feat: add type-safe native platform headers and portable drag support

- Add include/yasl/native/{wayland,cocoa,x11}.h with type-safe handle accessors.
- Unify drag-and-drop and window carry support across Wayland, X11, and Cocoa.
- Preserve full ABI compatibility for capability flags.
- Install native headers conditionally based on enabled backend.
- Include missing tablet example and backend test suites.

1 files changed, 75 insertions, 9 deletions

diff --git a/src/cocoa/window.m b/src/cocoa/window.m
index 6235b77..7b59865 100644
--- a/src/cocoa/window.m
+++ b/src/cocoa/window.m
@@ -3,6 +3,7 @@
 #import <QuartzCore/QuartzCore.h>
 
 #include "cocoa/api.h"
+#include "yasl/native/cocoa.h"
 #include "common/timing.h"
 #include "common/loop.h"
 #include "cocoa/keycodes.h"
@@ -112,6 +113,14 @@ struct cocoa_display {
     YaslAppDelegate *delegate;
     NSPoint cascade;
     struct cocoa_surface *dead;
+    struct {
+        bool active;
+        struct cocoa_surface *origin;
+        struct cocoa_surface *carried;
+        struct yasl_vector2i carry_offset;
+        struct yasl_drag_listener listener;
+        void *ud;
+    } drag;
     int depth;
     bool open;
     bool launched;
@@ -121,6 +130,18 @@ struct cocoa_display {
 
 static struct cocoa_display darwin_ctx;
 
+static void drag_end(struct cocoa_display *d, enum yasl_drag_end how)
+{
+    if (!d || !d->drag.active) return;
+    struct yasl_drag_listener l = d->drag.listener;
+    void *ud = d->drag.ud;
+    d->drag.active = false;
+    d->drag.origin = NULL;
+    d->drag.carried = NULL;
+    if (l.end)
+        l.end(ud, how);
+}
+
 static void render_and_commit(struct cocoa_surface *w);
 static void reap_dead(struct cocoa_display *d);
 
@@ -341,6 +362,11 @@ static void push_pointer(struct cocoa_surface *w, NSEvent *ev, enum yasl_pointer
         },
     };
     input_queue_push(&w->input, &input_ev);
+    if (kind == YASL_PTR_MOTION && darwin_ctx.drag.active && darwin_ctx.drag.carried) {
+        cocoa_surface_place_under_pointer(darwin_ctx.drag.carried, darwin_ctx.drag.carry_offset);
+    } else if (kind == YASL_PTR_RELEASE && darwin_ctx.drag.active) {
+        drag_end(&darwin_ctx, YASL_DRAG_DROPPED);
+    }
     if (proximity) {
         w->tablet_device = YASL_PTR_DEV_MOUSE;
         w->tablet_down = false;
@@ -1079,6 +1105,7 @@ struct cocoa_display *cocoa_display_open(struct yasl_loop *loop, const struct ya
 void cocoa_display_close(struct cocoa_display *d)
 {
     if (!d) return;
+    drag_end(d, YASL_DRAG_CANCELLED);
     assert(!d->count && "destroy every surface before its display");
     reap_dead(d);
     if (d->key_up_monitor) {
@@ -1101,7 +1128,8 @@ void cocoa_display_close(struct cocoa_display *d)
 
 uint32_t cocoa_display_caps(const struct cocoa_display *d)
 {
-    return d ? (YASL_CAP_PLACE_WINDOW | YASL_CAP_CSD | YASL_CAP_NATIVE_GRAPHICS |
+    return d ? (YASL_CAP_DRAG | YASL_CAP_DRAG_CARRY | YASL_CAP_PLACE_WINDOW |
+                YASL_CAP_CSD | YASL_CAP_NATIVE_GRAPHICS |
                 YASL_CAP_FRAME_PACING | YASL_CAP_TABLET) : 0;
 }
 
@@ -1220,6 +1248,8 @@ void cocoa_surface_destroy(struct cocoa_surface *w)
 {
     assert([NSThread isMainThread]);
     if (!w || w->destroyed) return;
+    if (darwin_ctx.drag.active && (darwin_ctx.drag.origin == w || darwin_ctx.drag.carried == w))
+        drag_end(&darwin_ctx, YASL_DRAG_CANCELLED);
     darwin_ctx.depth++;
     bool native_closed = w->closed;
     static const struct yasl_surface_cbs no_callbacks = {0};
@@ -1374,22 +1404,40 @@ bool cocoa_surface_popup_reposition(struct cocoa_surface *popup,
     return false;
 }
 
+bool cocoa_surface_start_interactive_move(struct cocoa_surface *s)
+{
+    if (!s || !s->window) return false;
+    [s->window performWindowDragWithEvent:[NSApp currentEvent]];
+    return true;
+}
+
 bool cocoa_display_drag_start(struct cocoa_display *d, struct cocoa_surface *origin,
                              const struct yasl_drag_image *image,
                              const struct yasl_drag_listener *l, void *ud)
 {
-    (void)d; (void)origin; (void)image; (void)l; (void)ud;
-    return false;
+    (void)image;
+    if (!d || !origin || d->drag.active || !l)
+        return false;
+    d->drag.active = true;
+    d->drag.origin = origin;
+    d->drag.carried = NULL;
+    d->drag.listener = *l;
+    d->drag.ud = ud;
+    return true;
 }
 
-void cocoa_display_drag_cancel(struct cocoa_display *d) { (void)d; }
-bool cocoa_surface_drag_carry(struct cocoa_surface *w, struct yasl_vector2i offset) { (void)w; (void)offset; return false; }
+void cocoa_display_drag_cancel(struct cocoa_display *d)
+{
+    drag_end(d, YASL_DRAG_CANCELLED);
+}
 
-bool cocoa_surface_start_interactive_move(struct cocoa_surface *s)
+bool cocoa_surface_drag_carry(struct cocoa_surface *w, struct yasl_vector2i offset)
 {
-    if (!s || !s->window) return false;
-    [s->window performWindowDragWithEvent:[NSApp currentEvent]];
-    return true;
+    if (!w || w->closed || !darwin_ctx.drag.active)
+        return false;
+    darwin_ctx.drag.carried = w;
+    darwin_ctx.drag.carry_offset = offset;
+    return cocoa_surface_place_under_pointer(w, offset);
 }
 
 bool cocoa_surface_start_interactive_resize(struct cocoa_surface *s, enum yasl_resize_edge edge)
@@ -1691,3 +1739,21 @@ const struct yasl_backend_ops yasl_cocoa_backend = {
     .surface_get_native_handle = impl_surface_get_native_handle,
     .surface_get_native_frame = impl_surface_get_native_frame,
 };
+
+NSApplication *yasl_cocoa_display_get_application(struct yasl_display *d)
+{
+    return (d && yasl_display_backend(d) == YASL_BACKEND_COCOA) ?
+        (NSApplication *)yasl_display_get_native_handle(d) : nil;
+}
+
+NSWindow *yasl_cocoa_surface_get_window(struct yasl_surface *s)
+{
+    return (s && s->display && yasl_display_backend(s->display) == YASL_BACKEND_COCOA) ?
+        (NSWindow *)yasl_surface_get_native_handle(s) : nil;
+}
+
+NSView *yasl_cocoa_surface_get_view(struct yasl_surface *s)
+{
+    NSWindow *w = yasl_cocoa_surface_get_window(s);
+    return w ? w.contentView : nil;
+}