Improve the hit testing of an interactive PageIndicator

The Universal style has relatively large spacing between the dots.
The small dots are hard to hit => select the nearest dot.

Change-Id: I2207e887706be38c1a6091bd8aca13d26b9957a8
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

src/templates/qquickpageindicator.cpp

@@ -37,6 +37,8 @@
 #include "qquickpageindicator_p.h"
 #include "qquickcontrol_p_p.h"
 
+#include <QtCore/qmath.h>
+#include <QtQuick/private/qquickitem_p.h>
 #include <QtQuick/private/qquickitemchangelistener_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -86,11 +88,33 @@ public:
 QQuickItem *QQuickPageIndicatorPrivate::itemAt(const QPoint &pos) const
 {
     Q_Q(const QQuickPageIndicator);
-    if (contentItem) {
-        QPointF mapped = q->mapToItem(contentItem, pos);
-        return contentItem->childAt(mapped.x(), mapped.y());
+    if (!contentItem || !q->contains(pos))
+        return Q_NULLPTR;
+
+    QPointF contentPos = q->mapToItem(contentItem, pos);
+    QQuickItem *item = contentItem->childAt(contentPos.x(), contentPos.y());
+    while (item && item->parentItem() != contentItem)
+        item = item->parentItem();
+    if (item && !QQuickItemPrivate::get(item)->isTransparentForPositioner())
+        return item;
+
+    // find the nearest
+    qreal distance = qInf();
+    QQuickItem *nearest = Q_NULLPTR;
+    foreach (QQuickItem *child, contentItem->childItems()) {
+        if (QQuickItemPrivate::get(child)->isTransparentForPositioner())
+            continue;
+
+        QPointF center = child->boundingRect().center();
+        QPointF pt = contentItem->mapToItem(child, contentPos);
+
+        qreal len = QLineF(center, pt).length();
+        if (len < distance) {
+            distance = len;
+            nearest = child;
+        }
     }
-    return Q_NULLPTR;
+    return nearest;
 }
 
 void QQuickPageIndicatorPrivate::updatePressed(bool pressed, const QPoint &pos)

tests/auto/controls/data/tst_pageindicator.qml

@@ -93,6 +93,24 @@ TestCase {
         mouseClick(control, control.width / 2, control.height / 2, Qt.LeftButton)
         compare(control.currentIndex, 2)
 
+        // test also clicking outside delegates => the nearest should be selected
+        control.padding = 10
+        control.spacing = 10
+
+        for (var i = 0; i < control.count; ++i) {
+            var child = control.contentItem.children[i]
+            for (var x = -2; x <= child.width + 2; ++x) {
+                for (var y = -2; y <= child.height + 2; ++y) {
+                    control.currentIndex = -1
+                    compare(control.currentIndex, -1)
+
+                    var pos = control.mapFromItem(child, x, y)
+                    mouseClick(control, pos.x, pos.y, Qt.LeftButton)
+                    compare(control.currentIndex, i)
+                }
+            }
+        }
+
         control.destroy()
     }
 }