Snapshot/SnapshotRegionGrabber.py

# -*- coding: utf-8 -*-

# Copyright (c) 2012 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing a grabber widget for a rectangular snapshot region.
"""

from PyQt4.QtCore import pyqtSignal, Qt, QRect, QPoint, QTimer
from PyQt4.QtGui import QWidget, QPixmap, QColor, QRegion, QApplication, QPainter, \
    QPalette, QToolTip, QPaintEngine, QPen, QBrush


def drawRect(painter, rect, outline, fill=QColor()):
    """
    Module function to draw a rectangle with the given parameters.
    
    @param painter reference to the painter to be used (QPainter)
    @param rect rectangle to be drawn (QRect)
    @param outline color of the outline (QColor)
    @param fill fill color (QColor)
    """
    clip = QRegion(rect)
    clip = clip.subtracted(QRegion(rect.adjusted(1, 1, -1, -1)))
    
    painter.save()
    painter.setClipRegion(clip)
    painter.setPen(Qt.NoPen)
    painter.setBrush(outline)
    painter.drawRect(rect)
    if fill.isValid():
        painter.setClipping(False)
        painter.setBrush(fill)
        painter.drawRect(rect.adjusted(1, 1, -1, -1))
    painter.restore()


class SnapshotRegionGrabber(QWidget):
    """
    Class implementing a grabber widget for a rectangular snapshot region.
    
    @signal grabbed(QPixmap) emitted after the region was grabbed
    """
    grabbed = pyqtSignal(QPixmap)
    
    StrokeMask = 0
    FillMask = 1
    
    Rectangle = 0
    Ellipse = 1
    
    def __init__(self, mode=Rectangle):
        """
        Constructor
        
        @param mode region grabber mode (SnapshotRegionGrabber.Rectangle or
            SnapshotRegionGrabber.Ellipse)
        """
        super().__init__(None,
            Qt.X11BypassWindowManagerHint | Qt.WindowStaysOnTopHint |
            Qt.FramelessWindowHint | Qt.Tool)
        
        assert mode in [SnapshotRegionGrabber.Rectangle,
                        SnapshotRegionGrabber.Ellipse]
        self.__mode = mode
        
        self.__selection = QRect()
        self.__mouseDown = False
        self.__newSelection = False
        self.__handleSize = 10
        self.__mouseOverHandle = None
        self.__showHelp = True
        self.__grabbing = False
        self.__dragStartPoint = QPoint()
        self.__selectionBeforeDrag = QRect()
        
        # naming conventions for handles
        # T top, B bottom, R Right, L left
        # 2 letters: a corner
        # 1 letter: the handle on the middle of the corresponding side
        self.__TLHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__TRHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__BLHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__BRHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__LHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__THandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__RHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__BHandle = QRect(0, 0, self.__handleSize, self.__handleSize)
        self.__handles = [self.__TLHandle, self.__TRHandle, self.__BLHandle,
                          self.__BRHandle, self.__LHandle, self.__THandle,
                          self.__RHandle, self.__BHandle]
        self.__helpTextRect = QRect()
        self.__helpText = self.trUtf8(
            "Select a region using the mouse. To take the snapshot, press the Enter key"
            " or double click. Press Esc to quit.")
        
        self.__pixmap = QPixmap()
        
        self.setMouseTracking(True)
        
        QTimer.singleShot(200, self.__initialize)
    
    def __initialize(self):
        """
        Private slot to initialize the rest of the widget.
        """
        self.__desktop = QApplication.desktop()
        x = self.__desktop.x()
        y = self.__desktop.y()
        self.__pixmap = QPixmap.grabWindow(self.__desktop.winId(), x, y,
            self.__desktop.width(), self.__desktop.height())
        self.resize(self.__pixmap.size())
        self.move(x, y)
        self.setCursor(Qt.CrossCursor)
        self.show()

        self.grabMouse()
        self.grabKeyboard()
    
    def paintEvent(self, evt):
        """
        Protected method handling paint events.
        
