Icons on X11 windows are configured using the _NET_WM_ICON property
described in Extended Window Manager Hints. Here we implement converison
from DIB bitmaps used by RAIL to the format expected by _NET_WM_ICON,
and actually set the icon for RAIL app windows.
Both DIB format and _NET_WM_ICON (or rather, Xlib) are weird. Let's
start with RAIL's format. That's the one used in BMP and ICO formats
on Windows. It has some strange properties but thankfully FreeRDP's
freerdp_image_copy() can handle most of them for us. (With an exception
of monochrome and 16-color formats that it does not support. Sorry, but
I'm too lazy to fix them. They are not seem to be used by any real
application either.) The one thing that it can't do is to apply the
alpha transparency bitmask so we have to do it manually. This instantly
reminds us that DIB format has HISTORY: it's vertically flipped and
each must be padded to 4 bytes. Both these quirks having reasonable
(for a certain definition of 'reason') explanations. Such is life.
(Also, 8-bit images require a color palette which we must fill in.)
So okay, now comes _NET_WM_ICON. It is more sane (or rather, easier to
deal with). The bitmap is represented with a tiny [width, height] header
followed by an array of pixels in ARGB format. There is no padding, no
weird color formats. But here's a catch: you can't simply take the
output of freerdp_image_copy() and cast to (unsigned char*) of colors.
We have to allocate an array of C's longs and copy the pixels there,
because that's what Xlib expects (and this is mentioned in the spec).
Simply casting an array of bytes causes crashes on 64-bit systems.
So don't try to cheat or "optimize" and read the docs, kids.
Note that XFlush() call after XChangeProperty(). It's there because it
seems to helps see the icon quicker with Unity on Ubuntu 14.04. I don't
know why. (And Unity does not support _NET_WM_ICON officially. But it
sorta kinda works sometimes.)
Oh, and while we're here, delete some old, unused, and commented out
code that was setting window icons in the past. It's not needed anymore.
This commit adds a cache for RAIL application icons. It is (surpisingly)
used to cache icons for remote applications. This mechanism is described
in MS-RDPERP 3.1.1.2 Icon Cache Support and related items.
Note that some (actually, most) of the icons are not cached. These are
marked with CacheId == 0xFF. In order to keep the code clean we do not
introduce a special case and instead use a 'scratch' icon and simply
pretend to return an xfRailIcon from cache.
We're going to set icons via _NET_WM_ICON property which explains
why we use "long" values to store pixel data. The icon conversion
is not implemented in this commit, it's only stubs.
However, we do implement processing of window information orders that
contain new icons or cached references to previously sent icons. Note
that it is important to not fail (i.e., to not return FALSE) if we
cannot find a window for the icon by its ID. The server occasionally
likes to be slow or something and send icon updates for nonexistent
windows. This behavior is mandated by the spec, too:
MS-RDPERP 3.2.5.1.6 Processing Window Information Orders
Upon receipt of a Window Information Order for an icon or
cached icon, as specified in sections 2.2.1.3.1.2.2 and
2.2.1.3.1.2.3, the client SHOULD locate the local RAIL window
that corresponds to the WindowId reported in the Hdr field
and apply the icon updates to the RAIL window. If no such
window can be found, the client SHOULD ignore the order.
Indeed, we silently ignore such orders now.
The spec says that CbColorTable field is present when Bpp is 1, 4, 8.
Actually, bpp == 2 is not supported by TS_ICON_INFO according to the
spec (though, DIB definitely supports 16-color images).
MS-RDPERP 2.2.1.2.3 Icon Info (TS_ICON_INFO)
CbColorTable (2 bytes):
This field is ONLY present if the bits per pixel (Bpp)
value is 1, 4, or 8.
Omitting 8-bit value breaks 256-color icons which are incorrectly
read with color and alpha data mixed up.
Martin Fleisz