[compiz] Greetings, first remarks about trying to do customizable drop-shadows

[David Reveman]

On Sun, 2006-04-02 at 12:09 +0200, Mirco Müller wrote:
> Hello there everybody!
> 
> 	Terrific... a mailing-list for compiz with David on board! Ok, I
> started off with writing some functions using cairo to draw me the
> needed elements for drop-shadows (atm stand-alone to focus on the proper
> generation of the shadow-parts) and currently still fiddle with the
> tweakable parameters. Right now I have...
> 
> 	shadow-radius (e.g. 20 pixels)
> 	2D-offset vector (e.g. 10 pixels right, 15 pixels downwards)
> 	start-color as rgba (e.g. 0.2/0.2/0.2/1.0)
> 	end-color as rgba (e.g. 0.2/0.2/0.2/0.0)
> 
> and try to figure out how I best approach the splitting up of the 5 to 8
> shadow-elements (top-left, top, top-right, left, right, bottom-left,
> bottom, bottom-right) depeding on the length of the offset-vector being
> =, < or > to the radius. I am also not sure how to attack the problem of
> rounded corners of the windows decoration-frame. If the shadow-textures
> will align with the outter edges of the decoration-frame there will be
> "unshadowed" gaps at the rounded corners. If I have the shadow-textures
> overlap a bit inwards it might look funny if the windows opacity changes
> to transparent. Right now the only solution for this is to fill the
> inner part of the drop-shadow with a rectangle having the start-color.
> But this solution causes heavy overdraw. While my midrange GeForce might
> deal with this happily I don't know how e.g. integrated graphic-chips
> from intel on shared memory can deal with the bandwidth issues that
> might arise from such an approach. What's your opinion on this? BTW, did
> I make myself clear enough or should I gimp up a quick schematic of the
> whole issue?

I assume that you want to put this code in compiz as a plugin. I suggest
not doing that. I've implemented drop-shadows like that before and it's
not a good solution. I strongly believe that drop shadows as part of the
decorations is currently the best solution. Like gnome-window-decorator
is doing but they should be made fully tweakable, of course.

Read the section about drop-shadows in the following post, if you
haven't already. 

http://lists.freedesktop.org/archives/compiz/2006-April/000009.html


-David