Re: Pixmap question

[John Cupitt <john cupitt ng-london org uk>]

Colin Thomas wrote:
> If I read it correctly, it seems you can overlay pixels on existing pixels
> ANDing the colour ? (Which is what I am after...)

Hiya, you can use this ... you'd have to:

- have an off-screen pixmap on the server for each layer in your view
- on redraw (eg. on layer delete), AND all your layers together to make
another off-screen pixmap
- repaint the window by blitting from your combined view to the screen

This is going to be rather slow, and will eat up memory inside the
server. For example, on a scroll, you'll have to ship a whole new set of
pixmaps over to the server.

I think a better technique is to do this in your application. Do the AND
yourself to a big array, then paint the window with gdkrgb. Less network
traffic (maybe), less memory use (certainly).

> I also would like to have dashed lines in rectangles et al. There seems to
> be the following, but again can it be used in gdk: I assume somehow it is
> called in the GC which the rectangle is drawn in ?? (Either of my 2 gtk+ books
> go into this depth)
> 
> ############################################
> typedef enum
> {
>   GDK_LINE_SOLID,
>   GDK_LINE_ON_OFF_DASH,
>   GDK_LINE_DOUBLE_DASH
> } GdkLineStyle;
> ############################################

The best place to look is a book on xlib programming - the gdk calls are
almost identical.

HTH, John
--
John Cupitt, john cupitt ng-london org uk, +44 (0)20 7747 2570
VASARI Lab, The National Gallery, Trafalgar Square, London, WC2N 5DN