def __static_text_elided_cache(
self, option: QStyleOptionViewItem, width: int) -> QStaticText:
"""
Return a QStaticText instance for depicting the text of the `option`
item.
"""
key = option.text, option.font.key(), option.textElideMode, width
try:
st = self.__static_text_lru_cache[key]
except KeyError:
fm = option.fontMetrics
text = fm.elidedText(option.text, option.textElideMode, width)
st = QStaticText(text)
st.prepare(QTransform(), option.font)
self.__static_text_lru_cache[key] = st
return st
class RollingLabel(QLabel):
def __init__(self, parent=None):
super(RollingLabel, self).__init__(parent)
self.timer = QTimer()
self.timer.timeout.connect(self.updateR)
self.timer.start(55)
self.wholeTextSize = QSize(0, 0)
self.singleTextWidth = 0
self.scrollEnabled = False
self.scrollPos = 0
self.buffer = QImage()
self.alphaChannel = QImage()
self.staticText = QStaticText("")
self.staticText.setTextFormat(Qt.PlainText)
self.setFixedHeight(self.fontMetrics().height())
self.leftMargin = self.height() / 3
self._text = ""
def text(self):
return self._text
def setText(self, text):
self._text = text
self.updateText()
self.update()
def paintEvent(self, event):
p = QPainter(self)
if self.scrollEnabled:
self.buffer.fill(qRgba(0, 0, 0, 0))
pb = QPainter(self.buffer)
pb.setPen(p.pen())
pb.setFont(p.font())
x = min(-self.scrollPos, 0) + self.leftMargin
while x < self.width():
pb.drawStaticText(
QPointF(x,
(self.height() - self.wholeTextSize.height()) / 2)
+ QPoint(2, 2), self.staticText)
x += self.wholeTextSize.width()
#Apply Alpha Channel
pb.setCompositionMode(QPainter.CompositionMode_DestinationIn)
pb.setClipRect(self.width() - 15, 0, 15, self.height())
pb.drawImage(0, 0, self.alphaChannel)
pb.setClipRect(0, 0, 15, self.height())
#initial situation: don't apply alpha channel in the left half of the image at all; apply it more and more until scrollPos gets positive
if self.scrollPos < 0:
pb.setOpacity((max(-8, self.scrollPos) + 8) / 8.0)
pb.drawImage(0, 0, self.alphaChannel)
p.drawImage(0, 0, self.buffer)
else:
x = (self.width() - self.wholeTextSize.width()) / 2
y = (self.height() - self.wholeTextSize.height()) / 2
p.drawStaticText(QPointF(x, y), self.staticText)
def updateR(self):
self.scrollPos = (self.scrollPos + 2) % self.wholeTextSize.width()
self.update()
def updateText(self):
self.timer.stop()
self.singleTextWidth = self.fontMetrics().width(self._text)
self.scrollEnabled = (self.singleTextWidth >
self.width() - self.leftMargin)
if self.scrollEnabled:
self.scrollPos = -64
self.staticText.setText(self._text)
self.timer.start()
else:
self.staticText.setText(self._text)
self.staticText.prepare(QTransform(), self.font())
self.wholeTextSize = QSize(
self.fontMetrics().width(self.staticText.text()),
self.fontMetrics().height())
def resizeEvent(self, event):
#When the widget is resized, we need to update the alpha channel.
self.alphaChannel = QImage(self.size(),
QImage.Format_ARGB32_Premultiplied)
self.buffer = QImage(self.size(), QImage.Format_ARGB32_Premultiplied)
#Create Alpha Channel:
if self.width() > 64:
#create first scanline
scanline = [0] * self.width()
for x in range(0, 15):
scanline[x] = scanline[self.width() - x - 1] = qRgba(
0, 0, 0, x << 4)
# Background
for x in range(15, self.width() - 15):
scanline[x] = qRgb(0, 0, 0)
#copy scanline to the other ones
for y in range(0, self.height()):
for x in range(0, self.width()):
self.alphaChannel.setPixel(x, y, scanline[x])
else:
self.alphaChannel.fill(qRgba(0, 0, 0, 0))
#Update scrolling state
newScrollEnabled = (self.singleTextWidth >
self.width() - self.leftMargin)
if newScrollEnabled != self.scrollEnabled:
self.updateText()