themes: add a switch that shows a small preview of each theme

src/cli/list_themes.zig

@@ -9,6 +9,9 @@ const internal_os = @import("../os/main.zig");
 const global_state = &@import("../global.zig").state;
 
 pub const Options = struct {
+    /// If true, show a small preview of the theme.
+    preview: bool = false,
+
     pub fn deinit(self: Options) void {
         _ = self;
     }
@@ -23,12 +26,26 @@ pub const Options = struct {
 /// The `list-themes` command is used to list all the available themes for
 /// Ghostty.
 ///
-/// Themes require that Ghostty have access to the resources directory. On macOS
+/// Two different directories will be searched for themes.
-/// this is embedded in the app bundle. On Linux, this is usually in `/usr/
+///
-/// share/ghostty`. If you're compiling from source, this is the `zig-out/share/
+/// The first directory is the `themes` subdirectory of your Ghostty
-/// ghostty` directory. You can also set the `GHOSTTY_RESOURCES_DIR` environment
+/// configuration directory. This is `$XDG_CONFIG_DIR/ghostty/themes` or
-/// variable to point to the resources directory. Themes live in the `themes`
+/// `~/.config/ghostty/themes`.
-/// subdirectory of the resources directory.
+///
+/// The second directory is the `themes` subdirectory of the Ghostty resources
+/// directory. Ghostty ships with a multitude of themes that will be installed
+/// into this directory. On macOS, this directory is the `Ghostty.app/Contents/
+/// Resources/ghostty/themes`. On Linux, this directory is the `share/ghostty/
+/// themes` (wherever you installed the Ghostty "share" directory). If you're
+/// running Ghostty from the source, this is the `zig-out/share/ghostty/themes`
+/// directory.
+///
+/// You can also set the `GHOSTTY_RESOURCES_DIR` environment variable to point
+/// to the resources directory.
+///
+/// Flags:
+///
+///   * `--preview`: Show a short preview of the theme colors.
 pub fn run(alloc: Allocator) !u8 {
     var opts: Options = .{};
     defer opts.deinit();
@@ -107,6 +124,40 @@ pub fn run(alloc: Allocator) !u8 {
 
     for (themes.items) |theme| {
         try stdout.print("{s} ({s})\n", .{ theme.theme, @tagName(theme.type) });
+
+        if (opts.preview) {
+            var config = try Config.default(alloc);
+            defer config.deinit();
+            if (config.loadFile(config._arena.?.allocator(), theme.path)) |_| {
+                if (!config._errors.empty()) {
+                    try stderr.print("  Problems were encountered trying to load the theme:\n", .{});
+                    for (config._errors.list.items) |err| {
+                        try stderr.print("    {s}\n", .{err.message});
+                    }
+                }
+                try stdout.print("\n   ", .{});
+                for (0..8) |i| {
+                    try stdout.print(" {d:2} \x1b[38;2;{d};{d};{d}m██\x1b[0m", .{
+                        i,
+                        config.palette.value[i].r,
+                        config.palette.value[i].g,
+                        config.palette.value[i].b,
+                    });
+                }
+                try stdout.print("\n   ", .{});
+                for (8..16) |i| {
+                    try stdout.print(" {d:2} \x1b[38;2;{d};{d};{d}m██\x1b[0m", .{
+                        i,
+                        config.palette.value[i].r,
+                        config.palette.value[i].g,
+                        config.palette.value[i].b,
+                    });
+                }
+                try stdout.print("\n\n", .{});
+            } else |err| {
+                try stderr.print("unable to load {s}: {}", .{ theme.path, err });
+            }
+        }
     }
 
     if (count == 0) {