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我正在开发一个 Python+Gtk+Cairo 应用程序。我的应用程序需要做一些非常复杂（且昂贵）的绘图。

出于性能原因，我首先在 ImageSurface（屏幕外）上绘制，然后在我的 DrawingArea 对象上绘制 ImageSurface 内容。

注意：我需要缩放/翻译我的图纸以使其可见；否则，大图纸会掉出窗外。

不幸的是，出了点问题：如您所见，我无法绘制 ImageSurface 的全部内容。通过使用“规范” Context.set_source_surface(imageSurface, xCoord, yCoord) Context.paint()

我只得到这个错误的输出：

这是我想要达到的结果：

如何强制绘制整个图像表面？

下面的示例代码：

import gtk
import cairo

def main():
    w = gtk.Window()
    w.add(RubberTest())
    w.show_all()
    gtk.main()


class RubberTest(gtk.DrawingArea):
    def __init__(self, model=None):
        gtk.DrawingArea.__init__(self)
        self.set_size_request(800, 500)
        self.connect("expose-event", self._expose, self.create_basic_image())
        self.add_events(gtk.gdk.EXPOSURE_MASK
                      | gtk.gdk.BUTTON_PRESS_MASK
                      | gtk.gdk.BUTTON_RELEASE_MASK
                      | gtk.gdk.POINTER_MOTION_MASK)

    def create_basic_image(self):
        img = cairo.ImageSurface(cairo.FORMAT_ARGB32, 24, 24)
        cr = cairo.Context(img)

        # due to large coordinates, the drawing fall out of the window
        self.points = [(10000, 10000), (790000, 10000), (790000, 490000), (10000, 490000)]

        xMax, yMax, xMin, yMin = max([c[0] for c in self.points]), max([c[1] for c in self.points]), min([c[0] for c in self.points]), min([c[1] for c in self.points])
        maxRectWidth = xMax - xMin
        maxRectHeight = yMax - yMin

        w = 800
        h = 500
        width_ratio = float(w) / maxRectWidth
        height_ratio = float(h) / maxRectHeight

        # scale factor
        scaleFactor = min(height_ratio, width_ratio)

        cr.set_line_width(4)
        cr.set_source_rgb(1, 0, 0)

        cr.save()

        # scale + translate
        cr.scale(scaleFactor, scaleFactor)
        cr.translate(-xMin, -yMin)

        for i in range(0, len(self.points)):
            currPoint = self.points[i]
            currX = float(currPoint[0])
            currY = float(currPoint[1])
            nextIndex = i + 1
            if (nextIndex == len(self.points)):
                nextIndex = 0
            nextPoint = self.points[nextIndex]
            nextX = nextPoint[0]
            nextY = nextPoint[1]
            cr.move_to(currX, currY)
            cr.line_to(nextX, nextY)
        cr.restore()
        cr.close_path()
        cr.stroke_preserve()
        return img

    def _expose(self, sender, event, img):
        cr = self.window.cairo_create()
        cr.set_source_surface(img, 0, 0)
        cr.paint()
        return True

if __name__ == '__main__':
    main()

谢谢，它

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