Added shortcuts for finishing and canceling object creation

Now the Return / Enter keys will finish object creation, and Escape will
cancel object creation.

Suggested by @noc7c9 in relation to #496 and matches Inkscape behavior
for creation of bezier curves / lines.

src/tiled/createobjecttool.cpp

@@ -34,6 +34,7 @@
 #include "utils.h"
 
 #include <QApplication>
+#include <QKeyEvent>
 #include <QPalette>
 
 using namespace Tiled;
@@ -100,6 +101,30 @@ void CreateObjectTool::deactivate(MapScene *scene)
     AbstractObjectTool::deactivate(scene);
 }
 
+void CreateObjectTool::keyPressed(QKeyEvent *event)
+{
+    switch (event->key()) {
+    case Qt::Key_Enter:
+    case Qt::Key_Return:
+        if (mNewMapObjectItem) {
+            if (mMode == CreatePolygon || mMode == CreatePolyline)
+                finishOrCancelPolygon();
+            else
+                finishNewMapObject();
+            return;
+        }
+        break;
+    case Qt::Key_Escape:
+        if (mNewMapObjectItem) {
+            cancelNewMapObject();
+            return;
+        }
+        break;
+    }
+
+    AbstractObjectTool::keyPressed(event);
+}
+
 void CreateObjectTool::mouseEntered()
 {
 }
@@ -200,13 +225,7 @@ void CreateObjectTool::mousePressed(QGraphicsSceneMouseEvent *event)
         case CreatePolygon:
         case CreatePolyline:
             if (event->button() == Qt::RightButton) {
-                // The polygon needs to have at least three points and a
-                // polyline needs at least two.
-                int min = mMode == CreatePolygon ? 3 : 2;
-                if (mNewMapObjectItem->mapObject()->polygon().size() >= min)
-                    finishNewMapObject();
-                else
-                    cancelNewMapObject();
+                finishOrCancelPolygon();
             } else if (event->button() == Qt::LeftButton) {
                 QPolygonF current = mNewMapObjectItem->mapObject()->polygon();
                 QPolygonF next = mOverlayPolygonObject->polygon();
@@ -377,3 +396,14 @@ void CreateObjectTool::finishNewMapObject()
                                                       objectGroup,
                                                       newMapObject));
 }
+
+void CreateObjectTool::finishOrCancelPolygon()
+{
+    // The polygon needs to have at least three points and a
+    // polyline needs at least two.
+    int min = mMode == CreatePolygon ? 3 : 2;
+    if (mNewMapObjectItem->mapObject()->polygon().size() >= min)
+        finishNewMapObject();
+    else
+        cancelNewMapObject();
+}

src/tiled/createobjecttool.h

@@ -49,6 +49,7 @@ class CreateObjectTool : public AbstractObjectTool
 
     void deactivate(MapScene *scene);
 
+    void keyPressed(QKeyEvent *event);
     void mouseEntered();
     void mouseMoved(const QPointF &pos,
                     Qt::KeyboardModifiers modifiers);
@@ -69,6 +70,7 @@ public slots:
     MapObject *clearNewMapObjectItem();
     void cancelNewMapObject();
     void finishNewMapObject();
+    void finishOrCancelPolygon();
 
     MapObjectItem *mNewMapObjectItem;
     ObjectGroup *mOverlayObjectGroup;