feat: cross-platform pen pressure, tilt, and stylus handling

- Hook up Cocoa tablet, stylus, and Force Touch pressure/tilt to push_pointer
- Ensure Wayland tablet tool pressure resets cleanly on tool up
- Visualize pressure-sensitive brush scaling and telemetry in simple_window

3 files changed, 74 insertions, 19 deletions

diff --git a/examples/simple_window.c b/examples/simple_window.c
index a8a2861..a6819f9 100644
--- a/examples/simple_window.c
+++ b/examples/simple_window.c
@@ -8,6 +8,20 @@ static int mouse_x = -1;
 static int mouse_y = -1;
 static bool mouse_down = false;
 static int color_theme = 0;
+static uint16_t pen_pressure = 0;
+static int8_t pen_tilt_x = 0;
+static int8_t pen_tilt_y = 0;
+static enum yasl_pointer_device pointer_device = YASL_PTR_DEV_MOUSE;
+
+static const char *device_name(enum yasl_pointer_device dev)
+{
+    switch (dev) {
+    case YASL_PTR_DEV_PEN:    return "Pen/Stylus";
+    case YASL_PTR_DEV_ERASER: return "Eraser";
+    case YASL_PTR_DEV_TOUCH:  return "Touch";
+    default:                  return "Mouse";
+    }
+}
 
 static void on_draw(struct yasl_surface *s, struct yasl_frame *frame, void *ud)
 {
@@ -42,12 +56,20 @@ static void on_draw(struct yasl_surface *s, struct yasl_frame *frame, void *ud)
                 break;
             }
 
-            /* Draw interactive pointer indicator */
+            /* Draw interactive pointer / stylus indicator */
             if (mouse_x >= 0 && mouse_y >= 0) {
                 int dx = x - mouse_x;
                 int dy = y - mouse_y;
                 int dist_sq = dx * dx + dy * dy;
-                int radius = mouse_down ? 36 : 20;
+
+                /* Pressure-sensitive radius: scales dynamically from 8px to 64px */
+                int radius;
+                if (pen_pressure > 0) {
+                    radius = 8 + (int)(((uint32_t)pen_pressure * 56) / 65535);
+                } else {
+                    radius = mouse_down ? 36 : 18;
+                }
+
                 if (dist_sq < radius * radius) {
                     r = (uint8_t)(255 - r / 2);
                     g = (uint8_t)(255 - g / 2);
@@ -87,7 +109,6 @@ static void on_quit(void *ud)
 
 int main(void)
 {
-    /* YASL manages its event loop internally when NULL is passed */
     struct yasl_display_cbs disp_cbs = { .quit = on_quit };
     struct yasl_display_spec disp_spec = {
         .app_id = "org.yasl.example",
@@ -100,7 +121,7 @@ int main(void)
     }
 
     struct yasl_surface_spec surf_spec = {
-        .title = "YASL Interactive Window",
+        .title = "YASL Interactive Window (Pen & Touch Enabled)",
         .size = { .x = 640, .y = 480 },
     };
     struct yasl_surface *s = yasl_surface_create_toplevel(d, &surf_spec);
@@ -119,9 +140,10 @@ int main(void)
     yasl_surface_schedule_redraw(s);
 
     printf("=== YASL Demo Running ===\n");
-    printf(" - Move or Click mouse inside window to interact\n");
-    printf(" - Press Space to cycle background themes\n");
-    printf(" - Press Escape or close window to exit\n\n");
+    printf(" - Stylus/Pen: full pressure (0..65535) and tilt detection\n");
+    printf(" - Mouse/Touch: interactive click/motion highlights\n");
+    printf(" - Space: cycle background themes\n");
+    printf(" - Escape: exit\n\n");
 
