Xscreensaver code giving BadMatch error

Question

I've been able to hack an Xscreensaver to where I'm getting my desired look (big thanks to luser droog for his aid). I added in some Cairo code because it was difficult to implement what I wanted with Xlib alone. Since this is just a hack for me I don't intend on distributing it.

Anyway, when I preview Fuzzyflakes in a window it looks fine, yet when I preview it fullscreen (like any good screensaver) it gives me this error:

X error in fuzzyflakes:
X Error of failed request: BadMatch (invalid parameter attribute)
  Major Optcode of failed request: 139 (RENDER)
  Minor optcode of failed request: 4 (RenderCreatePicture)
  Serial number of failed request: 528
  Current serial number in output stream: 1654

Here's some further information. I'm using Linux Mint 14, 64-bit edition. I'm using the nVidia proprietary drivers, version 304.88. I had to hack the Makefile generated by the xscreensaver configure script. I changed line 800 of the Makefile to this:

fuzzyflakes:    fuzzyflakes.o   $(HACK_OBJS) 
    $(CC_HACK) `pkg-config --cflags cairo` -g -o $@ $@.o    $(HACK_OBJS) $(HACK_LIBS) -lcairo -lm

For the full source code you can look here.

Answer 1

From a quick look, it seems like you are feeding cairo with invalid information:

flake->Fluff.gradient_image_background =
               cairo_xlib_surface_create(flake->dpy,
               flake->DB.b, DefaultVisual(flake->dpy, 0),
               flake->XGWA.width, flake->XGWA.height);

This claims that the drawable DB.p uses the display's first screen's default visual. However, the actual window seems to be an argument to fuzzyflakes_init() and thus could be using another visual.

From another quick look, please try replacing DefaultVisual(flake->dpy, 0) with flake->XGWA.visual.