如何刷新 QGraphicsView 以显示 QGraphicsScene 背景的变化
How to refresh QGraphicsView to show changes in the QGraphicsScene's background
我有一个自定义 QGraphicsView
和 QGraphicsScene
。在 QGraphicsScene
中,我已经覆盖了 void drawBackground(QPainter *painter, const QRectF &rect)
并且基于我想打开和关闭网格的布尔标志。我尝试在我的函数中调用 clear()
或调用 painter
的 eraseRect(sceneRect())
但它没有用。所以在做了一些阅读之后,我猜它不应该工作,因为在更改场景后你需要刷新视图。这就是为什么我发出一个叫做 signalUpdateViewport()
的信号
void Scene::drawBackground(QPainter *painter, const QRectF &rect) {
if(this->gridEnabled) {
// Draw grid
}
else {
// Erase using the painter
painter->eraseRect(sceneRect());
// or by calling
//clear();
}
// Trigger refresh of view
emit signalUpdateViewport();
QGraphicsScene::drawBackground(painter, rect);
}
然后由我的视图捕获:
void View::slotUpdateViewport() {
this->viewport()->update();
}
不用说这没有用。 不起作用 我的意思是结果(无论是从场景内部还是视图内部刷新)仅在更改小部件时可见,例如触发调整大小事件。
如何正确刷新场景视图以显示我在场景背景中所做的更改?
代码:
scene.h
#ifndef SCENE_HPP
#define SCENE_HPP
#include <QGraphicsScene>
class View;
class Scene : public QGraphicsScene
{
Q_OBJECT
Q_ENUMS(Mode)
Q_ENUMS(ItemType)
public:
enum Mode { Default, Insert, Select };
enum ItemType { None, ConnectionCurve, ConnectionLine, Node };
Scene(QObject* parent = Q_NULLPTR);
~Scene();
void setMode(Mode mode, ItemType itemType);
signals:
void signalCursorCoords(int x, int y);
void signalSceneModeChanged(Scene::Mode sceneMode);
void signalSceneItemTypeChanged(Scene::ItemType sceneItemType);
void signalGridDisplayChanged(bool gridEnabled);
void signalUpdateViewport();
public slots:
void slotSetSceneMode(Scene::Mode sceneMode);
void slotSetSceneItemType(Scene::ItemType sceneItemType);
void slotSetGridStep(int gridStep);
void slotToggleGrid(bool flag);
private:
Mode sceneMode;
ItemType sceneItemType;
bool gridEnabled;
int gridStep;
void makeItemsControllable(bool areControllable);
double round(double val);
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
void keyPressEvent(QKeyEvent *event);
void drawBackground(QPainter *painter, const QRectF &rect);
};
Q_DECLARE_METATYPE(Scene::Mode)
Q_DECLARE_METATYPE(Scene::ItemType)
#endif // SCENE_HPP
scene.cpp
#include <QGraphicsItem>
#include <QGraphicsView>
#include <QGraphicsSceneMouseEvent>
#include <QPainter>
#include <QRectF>
#include <QKeyEvent>
#include <QtDebug>
#include "scene.h"
Scene::Scene(QObject* parent)
: QGraphicsScene (parent),
sceneMode(Default),
sceneItemType(None),
gridEnabled(true),
gridStep(30)
{
}
Scene::~Scene()
{
}
void Scene::setMode(Mode mode, ItemType itemType)
{
this->sceneMode = mode;
this->sceneItemType = itemType;
QGraphicsView::DragMode vMode = QGraphicsView::NoDrag;
switch(mode) {
case Insert:
{
makeItemsControllable(false);
vMode = QGraphicsView::NoDrag;
break;
}
case Select:
{
makeItemsControllable(true);
vMode = QGraphicsView::RubberBandDrag;
break;
}
case Default:
{
makeItemsControllable(false);
vMode = QGraphicsView::NoDrag;
break;
}
}
QGraphicsView* mView = views().at(0);
if(mView) {
mView->setDragMode(vMode);
}
}
void Scene::slotSetSceneMode(Scene::Mode sceneMode)
{
this->sceneMode = sceneMode;
qDebug() << "SM" << (int)this->sceneMode;
emit signalSceneModeChanged(this->sceneMode);
}
void Scene::slotSetSceneItemType(Scene::ItemType sceneItemType)
{
this->sceneItemType = sceneItemType;
qDebug() << "SIT:" << (int)this->sceneItemType;
emit signalSceneItemTypeChanged(this->sceneItemType);
}
void Scene::slotSetGridStep(int gridStep)
{
this->gridStep = gridStep;
}
void Scene::slotToggleGrid(bool flag)
{
this->gridEnabled = flag;
invalidate(sceneRect(), BackgroundLayer);
qDebug() << "Grid " << (this->gridEnabled ? "enabled" : "disabled");
update(sceneRect());
emit signalGridDisplayChanged(this->gridEnabled);
}
void Scene::makeItemsControllable(bool areControllable)
{
foreach(QGraphicsItem* item, items()) {
if(/*item->type() == QCVN_Node_Top::Type
||*/ item->type() == QGraphicsLineItem::Type