        @param evt paint event (QPaintEvent)
        """
        if self.__grabbing:     # grabWindow() should just get the background
            return
        
        painter = QPainter(self)
        pal = QPalette(QToolTip.palette())
        font = QToolTip.font()
        
        handleColor = pal.color(QPalette.Active, QPalette.Highlight)
        handleColor.setAlpha(160)
        overlayColor = QColor(0, 0, 0, 160)
        textColor = pal.color(QPalette.Active, QPalette.Text)
        textBackgroundColor = pal.color(QPalette.Active, QPalette.Base)
        painter.drawPixmap(0, 0, self.__pixmap)
        painter.setFont(font)
        
        r = QRect(self.__selection)
        if not self.__selection.isNull():
            grey = QRegion(self.rect())
            if self.__mode == SnapshotRegionGrabber.Ellipse:
                reg = QRegion(r, QRegion.Ellipse)
            else:
                reg = QRegion(r)
            grey = grey.subtracted(reg)
            painter.setClipRegion(grey)
            painter.setPen(Qt.NoPen)
            painter.setBrush(overlayColor)
            painter.drawRect(self.rect())
            painter.setClipRect(self.rect())
            drawRect(painter, r, handleColor)
        
        if self.__showHelp:
            painter.setPen(textColor)
            painter.setBrush(textBackgroundColor)
            self.__helpTextRect = painter.boundingRect(self.rect().adjusted(2, 2, -2, -2),
                Qt.TextWordWrap, self.__helpText).translated(
                -self.__desktop.x(), -self.__desktop.y())
            self.__helpTextRect.adjust(-2, -2, 4, 2)
            drawRect(painter, self.__helpTextRect, textColor, textBackgroundColor)
            painter.drawText(self.__helpTextRect.adjusted(3, 3, -3, -3),
                Qt.TextWordWrap, self.__helpText)
        
        if self.__selection.isNull():
            return
        
        # The grabbed region is everything which is covered by the drawn
        # rectangles (border included). This means that there is no 0px
        # selection, since a 0px wide rectangle will always be drawn as a line.
        txt = "{0:n}, {1:n} ({2:n} x {3:n})".format(
            self.__selection.x(), self.__selection.y(),
            self.__selection.width(), self.__selection.height())
        textRect = painter.boundingRect(self.rect(), Qt.AlignLeft, txt)
        boundingRect = textRect.adjusted(-4, 0, 0, 0)
        
        if textRect.width() < r.width() - 2 * self.__handleSize and \
           textRect.height() < r.height() - 2 * self.__handleSize and \
           r.width() > 100 and \
           r.height() > 100:
            # center, unsuitable for small selections
            boundingRect.moveCenter(r.center())
            textRect.moveCenter(r.center())
        elif r.y() - 3 > textRect.height() and \
             r.x() + textRect.width() < self.rect().width():
            # on top, left aligned
            boundingRect.moveBottomLeft(QPoint(r.x(), r.y() - 3))
            textRect.moveBottomLeft(QPoint(r.x() + 2, r.y() - 3))
        elif r.x() - 3 > textRect.width():
            # left, top aligned
            boundingRect.moveTopRight(QPoint(r.x() - 3, r.y()))
            textRect.moveTopRight(QPoint(r.x() - 5, r.y()))
        elif r.bottom() + 3 + textRect.height() < self.rect().bottom() and \
             r.right() > textRect.width():
            # at bottom, right aligned
            boundingRect.moveTopRight(QPoint(r.right(), r.bottom() + 3))
            textRect.moveTopRight(QPoint(r.right() - 2, r.bottom() + 3))
        elif r.right() + textRect.width() + 3 < self.rect().width():
            # right, bottom aligned
            boundingRect.moveBottomLeft(QPoint(r.right() + 3, r.bottom()))
            textRect.moveBottomLeft(QPoint(r.right() + 5, r.bottom()))
        
        # If the above didn't catch it, you are running on a very tiny screen...
        drawRect(painter, boundingRect, textColor, textBackgroundColor)
        painter.drawText(textRect, Qt.AlignHCenter, txt)
        
        if (r.height() > self.__handleSize * 2 and \
            r.width() > self.__handleSize * 2) or \
           not self.__mouseDown:
            self.__updateHandles()
            painter.setPen(Qt.NoPen)
            painter.setBrush(handleColor)
            painter.setClipRegion(self.__handleMask(SnapshotRegionGrabber.StrokeMask))
            painter.drawRect(self.rect())
            handleColor.setAlpha(60)
            painter.setBrush(handleColor)
            painter.setClipRegion(self.__handleMask(SnapshotRegionGrabber.FillMask))
            painter.drawRect(self.rect())
    
    def resizeEvent(self, evt):
        """
        Protected method to handle resize events.
        
        @param evt resize event (QResizeEvent)
        """
        if self.__selection.isNull():
            return
        
        r = QRect(self.__selection)
        r.setTopLeft(self.__limitPointToRect(r.topLeft(), self.rect()))
        r.setBottomRight(self.__limitPointToRect(r.bottomRight(), self.rect()))
        if r.width() <= 1 or r.height() <= 1:
            # This just results in ugly drawing...
            self.__selection = QRect()
        else:
            self.__selection = self.__normalizeSelection(r)
    
    def mousePressEvent(self, evt):
        """
        Protected method to handle mouse button presses.
        
