python - 透明小部件背景

Question

我是 pygtk 的新手。我正在寻找一种方法来创建使用父背景作为自己的背景的自定义小部件，例如https://fbcdn-sphotos-ea.akamaihd.net/hphotos-ak-prn1/31617_421363141269410_1875576 ​​801_n.jpg

如何获取父位图并将其用作自己的位图？

class RoundRectPanel(gtk.DrawingArea, PanelBase):
    """
    Panel That represents
    """
    def __init__(self):
        super(ProximityPanel, self).__init__()

    def initialize(self):
        super(RoundRectPanel, self).initialize()

        self.set_size_request(340, 300)
        self.connect('expose-event', self.expose)

    def terminate(self):
        pass

    def rounded_rectangle(self, cr, x, y, w, h, r=20):
        #   A****BQ
        #  H      C
        #  *      *
        #  G      D
        #   F****E

        cr.move_to(x+r,y)                      # Move to A
        cr.line_to(x+w-r,y)                    # Straight line to B
        cr.curve_to(x+w,y,x+w,y,x+w,y+r)       # Curve to C, Control points are both at Q
        cr.line_to(x+w,y+h-r)                  # Move to D
        cr.curve_to(x+w,y+h,x+w,y+h,x+w-r,y+h) # Curve to E
        cr.line_to(x+r,y+h)                    # Line to F
        cr.curve_to(x,y+h,x,y+h,x,y+h-r)       # Curve to G
        cr.line_to(x,y+r)                      # Line to H
        cr.curve_to(x,y,x,y,x+r,y)             # Curve to A

    def expose(self, canvas, event):
        # Create cairo context
        cr = canvas.window.cairo_create()

        # TODO: 1. GET PARENT background
        # 2. set it as canvas background

        # 3. draw on it
        self.rounded_rectangle(cr, 0, 0, 340, 300)
        cr.stroke_preserve()
        cr.set_source_rgba(1.0, 1.0, 1.0, 0.5)
        cr.fill()

Answer 1

目前找到了解决方法，这需要自定义小部件与他的父窗口（绘制背景图像的位置）进行通信。CustomWidget 需要关于背景图像的父信息（窗口上的文件名和图像位置）

class CustomWidget(gtk.DrawingArea):
def __init__(self, parent):
    super(CustomWidget, self).__init__()
    self.set_size_request(340, 300)
    self._parent = parent

    self.connect('expose-event', self._expose_event)

def _expose_event(self, widget, event):
    cr = widget.window.cairo_create()

    self.draw_context(cr, widget)

def draw_context(self, cr, widget):
    ctx = cr
    x, y, width, height = widget.allocation

    # parent window should have file name that is used as a background
    pixbuf = gtk.gdk.pixbuf_new_from_file(self._parent.file)
    ctx.save()
    # copy particular image region where your custom widget is located
    ctx.set_source_pixbuf(pixbuf, (-x) + self._parent.image.allocation.x, (-y) + self._parent.image.allocation.y)

    # draw background for custom widget
    ctx.paint()
    ctx.restore()

    # now draw what ever you want
    self.rounded_rectangle(cr, 0, 0, width, height)
    cr.set_line_width(1.0)
    cr.set_source_color(gtk.gdk.color_parse('grey'))
    cr.stroke_preserve()

    gradient = cairo.LinearGradient(width/2, 0, width/2, height)
    gradient.add_color_stop_rgba(0.00, 1, 1, 1, 0.9)
    gradient.add_color_stop_rgba(1.00, 0.4, 0.4, 0.4, 0.5)
    cr.set_source(gradient)
    cr.fill()