|| item->type() == QGraphicsPathItem::Type) {
item->setFlag(QGraphicsItem::ItemIsMovable, areControllable);
item->setFlag(QGraphicsItem::ItemIsSelectable, areControllable);
}
}
}
double Scene::round(double val)
{
int tmp = int(val) + this->gridStep/2;
tmp -= tmp % this->gridStep;
return double(tmp);
}
void Scene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsScene::mousePressEvent(event);
}
void Scene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
emit signalCursorCoords(int(event->scenePos().x()), int(event->scenePos().y()));
QGraphicsScene::mouseMoveEvent(event);
}
void Scene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsScene::mouseReleaseEvent(event);
}
void Scene::keyPressEvent(QKeyEvent* event)
{
if(event->key() == Qt::Key_M) {
slotSetSceneMode(static_cast<Mode>((int(this->sceneMode) + 1) % 3));
}
else if(event->key() == Qt::Key_G) {
slotToggleGrid(!this->gridEnabled);
}
QGraphicsScene::keyPressEvent(event);
}
void Scene::drawBackground(QPainter *painter, const QRectF &rect)
{
// FIXME Clearing and drawing the grid happens only when scene size or something else changes
if(this->gridEnabled) {
painter->setPen(QPen(QColor(200, 200, 255, 125)));
// draw horizontal grid
double start = round(rect.top());
if (start > rect.top()) {
start -= this->gridStep;
}
for (double y = start - this->gridStep; y < rect.bottom(); ) {
y += this->gridStep;
painter->drawLine(int(rect.left()), int(y), int(rect.right()), int(y));
}
// now draw vertical grid
start = round(rect.left());
if (start > rect.left()) {
start -= this->gridStep;
}
for (double x = start - this->gridStep; x < rect.right(); x += this->gridStep) {
painter->drawLine(int(x), int(rect.top()), int(x), int(rect.bottom()));
}
}
else {
// Erase whole scene's background
painter->eraseRect(sceneRect());
}
slotToggleGrid(this->gridEnabled);
QGraphicsScene::drawBackground(painter, rect);
}
View
当前不包含任何内容 - 都是默认值。我的 Scene
和 View
实例在我的 QMainWindow
中的设置如下:
void App::initViewer()
{
this->scene = new Scene(this);
this->view = new View(this->scene, this);
this->viewport = new QGLWidget(QGLFormat(QGL::SampleBuffers), this->view);
this->view->setRenderHints(QPainter::Antialiasing);
this->view->setViewport(this->viewport);
this->view->setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
this->view->setCacheMode(QGraphicsView::CacheBackground);
setCentralWidget(this->view);
}
编辑: 我尝试在 update()
、clear()
或任何我之前调用 invalidate(sceneRect()
, BackgroundLayer
)试图触发刷新。
我也在场景中尝试了 QGraphicsScene::update()
,但它没有用 将两者都没有参数传递给函数调用,然后传递 sceneRect()
并没有导致任何与我不同的结果如上所述。
当您更改网格设置时,无论是打开还是关闭(或颜色等),您都需要调用 QGraphicsScene::update。这也是一个插槽,因此您可以根据需要将信号连接到它。您还可以指定暴露区域;如果你不这样做,那么它会使用所有的默认值。对于网格,这可能就是您想要的。
您不需要清除网格。更新调用确保更新的区域被清除,然后如果你想要网格,你可以在上面绘制,或者如果网格不应该在那里,则不要在上面绘制。
发现问题 - 我忘记设置场景矩形的大小:
this->scene->setSceneRect(QRectF(QPointF(-1000, 1000), QSizeF(2000, 2000)));
我实际上是通过决定打印 sceneRect()
调用返回的 QRectF
的大小来发现问题的,当我查看输出时我看到了 0, 0
所以基本上我是确实触发了更新,但在面积为 0 的场景中(显然)不会产生任何结果。
我测试和工作的另一件事是删除我的视图的后台缓存。
有时 view/scene 直接拒绝 运行 update(),在 update() 修复它之前处理应用程序事件,如下所示:
qApp->processEvents();
update();
我有一个自定义 QGraphicsView
和 QGraphicsScene
。在 QGraphicsScene
中,我已经覆盖了 void drawBackground(QPainter *painter, const QRectF &rect)
并且基于我想打开和关闭网格的布尔标志。我尝试在我的函数中调用 clear()
或调用 painter
的 eraseRect(sceneRect())
但它没有用。所以在做了一些阅读之后,我猜它不应该工作,因为在更改场景后你需要刷新视图。这就是为什么我发出一个叫做 signalUpdateViewport()
void Scene::drawBackground(QPainter *painter, const QRectF &rect) {
if(this->gridEnabled) {
// Draw grid
}
else {
// Erase using the painter
painter->eraseRect(sceneRect());
// or by calling
//clear();
}
// Trigger refresh of view
emit signalUpdateViewport();
QGraphicsScene::drawBackground(painter, rect);
}
然后由我的视图捕获:
void View::slotUpdateViewport() {
this->viewport()->update();
}
不用说这没有用。 不起作用 我的意思是结果(无论是从场景内部还是视图内部刷新)仅在更改小部件时可见,例如触发调整大小事件。
如何正确刷新场景视图以显示我在场景背景中所做的更改?
