[cairo] Erasing A Line
allen.saucier at cas-inc.com
Fri Jun 29 05:28:39 PDT 2007
this seems to be an even shorter method to draw.
1. re-drawn exposed image
2. draw new line & don't worry w/ drawing old line because it will be
erased anyway w/ the "expose" event.
Ivan Baldo wrote:
> But if you have a background image, then almost certainly you will
> end having a Cairo Surface for it, so what you do after the user moves
> the mouse is this:
Ok, here I"m having to check for the event "motion move" which sends
back oodles & oodles & signals. But if I confine the motion_notify
events that I'm interested in by only responding to ones that start w/ a
button_press_event, then I think this method will work. For the final
line will be shown by the time the user preforms a button_release event
and I will not have to process any further motion_notify events
> - generate an expose event for the area occupied by the old line
> and the new line, 2 calls to gtk_widget_queue_draw_area (it will join
> both rectangles and generate only 1 expose event).
> - on the expose event of the DrawingArea or Image you draw with
> Cairo, first clip with gdk_cairo_region(cr, event->region);
> cairo_clip(cr), then draw first the background image, then the line at
> the place where the mouse is pointing.
> You really don't need transparency or real layers, just draw things
> in the correct order.
This is really cool. Thanks for the info. I really appreciate it. This
is great! thanks everyone!!! You're very nice & very helpful. I hope
to be helpful as I get better.
Gene Allen Saucier, Jr
Madison Research Park, Bld 111
111 Research Blvd
Madison, AL 35758
"...As for I and my house, we shall follow the Lord" Joshua 24:15
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