Implement keyframes snapping

When shift is down while dragging keyframe(s), they snap to ruler ticks,
keyframes, and the playhead.

Task-number: QDS-1068
Change-Id: Iea5fec9e578d3f1db51c429cbd565ad145a90fe8
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

3 files changed, 31 insertions, 15 deletions

diff --git a/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.cpp b/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.cpp
index f212d52916..96d37f395a 100644
--- a/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.cpp
+++ b/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.cpp
@@ -181,10 +181,10 @@ void TimelineGraphicsScene::updateKeyframePositionsCache()
 }
 
 // snap a frame to nearest keyframe or ruler tick
-qreal TimelineGraphicsScene::snap(qreal frame)
+qreal TimelineGraphicsScene::snap(qreal frame, bool snapToPlayhead)
 {
-    qreal frameTick = m_layout->ruler()->getFrameTick();
-    qreal rulerTicksSnapframe = qRound(frame / frameTick) * frameTick;
+    qreal rulerFrameTick = m_layout->ruler()->getFrameTick();
+    qreal nearestRulerTickFrame = qRound(frame / rulerFrameTick) * rulerFrameTick;
     // get nearest keyframe to the input frame
     bool nearestKeyframeFound = false;
     qreal nearestKeyframe = 0;
@@ -202,23 +202,30 @@ qreal TimelineGraphicsScene::snap(qreal frame)
         }
     }
 
-    if (!nearestKeyframeFound && !m_keyframePositionsCache.empty()) {
-        // playhead past last keyframe case
+    // playhead past last keyframe case
+    if (!nearestKeyframeFound && !m_keyframePositionsCache.empty())
         nearestKeyframe = m_keyframePositionsCache.last();
-        nearestKeyframeFound = true;
-    }
 
-    // return nearest snappable keyframe or ruler tick
-    return nearestKeyframeFound  && qAbs(nearestKeyframe - frame)
-                                  < qAbs(rulerTicksSnapframe - frame) ? nearestKeyframe
-                                                                      : rulerTicksSnapframe;
+    qreal playheadFrame = m_currentFrameIndicator->position();
+
+    qreal dKeyframe = qAbs(nearestKeyframe - frame);
+    qreal dPlayhead = snapToPlayhead ? qAbs(playheadFrame - frame) : 99999.;
+    qreal dRulerTick = qAbs(nearestRulerTickFrame - frame);
+
+    if (dKeyframe <= qMin(dPlayhead, dRulerTick))
+        return nearestKeyframe;
+
+    if (dRulerTick <= dPlayhead)
+        return nearestRulerTickFrame;
+
+    return playheadFrame;
 }
 
 void TimelineGraphicsScene::setCurrenFrame(const QmlTimeline &timeline, qreal frame)
 {
     if (timeline.isValid()) {
         if (QApplication::keyboardModifiers() & Qt::ShiftModifier) // playhead snapping
-            frame = snap(frame);
+            frame = snap(frame, false);
         m_currentFrameIndicator->setPosition(frame);
     } else {
         m_currentFrameIndicator->setPosition(0);
diff --git a/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.h b/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.h
index fd2c641dd4..ba0c10bcd5 100644
--- a/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.h
+++ b/src/plugins/qmldesigner/components/timelineeditor/timelinegraphicsscene.h
@@ -97,6 +97,8 @@ public:
     QVector<qreal> keyframePositions() const;
     QVector<qreal> keyframePositions(const QmlTimelineKeyframeGroup &frames) const;
 
+    qreal snap(qreal frame, bool snapToPlayhead = true);
+
     void setRulerScaling(int scaling);
 
     void commitCurrentFrame(qreal frame);
@@ -167,7 +169,6 @@ private:
     QList<QGraphicsItem *> itemsAt(const QPointF &pos);
 
 private:
-    qreal snap(qreal frame);
 
     TimelineWidget *m_parent = nullptr;
 
diff --git a/src/plugins/qmldesigner/components/timelineeditor/timelinemovetool.cpp b/src/plugins/qmldesigner/components/timelineeditor/timelinemovetool.cpp
index 785b1bb268..7c3d7a79e4 100644
--- a/src/plugins/qmldesigner/components/timelineeditor/timelinemovetool.cpp
+++ b/src/plugins/qmldesigner/components/timelineeditor/timelinemovetool.cpp
@@ -90,7 +90,7 @@ void TimelineMoveTool::mouseMoveEvent(TimelineMovableAbstractItem *item,
             return;
 
         const qreal sourceFrame = qRound(current->mapFromSceneToFrame(current->rect().center().x()));
-        const qreal targetFrame = qRound(current->mapFromSceneToFrame(event->scenePos().x()));
+        qreal targetFrame = qRound(current->mapFromSceneToFrame(event->scenePos().x()));
         qreal deltaFrame = targetFrame - sourceFrame - m_pressKeyframeDelta;
 
         const qreal minFrame = scene()->startFrame();
@@ -106,8 +106,16 @@ void TimelineMoveTool::mouseMoveEvent(TimelineMovableAbstractItem *item,
         else if (firstFrame + deltaFrame < minFrame)
             deltaFrame = minFrame - firstFrame;
 
+        targetFrame = sourceFrame + deltaFrame;
+
+        if (QApplication::keyboardModifiers() & Qt::ShiftModifier) { // keyframe snapping
+            qreal snappedTargetFrame = scene()->snap(targetFrame);
+            deltaFrame += snappedTargetFrame - targetFrame;
+            targetFrame = snappedTargetFrame;
+        }
+
         scene()->statusBarMessageChanged(tr(TimelineConstants::statusBarKeyframe)
-                                         .arg(sourceFrame + deltaFrame));
+                                         .arg(targetFrame));
 
         const QList<TimelineKeyframeItem *> selectedKeyframes = scene()->selectedKeyframes();
         for (auto *keyframe : selectedKeyframes) {