     while (running) {
         yasl_display_dispatch(d);
@@ -138,24 +160,34 @@ int main(void)
                     }
                 }
             } else if (ev.kind == YASL_INPUT_MOUSE) {
-                if (ev.mouse.kind == YASL_PTR_MOTION) {
-                    mouse_x = ev.mouse.pos.x;
-                    mouse_y = ev.mouse.pos.y;
-                    yasl_surface_schedule_redraw(s);
-                } else if (ev.mouse.kind == YASL_PTR_PRESS) {
+                mouse_x = ev.mouse.pos.x;
+                mouse_y = ev.mouse.pos.y;
+                pen_pressure = ev.mouse.pen.pressure;
+                pen_tilt_x = ev.mouse.pen.tilt_x;
+                pen_tilt_y = ev.mouse.pen.tilt_y;
+                pointer_device = ev.mouse.device;
+
+                if (ev.mouse.kind == YASL_PTR_PRESS) {
                     mouse_down = true;
-                    mouse_x = ev.mouse.pos.x;
-                    mouse_y = ev.mouse.pos.y;
-                    yasl_surface_schedule_redraw(s);
+                    if (pen_pressure > 0 || pointer_device == YASL_PTR_DEV_PEN) {
+                        printf("[Pen Down] Pressure: %5u/65535 (%.1f%%) | Tilt: (%+3d°, %+3d°) | Device: %s\n",
+                               pen_pressure, (pen_pressure * 100.0) / 65535.0,
+                               pen_tilt_x, pen_tilt_y, device_name(pointer_device));
+                    }
                 } else if (ev.mouse.kind == YASL_PTR_RELEASE) {
                     mouse_down = false;
-                    yasl_surface_schedule_redraw(s);
+                    pen_pressure = 0;
+                } else if (ev.mouse.kind == YASL_PTR_MOTION && pen_pressure > 0) {
+                    printf("[Pen Move] Pressure: %5u/65535 (%.1f%%) | Tilt: (%+3d°, %+3d°) | Device: %s\n",
+                           pen_pressure, (pen_pressure * 100.0) / 65535.0,
+                           pen_tilt_x, pen_tilt_y, device_name(pointer_device));
                 } else if (ev.mouse.kind == YASL_PTR_LEAVE) {
                     mouse_x = -1;
                     mouse_y = -1;
                     mouse_down = false;
-                    yasl_surface_schedule_redraw(s);
+                    pen_pressure = 0;
                 }
+                yasl_surface_schedule_redraw(s);
             }
         }
 
diff --git a/src/cocoa/window.m b/src/cocoa/window.m
index 6c28f3f..451f448 100644
--- a/src/cocoa/window.m
+++ b/src/cocoa/window.m
@@ -317,14 +317,36 @@ static void push_pointer(struct yasl_surface *w, NSEvent *ev, enum yasl_pointer_
     w->mods = cocoa_mods(ev.modifierFlags);
     if (kind != YASL_PTR_LEAVE)
         w->pointer = event_pos(w, ev);
+
+    enum yasl_pointer_device device = YASL_PTR_DEV_MOUSE;
+    struct yasl_pointer_pen pen = {0};
+
+    float press = (float)ev.pressure;
+    if (ev.subtype == NSEventSubtypeTabletPoint || press > 0.0f) {
+        if (ev.pointingDeviceType == NSPointingDeviceTypeEraser)
+            device = YASL_PTR_DEV_ERASER;
+        else if (ev.pointingDeviceType == NSPointingDeviceTypePen)
+            device = YASL_PTR_DEV_PEN;
+
+        if (press > 1.0f) press = 1.0f;
+        if (press > 0.0f)
+            pen.pressure = (uint16_t)(press * 65535.0f);
+
+        NSPoint tilt = ev.tilt;
+        pen.tilt_x = (int8_t)(tilt.x * 90.0);
+        pen.tilt_y = (int8_t)(tilt.y * 90.0);
+    }
+
     struct yasl_input_event input_ev = {
-        .kind = YASL_INPUT_MOUSE,
         .surface = w,
+        .kind = YASL_INPUT_MOUSE,
         .mouse = {
             .pos = w->pointer,
-            .button = button,
+            .button = (int16_t)button,
             .kind = kind,
+            .device = device,
             .mods = w->mods,
+            .pen = pen,
         },
     };
     input_queue_push(&w->input, &input_ev);
diff --git a/src/wayland/pointer.c b/src/wayland/pointer.c
index 006eadd..5f97370 100644
--- a/src/wayland/pointer.c
+++ b/src/wayland/pointer.c
@@ -785,6 +785,7 @@ static void tablet_tool_up(void *data, struct zwp_tablet_tool_v2 *tool)
     struct seat *s = ((struct tablet_tool *)data)->seat;
     struct yasl_surface *w = s->tablet_focus;
     if (!w) return;
+    s->pen.pressure = 0;
     press_queue_push(&s->tool_presses, w, s->tool_pos, 0, true);
 }