代码:
scene.h
#ifndef SCENE_HPP
#define SCENE_HPP
#include <QGraphicsScene>
class View;
class Scene : public QGraphicsScene
{
Q_OBJECT
Q_ENUMS(Mode)
Q_ENUMS(ItemType)
public:
enum Mode { Default, Insert, Select };
enum ItemType { None, ConnectionCurve, ConnectionLine, Node };
Scene(QObject* parent = Q_NULLPTR);
~Scene();
void setMode(Mode mode, ItemType itemType);
signals:
void signalCursorCoords(int x, int y);
void signalSceneModeChanged(Scene::Mode sceneMode);
void signalSceneItemTypeChanged(Scene::ItemType sceneItemType);
void signalGridDisplayChanged(bool gridEnabled);
void signalUpdateViewport();
public slots:
void slotSetSceneMode(Scene::Mode sceneMode);
void slotSetSceneItemType(Scene::ItemType sceneItemType);
void slotSetGridStep(int gridStep);
void slotToggleGrid(bool flag);
private:
Mode sceneMode;
ItemType sceneItemType;
bool gridEnabled;
int gridStep;
void makeItemsControllable(bool areControllable);
double round(double val);
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
void keyPressEvent(QKeyEvent *event);
void drawBackground(QPainter *painter, const QRectF &rect);
};
Q_DECLARE_METATYPE(Scene::Mode)
Q_DECLARE_METATYPE(Scene::ItemType)
#endif // SCENE_HPP
scene.cpp
#include <QGraphicsItem>
#include <QGraphicsView>
#include <QGraphicsSceneMouseEvent>
#include <QPainter>
#include <QRectF>
#include <QKeyEvent>
#include <QtDebug>
#include "scene.h"
Scene::Scene(QObject* parent)
: QGraphicsScene (parent),
sceneMode(Default),
sceneItemType(None),
gridEnabled(true),
gridStep(30)
{
}
Scene::~Scene()
{
}
void Scene::setMode(Mode mode, ItemType itemType)
{
this->sceneMode = mode;
this->sceneItemType = itemType;
QGraphicsView::DragMode vMode = QGraphicsView::NoDrag;
switch(mode) {
case Insert:
{
makeItemsControllable(false);
vMode = QGraphicsView::NoDrag;
break;
}
case Select:
{
makeItemsControllable(true);
vMode = QGraphicsView::RubberBandDrag;
break;
}
case Default:
{
makeItemsControllable(false);
vMode = QGraphicsView::NoDrag;
break;
}
}
QGraphicsView* mView = views().at(0);
if(mView) {
mView->setDragMode(vMode);
}
}
void Scene::slotSetSceneMode(Scene::Mode sceneMode)
{
this->sceneMode = sceneMode;
qDebug() << "SM" << (int)this->sceneMode;
emit signalSceneModeChanged(this->sceneMode);
}
void Scene::slotSetSceneItemType(Scene::ItemType sceneItemType)
{
this->sceneItemType = sceneItemType;
qDebug() << "SIT:" << (int)this->sceneItemType;
emit signalSceneItemTypeChanged(this->sceneItemType);
}
void Scene::slotSetGridStep(int gridStep)
{
this->gridStep = gridStep;
}
void Scene::slotToggleGrid(bool flag)
{
this->gridEnabled = flag;
invalidate(sceneRect(), BackgroundLayer);
qDebug() << "Grid " << (this->gridEnabled ? "enabled" : "disabled");
update(sceneRect());
emit signalGridDisplayChanged(this->gridEnabled);
}
void Scene::makeItemsControllable(bool areControllable)
{
foreach(QGraphicsItem* item, items()) {
if(/*item->type() == QCVN_Node_Top::Type
||*/ item->type() == QGraphicsLineItem::Type
|| item->type() == QGraphicsPathItem::Type) {
