RE: GDK_POINTER_MOTION_HINT_MASK has no effect

["Stewart Weiss" <stewart weiss acm org>]

John,

I will study the application you sent me the link to.
My  program is not raster; it lets the user draw with a brush
or use a line tool in the window. Since the user has drawn with a
brush already, the underlying layer is in a pixmap.
First I will look at your application's  code, and if I cannot figure it
out,
I will post again.

Many thanks
Stewart

> -----Original Message-----
> From: jcupitt gmail com [mailto:jcupitt gmail com]
> Sent: Thursday, November 29, 2007 4:48 PM
> To: stewart weiss acm org
> Cc: gtk-list
> Subject: Re: GDK_POINTER_MOTION_HINT_MASK has no effect
>
>
> On 11/29/07, Stewart Weiss <stewart weiss acm org> wrote:
> > 1. I am assuming that when I queue a draw for the old position of
> > the rubberbanded line, I am using XOR to draw it, so that it is in
> > effect, an erasing, right?
>
> Actually, I'd suggest using a plain draw rather than an XOR.
>
> XOR rubberbanding works if you can treat your display as something you
> can draw incrementally, that is, you know what is on the screen and
> therefore you know whether this XOR draw will set or unset a line.
>
> This is often not the case, especially in a complex application.
> Instead, you should think of your window as being composed from a
> number of separate layers (like photoshop layers), and that on an
> expose you should completely repaint that section of the window by
> drawing all layers from the back forwards.
>
> > Right now, my function to draw a line uses gdk_draw_line into the pixmap
> > and then calls gdk_window_invalidate_rect to send the expose
> event later.
> > If I actually call the gdk_draw_line in the expose event
> handler, directly
> > into the pixmap, would I then use gdk_draw_drawable to copy the
> pixmap into
> > the window?   I know I can't queue a drawing event in the
> handler or else
> > I have an infinite indirect recursive loop. Is this how?
>
> Is this a raster drawing program, or a vector one?
>
> Assuming it's raster, you should have two separate data structures.
> Keep a large image around which has the current state of your user's
> image. Only drawing operations go into this, no rubberbanding. This is
> your background layer. Rubberband operations are in another layer
> which floats on top of this.
>
> On an expose, use your background image to paint the exposed pixels.
> Then, if there's a rubber band active at the moment and if the
> bounding box of the rubber band intersects the expose, draw that as
> well on top of the image.
>
> If you're curious, my app is here:
>
>   http://www.vips.ecs.soton.ac.uk
>
> To see the rubberbanding, load an image, doubleclick the thumbnail to
> get a view window, then hold down CTRL and click and drag up and left
> to get a vector, down and right to get a region, just click to get a
> point, or drag from a ruler to get a guide.
>
> If you try resizing outside the edge of the window, the window will
> scroll in the background. You can move objects around by dragging on
> their names. Hopefully you'll see all the objects, including the
> animated ones, float over each other smoothly. There's a simple
> paintbox on the View menu which also does some rubberbanding with some
> of the tools.
>
> John