Increase fine-grained signals for some properties in Flickable

Flickable.at[X/Y][Beginning/End] were being always notified of changes
at bulk. This is can be harmful in performance of QML applications that
will trigger change requests on the program whenever a property is
modified.

This introduces separate signals so it's not a problem anymore.

Change-Id: I729852df665ec34f532812dd0a45507d053d624c
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

1 files changed, 15 insertions, 6 deletions

diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index de3f835dc0..83d383d7c0 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -509,7 +509,8 @@ static bool fuzzyLessThanOrEqualTo(qreal a, qreal b)
 void QQuickFlickablePrivate::updateBeginningEnd()
 {
     Q_Q(QQuickFlickable);
-    bool atBoundaryChange = false;
+    bool atXBeginningChange = false, atXEndChange = false;
+    bool atYBeginningChange = false, atYEndChange = false;
 
     // Vertical
     const qreal maxyextent = -q->maxYExtent();
@@ -520,11 +521,11 @@ void QQuickFlickablePrivate::updateBeginningEnd()
 
     if (atBeginning != vData.atBeginning) {
         vData.atBeginning = atBeginning;
-        atBoundaryChange = true;
+        atYBeginningChange = true;
     }
     if (atEnd != vData.atEnd) {
         vData.atEnd = atEnd;
-        atBoundaryChange = true;
+        atYEndChange = true;
     }
 
     // Horizontal
@@ -536,11 +537,11 @@ void QQuickFlickablePrivate::updateBeginningEnd()
 
     if (atBeginning != hData.atBeginning) {
         hData.atBeginning = atBeginning;
-        atBoundaryChange = true;
+        atXBeginningChange = true;
     }
     if (atEnd != hData.atEnd) {
         hData.atEnd = atEnd;
-        atBoundaryChange = true;
+        atXEndChange = true;
     }
 
     if (vData.extentsChanged) {
@@ -561,8 +562,16 @@ void QQuickFlickablePrivate::updateBeginningEnd()
         }
     }
 
-    if (atBoundaryChange)
+    if (atXEndChange || atYEndChange || atXBeginningChange || atYBeginningChange)
         emit q->isAtBoundaryChanged();
+    if (atXEndChange)
+        emit q->atXEndChanged();
+    if (atXBeginningChange)
+        emit q->atXBeginningChanged();
+    if (atYEndChange)
+        emit q->atYEndChanged();
+    if (atYBeginningChange)
+        emit q->atYBeginningChanged();
 
     if (visibleArea)
         visibleArea->updateVisible();