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<chapter>
<title>Windowing system</title>
<sect1>
<title>USER Module</title>
<para>
USER implements windowing and messaging subsystems. It also
contains code for common controls and for other
miscellaneous stuff (rectangles, clipboard, WNet, etc).
Wine USER code is located in <filename>windows/</filename>,
<filename>controls/</filename>, and
<filename>misc/</filename> directories.
</para>
<sect2>
<title>Windowing subsystem</title>
<para><filename>windows/win.c</filename></para>
<para><filename>windows/winpos.c</filename></para>
<para>
Windows are arranged into parent/child hierarchy with one
common ancestor for all windows (desktop window). Each
window structure contains a pointer to the immediate
ancestor (parent window if <constant>WS_CHILD</constant>
style bit is set), a pointer to the sibling (returned by
<function>GetWindow(..., GW_NEXT)</function>), a pointer
to the owner window (set only for popup window if it was
created with valid <varname>hwndParent</varname>
parameter), and a pointer to the first child window
(<function>GetWindow(.., GW_CHILD)</function>). All popup
and non-child windows are therefore placed in the first
level of this hierarchy and their ancestor link
(<varname>wnd-&gt;parent</varname>) points to the desktop
window.
</para>
<screen>
Desktop window - root window
| \ `-.
| \ `-.
popup -&gt; wnd1 -&gt; wnd2 - top level windows
| \ `-. `-.
| \ `-. `-.
child1 child2 -&gt; child3 child4 - child windows
</screen>
<para>
Horizontal arrows denote sibling relationship, vertical
lines - ancestor/child. To summarize, all windows with the
same immediate ancestor are sibling windows, all windows
which do not have desktop as their immediate ancestor are
child windows. Popup windows behave as topmost top-level
windows unless they are owned. In this case the only
requirement is that they must precede their owners in the
top-level sibling list (they are not topmost). Child
windows are confined to the client area of their parent
windows (client area is where window gets to do its own
drawing, non-client area consists of caption, menu,
borders, intrinsic scrollbars, and
minimize/maximize/close/help buttons).
</para>
<para>
Another fairly important concept is
<firstterm>z-order</firstterm>. It is derived from the
ancestor/child hierarchy and is used to determine
"above/below" relationship. For instance, in the example
above, z-order is
</para>
<screen>
child1-&gt;popup-&gt;child2-&gt;child3-&gt;wnd1-&gt;child4-&gt;wnd2-&gt;desktop.
</screen>
<para>
Current active window ("foreground window" in Win32) is
moved to the front of z-order unless its top-level
ancestor owns popup windows.
</para>
<para>
All these issues are dealt with (or supposed to be) in
<filename>windows/winpos.c</filename> with
<function>SetWindowPos()</function> being the primary
interface to the window manager.
</para>
<para>
Wine specifics: in default and managed mode each top-level
window gets its own X counterpart with desktop window
being basically a fake stub. In desktop mode, however,
only desktop window has an X window associated with it.
Also, <function>SetWindowPos()</function> should
eventually be implemented via
<function>Begin/End/DeferWindowPos()</function> calls and
not the other way around.
</para>
<sect3>
<title>Visible region, clipping region and update region</title>
<para><filename>windows/dce.c</filename></para>
<para><filename>windows/winpos.c</filename></para>
<para><filename>windows/painting.c</filename></para>
<screen>
________________________
|_________ | A and B are child windows of C
| A |______ |
| | | |
|---------' | |
| | B | |
| | | |
| `------------' |
| C |
`------------------------'
</screen>
<para>
Visible region determines which part of the window is
not obscured by other windows. If a window has the
<constant>WS_CLIPCHILDREN</constant> style then all
areas below its children are considered invisible.
Similarly, if the <constant>WS_CLIPSIBLINGS</constant>
bit is in effect then all areas obscured by its siblings
are invisible. Child windows are always clipped by the
boundaries of their parent windows.
