Fix CreateImGuiRangesFrom to omit null char (#1709)

* Fix CreateImGuiRangesFrom to omit null char

UnicodeRanges.BasicLatin is [0, 127], but ImGui stops reading the glyph
range list on encountering a zero. Fixed that by ensuring that 0 never
appears in the glyph range list.

* Make problems explicit

---------

Co-authored-by: goat <16760685+goaaats@users.noreply.github.com>

Dalamud/Interface/ManagedFontAtlas/IFontAtlas.cs

@@ -85,6 +85,10 @@ public interface IFontAtlas : IDisposable
     /// <summary>Creates a new <see cref="IFontHandle"/> from game's built-in fonts.</summary>
     /// <param name="style">Font to use.</param>
     /// <returns>Handle to a font that may or may not be ready yet.</returns>
+    /// <exception cref="InvalidOperationException">When called during <see cref="BuildStepChange"/>,
+    /// <see cref="UiBuilder.BuildFonts"/>, <see cref="UiBuilder.AfterBuildFonts"/>, and alike. Move the font handle
+    /// creating code outside those handlers, and only initialize them once. Call <see cref="IDisposable.Dispose"/>
+    /// on a previous font handle if you're replacing one.</exception>
     /// <remarks>This function does not throw. <see cref="IFontHandle.LoadException"/> will be populated instead, if
     /// the build procedure has failed. <see cref="IFontHandle.Push"/> can be used regardless of the state of the font
     /// handle.</remarks>
@@ -93,6 +97,13 @@ public interface IFontAtlas : IDisposable
     /// <summary>Creates a new IFontHandle using your own callbacks.</summary>
     /// <param name="buildStepDelegate">Callback for <see cref="IFontAtlas.BuildStepChange"/>.</param>
     /// <returns>Handle to a font that may or may not be ready yet.</returns>
+    /// <exception cref="InvalidOperationException">When called during <see cref="BuildStepChange"/>,
+    /// <see cref="UiBuilder.BuildFonts"/>, <see cref="UiBuilder.AfterBuildFonts"/>, and alike. Move the font handle
+    /// creating code outside those handlers, and only initialize them once. Call <see cref="IDisposable.Dispose"/>
+    /// on a previous font handle if you're replacing one.</exception>
+    /// <remarks>Consider calling <see cref="IFontAtlasBuildToolkitPreBuild.AttachExtraGlyphsForDalamudLanguage"/> to
+    /// support glyphs that are not supplied by the game by default; this mostly affects Chinese and Korean language
+    /// users.</remarks>
     /// <remarks>
     /// <para>Consider calling <see cref="IFontAtlasBuildToolkitPreBuild.AttachExtraGlyphsForDalamudLanguage"/> to
     /// support glyphs that are not supplied by the game by default; this mostly affects Chinese and Korean language

Dalamud/Interface/ManagedFontAtlas/Internals/FontAtlasFactory.Implementation.cs

@@ -35,6 +35,9 @@ internal sealed partial class FontAtlasFactory
     /// </summary>
     public const string EllipsisCodepoints = "\u2026\u0085";
 
+    /// <summary>Marker for tasks on whether it's being called inside a font build cycle.</summary>
+    public static readonly AsyncLocal<bool> IsBuildInProgressForTask = new();
+
     /// <summary>
     /// If set, disables concurrent font build operation.
     /// </summary>
@@ -427,11 +430,28 @@ internal sealed partial class FontAtlasFactory
         }
 
         /// <inheritdoc/>
-        public IFontHandle NewGameFontHandle(GameFontStyle style) => this.gameFontHandleManager.NewFontHandle(style);
+        public IFontHandle NewGameFontHandle(GameFontStyle style)
+        {
+            if (IsBuildInProgressForTask.Value)
+            {
+                throw new InvalidOperationException(
+                    $"{nameof(this.NewGameFontHandle)} may not be called during {nameof(this.BuildStepChange)}, the callback of {nameof(this.NewDelegateFontHandle)}, {nameof(UiBuilder.BuildFonts)} or {nameof(UiBuilder.AfterBuildFonts)}.");
+            }
+
+            return this.gameFontHandleManager.NewFontHandle(style);
+        }
 