        @param evt mouse press event (QMouseEvent)
        """
        self.__showHelp = not self.__helpTextRect.contains(evt.pos())
        if evt.button() == Qt.LeftButton:
            self.__mouseDown = True
            self.__dragStartPoint = evt.pos()
            self.__selectionBeforeDrag = QRect(self.__selection)
            if not self.__selection.contains(evt.pos()):
                self.__newSelection = True
                self.__selection = QRect()
            else:
                self.setCursor(Qt.ClosedHandCursor)
        elif evt.button() == Qt.RightButton:
            self.__newSelection = False
            self.__selection = QRect()
            self.setCursor(Qt.CrossCursor)
        self.update()
    
    def mouseMoveEvent(self, evt):
        """
        Protected method to handle mouse movements.
        
        @param evt mouse move event (QMouseEvent)
        """
        shouldShowHelp = not self.__helpTextRect.contains(evt.pos())
        if shouldShowHelp != self.__showHelp:
            self.__showHelp = shouldShowHelp
            self.update()
        
        if self.__mouseDown:
            if self.__newSelection:
                p = evt.pos()
                r = self.rect()
                self.__selection = self.__normalizeSelection(
                    QRect(self.__dragStartPoint, self.__limitPointToRect(p, r)))
            elif self.__mouseOverHandle is None:
                # moving the whole selection
                r = self.rect().normalized()
                s = self.__selectionBeforeDrag.normalized()
                p = s.topLeft() + evt.pos() - self.__dragStartPoint
                r.setBottomRight(
                    r.bottomRight() - QPoint(s.width(), s.height()) + QPoint(1, 1))
                if not r.isNull() and r.isValid():
                    self.__selection.moveTo(self.__limitPointToRect(p, r))
            else:
                # dragging a handle
                r = QRect(self.__selectionBeforeDrag)
                offset = evt.pos() - self.__dragStartPoint
                
                if self.__mouseOverHandle in \
                   [self.__TLHandle, self.__THandle, self.__TRHandle]:
                    r.setTop(r.top() + offset.y())
                
                if self.__mouseOverHandle in \
                   [self.__TLHandle, self.__LHandle, self.__BLHandle]:
                    r.setLeft(r.left() + offset.x())
                
                if self.__mouseOverHandle in \
                   [self.__BLHandle, self.__BHandle, self.__BRHandle]:
                    r.setBottom(r.bottom() + offset.y())
                
                if self.__mouseOverHandle in \
                   [self.__TRHandle, self.__RHandle, self.__BRHandle]:
                    r.setRight(r.right() + offset.x())
                
                r.setTopLeft(self.__limitPointToRect(r.topLeft(), self.rect()))
                r.setBottomRight(self.__limitPointToRect(r.bottomRight(), self.rect()))
                self.__selection = self.__normalizeSelection(r)
            
            self.update()
        else:
            if self.__selection.isNull():
                return
            
            found = False
            for r in self.__handles:
                if r.contains(evt.pos()):
                    self.__mouseOverHandle = r
                    found = True
                    break
            
            if not found:
                self.__mouseOverHandle = None
                if self.__selection.contains(evt.pos()):
                    self.setCursor(Qt.OpenHandCursor)
                else:
                    self.setCursor(Qt.CrossCursor)
            else:
                if self.__mouseOverHandle in [self.__TLHandle, self.__BRHandle]:
                    self.setCursor(Qt.SizeFDiagCursor)
                elif self.__mouseOverHandle in [self.__TRHandle, self.__BLHandle]:
                    self.setCursor(Qt.SizeBDiagCursor)
                elif self.__mouseOverHandle in [self.__LHandle, self.__RHandle]:
                    self.setCursor(Qt.SizeHorCursor)
                elif self.__mouseOverHandle in [self.__THandle, self.__BHandle]:
                    self.setCursor(Qt.SizeVerCursor)
    
    def mouseReleaseEvent(self, evt):
        """
        Protected method to handle mouse button releases.
        
        @param evt mouse release event (QMouseEvent)
        """
        self.__mouseDown = False
        self.__newSelection = False
        if self.__mouseOverHandle is None and \
           self.__selection.contains(evt.pos()):
            self.setCursor(Qt.OpenHandCursor)
        self.update()
    
    def mouseDoubleClickEvent(self, evt):
        """
        Protected method to handle mouse double clicks.
        
        @param evt mouse double click event (QMouseEvent)
        """
        self.__grabRect()
    
    def keyPressEvent(self, evt):
        """
        Protected method to handle key presses.
        
