美化QTabWidget[通俗易懂]

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美化QTabWidget

1.效果展示

2.用法展示

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{ 

ui->setupUi(this);
setupUI();
ui->tabWidget->addTab2(new QWidget(), tr("this is first tab"));
}
MainWindow::~MainWindow()
{ 

delete ui;
}
void MainWindow::setupUI()
{ 

connect(ui->tabWidget, SIGNAL(TabInserted(int)), this, SLOT(OnTabInserted(int)));
connect(ui->tabWidget, SIGNAL(AddBtnClicked()), this, SLOT(OnAddBtnClicked()));
connect(ui->tabWidget, SIGNAL(TabClosed(int)), this, SLOT(OnCloseTab(int)));
}
void MainWindow::OnTabInserted(int index)
{ 

QPushButton *button = new QPushButton();
button->setFixedSize(this->iconSize());
button->setStyleSheet("border-image: url(:/images/x-capture-options.png);");
ui->tabWidget->setTabButton2(index, QTabBar::LeftSide, button);
button = new QPushButton();
button->setStyleSheet("QPushButton{border-image: url(:/images/close.png)}"
"QPushButton:hover{border-image: url(:/images/close_hover.png)}");
ui->tabWidget->setTabButton2(index, QTabBar::RightSide, button);
}
void MainWindow::OnTabClosed(int index)
{ 

//todo something
}
void MainWindow::OnAddBtnClicked()
{ 

ui->tabWidget->addTab2(new QWidget(), tr("this is first tab"));
}

3.原理简介

主要原理就是对paintEvent重写，以及QProxyStyle继承重新实现。我也是翻了很多资料，看了实现的源码才知道的。

• QExtTabBarStyle继承自QProxyStyle

void QExtTabBarStyle::drawPrimitive(PrimitiveElement pe, 
const QStyleOption *option, 
QPainter *painter,
const QWidget *widget) const
{ 

if (pe == QStyle::PE_IndicatorArrowLeft) { 

drawArrow(pe, option, painter, widget);
} else if (pe == QStyle::PE_IndicatorArrowRight) { 

drawArrow(pe, option, painter, widget);
} else{ 

QProxyStyle::drawPrimitive(pe, option, painter, widget);
}
}
int QExtTabBarStyle::pixelMetric(PixelMetric metric, 
const QStyleOption *option, 
const QWidget *widget) const
{ 

if (PM_TabBarScrollButtonWidth == metric) { 

return 30;
} else { 

return QProxyStyle::pixelMetric(metric, option, widget);
}
}
QRect QExtTabBarStyle::subElementRect(SubElement element, 
const QStyleOption *option, 
const QWidget *widget) const
{ 

if (SE_TabBarTabLeftButton == element) { 

return calcIconRect(true, option);
} else if (SE_TabBarTabRightButton == element) { 

return calcIconRect(false, option);
} else { 

return QProxyStyle::subElementRect(element, option, widget);
}
}
QRect QExtTabBarStyle::calcIconRect(bool left, const QStyleOption *option) const
{ 

const QStyleOptionTab *tab_option = qstyleoption_cast<const QStyleOptionTab *>(option);
QSize icon_size = tab_option->iconSize;
const QRect tab_rect = tab_option->rect;
QPoint center_pos;
QRect button_rect;
const int icon_padding = 8;
if (left) { 

center_pos = QPoint(icon_padding+icon_size.width()/2+tab_rect.x(), 
tab_rect.y()+(tab_rect.height()-icon_size.height())/2+icon_size.height()/2);
} else { 

center_pos = QPoint(tab_rect.x()+tab_rect.width()-icon_padding-icon_size.width()/2, 
tab_rect.y()+(tab_rect.height()-icon_size.height())/2+icon_size.height()/2);
}
button_rect = QRect(QPoint(0, 0), icon_size);
button_rect.moveCenter(center_pos);
return button_rect;
}
void QExtTabBarStyle::drawArrow(PrimitiveElement pe, const QStyleOption *option, 
QPainter *painter,
const QWidget *widget) const
{ 