</para>
<para>
B has a <constant>WS_CLIPSIBLINGS</constant> style:
</para>
<screen>
. ______
: | |
| ,-----' |
| | B | - visible region of B
| | |
: `------------'
</screen>
<para>
When the program requests a <firstterm>display
context</firstterm> (DC) for a window it can specify
an optional clipping region that further restricts the
area where the graphics output can appear. This area is
calculated as an intersection of the visible region and
a clipping region.
</para>
<para>
Program asked for a DC with a clipping region:
</para>
<screen>
______
,--|--. | . ,--.
,--+--' | | : _: |
| | B | | =&gt; | | | - DC region where the painting will
| | | | | | | be visible
`--|-----|---' : `----'
`-----'
</screen>
<para>
When the window manager detects that some part of the window
became visible it adds this area to the update region of this
window and then generates <constant>WM_ERASEBKGND</constant> and
<constant>WM_PAINT</constant> messages. In addition,
<constant>WM_NCPAINT</constant> message is sent when the
uncovered area intersects a nonclient part of the window.
Application must reply to the <constant>WM_PAINT</constant>
message by calling the
<function>BeginPaint()</function>/<function>EndPaint()</function>
pair of functions. <function>BeginPaint()</function> returns a DC
that uses accumulated update region as a clipping region. This
operation cleans up invalidated area and the window will not
receive another <constant>WM_PAINT</constant> until the window
manager creates a new update region.
</para>
<para>
A was moved to the left:
</para>
<screen>
________________________ ... / C update region
|______ | : .___ /
| A |_________ | =&gt; | ...|___|..
| | | | | : | |
|------' | | | : '---'
| | B | | | : \
| | | | : \
| `------------' | B update region
| C |
`------------------------'
</screen>
<para>
Windows maintains a display context cache consisting of
entries that include the DC itself, the window to which
it belongs, and an optional clipping region (visible
region is stored in the DC itself). When an API call
changes the state of the window tree, window manager has
to go through the DC cache to recalculate visible
regions for entries whose windows were involved in the
operation. DC entries (DCE) can be either private to the
window, or private to the window class, or shared
between all windows (Windows 3.1 limits the number of
shared DCEs to 5).
</para>
</sect3>
</sect2>
<sect2>
<title>Messaging subsystem</title>
<para><filename>windows/queue.c</filename></para>
<para><filename>windows/message.c</filename></para>
<para>
Each Windows task/thread has its own message queue - this
is where it gets messages from. Messages can be:
<orderedlist>
<listitem>
<para>
generated on the fly (<constant>WM_PAINT</constant>,
<constant>WM_NCPAINT</constant>,
<constant>WM_TIMER</constant>)
</para>
</listitem>
<listitem>
<para>
created by the system (hardware messages)
</para>
</listitem>
<listitem>
<para>
posted by other tasks/threads (<function>PostMessage</function>)
</para>
</listitem>
<listitem>
<para>
sent by other tasks/threads (<function>SendMessage</function>)
</para>
</listitem>
</orderedlist>
</para>
<para>
Message priority:
</para>
<para>
First the system looks for sent messages, then for posted
messages, then for hardware messages, then it checks if
the queue has the "dirty window" bit set, and, finally, it
checks for expired timers. See
<filename>windows/message.c</filename>.
</para>
<para>
From all these different types of messages, only posted
messages go directly into the private message queue.
System messages (even in Win95) are first collected in the
system message queue and then they either sit there until
<function>Get/PeekMessage</function> gets to process them
or, as in Win95, if system queue is getting clobbered, a
special thread ("raw input thread") assigns them to the
private queues. Sent messages are queued separately and
the sender sleeps until it gets a reply. Special messages
are generated on the fly depending on the window/queue
state. If the window update region is not empty, the
system sets the <constant>QS_PAINT</constant> bit in the
owning queue and eventually this window receives a
<constant>WM_PAINT</constant> message
(<constant>WM_NCPAINT</constant> too if the update region
intersects with the non-client area). A timer event is
raised when one of the queue timers expire. Depending on
the timer parameters <function>DispatchMessage</function>
either calls the callback function or the window
procedure. If there are no messages pending the
task/thread sleeps until messages appear.
