList ?? new List<TextBuilderGlyph>();
             this.neverFixedWidthCharacters = neverFixedWidthCharacters ?? Array.Empty<char>();
             this.fallbackCharacter = fallbackCharacter;
@@ -196,13 +205,18 @@ public bool AddCharacter(char character)
         /// Adds a new line to this <see cref="TextBuilder"/>.
         /// </summary>
         /// <remarks>
-        /// A height equal to that of the font size will be assumed if the current line is empty, regardless of <see cref="useFontSizeAsHeight"/>.
+        /// A height equal to that of the font size will be assumed if the current line is empty, regardless of <see cref="useFullGlyphHeight"/>.
         /// </remarks>
         public void AddNewLine()
         {
             if (currentNewLine)
+            {
                 currentLineHeight = font.Size;
 
+                if (font.CssScaling && fontGlyphStore?.Metrics is FontMetrics metrics)
+                    currentLineHeight *= metrics.GlyphScale;
+            }
+
             // Reset + vertically offset the current position
             currentPos.X = startOffset.X;
             currentPos.Y += currentLineHeight + spacing.Y;