How to edit Drawable/XdbeBackBuffer data?...

[Lee Fallat]

Alright, well I've decided to take another approach. I'm XGetImage()ing the
root window, then I darken my pixels, then, I go to store the data in a
Drawable via XPutImage, but this Drawable isn't retaining the data, it's
just white when I XCopyArea() over to what I want shown. Any
suggestions/reasons why this is happening?

Code sample:

static XImage
*xi;



void XTintBG(Monitor *m, int x, int y, int w, int h)
{

  unsigned long
new_color;

  unsigned long
r,g,b;



  XCopyArea(dpy, root, m->barwin, dc.gc, x, y, w, h, x,
y);

  xi = XGetImage(dpy, m->barwin, x, y, w, h, AllPlanes,
XYPixmap);



  for(int pix_y = 0; pix_y < h; pix_y++)
{

    for(int pix_x = 0; pix_x < w; pix_x++)
{

      new_color = XGetPixel(xi, pix_x,
pix_y);

      r = g = b =
0x00000000;

      r = (new_color & 0x00FF0000) >>
16;

      g = (new_color & 0x0000FF00) >>
8;

      b = (new_color & 0x000000FF) >>
0;

      r -=
32;

      g -=
32;

      b -=
32;

      if(r > 255) r =
255;

      if(r < 0) r =
0;

      if(g > 255) g =
255;

      if(g < 0) g =
0;

      if(b > 255) b =
255;

      if(b < 0) b =
0;

      new_color = r <<
16;

      new_color = new_color | (g <<
8);

      new_color = new_color | (b <<
0);

      XPutPixel(xi, pix_x, pix_y,
new_color);


}


}



  XPutImage(dpy, m->barwin, dc.gc, xi, 0, 0, 0, 0, m->ww,
bh);

  XCopyArea(dpy, m->barwin, dc.bg, dc.gc, 0, 0, m->ww, bh, 0,
0);

}



int ftime =
1;



void

drawbar(Monitor *m)
{

  int
x;

  unsigned int i, occ = 0, urg =
0;

  XftColor
*col;

  Client
*c;



  if(ftime == 1)
{

  ftime =
0;

  XTintBG(m, 0, 0, m->ww,
bh);


}



  XCopyArea(dpy, dc.bg, dc.drawable, dc.gc, 0, 0, m->ww, bh, 0, 0);

<More functions here but not relative to what I need>

}

On Mon, Aug 20, 2012 at 3:17 PM, Adam Jackson <ajax at redhat.com> wrote:

> On 8/20/12 2:08 PM, Lee Fallat wrote:
>
>> Hey,
>>
>> I'm trying to darken/lighten the image data in a Drawable/XdbeBackBuffer.
>> Any ideas on how to get access to the data?...I've done an XGetImage() on
>> Drawable but that really slows down the application I'm editing...
>>
>
> That is, in fact, how you do it.  GetImage is not fast.  ShmGetImage is
> faster, and as fast as you're going to get, if you insist on doing this by
> pulling all the pixels down to the client and then pushing them back up.
>
> You may instead wish to use the Render extension, which gives you the
> usual set of Porter-Duff blend operations, and which runs in the server so
> you're not copying all that data around.
>
> - ajax
>
>
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