From ad8a48e8f1b336099eab2a00c1c1e59abad8e717 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@qt.io>
Date: Sun, 10 Sep 2017 14:58:49 +0200
Subject: Add QGuiApplication::screenAt()
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[ChangeLog][QtGui] It's now possible to retrieve the screen
at a given point via QGuiApplication::screenAt().

Change-Id: Ic09514ec731d8cce5d453833e98fcd118a70600e
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>
Reviewed-by: Błażej Szczygieł <spaz16@wp.pl>
---
 src/gui/kernel/qguiapplication.cpp    | 63 ++++++++++++++++++-----------------
 src/gui/kernel/qguiapplication.h      |  2 ++
 src/widgets/kernel/qdesktopwidget.cpp | 22 ++----------
 3 files changed, 36 insertions(+), 51 deletions(-)

(limited to 'src')

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index a29ddbe44e..63539c0103 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -987,6 +987,34 @@ QList<QScreen *> QGuiApplication::screens()
     return QGuiApplicationPrivate::screen_list;
 }
 
+/*!
+    Returns the screen at \a point, or \c nullptr if outside of any screen.
+
+    The \a point is in relation to the virtualGeometry() of each set of virtual
+    siblings. If the point maps to more than one set of virtual siblings the first
+    match is returned.
+
+    \since 5.10
+*/
+QScreen *QGuiApplication::screenAt(const QPoint &point)
+{
+    QVarLengthArray<const QScreen *, 8> visitedScreens;
+    for (const QScreen *screen : QGuiApplication::screens()) {
+        if (visitedScreens.contains(screen))
+            continue;
+
+        // The virtual siblings include the screen itself, so iterate directly
+        for (QScreen *sibling : screen->virtualSiblings()) {
+            if (sibling->geometry().contains(point))
+                return sibling;
+
+            visitedScreens.append(sibling);
+        }
+    }
+
+    return nullptr;
+}
+
 /*!
     \fn void QGuiApplication::screenAdded(QScreen *screen)
 
@@ -1050,38 +1078,11 @@ qreal QGuiApplication::devicePixelRatio() const
 */
 QWindow *QGuiApplication::topLevelAt(const QPoint &pos)
 {
-    const QList<QScreen *> screens = QGuiApplication::screens();
-    if (!screens.isEmpty()) {
-        const QList<QScreen *> primaryScreens = screens.first()->virtualSiblings();
-        QScreen *windowScreen = Q_NULLPTR;
-
-        // Find the window on the primary virtual desktop first
-        for (QScreen *screen : primaryScreens) {
-            if (screen->geometry().contains(pos)) {
-                windowScreen = screen;
-                break;
-            }
-        }
-
-        // If the window is not found on primary virtual desktop, find it on all screens
-        // except the first which was for sure in the previous loop. Some other screens
-        // may repeat. Find only when there is more than one virtual desktop.
-        if (!windowScreen && screens.count() != primaryScreens.count()) {
-            for (int i = 1; i < screens.size(); ++i) {
-                QScreen *screen = screens.at(i);
-                if (screen->geometry().contains(pos)) {
-                    windowScreen = screen;
-                    break;
-                }
-            }
-        }
-
-        if (windowScreen) {
-            const QPoint devicePosition = QHighDpi::toNativePixels(pos, windowScreen);
-            return windowScreen->handle()->topLevelAt(devicePosition);
-        }
+    if (QScreen *windowScreen = screenAt(pos)) {
+        const QPoint devicePosition = QHighDpi::toNativePixels(pos, windowScreen);
+        return windowScreen->handle()->topLevelAt(devicePosition);
     }
-    return Q_NULLPTR;
+    return nullptr;
 }
 
 /*!
diff --git a/src/gui/kernel/qguiapplication.h b/src/gui/kernel/qguiapplication.h
index 6721970222..e130553b9d 100644
--- a/src/gui/kernel/qguiapplication.h
+++ b/src/gui/kernel/qguiapplication.h
@@ -110,6 +110,8 @@ public:
 
     static QScreen *primaryScreen();
     static QList<QScreen *> screens();
+    static QScreen *screenAt(const QPoint &point);
+
     qreal devicePixelRatio() const;
 
 #ifndef QT_NO_CURSOR
diff --git a/src/widgets/kernel/qdesktopwidget.cpp b/src/widgets/kernel/qdesktopwidget.cpp
index 6077ac38db..1b9cf88efe 100644
--- a/src/widgets/kernel/qdesktopwidget.cpp
+++ b/src/widgets/kernel/qdesktopwidget.cpp
@@ -352,26 +352,8 @@ int QDesktopWidget::screenNumber(const QPoint &p) const
 
 int QDesktopWidgetPrivate::screenNumber(const QPoint &p)
 {
-    const QList<QScreen *> screens = QGuiApplication::screens();
-    if (!screens.isEmpty()) {
-        const QList<QScreen *> primaryScreens = screens.first()->virtualSiblings();
-        // Find the screen index on the primary virtual desktop first
-        foreach (QScreen *screen, primaryScreens) {
-            if (screen->geometry().contains(p))
-                return screens.indexOf(screen);
-        }
-        // If the screen index is not found on primary virtual desktop, find
-        // the screen index on all screens except the first which was for
-        // sure in the previous loop. Some other screens may repeat. Find
-        // only when there is more than one virtual desktop.
-        if (screens.count() != primaryScreens.count()) {
-            for (int i = 1; i < screens.size(); ++i) {
-                if (screens[i]->geometry().contains(p))
-                    return i;
-            }
-        }
-    }
-    return primaryScreen(); //even better would be closest screen
+    QScreen *screen = QGuiApplication::screenAt(p);
+    return screen ? QGuiApplication::screens().indexOf(screen) : primaryScreen();
 }
 
 void QDesktopWidget::resizeEvent(QResizeEvent *)
-- 
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