         /// <inheritdoc/>
-        public IFontHandle NewDelegateFontHandle(FontAtlasBuildStepDelegate buildStepDelegate) =>
-            this.delegateFontHandleManager.NewFontHandle(buildStepDelegate);
+        public IFontHandle NewDelegateFontHandle(FontAtlasBuildStepDelegate buildStepDelegate)
+        {
+            if (IsBuildInProgressForTask.Value)
+            {
+                throw new InvalidOperationException(
+                    $"{nameof(this.NewDelegateFontHandle)} may not be called during {nameof(this.BuildStepChange)} or the callback of {nameof(this.NewDelegateFontHandle)}, {nameof(UiBuilder.BuildFonts)} or {nameof(UiBuilder.AfterBuildFonts)}.");
+            }
+
+            return this.delegateFontHandleManager.NewFontHandle(buildStepDelegate);
+        }
 
         /// <inheritdoc/>
         public void BuildFontsOnNextFrame()
@@ -630,6 +650,8 @@ internal sealed partial class FontAtlasFactory
             FontAtlasBuiltData? res = null;
             nint atlasPtr = 0;
             BuildToolkit? toolkit = null;
+
+            IsBuildInProgressForTask.Value = true;
             try
             {
                 res = new(this, scale);
@@ -754,6 +776,7 @@ internal sealed partial class FontAtlasFactory
                 // ReSharper disable once ConstantConditionalAccessQualifier
                 toolkit?.Dispose();
                 this.buildQueued = false;
+                IsBuildInProgressForTask.Value = false;
             }
 
             unsafe bool ValidateMergeFontReferences(ImFontPtr replacementDstFont)

Dalamud/Interface/UiBuilder.cs

@@ -516,9 +516,16 @@ public sealed class UiBuilder : IDisposable
     /// <returns>Handle to the game font which may or may not be available for use yet.</returns>
     [Obsolete($"Use {nameof(this.FontAtlas)}.{nameof(IFontAtlas.NewGameFontHandle)} instead.", false)]
     [Api10ToDo(Api10ToDoAttribute.DeleteCompatBehavior)]
-    public GameFontHandle GetGameFontHandle(GameFontStyle style) => new(
-        (GamePrebakedFontHandle)this.FontAtlas.NewGameFontHandle(style),
-        Service<FontAtlasFactory>.Get());
+    public GameFontHandle GetGameFontHandle(GameFontStyle style)
+    {
+        var prevValue = FontAtlasFactory.IsBuildInProgressForTask.Value;
+        FontAtlasFactory.IsBuildInProgressForTask.Value = false;
+        var v = new GameFontHandle(
+            (GamePrebakedFontHandle)this.FontAtlas.NewGameFontHandle(style),
+            Service<FontAtlasFactory>.Get());
+        FontAtlasFactory.IsBuildInProgressForTask.Value = prevValue;
+        return v;
+    }
 
     /// <summary>
     /// Call this to queue a rebuild of the font atlas.<br/>

Dalamud/Interface/Utility/ImGuiHelpers.cs

@@ -493,12 +493,13 @@ public static class ImGuiHelpers
     /// <returns>The range array that can be used for <see cref="SafeFontConfig.GlyphRanges"/>.</returns>
     public static ushort[] CreateImGuiRangesFrom(IEnumerable<UnicodeRange> ranges) =>
         ranges
-            .Where(x => x.FirstCodePoint <= ushort.MaxValue)
+            .Select(x => (First: Math.Max(x.FirstCodePoint, 1), Last: x.FirstCodePoint + x.Length))
+            .Where(x => x.First <= ushort.MaxValue && x.First <= x.Last)
             .SelectMany(
                 x => new[]
                 {
-                    (ushort)Math.Min(x.FirstCodePoint, ushort.MaxValue),
-                    (ushort)Math.Min(x.FirstCodePoint + x.Length, ushort.MaxValue),
+                    (ushort)Math.Min(x.First, ushort.MaxValue),
+                    (ushort)Math.Min(x.Last, ushort.MaxValue),
                 })
             .Append((ushort)0)
             .ToArray();