</para>
<para>
There are several tricky moments (open for discussion) -
</para>
<itemizedlist>
<listitem>
<para>
System message order has to be honored and messages
should be processed within correct task/thread
context. Therefore when <function>Get/PeekMessage</function> encounters
unassigned system message and this message appears not
to be for the current task/thread it should either
skip it (or get rid of it by moving it into the
private message queue of the target task/thread -
Win95, AFAIK) and look further or roll back and then
yield until this message gets processed when system
switches to the correct context (Win16). In the first
case we lose correct message ordering, in the second
case we have the infamous synchronous system message
queue. Here is a post to one of the OS/2 newsgroup I
found to be relevant:
</para>
<blockquote>
<attribution>by David Charlap</attribution>
<para>
" Here's the problem in a nutshell, and there is no
good solution. Every possible solution creates a
different problem.
</para>
<para>
With a windowing system, events can go to many
different windows. Most are sent by applications or
by the OS when things relating to that window happen
(like repainting, timers, etc.)
</para>
<para>
Mouse input events go to the window you click on
(unless some window captures the mouse).
</para>
<para>
So far, no problem. Whenever an event happens, you
put a message on the target window's message queue.
Every process has a message queue. If the process
queue fills up, the messages back up onto the system
queue.
</para>
<para>
This is the first cause of apps hanging the GUI. If
an app doesn't handle messages and they back up into
the system queue, other apps can't get any more
messages. The reason is that the next message in
line can't go anywhere, and the system won't skip
over it.
</para>
<para>
This can be fixed by making apps have bigger private
message queues. The SIQ fix does this. PMQSIZE does
this for systems without the SIQ fix. Applications
can also request large queues on their own.
</para>
<para>
Another source of the problem, however, happens when
you include keyboard events. When you press a key,
there's no easy way to know what window the
keystroke message should be delivered to.
</para>
<para>
Most windowing systems use a concept known as
"focus". The window with focus gets all incoming
keyboard messages. Focus can be changed from window
to window by apps or by users clicking on windows.
</para>
<para>
This is the second source of the problem. Suppose
window A has focus. You click on window B and start
typing before the window gets focus. Where should
the keystrokes go? On the one hand, they should go
to A until the focus actually changes to B. On the
other hand, you probably want the keystrokes to go
to B, since you clicked there first.
</para>
<para>
OS/2's solution is that when a focus-changing event
happens (like clicking on a window), OS/2 holds all
messages in the system queue until the focus change
actually happens. This way, subsequent keystrokes
go to the window you clicked on, even if it takes a
while for that window to get focus.
</para>
<para>
The downside is that if the window takes a real long
time to get focus (maybe it's not handling events,
or maybe the window losing focus isn't handling
events), everything backs up in the system queue and
the system appears hung.
</para>
<para>
There are a few solutions to this problem.
</para>
<para>
One is to make focus policy asynchronous. That is,
focus changing has absolutely nothing to do with the
keyboard. If you click on a window and start typing
before the focus actually changes, the keystrokes go
to the first window until focus changes, then they
go to the second. This is what X-windows does.
</para>
<para>
Another is what NT does. When focus changes,
keyboard events are held in the system message
queue, but other events are allowed through. This is
"asynchronous" because the messages in the system
queue are delivered to the application queues in a
different order from that with which they were
posted. If a bad app won't handle the "lose focus"
message, it's of no consequence - the app receiving
focus will get its "gain focus" message, and the
keystrokes will go to it.
</para>
<para>
The NT solution also takes care of the application
queue filling up problem. Since the system delivers
messages asynchronously, messages waiting in the
system queue will just sit there and the rest of the
messages will be delivered to their apps.
</para>
<para>
The OS/2 SIQ solution is this: When a
focus-changing event happens, in addition to
blocking further messages from the application
queues, a timer is started. When the timer goes
off, if the focus change has not yet happened, the
bad app has its focus taken away and all messages
targeted at that window are skipped. When the bad
app finally handles the focus change message, OS/2
will detect this and stop skipping its messages.
