Accept concurrent input from multiple tablet devices in QGuiApplication

As a follow-up to 352c357e6f0785c0775a85151d6716b47aea1006 enabling
support for multiple evdevtablet plugins at runtime (one per device),
we also need to adjust the way QGuiApplication handles the events
received from those plugins, in particular when multiple devices
are sending tablet events concurrently.

Replace the static members in QGuiApplication by a vector storing
the same data per-device, so tablet press/release events can be
recognized independently.

Change-Id: Ie0975cdb03a8f6d05903e2e2e57ceb9de73a74a4
Reviewed-by: Jake Petroules <jake.petroules@theqtcompany.com>

4 files changed, 44 insertions, 18 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 0b1c49dd60..248a7d0d1d 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -124,8 +124,6 @@ Qt::KeyboardModifiers QGuiApplicationPrivate::modifier_buttons = Qt::NoModifier;
 
 QPointF QGuiApplicationPrivate::lastCursorPosition(qInf(), qInf());
 
-Qt::MouseButtons QGuiApplicationPrivate::tabletState = Qt::NoButton;
-QWindow *QGuiApplicationPrivate::tabletPressTarget = 0;
 QWindow *QGuiApplicationPrivate::currentMouseWindow = 0;
 
 QString QGuiApplicationPrivate::styleOverride;
@@ -134,6 +132,8 @@ Qt::ApplicationState QGuiApplicationPrivate::applicationState = Qt::ApplicationI
 
 bool QGuiApplicationPrivate::highDpiScalingUpdated = false;
 
+QVector<QGuiApplicationPrivate::TabletPointData> QGuiApplicationPrivate::tabletDevicePoints;
+
 QPlatformIntegration *QGuiApplicationPrivate::platform_integration = 0;
 QPlatformTheme *QGuiApplicationPrivate::platform_theme = 0;
 
@@ -2198,12 +2198,26 @@ void QGuiApplicationPrivate::processFileOpenEvent(QWindowSystemInterfacePrivate:
     QGuiApplication::sendSpontaneousEvent(qApp, &event);
 }
 
+QGuiApplicationPrivate::TabletPointData &QGuiApplicationPrivate::tabletDevicePoint(qint64 deviceId)
+{
+    for (int i = 0; i < tabletDevicePoints.size(); ++i) {
+        TabletPointData &pointData = tabletDevicePoints[i];
+        if (pointData.deviceId == deviceId)
+            return pointData;
+    }
+
+    tabletDevicePoints.append(TabletPointData(deviceId));
+    return tabletDevicePoints.last();
+}
+
 void QGuiApplicationPrivate::processTabletEvent(QWindowSystemInterfacePrivate::TabletEvent *e)
 {
 #ifndef QT_NO_TABLETEVENT
+    TabletPointData &pointData = tabletDevicePoint(e->uid);
+
     QEvent::Type type = QEvent::TabletMove;
-    if (e->buttons != tabletState)
-        type = (e->buttons > tabletState) ? QEvent::TabletPress : QEvent::TabletRelease;
+    if (e->buttons != pointData.state)
+        type = (e->buttons > pointData.state) ? QEvent::TabletPress : QEvent::TabletRelease;
 
     QWindow *window = e->window.data();
     modifier_buttons = e->modifiers;
@@ -2219,14 +2233,14 @@ void QGuiApplicationPrivate::processTabletEvent(QWindowSystemInterfacePrivate::T
         }
         if (!window)
             return;
-        tabletPressTarget = window;
+        pointData.target = window;
     } else {
         if (e->nullWindow()) {
-            window = tabletPressTarget;
+            window = pointData.target;
             localValid = false;
         }
         if (type == QEvent::TabletRelease)
-            tabletPressTarget = 0;
+            pointData.target = Q_NULLPTR;
         if (!window)
             return;
     }
@@ -2235,7 +2249,7 @@ void QGuiApplicationPrivate::processTabletEvent(QWindowSystemInterfacePrivate::T
         QPointF delta = e->global - e->global.toPoint();
         local = window->mapFromGlobal(e->global.toPoint()) + delta;
     }
-    Qt::MouseButtons stateChange = e->buttons ^ tabletState;
+    Qt::MouseButtons stateChange = e->buttons ^ pointData.state;
     Qt::MouseButton button = Qt::NoButton;
     for (int check = Qt::LeftButton; check <= int(Qt::MaxMouseButton); check = check << 1) {
         if (check & stateChange) {
@@ -2249,7 +2263,7 @@ void QGuiApplicationPrivate::processTabletEvent(QWindowSystemInterfacePrivate::T
                     e->modifiers, e->uid, button, e->buttons);
     ev.setTimestamp(e->timestamp);
     QGuiApplication::sendSpontaneousEvent(window, &ev);
-    tabletState = e->buttons;
+    pointData.state = e->buttons;
 #else
     Q_UNUSED(e)
 #endif
@@ -2261,7 +2275,7 @@ void QGuiApplicationPrivate::processTabletEnterProximityEvent(QWindowSystemInter
     QTabletEvent ev(QEvent::TabletEnterProximity, QPointF(), QPointF(),
                     e->device, e->pointerType, 0, 0, 0,
                     0, 0, 0,
-                    Qt::NoModifier, e->uid, Qt::NoButton, tabletState);
+                    Qt::NoModifier, e->uid, Qt::NoButton, tabletDevicePoint(e->uid).state);
     ev.setTimestamp(e->timestamp);
     QGuiApplication::sendSpontaneousEvent(qGuiApp, &ev);
 #else
@@ -2275,7 +2289,7 @@ void QGuiApplicationPrivate::processTabletLeaveProximityEvent(QWindowSystemInter
     QTabletEvent ev(QEvent::TabletLeaveProximity, QPointF(), QPointF(),
                     e->device, e->pointerType, 0, 0, 0,
                     0, 0, 0,
-                    Qt::NoModifier, e->uid, Qt::NoButton, tabletState);
+                    Qt::NoModifier, e->uid, Qt::NoButton, tabletDevicePoint(e->uid).state);
     ev.setTimestamp(e->timestamp);
     QGuiApplication::sendSpontaneousEvent(qGuiApp, &ev);
 #else
diff --git a/src/gui/kernel/qguiapplication_p.h b/src/gui/kernel/qguiapplication_p.h
index 4d5797a8fa..5ef8dee8b7 100644
--- a/src/gui/kernel/qguiapplication_p.h
+++ b/src/gui/kernel/qguiapplication_p.h
@@ -198,13 +198,20 @@ public:
     static int mousePressY;
     static int mouse_double_click_distance;
     static QPointF lastCursorPosition;
-    static Qt::MouseButtons tabletState;
-    static QWindow *tabletPressTarget;
     static QWindow *currentMouseWindow;
     static QWindow *currentMousePressWindow;
     static Qt::ApplicationState applicationState;
     static bool highDpiScalingUpdated;
 
