generate fake mouseevents on touch for xwayland

on xwayland clients, send mouse press, move and release
corresponding to touchDown, move and release
this gives a very basic touchscreen support on
xwayland clients

reviewed-by: Martin Graesslin <mgraesslin@kde.org>

src/wayland/seat_interface.cpp

@@ -862,7 +862,19 @@ qint32 SeatInterface::touchDown(const QPointF &globalPosition)
     const quint32 serial = display()->nextSerial();
     if (d->touchInterface.focus.touch && d->touchInterface.focus.surface) {
         d->touchInterface.focus.touch->down(id, serial, globalPosition - d->touchInterface.focus.offset);
+    } else if (id == 0 && focusedTouchSurface()) {
+        auto p = d->pointerForSurface(focusedTouchSurface());
+        if (!p) {
+            return id;
+        }
+        const QPointF pos = globalPosition - d->touchInterface.focus.offset;
+        wl_pointer_send_enter(p->resource(), serial,
+                          focusedTouchSurface()->resource(),
+                          wl_fixed_from_double(pos.x()), wl_fixed_from_double(pos.y()));
+
+        wl_pointer_send_button(p->resource(), serial, timestamp(), BTN_LEFT, WL_POINTER_BUTTON_STATE_PRESSED);
     }
+
     d->touchInterface.ids << id;
     return id;
 }
@@ -872,7 +884,16 @@ void SeatInterface::touchMove(qint32 id, const QPointF &globalPosition)
     Q_D();
     if (d->touchInterface.focus.touch && d->touchInterface.focus.surface) {
         d->touchInterface.focus.touch->move(id, globalPosition - d->touchInterface.focus.offset);
-    }
+    } else if (id == 0 && focusedTouchSurface()) {
+        auto p = d->pointerForSurface(focusedTouchSurface());
+        if (!p) {
+            return;
+        }
+
+        const QPointF pos = globalPosition - d->touchInterface.focus.offset;
+        wl_pointer_send_motion(p->resource(), timestamp(),
+                                wl_fixed_from_double(pos.x()), wl_fixed_from_double(pos.y()));
+    } 
 }
 
 void SeatInterface::touchUp(qint32 id)
@@ -881,6 +902,14 @@ void SeatInterface::touchUp(qint32 id)
     Q_ASSERT(d->touchInterface.ids.contains(id));
     if (d->touchInterface.focus.touch && d->touchInterface.focus.surface) {
         d->touchInterface.focus.touch->up(id, display()->nextSerial());
+    } else if (id == 0 && focusedTouchSurface()) {
+        const quint32 serial = display()->nextSerial();
+        auto p = d->pointerForSurface(focusedTouchSurface());
+        if (!p) {
+            return;
+        }
+
+        wl_pointer_send_button(p->resource(), serial, timestamp(), BTN_LEFT, WL_POINTER_BUTTON_STATE_RELEASED);
     }
     d->touchInterface.ids.removeAll(id);
 }