        @param evt key press event (QKeyEvent)
        """
        if evt.key() == Qt.Key_Escape:
            self.grabbed.emit(QPixmap())
        elif evt.key() in [Qt.Key_Enter, Qt.Key_Return]:
            self.__grabRect()
        else:
            evt.ignore()
    
    def __updateHandles(self):
        """
        Private method to update the handles.
        """
        r = QRect(self.__selection)
        s2 = self.__handleSize // 2
        
        self.__TLHandle.moveTopLeft(r.topLeft())
        self.__TRHandle.moveTopRight(r.topRight())
        self.__BLHandle.moveBottomLeft(r.bottomLeft())
        self.__BRHandle.moveBottomRight(r.bottomRight())
        
        self.__LHandle.moveTopLeft(QPoint(r.x(), r.y() + r.height() // 2 - s2))
        self.__THandle.moveTopLeft(QPoint(r.x() + r.width() // 2 - s2, r.y()))
        self.__RHandle.moveTopRight(QPoint(r.right(), r.y() + r.height() // 2 - s2))
        self.__BHandle.moveBottomLeft(QPoint(r.x() + r.width() // 2 - s2, r.bottom()))
    
    def __handleMask(self, maskType):
        """
        Private method to calculate the handle mask.
        
        @param maskType type of the mask to be used (SnapshotRegionGrabber.FillMask or
            SnapshotRegionGrabber.StrokeMask)
        @return calculated mask (QRegion)
        """
        mask = QRegion()
        for rect in self.__handles:
            if maskType == SnapshotRegionGrabber.StrokeMask:
                r = QRegion(rect)
                mask += r.subtracted(QRegion(rect.adjusted(1, 1, -1, -1)))
            else:
                mask += QRegion(rect.adjusted(1, 1, -1, -1))
        return mask
    
    def __limitPointToRect(self, point, rect):
        """
        Private method to limit the given point to the given rectangle.
        
        @param point point to be limited (QPoint)
        @param rect rectangle the point shall be limited to (QRect)
        @return limited point (QPoint)
        """
        q = QPoint()
        if point.x() < rect.x():
            q.setX(rect.x())
        elif point.x() < rect.right():
            q.setX(point.x())
        else:
            q.setX(rect.right())
        if point.y() < rect.y():
            q.setY(rect.y())
        elif point.y() < rect.bottom():
            q.setY(point.y())
        else:
            q.setY(rect.bottom())
        return q
    
    def __normalizeSelection(self, sel):
        """
        Private method to normalize the given selection.
        
        @param sel selection to be normalized (QRect)
        @return normalized selection (QRect)
        """
        r = QRect(sel)
        if r.width() <= 0:
            l = r.left()
            w = r.width()
            r.setLeft(l + w - 1)
            r.setRight(l)
        if r.height() <= 0:
            t = r.top()
            h = r.height()
            r.setTop(t + h - 1)
            r.setBottom(t)
        return r
    
    def __grabRect(self):
        """
        Private method to grab the selected rectangle (i.e. do the snapshot).
        """
        if self.__mode == SnapshotRegionGrabber.Ellipse:
            ell = QRegion(self.__selection, QRegion.Ellipse)
            if not ell.isEmpty():
                self.__grabbing = True
                
                xOffset = self.__pixmap.rect().x() - ell.boundingRect().x()
                yOffset = self.__pixmap.rect().y() - ell.boundingRect().y()
                translatedEll = ell.translated(xOffset, yOffset)
                
                pixmap2 = QPixmap(ell.boundingRect().size())
                pixmap2.fill(Qt.transparent)
                
                pt = QPainter()
                pt.begin(pixmap2)
                if pt.paintEngine().hasFeature(QPaintEngine.PorterDuff):
                    pt.setRenderHints(QPainter.Antialiasing | \
                        QPainter.HighQualityAntialiasing | QPainter.SmoothPixmapTransform,
                        True)
                    pt.setBrush(Qt.black)
                    pt.setPen(QPen(QBrush(Qt.black), 0.5))
                    pt.drawEllipse(translatedEll.boundingRect())
                    pt.setCompositionMode(QPainter.CompositionMode_SourceIn)
                else:
                    pt.setClipRegion(translatedEll)
                    pt.setCompositionMode(QPainter.CompositionMode_Source)
                
                pt.drawPixmap(pixmap2.rect(), self.__pixmap, ell.boundingRect())
                pt.end()
                
                self.grabbed.emit(pixmap2)
        else:
            r = QRect(self.__selection)
            if not r.isNull() and r.isValid():
                self.__grabbing = True
                self.grabbed.emit(self.__pixmap.copy(r))