+    struct TabletPointData {
+        TabletPointData(qint64 devId = 0) : deviceId(devId), state(Qt::NoButton), target(Q_NULLPTR) {}
+        qint64 deviceId;
+        Qt::MouseButtons state;
+        QWindow *target;
+    };
+    static QVector<TabletPointData> tabletDevicePoints;
+    static TabletPointData &tabletDevicePoint(qint64 deviceId);
+
 #ifndef QT_NO_CLIPBOARD
     static QClipboard *qt_clipboard;
 #endif
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 3f971d700e..2b9340c04d 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -1680,8 +1680,12 @@ void QWindow::destroy()
         QGuiApplicationPrivate::currentMouseWindow = parent();
     if (QGuiApplicationPrivate::currentMousePressWindow == this)
         QGuiApplicationPrivate::currentMousePressWindow = parent();
-    if (QGuiApplicationPrivate::tabletPressTarget == this)
-        QGuiApplicationPrivate::tabletPressTarget = parent();
+
+    for (int i = 0; i < QGuiApplicationPrivate::tabletDevicePoints.size(); ++i) {
+        QGuiApplicationPrivate::TabletPointData &pointData = QGuiApplicationPrivate::tabletDevicePoints[i];
+        if (pointData.target == this)
+            pointData.target = parent();
+    }
 
     bool wasVisible = isVisible();
     d->visibilityOnDestroy = wasVisible && d->platformWindow;
diff --git a/src/plugins/platforms/windows/qwindowstabletsupport.cpp b/src/plugins/platforms/windows/qwindowstabletsupport.cpp
index b27811df9e..d5aae9746d 100644
--- a/src/plugins/platforms/windows/qwindowstabletsupport.cpp
+++ b/src/plugins/platforms/windows/qwindowstabletsupport.cpp
@@ -391,6 +391,7 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
 
     const int currentDevice = m_devices.at(m_currentDevice).currentDevice;
     const int currentPointer = m_devices.at(m_currentDevice).currentPointerType;
+    const qint64 uniqueId = m_devices.at(m_currentDevice).uniqueId;
 
     // The tablet can be used in 2 different modes, depending on it settings:
     // 1) Absolute (pen) mode:
@@ -407,7 +408,7 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
     const QRect virtualDesktopArea = QGuiApplication::primaryScreen()->virtualGeometry();
 
     qCDebug(lcQpaTablet) << __FUNCTION__ << "processing " << packetCount
-        << "target:" << QGuiApplicationPrivate::tabletPressTarget;
+        << "target:" << QGuiApplicationPrivate::tabletDevicePoint(uniqueId).target;
 
     const Qt::KeyboardModifiers keyboardModifiers = QWindowsKeyMapper::queryKeyboardModifiers();
 
@@ -420,7 +421,7 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
         QPointF globalPosF = m_oldGlobalPosF;
         m_oldGlobalPosF = m_devices.at(m_currentDevice).scaleCoordinates(packet.pkX, packet.pkY, virtualDesktopArea);
 
-        QWindow *target = QGuiApplicationPrivate::tabletPressTarget; // Pass to window that grabbed it.
+        QWindow *target = QGuiApplicationPrivate::tabletDevicePoint(uniqueId).target; // Pass to window that grabbed it.
         QPoint globalPos = globalPosF.toPoint();
 
         // Get Mouse Position and compare to tablet info
@@ -484,7 +485,7 @@ bool QWindowsTabletSupport::translateTabletPacketEvent()
                                                   static_cast<Qt::MouseButtons>(packet.pkButtons),
                                                   pressureNew, tiltX, tiltY,
                                                   tangentialPressure, rotation, z,
-                                                  m_devices.at(m_currentDevice).uniqueId,
+                                                  uniqueId,
                                                   keyboardModifiers);
     }
     return true;