</para>
<para>
As for the pros and cons:
</para>
<para>
The X-windows solution is probably the easiest. The
problem is that users generally don't like having to
wait for the focus to change before they start
typing. On many occasions, you can type and the
characters end up in the wrong window because
something (usually heavy system load) is preventing
the focus change from happening in a timely manner.
</para>
<para>
The NT solution seems pretty nice, but making the
system message queue asynchronous can cause similar
problems to the X-windows problem. Since messages
can be delivered out of order, programs must not
assume that two messages posted in a particular
order will be delivered in that same order. This
can break legacy apps, but since Win32 always had an
asynchronous queue, it is fair to simply tell app
designers "don't do that". It's harder to tell app
designers something like that on OS/2 - they'll
complain "you changed the rules and our apps are
breaking."
</para>
<para>
The OS/2 solution's problem is that nothing happens
until you try to change window focus, and then wait
for the timeout. Until then, the bad app is not
detected and nothing is done."
</para>
</blockquote>
</listitem>
<listitem>
<para>
Intertask/interthread
<function>SendMessage</function>. The system has to
inform the target queue about the forthcoming message,
then it has to carry out the context switch and wait
until the result is available. Win16 stores necessary
parameters in the queue structure and then calls
<function>DirectedYield()</function> function.
However, in Win32 there could be several messages
pending sent by preemptively executing threads, and in
this case <function>SendMessage</function> has to
build some sort of message queue for sent messages.
Another issue is what to do with messages sent to the
sender when it is blocked inside its own
<function>SendMessage</function>.
</para>
</listitem>
</itemizedlist>
</sect2>
<sect2 id="accel-impl">
<title>Accelerators</title>
<para>
There are <emphasis>three</emphasis> differently sized
accelerator structures exposed to the user:
</para>
<orderedlist>
<listitem>
<para>
Accelerators in NE resources. This is also the internal
layout of the global handle <type>HACCEL</type> (16 and
32) in Windows 95 and Wine. Exposed to the user as Win16
global handles <type>HACCEL16</type> and
<type>HACCEL32</type> by the Win16/Win32 API.
These are 5 bytes long, with no padding:
<programlisting>
BYTE fVirt;
WORD key;
WORD cmd;
</programlisting>
</para>
</listitem>
<listitem>
<para>
Accelerators in PE resources. They are exposed to the
user only by direct accessing PE resources. These have a
size of 8 bytes:
</para>
<programlisting>
BYTE fVirt;
BYTE pad0;
WORD key;
WORD cmd;
WORD pad1;
</programlisting>
</listitem>
<listitem>
<para>
Accelerators in the Win32 API. These are exposed to the
user by the <function>CopyAcceleratorTable</function>
and <function>CreateAcceleratorTable</function> functions
in the Win32 API.
These have a size of 6 bytes:
</para>
<programlisting>
BYTE fVirt;
BYTE pad0;
WORD key;
WORD cmd;
</programlisting>
</listitem>
</orderedlist>
<para>
Why two types of accelerators in the Win32 API? We can only
guess, but my best bet is that the Win32 resource compiler
can/does not handle struct packing. Win32 <type>ACCEL</type>
is defined using <function>#pragma(2)</function> for the
compiler but without any packing for RC, so it will assume
<function>#pragma(4)</function>.
</para>
</sect2>
</sect1>
<sect1>
<title>X Windows System interface</title>
<para></para>
<sect2>
<title>Keyboard mapping</title>
<para>
Wine now needs to know about your keyboard layout. This
requirement comes from a need from many apps to have the
correct scancodes available, since they read these directly,
instead of just taking the characters returned by the X
server. This means that Wine now needs to have a mapping
from X keys to the scancodes these programs expect.
</para>
<para>
On startup, Wine will try to recognize the active X layout
by seeing if it matches any of the defined tables. If it
does, everything is alright. If not, you need to define it.
</para>
<para>
To do this, open the file
<filename>dlls/x11drv/keyboard.c</filename> and take a look
at the existing tables. Make a backup copy of it, especially
if you don't use CVS.
