[backends/virtual] Add possibility to have multiple virtual screens

Very basic: all screens have same size and are ordered from left to
right. It's mostly meant to allow easy test cases with multi-screen.

The quick tiling test demonstrates how it's used.

autotests/wayland/quick_tiling_test.cpp

@@ -70,9 +70,13 @@ void QuickTilingTest::initTestCase()
     QSignalSpy workspaceCreatedSpy(kwinApp(), &Application::workspaceCreated);
     QVERIFY(workspaceCreatedSpy.isValid());
     waylandServer()->backend()->setInitialWindowSize(QSize(1280, 1024));
+    QMetaObject::invokeMethod(waylandServer()->backend(), "setOutputCount", Qt::DirectConnection, Q_ARG(int, 2));
     waylandServer()->init(s_socketName.toLocal8Bit());
     kwinApp()->start();
     QVERIFY(workspaceCreatedSpy.wait());
+    QCOMPARE(screens()->count(), 2);
+    QCOMPARE(screens()->geometry(0), QRect(0, 0, 1280, 1024));
+    QCOMPARE(screens()->geometry(1), QRect(1280, 0, 1280, 1024));
 }
 
 void QuickTilingTest::init()
@@ -120,6 +124,8 @@ void QuickTilingTest::init()
     QVERIFY(m_shm->isValid());
     m_shell = registry.createShell(shellSpy.first().first().value<quint32>(), shellSpy.first().last().value<quint32>(), this);
     QVERIFY(m_shell->isValid());
+
+    screens()->setCurrent(0);
 }
 
 void QuickTilingTest::cleanup()

backends/virtual/screens_virtual.cpp

@@ -42,29 +42,46 @@ void VirtualScreens::init()
 
 QRect VirtualScreens::geometry(int screen) const
 {
-    if (screen == 0) {
-        return QRect(QPoint(0, 0), size(screen));
+    if (screen >= m_geometries.count()) {
+        return QRect();
     }
-    return QRect();
+    return m_geometries.at(screen);
 }
 
 QSize VirtualScreens::size(int screen) const
 {
-    if (screen == 0) {
-        return m_backend->size();
-    }
-    return QSize();
+    return geometry(screen).size();
 }
 
 void VirtualScreens::updateCount()
 {
-    setCount(1);
+    m_geometries.clear();
+    const QSize size = m_backend->size();
+    for (int i = 0; i < m_backend->outputCount(); ++i) {
+        m_geometries.append(QRect(size.width() * i, 0, size.width(), size.height()));
+    }
+    setCount(m_backend->outputCount());
 }
 
 int VirtualScreens::number(const QPoint &pos) const
 {
-    Q_UNUSED(pos)
-    return 0;
+    int bestScreen = 0;
+    int minDistance = INT_MAX;
+    for (int i = 0; i < m_geometries.count(); ++i) {
+        const QRect &geo = m_geometries.at(i);
+        if (geo.contains(pos)) {
+            return i;
+        }
+        int distance = QPoint(geo.topLeft() - pos).manhattanLength();
+        distance = qMin(distance, QPoint(geo.topRight() - pos).manhattanLength());
+        distance = qMin(distance, QPoint(geo.bottomRight() - pos).manhattanLength());
+        distance = qMin(distance, QPoint(geo.bottomLeft() - pos).manhattanLength());
+        if (distance < minDistance) {
+            minDistance = distance;
+            bestScreen = i;
+        }
+    }
+    return bestScreen;
 }
 
 }

backends/virtual/screens_virtual.h

@@ -20,6 +20,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifndef KWIN_SCREENS_VIRTUAL_H
 #define KWIN_SCREENS_VIRTUAL_H
 #include "screens.h"
+#include <QVector>
 
 namespace KWin
 {
@@ -39,6 +40,7 @@ public:
 
 private:
     VirtualBackend *m_backend;
+    QVector<QRect> m_geometries;
 };
 
 }

backends/virtual/virtual_backend.h

@@ -45,6 +45,9 @@ public:
     QSize size() const {
         return m_size;
     }
+    int outputCount() const {
+        return m_outputCount;
+    }
 
     bool saveFrames() const {
         return !m_screenshotDir.isNull();
@@ -55,11 +58,16 @@ public:
     QPainterBackend* createQPainterBackend() override;
     OpenGLBackend *createOpenGLBackend() override;
 
+    Q_INVOKABLE void setOutputCount(int count) {
+        m_outputCount = count;
+    }
+
 Q_SIGNALS:
     void sizeChanged();
 
 private:
     QSize m_size;
+    int m_outputCount = 1;
     QScopedPointer<QTemporaryDir> m_screenshotDir;
 };