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Tidy up collidingmice example documentation.

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Change-Id: I22dc325319389d146a99a5beb1e0c1c78283af63
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
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Mitch Curtis 2013-08-13 10:00:00 +02:00 committed by The Qt Project
parent 490bf800e6
commit 4aea44c1bf
1 changed files with 26 additions and 28 deletions
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54
examples/widgets/doc/src/collidingmice-example.qdoc
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@ -48,7 +48,7 @@
application window.
We will first review the \c Mouse class to see how to animate
items and detect item collision, and then we will review the \c
items and detect item collisions, and then we will review the \c
main() function to see how to put the items into a scene and how to
implement the corresponding view.
@ -90,7 +90,7 @@
calling the item's \l {QGraphicsItem::setRotation()}{setRotation()} function
we alter the direction in which the mouse will start moving.
When the QGraphicsScene decides to advance the scene a frame it will
When the QGraphicsScene decides to advance the scene by 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.
@ -98,10 +98,10 @@
\snippet graphicsview/collidingmice/mouse.cpp 5
\snippet graphicsview/collidingmice/mouse.cpp 6
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.
First, we don't bother doing any advance if the step is \c 0. This is because
advance() is called twice: once with step == \c 0, indicating that items
are about to advance, and then with step == \c 1 for the actual advance.
We also ensure that the mouse 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
@ -126,7 +126,7 @@
the parent's coordinate system. For items with no parent, the
given position is interpreted as scene coordinates. QGraphicsItem
also provides a \l {QGraphicsItem::}{mapToParent()} function to
map a position given in item coordinates, to the parent's
map a position given in item coordinates to the parent's
coordinate system. If the item has no parent, the position will be
mapped to the scene's coordinate system instead.
@ -140,7 +140,7 @@
defines the outer bounds of the item as a rectangle. Note that the
Graphics View framework uses the bounding rectangle to determine
whether the item requires redrawing, so all painting must be
restricted inside this rectangle.
done inside this rectangle.
\snippet graphicsview/collidingmice/mouse.cpp 3
@ -148,7 +148,7 @@
{QGraphicsItem::paint()}{paint()} function to paint the contents
of the item; the function paints the item in local coordinates.
Note the painting of the ears: Whenever a mouse item collides with
Note the painting of the ears: whenever a mouse item collides with
other mice items its ears are filled with red; otherwise they are
filled with dark yellow. We use the
QGraphicsScene::collidingItems() function to check if there are
@ -166,17 +166,15 @@
{QGraphicsItem::collidesWithItem()}{collidesWithItem()} function
to provide your own custom item and shape collision algorithm.
This completes the \c Mouse class implementation, it is now ready
This completes the \c Mouse class implementation; it is now ready
for use. Let's take a look at the \c main() function to see how to
implement a scene for the mice and a view for displaying the
contents of the scene.
\section1 The Main() Function
In this example we have chosen to let the \c main() function
provide the main application window, creating the items and the
scene, putting the items into the scene and creating a
corresponding view.
The \c main() function provides the main application window,
as well as creating the items, their scene, and a corresponding view.
\snippet graphicsview/collidingmice/main.cpp 0
@ -192,18 +190,18 @@
The QGraphicsScene class serves as a container for
QGraphicsItems. It also provides functionality that lets you
efficiently determine the location of items as well as determining
which items that are visible within an arbitrary area on the
which items are visible within an arbitrary area on the
scene.
When creating a scene it is recommended to set the scene's
rectangle, i.e., the rectangle that defines the extent of the
rectangle; the rectangle that defines the extent of the
scene. It is primarily used by QGraphicsView to determine the
view's default scrollable area, and by QGraphicsScene to manage
item indexing. If not explicitly set, the scene's default
rectangle will be the largest bounding rectangle of all the items
on the scene since the scene was created (i.e., the rectangle will
grow when items are added or moved in the scene, but it will never
shrink).
on the scene since the scene was created. This means that the
rectangle will grow when items are added or moved in the scene,
but it will never shrink.
\snippet graphicsview/collidingmice/main.cpp 2
@ -213,8 +211,8 @@
searched. Adding, moving and removing items, however, is done in
constant time. This approach is ideal for dynamic scenes, where
many items are added, moved or removed continuously. The
alternative is \l {QGraphicsScene::BspTreeIndex}{BspTreeIndex}
which makes use of binary search resulting in item location
alternative is \l {QGraphicsScene::BspTreeIndex}{BspTreeIndex},
which makes use of a binary search to achieve item location
algorithms that are of an order closer to logarithmic complexity.
\snippet graphicsview/collidingmice/main.cpp 3
@ -223,9 +221,9 @@
\snippet graphicsview/collidingmice/main.cpp 4
To be able to view the scene we must also create a QGraphicsView
To be able to view the scene, we must also create a QGraphicsView
widget. The QGraphicsView class visualizes the contents of a scene
in a scrollable viewport. We also ensure that the contents is
in a scrollable viewport. We also ensure that the contents are
rendered using antialiasing, and we create the cheese background
by setting the view's background brush.
@ -240,14 +238,14 @@
Then we set the cache mode; QGraphicsView can cache pre-rendered
content in a pixmap, which is then drawn onto the viewport. The
purpose of such caching is to speed up the total rendering time
for areas that are slow to render, e.g., texture, gradient and
for areas that are slow to render, for example: texture, gradient, and
alpha blended backgrounds. The \l
{QGraphicsView::CacheMode}{CacheMode} property holds which parts
of the view that are cached, and the \l
of the view are cached, and the \l
{QGraphicsView::CacheBackground}{CacheBackground} flag enables
caching of the view's background.
By setting the \l {QGraphicsView::dragMode}{dragMode} property we
By setting the \l {QGraphicsView::dragMode}{dragMode} property, we
define what should happen when the user clicks on the scene
background and drags the mouse. The \l
{QGraphicsView::ScrollHandDrag}{ScrollHandDrag} flag makes the
@ -264,9 +262,9 @@
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
We then tell the timer to fire every 1000/33 milliseconds. 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
animations. Doing the animation with a single timer connection 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.