const QToolButton *tool_btn = static_cast<const QToolButton *>(widget);
if (nullptr != tool_btn && !tool_btn->isVisible()) 
return;
painter->save();
const QStyleOptionTab *tab_option = qstyleoption_cast<const QStyleOptionTab *>(option);
QBrush rect_brush;
if (!tool_btn->isEnabled()) { 

rect_brush = Qt::transparent;
} else if (tool_btn->underMouse()) { 

rect_brush = QColor(214, 214, 214);
} else { 

rect_brush = Qt::transparent;
}
QRect draw_rect = QRect(0, 0, 16, 16);
draw_rect.moveCenter(option->rect.center());
RoundShadowHelper round_helper;
round_helper.FillRoundShadow(painter, option->rect,rect_brush.color(), 4);
painter->restore();
QProxyStyle::drawPrimitive(pe, option, painter, widget);
}

• QTabBar中的paintEvent重写

void QtExtTabBar::paintEvent(QPaintEvent *event)
{ 

QPainter painter(this);
drawTab(&painter);
if (tab_add_button_.draw_plus_btn_)
drawPlusBtn(&painter);
}
void QtExtTabBar::drawTab(QPainter *painter)
{ 

RoundShadowHelper helper(6,4);
int border = helper.GetShadowWidth()/2.0;
painter->save();
int tab_count = tab_add_button_.draw_plus_btn_ ? count()-1 : count();
QStyleOptionTabV3 option;
for (int index = 0; index < tab_count; index++) { 

QRect rect = tabRect(index);
initStyleOption(&option, index);
// draw background 
QRect draw_rect = QRect(QPoint(rect.x()+border, rect.y() + border), QSize(rect.width()-border*2, rect.height()-border*2));
drawTabBg(painter, helper, option, draw_rect, rect);
drawTabText(painter, draw_rect, option);
}
painter->restore();
}
void QtExtTabBar::drawTabText(QPainter *painter, const QRect &draw_rect, const QStyleOptionTabV3 &option)
{ 

// draw text
QColor text_color = tb_text_color_.Normal_;
QRect text_rect = draw_rect.marginsAdded(margins_);
if (QStyle::State_Selected & option.state) { 

text_color = tb_text_color_.Selected_;
} else if (QStyle::State_MouseOver & option.state) { 

text_color = tb_text_color_.Hover_;
}
painter->setPen(text_color);
QString text = fontMetrics().elidedText(option.text, Qt::ElideRight, text_rect.width(), 0); 
painter->drawText(text_rect, Qt::AlignLeft | Qt::AlignVCenter, text);
}
void QtExtTabBar::drawTabBg(QPainter *painter, RoundShadowHelper &helper, 
const QStyleOptionTabV3 &option, QRect draw_rect, QRect real_rect)
{ 

painter->setPen(Qt::NoPen);
if(QStyle::State_Selected & option.state) { 

helper.RoundShadow(painter, real_rect);
helper.FillRoundShadow(painter, draw_rect, tb_bg_color_.Selected_, helper.GetRadius());
} else if(QStyle::State_MouseOver & option.state) { 

helper.FillRoundShadow(painter, draw_rect, tb_bg_color_.Hover_, helper.GetRadius());
}
}
void QtExtTabBar::drawPlusBtn(QPainter *painter)
{ 

painter->save();
int last_index = count()-1;
QStyleOptionTabV3 option;
initStyleOption(&option, last_index);
QRect draw_rect = QRect(QPoint(0, 0), tab_add_button_.tab_add_btn_size_);
draw_rect.moveCenter(tabRect(last_index).center());
DrawCircle::Draw(painter, draw_rect, tab_btn_add_color_);
DrawCharacter::DrawPlus(painter, draw_rect);
painter->restore();
}

4.属性设置

• 可以自定义tab中的左右button。

• 可以自定义tab中文字的颜色。

• 可以设置是否需要绘制“+”按钮。

其他的都可以在代码中找到

5.todo list

• 不支持tab拖拽
• 不支持tab, tab button 贴图。

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