WIP: implement touch scrolling

input.c

@@ -411,7 +411,7 @@ execute_binding(struct seat *seat, struct terminal *term,
 
             term_damage_view(term);
             render_refresh(term);
-            break; 
+            break;
         }
 
         return true;
@@ -2634,3 +2634,98 @@ const struct wl_pointer_listener pointer_listener = {
     .axis_stop = wl_pointer_axis_stop,
     .axis_discrete = wl_pointer_axis_discrete,
 };
+
+static void
+wl_touch_down(void *data, struct wl_touch *wl_touch, uint32_t serial,
+              uint32_t time, struct wl_surface *surface, int32_t id,
+              int32_t x, int32_t y)
+{
+    struct seat *seat = data;
+    if (seat->touch.id != 0) // Multi-touch is not supported
+        return;
+    seat->touch.id = id;
+
+    struct terminal *term = ((const struct wl_window *)wl_surface_get_user_data(surface))->term;
+    xassert(term != NULL);
+
+    seat->touch.serial = serial;
+    seat->touch.x = wl_fixed_to_int(x) * term->scale;
+    seat->touch.y = wl_fixed_to_int(y) * term->scale;
+    seat->touch.surface = surface;
+}
+
+static void
+wl_touch_up(void *data, struct wl_touch *wl_touch, uint32_t serial,
+              uint32_t time, int32_t id)
+{
+    struct seat *seat = data;
+    if (seat->touch.id != id) // Not our touch point.
+        return;
+
+    seat->touch.id = 0;
+}
+
+static void
+wl_touch_motion(void *data, struct wl_touch *wl_touch, uint32_t time,
+                int32_t id, wl_fixed_t x, wl_fixed_t y)
+{
+    struct seat *seat = data;
+    if (seat->touch.id != id) // Not our touch point.
+        return;
+
+    struct terminal *term = ((const struct wl_window *)wl_surface_get_user_data(seat->touch.surface))->term;
+    xassert(term != NULL);
+
+    int new_y = wl_fixed_to_int(y) * term->scale;
+
+    int32_t distance = (new_y - seat->touch.y);
+    int32_t lines = distance  / term->cell_height;
+    if (lines == 0) {
+        // Don't update the origin 'y'.
+        // This half-cell motion might compound with the next one.
+        return;
+    }
+    seat->touch.y = new_y;
+
+    if (lines > 0) {
+        cmd_scrollback_up(term, lines);
+    } else if (lines < 0) {
+        cmd_scrollback_down(term, -lines);
+    }
+}
+static void
+wl_touch_frame(void *data, struct wl_touch *wl_touch)
+{
+    // no-op
+}
+
+static void
+wl_touch_cancel(void *data, struct wl_touch *wl_touch)
+{
+    struct seat *seat = data;
+    seat->touch.id = 0;
+}
+
+static void
+wl_touch_shape(void *data, struct wl_touch *wl_touch,
+               int32_t id, int32_t major, int32_t minor)
+{
+    // no-op
+}
+
+static void
+wl_touch_orientation(void *data, struct wl_touch *wl_touch,
+                     int32_t id, int32_t orientation)
+{
+    // no-op
+}
+
+const struct wl_touch_listener touch_listener = {
+    .down = wl_touch_down,
+    .up = wl_touch_up,
+    .motion = wl_touch_motion,
+    .frame = wl_touch_frame,
+    .cancel = wl_touch_cancel,
+    .shape = wl_touch_shape,
+    .orientation = wl_touch_orientation,
+};

input.h

@@ -25,6 +25,7 @@
 
 extern const struct wl_keyboard_listener keyboard_listener;
 extern const struct wl_pointer_listener pointer_listener;
+extern const struct wl_touch_listener touch_listener;
 
 void input_repeat(struct seat *seat, uint32_t key);
 

wayland.c

@@ -270,9 +270,10 @@ seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
     struct seat *seat = data;
     xassert(seat->wl_seat == wl_seat);
 
-    LOG_DBG("%s: keyboard=%s, pointer=%s", seat->name,
+    LOG_DBG("%s: keyboard=%s, pointer=%s, touch=%s", seat->name,
             (caps & WL_SEAT_CAPABILITY_KEYBOARD) ? "yes" : "no",
-            (caps & WL_SEAT_CAPABILITY_POINTER) ? "yes" : "no");
+            (caps & WL_SEAT_CAPABILITY_POINTER) ? "yes" : "no",
+            (caps & WL_SEAT_CAPABILITY_TOUCH) ? "yes" : "no");
 
     if (caps & WL_SEAT_CAPABILITY_KEYBOARD) {
         if (seat->wl_keyboard == NULL) {
@@ -313,6 +314,18 @@ seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
             seat->pointer.cursor = NULL;
         }
     }
+
+    if (caps & WL_SEAT_CAPABILITY_TOUCH) {
+        if (seat->wl_touch == NULL) {
+            seat->wl_touch = wl_seat_get_touch(wl_seat);
+            wl_touch_add_listener(seat->wl_touch, &touch_listener, seat);
+        }
+    } else {
+        if (seat->wl_touch != NULL) {
+            wl_touch_release(seat->wl_touch);
+            seat->wl_touch = NULL;
+        }
+    }
 }
 
 static void

wayland.h

@@ -157,6 +157,16 @@ struct seat {
         bool have_discrete;
     } mouse;
 
+    /* Pointer state */
+    struct wl_touch *wl_touch;
+    struct {
+        uint32_t serial; // Unused for now; usable later for copying.
+        int32_t id;
+        struct wl_surface *surface;
+        int32_t x;
+        int32_t y;
+    } touch;
+
     /* Clipboard */
     struct wl_data_device *data_device;
     struct zwp_primary_selection_device_v1 *primary_selection_device;