macos: hacky API to get a CTFont for QuickLook

include/ghostty.h

@@ -556,6 +556,7 @@ uintptr_t ghostty_surface_selection(ghostty_surface_t, char*, uintptr_t);
 
 #ifdef __APPLE__
 void ghostty_surface_set_display_id(ghostty_surface_t, uint32_t);
+void* ghostty_surface_quicklook_font(ghostty_surface_t);
 #endif
 
 ghostty_inspector_t ghostty_surface_inspector(ghostty_surface_t);

macos/Sources/Ghostty/SurfaceView_AppKit.swift

@@ -1,4 +1,5 @@
 import SwiftUI
+import CoreText
 import UserNotifications
 import GhosttyKit
 
@@ -929,7 +930,13 @@ extension Ghostty.SurfaceView: NSTextInputClient {
     }
 
     func selectedRange() -> NSRange {
-        return NSRange()
+        guard let surface = self.surface else { return NSRange() }
+        guard ghostty_surface_has_selection(surface) else { return NSRange() }
+        
+        // If we have a selection, we just return a non-empty range. The actual
+        // values are meaningless but the non-emptiness of it tells AppKit we
+        // have a selection.
+        return NSRange(location: 0, length: 1)
     }
 
     func setMarkedText(_ string: Any, selectedRange: NSRange, replacementRange: NSRange) {
@@ -954,7 +961,33 @@ extension Ghostty.SurfaceView: NSTextInputClient {
     }
 
     func attributedSubstring(forProposedRange range: NSRange, actualRange: NSRangePointer?) -> NSAttributedString? {
-        return nil
+        // We ignore the proposed range and always return the selection from
+        // this (if we have one). This enables features like QuickLook. I don't
+        // know if this breaks anything else...
+        guard let surface = self.surface else { return nil }
+        guard ghostty_surface_has_selection(surface) else { return nil }
+        
+        // Get our selection. We cap it at 1MB for the purpose of this. This is
+        // arbitrary. If this is a good reason to increase it I'm happy to.
+        let v = String(unsafeUninitializedCapacity: 1000000) {
+            Int(ghostty_surface_selection(surface, $0.baseAddress, UInt($0.count)))
+        }
+        
+        // If we can get a font then we use the font. This should always work
+        // since we always have a primary font. The only scenario this doesn't
+        // work is if someone is using a non-CoreText build which would be
+        // unofficial.
+        var attributes: [ NSAttributedString.Key : Any ] = [:];
+        if let fontRaw = ghostty_surface_quicklook_font(surface) {
+            // Memory management here is wonky: ghostty_surface_quicklook_font
+            // will create a copy of a CTFont, Swift will auto-retain the
+            // unretained value passed into the dict, so we release the original.
+            let font = Unmanaged<CTFont>.fromOpaque(fontRaw)
+            attributes[.font] = font.takeUnretainedValue()
+            font.release()
+        }
+
+        return .init(string: v, attributes: attributes)
     }
 
     func characterIndex(for point: NSPoint) -> Int {

src/apprt/embedded.zig

@@ -10,6 +10,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const objc = @import("objc");
 const apprt = @import("../apprt.zig");
+const font = @import("../font/main.zig");
 const input = @import("../input.zig");
 const renderer = @import("../renderer.zig");
 const terminal = @import("../terminal/main.zig");
@@ -1771,6 +1772,37 @@ pub const CAPI = struct {
             surface.renderer_thread.wakeup.notify() catch {};
         }
 
+        /// This returns a CTFontRef that should be used for quicklook
+        /// highlighted text. This is always the primary font in use
+        /// regardless of the selected text. If coretext is not in use
+        /// then this will return nothing.
+        export fn ghostty_surface_quicklook_font(ptr: *Surface) ?*anyopaque {
+            // For non-CoreText we just return null.
+            if (comptime font.options.backend != .coretext) {
+                return null;
+            }
+
+            // Get the shared font grid. We acquire a read lock to
+            // read the font face. It should not be deffered since
+            // we're loading the primary face.
+            const grid = ptr.core_surface.renderer.font_grid;
+            grid.lock.lockShared();
+            defer grid.lock.unlockShared();
+
+            const collection = &grid.resolver.collection;
+            const face = collection.getFace(.{}) catch return null;
+
+            // The font is not the right size by default so we need
+            // to set it to our configured window size.
+            const copy = face.font.copyWithAttributes(
+                ptr.app.config.@"font-size",
+                null,
+                null,
+            ) catch return null;
+
+            return copy;
+        }
+
         export fn ghostty_inspector_metal_init(ptr: *Inspector, device: objc.c.id) bool {
             return ptr.initMetal(objc.Object.fromId(device));
         }