我刚开始使用pycairo,遇到了以下有趣的错误。我编写的程序创建了一个简单的gtk窗口,绘制了一个矩形,然后有一个回调函数在任何键盘输入时绘制一条随机线。但是,似乎每次键盘输入时,我都必须创建一个新的上下文,否则在程序接收到第一次键盘输入时(具体来说,在.stroke()行上),就会出现错误。如果有关系,错误如下所示:'BadDrawable(无效的Pixmap或Window参数)'。(详细信息:serial 230 error_code 9 request_code 53 minor_code 0)
#! /usr/bin/env python
import pygtk
pygtk.require('2.0')
import gtk, gobject, cairo, math, random
# Create a GTK+ widget on which we will draw using Cairo
class Screen(gtk.DrawingArea):
# Draw in response to an expose-event
__gsignals__ = { "expose-event": "override" }
# Handle the expose-event by drawing
def do_expose_event(self, event):
# Create the cairo context
self.cr = self.window.cairo_create()
# Restrict Cairo to the exposed area; avoid extra work
self.cr.rectangle(event.area.x, event.area.y, event.area.width, event.area.height)
self.cr.clip()
self.draw(*self.window.get_size())
def key_press_event(self, *args):
# print args
self.cr = self.window.cairo_create() # This is the line I have to add
# in order to make this function not throw the error. Note that cr is only
# given as attribute of self in order to stop it going out of scope when this line
# doesn't exist
self.cr.set_source_rgb(random.random(), random.random(), random.random())
self.cr.move_to(*[z/2.0 for z in self.window.get_size()])
self.cr.line_to(*[z*random.random() for z in self.window.get_size()])
self.cr.stroke()
def draw(self, width, height):
# Fill the background with gray
self.cr.set_source_rgb(.5,.5,.5)
self.cr.rectangle(0, 0, width,height)
self.cr.fill()
self.cr.set_source_rgb(1,0,0)
self.cr.arc(width/2.0, height/2.0, min(width,height)/2.0 - 20.0, 0.0, 2.0*math.pi)
self.cr.stroke()
#create a gtk window, attach to exit button, and whatever is passed as arg becomes the body of the window. AWESOME
def run(Widget):
window = gtk.Window()
widget = Widget()
window.connect("delete-event", gtk.main_quit)
window.connect('key-press-event',widget.key_press_event)
widget.show()
window.add(widget)
window.present()
gtk.main()
if __name__ == "__main__":
run(Screen)
感谢您的帮助!
更新:我在尝试时发现以下问题:当我调整窗口大小时,所有新添加的对象都会被删除(或者至少不再出现?)