item->setFlag(QGraphicsItem::ItemIsMovable, areControllable);
item->setFlag(QGraphicsItem::ItemIsSelectable, areControllable);
}
}
}
double Scene::round(double val)
{
int tmp = int(val) + this->gridStep/2;
tmp -= tmp % this->gridStep;
return double(tmp);
}
void Scene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsScene::mousePressEvent(event);
}
void Scene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
emit signalCursorCoords(int(event->scenePos().x()), int(event->scenePos().y()));
QGraphicsScene::mouseMoveEvent(event);
}
void Scene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
QGraphicsScene::mouseReleaseEvent(event);
}
void Scene::keyPressEvent(QKeyEvent* event)
{
if(event->key() == Qt::Key_M) {
slotSetSceneMode(static_cast<Mode>((int(this->sceneMode) + 1) % 3));
}
else if(event->key() == Qt::Key_G) {
slotToggleGrid(!this->gridEnabled);
}
QGraphicsScene::keyPressEvent(event);
}
void Scene::drawBackground(QPainter *painter, const QRectF &rect)
{
// FIXME Clearing and drawing the grid happens only when scene size or something else changes
if(this->gridEnabled) {
painter->setPen(QPen(QColor(200, 200, 255, 125)));
// draw horizontal grid
double start = round(rect.top());
if (start > rect.top()) {
start -= this->gridStep;
}
for (double y = start - this->gridStep; y < rect.bottom(); ) {
y += this->gridStep;
painter->drawLine(int(rect.left()), int(y), int(rect.right()), int(y));
}
// now draw vertical grid
start = round(rect.left());
if (start > rect.left()) {
start -= this->gridStep;
}
for (double x = start - this->gridStep; x < rect.right(); x += this->gridStep) {
painter->drawLine(int(x), int(rect.top()), int(x), int(rect.bottom()));
}
}
else {
// Erase whole scene's background
painter->eraseRect(sceneRect());
}
slotToggleGrid(this->gridEnabled);
QGraphicsScene::drawBackground(painter, rect);
}
View
当前不包含任何内容 - 都是默认值。我的 Scene
和 View
实例在我的 QMainWindow
中的设置如下:
void App::initViewer()
{
this->scene = new Scene(this);
this->view = new View(this->scene, this);
this->viewport = new QGLWidget(QGLFormat(QGL::SampleBuffers), this->view);
this->view->setRenderHints(QPainter::Antialiasing);
this->view->setViewport(this->viewport);
this->view->setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
this->view->setCacheMode(QGraphicsView::CacheBackground);
setCentralWidget(this->view);
}
编辑: 我尝试在 update()
、clear()
或任何我之前调用 invalidate(sceneRect()
, BackgroundLayer
)试图触发刷新。
我也在场景中尝试了 QGraphicsScene::update()
,但它没有用 将两者都没有参数传递给函数调用,然后传递 sceneRect()
并没有导致任何与我不同的结果如上所述。
当您更改网格设置时,无论是打开还是关闭(或颜色等),您都需要调用 QGraphicsScene::update。这也是一个插槽,因此您可以根据需要将信号连接到它。您还可以指定暴露区域;如果你不这样做,那么它会使用所有的默认值。对于网格,这可能就是您想要的。
您不需要清除网格。更新调用确保更新的区域被清除,然后如果你想要网格,你可以在上面绘制,或者如果网格不应该在那里,则不要在上面绘制。
发现问题 - 我忘记设置场景矩形的大小:
this->scene->setSceneRect(QRectF(QPointF(-1000, 1000), QSizeF(2000, 2000)));
我实际上是通过决定打印 sceneRect()
调用返回的 QRectF
的大小来发现问题的,当我查看输出时我看到了 0, 0
所以基本上我是确实触发了更新,但在面积为 0 的场景中(显然)不会产生任何结果。
我测试和工作的另一件事是删除我的视图的后台缓存。
有时 view/scene 直接拒绝 运行 update(),在 update() 修复它之前处理应用程序事件,如下所示:
qApp->processEvents();
update();