</para>
<para>
What you really would need to do, is find out which scancode
each key needs to generate. Find it in the
<function>main_key_scan</function> table, which looks like
this:
</para>
<programlisting>
static const int main_key_scan[MAIN_LEN] =
{
/* this is my (102-key) keyboard layout, sorry if it doesn't quite match yours */
0x29,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,
0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,
0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,0x2B,
0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0x34,0x35,
0x56 /* the 102nd key (actually to the right of l-shift) */
};
</programlisting>
<para>
Next, assign each scancode the characters imprinted on the
keycaps. This was done (sort of) for the US 101-key keyboard,
which you can find near the top in
<filename>keyboard.c</filename>. It also shows that if there
is no 102nd key, you can skip that.
</para>
<para>
However, for most international 102-key keyboards, we have
done it easy for you. The scancode layout for these already
pretty much matches the physical layout in the
<function>main_key_scan</function>, so all you need to do is
to go through all the keys that generate characters on your
main keyboard (except spacebar), and stuff those into an
appropriate table. The only exception is that the 102nd key,
which is usually to the left of the first key of the last
line (usually <keycap>Z</keycap>), must be placed on a
separate line after the last line.
</para>
<para>
For example, my Norwegian keyboard looks like this
</para>
<screen>
§ ! " # ¤ % & / ( ) = ? ` Back-
| 1 2@ 3£ 4$ 5 6 7{ 8[ 9] 0} + \´ space
Tab Q W E R T Y U I O P Å ^
¨~
Enter
Caps A S D F G H J K L Ø Æ *
Lock '
Sh- > Z X C V B N M ; : _ Shift
ift &lt; , . -
Ctrl Alt Spacebar AltGr Ctrl
</screen>
<para>
Note the 102nd key, which is the <keycap>&lt;></keycap> key, to
the left of <keycap>Z</keycap>. The character to the right of
the main character is the character generated by
<keycap>AltGr</keycap>.
</para>
<para>
This keyboard is defined as follows:
</para>
<programlisting>
static const char main_key_NO[MAIN_LEN][4] =
{
"|§","1!","2\"@","3#£","4¤$","5%","6&","7/{","8([","9)]","0=}","+?","\\´",
"qQ","wW","eE","rR","tT","yY","uU","iI","oO","pP","åÅ","¨^~",
"aA","sS","dD","fF","gG","hH","jJ","kK","lL","øØ","æÆ","'*",
"zZ","xX","cC","vV","bB","nN","mM",",;",".:","-_",
"&lt;>"
};
</programlisting>
<para>
Except that " and \ needs to be quoted with a backslash, and
that the 102nd key is on a separate line, it's pretty
straightforward.
</para>
<para>
After you have written such a table, you need to add it to the
<function>main_key_tab[]</function> layout index table. This
will look like this:
</para>
<programlisting>
static struct {
WORD lang, ansi_codepage, oem_codepage;
const char (*key)[MAIN_LEN][4];
} main_key_tab[]={
...
...
{MAKELANGID(LANG_NORWEGIAN,SUBLANG_DEFAULT), 1252, 865, &amp;main_key_NO},
...
</programlisting>
<para>
After you have added your table, recompile Wine and test that
it works. If it fails to detect your table, try running
</para>
<screen>
WINEDEBUG=+key,+keyboard wine > key.log 2>&1
</screen>
<para>
and look in the resulting <filename>key.log</filename> file to
find the error messages it gives for your layout.
</para>
<para>
Note that the <constant>LANG_*</constant> and
<constant>SUBLANG_*</constant> definitions are in
<filename>include/winnls.h</filename>, which you might need
to know to find out which numbers your language is assigned,
and find it in the WINEDEBUG output. The numbers will be
<literal>(SUBLANG * 0x400 + LANG)</literal>, so, for example
the combination <literal>LANG_NORWEGIAN (0x14)</literal> and
<literal>SUBLANG_DEFAULT (0x1)</literal> will be (in hex)
<literal>14 + 1*400 = 414</literal>, so since I'm Norwegian,
I could look for <literal>0414</literal> in the WINEDEBUG
output to find out why my keyboard won't detect.
</para>
</sect2>
</sect1>
</chapter>
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