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-rw-r--r--doc/src/examples/collidingmice-example.qdoc39
1 files changed, 21 insertions, 18 deletions
diff --git a/doc/src/examples/collidingmice-example.qdoc b/doc/src/examples/collidingmice-example.qdoc
index 7ea2ca2..657a204 100644
--- a/doc/src/examples/collidingmice-example.qdoc
+++ b/doc/src/examples/collidingmice-example.qdoc
@@ -66,7 +66,7 @@
\section1 Mouse Class Definition
- The \c mouse class inherits both QObject and QGraphicsItem. The
+ The \c mouse class inherits from QGraphicsItem. The
QGraphicsItem class is the base class for all graphical items in
the Graphics View framework, and provides a light-weight
foundation for writing your own custom items.
@@ -78,14 +78,11 @@
{QGraphicsItem::}{boundingRect()}, which returns an estimate of
the area painted by the item, and \l {QGraphicsItem::}{paint()},
which implements the actual painting. In addition, we reimplement
- the \l {QGraphicsItem::}{shape()} function to return an accurate
+ the \l {QGraphicsItem::}{shape()} and \l {QGraphicsItem::}{advance()}.
+ We reimplement \l {QGraphicsItem::}{shape()} to return an accurate
shape of our mouse item; the default implementation simply returns
- the item's bounding rectangle.
-
- The rationale for deriving from QObject in addition to
- QGraphicsItem is to be able to animate our items by reimplementing
- QObject's \l {QObject::}{timerEvent()} function and use
- QObject::startTimer() to generate timer events.
+ the item's bounding rectangle. We reimplement \l {QGraphicsItem::}{advance()}
+ to handle the animation so it all happens on one update.
\section1 Mouse Class Definition
@@ -105,19 +102,18 @@
calling the item's \l {QGraphicsItem::rotate()}{rotate()} function
we alter the direction in which the mouse will start moving.
- In the end we call QObject's \l {QObject::}{startTimer()}
- function, emitting a timer event every 1000/33 millisecond. This
- enables us to animate our mouse item using our reimplementation of
- the \l {QObject::}{timerEvent()} function; whenever a mouse
- receives a timer event it will trigger \l
- {QObject::}{timerEvent()}:
-
+ When the QGraphicsScene decides to advance the scene a frame it will call
+ QGraphicsItem::advance() on each of the items. This enables us to animate
+ our mouse using our reimplementation of the advance() function.
+
\snippet examples/graphicsview/collidingmice/mouse.cpp 4
\snippet examples/graphicsview/collidingmice/mouse.cpp 5
\snippet examples/graphicsview/collidingmice/mouse.cpp 6
- First we ensure that the mice stays within a circle with a radius
- of 150 pixels.
+ First, we don't bother doing any advance if the step is 0 since we want to our advance in
+ the actual advance (advance() is called twice, once with step == 0 indicating that items
+ are about to advance and with step == 1 for the actual advance). We also ensure that the
+ mice stays within a circle with a radius of 150 pixels.
Note the \l {QGraphicsItem::mapFromScene()}{mapFromScene()}
function provided by QGraphicsItem. This function maps a position
@@ -275,5 +271,12 @@
In the end, we set the application window's title and size before
we enter the main event loop using the QApplication::exec()
function.
-*/
+ Finally, we create a QTimer and connect its timeout() signal to the advance()
+ slot of the scene. Every time the timer fires, the scene will advance one frame.
+ We then tell the timer to fire every 1000/33 millisecond. This will
+ give us a frame rate of 30 frames a second, which is fast enough for most animations.
+ Doing the animation with a single timer connect to advance the scene ensures that all the
+ mice are moved at one point and, more importantly, only one update is sent to the screen
+ after all the mice have moved.
+*/ \ No newline at end of file