Subclassing QWidget in Java Make code 128 barcode in Java Subclassing QWidget

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Subclassing QWidget generate, create code128 none in java projects Internatioanl Orgnization for Standardization We create a QP tomcat Code128 ainter and set its render hints to give us antialiased drawing. Then we set the pen (which is used for shape outlines and for drawing text) and the brush (which is used for lls), and draw a rectangle over the entire widget. Because we used different shades for the pen and brush, this has the effect of giving the widget a border and a slightly indented look.

The QApplication object has a QPalette that contains colors for various purposes, such as text foreground and background colors, button colors, and so on. The colors are identi ed by their roles, such as QPalette.Text or QPalette.

Highlight, although we have used rather more obscure roles in this example. There are, in fact, three sets of these colors, one for each of the widget states: active , disabled , and inactive . Every QWidget also has a QPalette, with colors inherited from the QApplication palette which in turn is initialized with colors from the underlying window system and therefore re ects the user s preferences.

PyQt tries very hard to ensure that the colors in a palette work well together, providing good contrast, for example. As programmers, we are free to use whatever colors we like, but especially for standard requirements such as text colors and backgrounds, it is best to use the palette..

segColor = QCo lor( segLineColor = segColor.

dark() painter.setPen(segLineColor) painter.setBrush(segColor) painter.

drawRect(FractionSlider.XMARGIN, FractionSlider.YMARGIN, span, fm.

height()). We create a da code 128c for Java rk green color for the segments, and an even darker green for the vertical lines that mark them out. Then we draw a rectangle that encompasses all the segments..

textColor = se lf.palette().color(QPalette.

Text) segWidth = span / self.__denominator segHeight = fm.height() * 2 nRect = fm.

boundingRect(FractionSlider.WSTRING) x = FractionSlider.XMARGIN yOffset = segHeight + fm.

height(). Here, we set t Code 128 Code Set B for Java he text color to use based on the user s palette. Then we work out the width and height of each segment, and set an initial x position and a yOffset. The nRect is a rectangle large enough to contain a number with some left and right margin space.

. for i in range (self.__denominator + 1): painter.setPen(segLineColor) painter.

drawLine(x, FractionSlider.YMARGIN, x, segHeight) painter.setPen(textColor) y = segHeight rect = QRectF(nRect).

11. Custom Widgets rect.moveCente r(QPointF(x, y + fm.height() / 2.

0)) painter.drawText(rect, Qt.AlignCenter, QString.

number(i)) y = yOffset rect.moveCenter(QPointF(x, y + fm.height() / 2.

0)) painter.drawText(rect, Qt.AlignCenter, QString.

number(self.__denominator)) painter.drawLine(QPointF(rect.

left() + indent, y), QPointF(rect.right() - indent, y)) x += segWidth. In this loop w spring framework code-128c e draw the vertical lines that mark out each segment, the numerator below each segment, and the denominator below each numerator, along with the dividing line between them. For the drawText() calls we provide a rectangle in which the text should be drawn, and by using Qt.AlignCenter, we ensure that the text is vertically and horizontally centered inside the speci ed rectangle.

We use the same rectangle, but indented at the left and right, to calculate the end points of the dividing line, which we then draw. The y offsets are xed for every line, numerator, and denominator, but the x offsets increase by one segment width after drawing each fraction..

span = int(spa n) y = FractionSlider.YMARGIN - 0.5 triangle = [QPointF(value * span, y), QPointF((value * span) + \ (2 * FractionSlider.

XMARGIN), y), QPointF((value * span) + \ FractionSlider.XMARGIN, fm.height())] painter.

setPen(Qt.yellow) painter.setBrush(Qt.

darkYellow) painter.drawPolygon(QPolygonF(triangle)). At the end we Code 128 for Java draw the gold triangle that shows the user which fraction is selected. We specify polygons by providing a list of points. We don t have to duplicate the rst point at the end, since if we use drawPolygon(), PyQt will automatically join the rst and last points and ll the enclosed area.

In the next chapter we will see more advanced drawing techniques, including the use of the very versatile QPainterPath class. We have now completed the generic FractionSlider widget. It has both keyboard and mouse support, looks reasonable on all platforms, and interacts properly with the layout managers.

The QPainter class offers many more possibilities than we have needed for this widget, but in the next subsection we will see more of what can be done, including drawing un lled polygons and polygons that use gradient lls. We will also see how to include other widgets inside a custom widget..

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