ZoomableScrollArea.py

Go to the documentation of this file.

from PyQt4.QtCore import *
from PyQt4.QtGui import *

from Vispa.Gui.Zoomable import Zoomable
from Vispa.Gui.ZoomableWidget import ZoomableWidget

class ZoomableScrollArea(Zoomable, QScrollArea):
    """ Standard QScrollArea extended by zooming capabilties.
    """
    
    def __init__(self, parent=None):
        """ Constructor.
        """
        QScrollArea.__init__(self, parent)
        Zoomable.__init__(self)               # Call after QScrollArea constructor, required by setZoom()
        
        self.connect(self.verticalScrollBar(), SIGNAL("valueChanged(int)"), self.scrollBarValueChanged)
        self.connect(self.horizontalScrollBar(), SIGNAL("valueChanged(int)"), self.scrollBarValueChanged)
        
    def wheelEvent(self, event):
        """ If wheelEvent occurs either zoom window (ctrl-key pressed) or scroll the area.
        """
        if event.modifiers() == Qt.ControlModifier:
            oldZoom = self.zoom()
            oldLeft = self.widget().mapFrom(self,QPoint(event.x(),0)).x()
            oldTop = self.widget().mapFrom(self,QPoint(0,event.y())).y()
            
            if event.delta() > 0:
                self.incrementZoom()
            else:
                self.decrementZoom()
                
            newZoom = self.zoom()
            zoomFactor = newZoom / oldZoom
            newLeft = oldLeft * zoomFactor 
            newTop = oldTop * zoomFactor

            self.autosizeScrollWidget()
            self.ensureVisible(newLeft-event.x()+self.viewport().width()/2.0,newTop-event.y()+self.viewport().height()/2.0,self.viewport().width()/2.0,self.viewport().height()/2.0)
            self.emit(SIGNAL('wheelZoom()'))
        else:
            QScrollArea.wheelEvent(self, event)

    def setZoom(self, zoom):
        """ Sets its own zoom factor and passes it to it's child widget if child is Zoomable.
        """
        Zoomable.setZoom(self, zoom)
        if isinstance(self.widget(), ZoomableWidget):
            self.widget().setZoom(zoom)
        self.autosizeScrollWidget()
        self.emit(SIGNAL("zoomChanged(float)"), zoom)
    
    def resizeEvent(self, event):
        """Calls autosizeScrollWidget().
        """
        self.autosizeScrollWidget()
        QScrollArea.resizeEvent(self, event)
            
    def autosizeScrollWidget(self):
        """Sets size of child widget to the size needed to fit whole content.
        """
        if not self.widget():
            return
        childrenRect = self.widget().childrenRect()
        width = max(self.viewport().width(), childrenRect.bottomRight().x()) - min(0, childrenRect.topLeft().x())
        height = max(self.viewport().height(), childrenRect.bottomRight().y()) - min(0, childrenRect.topLeft().y())
        self.widget().resize(width, height)
        
    def mousePressEvent(self, event):
        """ Forward mousePressEvent.
        """
        self.widget().mousePressEvent(event)
        
    def scrollBarValueChanged(self, value):
        """ Forward valueChanged(int) signal from scroll bars to viewport widget.
        
        If the widget (see QScrollArea.widget()) has a function called "scrollBarValueChanged", it will be called.
        """
        if hasattr(self.widget(), "scrollBarValueChanged"):
            self.widget().scrollBarValueChanged(value)