I'm working on an application written in Cairo + Gtk. Please note that, due to retrocompatibility issues, I am forced to use Python as programming language, PyGTK as wrapper, and GTK libraries, v.2.24. No chance to use C/C++ and/or GTK3!
My app need to (re)draw a big amount of data on screen for each invocation of expose method(obviously).
I would simply give to users a chance to manually select some objects previously drawn with Cairo. Since I'm drawing on gtk.DrawingAreas, it seems that I must manually implement the rubber band selection functionality.
This is the question:
Is there any way to redraw the rubber band rectangle at every mouse move, avoiding to redraw all others objects on screen?
I would redraw only the selection rectangle for performance reasons.
Due to the big amount of graphical objects, my GUI is terribly slow. Unfortunately, despite several attempts, I have no choice: redraw all or redraw anything!
First thing that came in my mind: is there any way to overlay an intermediate level between the DrawingArea with most of data and the mouse cursor? by calling queue_draw_area() function there aren't performance gains.
A simple, self containing code example below: obviously, in this case Ionly use cairo to draw extremely simple graphic objects.
import gtk
from gtk import gdk
class Canvas(gtk.DrawingArea):
# the list of points is passed as argument
def __init__(self, points):
super(Canvas, self).__init__()
self.points = points
self.set_size_request(400, 400)
# Coordinates of the left-top angle of the selection rect
self.startPoint = None
self.endPoint = None
# Pixmap to drawing rubber band selection
self.pixmap = None
self.connect("expose_event", self.expose_handler)
self.connect("motion_notify_event", self.mouseMove_handler)
self.set_events(gtk.gdk.EXPOSURE_MASK
| gtk.gdk.LEAVE_NOTIFY_MASK
| gtk.gdk.BUTTON_PRESS_MASK
| gtk.gdk.POINTER_MOTION_MASK
| gtk.gdk.POINTER_MOTION_HINT_MASK)
# Method to paint lines and/or rubberband on screen
def expose_handler(self, widget, event):
rect = widget.get_allocation()
w = rect.width
h = rect.height
ctx = widget.window.cairo_create()
ctx.set_line_width(7)
ctx.set_source_rgb(255, 0, 0)
ctx.save()
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)):
continue
nextPoint = self.points[nextIndex]
nextX = float(nextPoint[0])
nextY = float(nextPoint[1])
ctx.move_to(currX, currY)
ctx.line_to(nextX, nextY)
ctx.restore()
ctx.close_path()
ctx.stroke()
# rubber band
if self.pixmap != None:
width = self.endPoint[0] - self.startPoint[0]
height = self.endPoint[1] - self.startPoint[1]
if width < 0 or height < 0:
tempEndPoint = self.endPoint
self.endPoint = self.startPoint
self.startPoint = tempEndPoint
height = self.endPoint[1] - self.startPoint[1]
width = self.endPoint[0] - self.startPoint[0]
widget.window.draw_drawable(widget.get_style().fg_gc[gtk.STATE_NORMAL], self.pixmap, self.startPoint[0], self.startPoint[1], self.startPoint[0], self.startPoint[1], abs(width), abs(height))
def mouseMove_handler(self, widget, event):
x, y, state = event.window.get_pointer()
if (state & gtk.gdk.BUTTON1_MASK):
if (state & gtk.gdk.CONTROL_MASK):
if self.startPoint == None:
self.startPoint = (x,y)
self.endPoint = (x,y)
else:
self.endPoint = (x,y)
tempPixmap = gtk.gdk.Pixmap(widget.window, 400, 400)
height = self.endPoint[1] - self.startPoint[1]
width = self.endPoint[0] - self.startPoint[0]
gc = self.window.new_gc()
gc.set_foreground(self.get_colormap().alloc_color("#FF8000"))
gc.fill = gtk.gdk.STIPPLED
tempPixmap.draw_rectangle(gc, True, self.startPoint[0], self.startPoint[1], abs(width), abs(height))
self.pixmap = tempPixmap
# widget.queue_draw_area()
widget.queue_draw()
else:
if (self.pixmap != None):
self.pixmap = None
# ...do something...
# widget.queue_draw_area(self.startPoint[0], self.startPoint[1], )
widget.queue_draw()
li1 = [(20,20), (380,20), (380,380), (20,380)]
window = gtk.Window()
canvas = Canvas(li1)
window.add(canvas)
window.connect("destroy", lambda w: gtk.main_quit())
window.show_all()
gtk.main()
Thanks!
IT