feat(settings): add ThemePicker with five categories and switch lock

HellionChat/PluginHostFactory.cs

@@ -147,6 +147,10 @@ internal static class PluginHostFactory
             sp.GetRequiredService<FontManager>()
         ));
         services.AddSingleton(sp => new Ui.Components.Settings.ContentArea());
+        services.AddSingleton(sp => new Ui.Components.Settings.ThemePicker(
+            sp.GetRequiredService<ThemeRegistry>(),
+            sp.GetRequiredService<Plugin>()
+        ));
         services.AddSingleton(sp => new Ui.Components.StatusBar(
             sp.GetRequiredService<ThemeRegistry>(),
             sp.GetRequiredService<FontManager>()

HellionChat/Ui/Components/Settings/ThemePicker.cs

@@ -0,0 +1,125 @@
+using System.Numerics;
+using Dalamud.Bindings.ImGui;
+using Dalamud.Interface.Utility.Raii;
+using HellionChat.Themes;
+using HellionChat.Util;
+
+namespace HellionChat.Ui.Components.Settings;
+
+internal sealed class ThemePicker
+{
+    private static readonly (string Category, string[] Slugs, bool DefaultExpanded)[] CategoryMap =
+    {
+        (
+            "Hellion Brand",
+            new[] { "hellion-arctic", "hellion-spectrum", "forge-merchantman" },
+            true
+        ),
+        (
+            "Cool",
+            new[] { "night-blue", "event-horizon", "indigo-violet", "crystal-nocturne" },
+            false
+        ),
+        ("Natural", new[] { "mint-grove" }, false),
+        ("Classic", new[] { "chat2-classic" }, false),
+        ("Retro", new[] { "synthwave-sunset" }, false),
+    };
+
+    // T2 ThemePickerCategoryStep diffs this against ThemeRegistry.BuiltinSlugs
+    // to enforce coverage. Kept on the static map so the test does not pierce instance state.
+    internal static IEnumerable<string> CategoryMapSlugs => CategoryMap.SelectMany(c => c.Slugs);
+
+    private readonly ThemeRegistry _themes;
+    private readonly Plugin _plugin;
+
+    public ThemePicker(ThemeRegistry themes, Plugin plugin)
+    {
+        _themes = themes;
+        _plugin = plugin;
+    }
+
+    public void Draw()
+    {
+        var locked = _themes.EditingThemeBuffer is not null;
+
+        using (ImRaii.Disabled(locked))
+        {
+            foreach (var (category, slugs, defaultExpanded) in CategoryMap)
+            {
+                var flags = defaultExpanded
+                    ? ImGuiTreeNodeFlags.DefaultOpen
+                    : ImGuiTreeNodeFlags.None;
+                if (ImGui.CollapsingHeader(category, flags))
+                {
+                    foreach (var slug in slugs)
+                    {
+                        DrawCard(slug);
+                    }
+                }
+            }
+        }
+
+        if (locked && ImGui.IsItemHovered(ImGuiHoveredFlags.AllowWhenDisabled))
+        {
+            ImGui.SetTooltip("Save or discard your edits first");
+        }
+    }
+
+    private void DrawCard(string slug)
+    {
+        if (!_themes.TryGet(slug, out var theme))
+        {
+            return;
+        }
+
+        var active = _themes.Active.Slug == slug;
+        var label = $"{theme.Name}  —  {theme.Author}##theme-card-{slug}";
+
+        // Selectable uses ImGui's default Header colour, not the theme's Surface.
+        // Swatch overlay below carries the theme cue; v1.7.x-polish if testers flag the mismatch.
+        if (ImGui.Selectable(label, active, ImGuiSelectableFlags.None, new Vector2(0, 40)))
+        {
+            _themes.Switch(slug);
+            Plugin.Config.Theme = slug;
+            _plugin.SaveConfig();
+        }
+
+        // Mini-Preview-Swatch overlay (3 ABGR boxes on the right side of the card).
+        // Selectable owns the hit-box; the DrawList overlay is decorative — full card area
+        // remains the click target, not just the swatch.
+        //
+        // RGBA-vs-ABGR-Disziplin: ThemeColors slots hold uint values in 0xRRGGBBAA layout
+        // (see ThemeColors.cs header comment). ImGui draw calls expect ABGR (native byte order)
+        // — pass theme colours through ColourUtil.RgbaToAbgr before any AddRectFilled / AddText
+        // / AddLine. The repo-wide pattern is "swap at the boundary" (see InputBar swap-at-
+        // boundary pattern). Forgetting the swap renders Red and Blue channels swapped and
+        // shifts the alpha byte into the green slot.
+        var draw = ImGui.GetWindowDrawList();
+        var max = ImGui.GetItemRectMax();
+        var min = ImGui.GetItemRectMin();
+        var swatchY = min.Y + 12;
+        DrawSwatch(
+            draw,
+            new Vector2(max.X - 60, swatchY),
+            ColourUtil.RgbaToAbgr(theme.Colors.Surface)
+        );
+        DrawSwatch(
+            draw,
+            new Vector2(max.X - 42, swatchY),
+            ColourUtil.RgbaToAbgr(theme.Colors.Primary)
+        );
+        DrawSwatch(
+            draw,
+            new Vector2(max.X - 24, swatchY),
+            ColourUtil.RgbaToAbgr(theme.Colors.Accent)
+        );
+    }
+
+    // Caller contract: `colorAbgr` is already byte-swapped from the ThemeColors RGBA backing
+    // field via ColourUtil.RgbaToAbgr. Passing a raw RGBA value here renders with the wrong
+    // channel order.
+    private static void DrawSwatch(ImDrawListPtr draw, Vector2 topLeft, uint colorAbgr)
+    {
+        draw.AddRectFilled(topLeft, topLeft + new Vector2(14, 14), colorAbgr, 2f);
+    }
+}