Tracking the mouse buttons during Default Drag/Size operations ???

[Chris Boss]

When the API function DefWindowProc begins a drag/size
operation generated by messages like : WM_NCLBUTTONDOWN
There is NO WM_NCLBUTTONUP message generated when the mouse button
goes up (ending the drag/size operation). The MSDN docs say that
WM_NCLBUTTONUP isn't posted.

How do you "test" to see that the drag/size operation has
finished (mouse button up), when you can't use either
WM_MOVE or WM_SIZE ?

When the end users system is set to "show window contents while dragging"
the window will receive "multiple" WM_SIZE or WM_MOVE messages, so
they can't be relied upon to test for the "end of the drag operation"
(mouse up).

Does anybody have any ideas of how to handle this ?

I have to know when the mouse button has been released !




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[Semen Matusovski]

Chris --
SetCapture doesn't work (in combination with WM_LBUTTONUP) ?

BTW, I used WM_SIZE event in following context:
1) In WM_SIZE: SetTimer (for example, 200 ms)
Further WM_SIZE resets a timer again.
2) If occurs timer event - sizing is finished.

[This message has been edited by Semen Matusovski (edited November 29, 2000).]

[Dominic Mitchell]

Chris,
When the mouse button is released you should receive a WM_CAPTURECHANGED
(Windows95) or WM_CANCELMODE(Windows NT).

Semen,
Using WM_LBUTTONUP to test for the end of a drag operation is not a good
method. For example, your application will not get a WM_LBUTTONUP if the
user releases the button outside of the window where the drag operation
was initiated.

Clean up code etc. should be placed in either WM_CAPTURECHANGED or
WM_CANCELMODE.

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Dominic Mitchell

[Chris Boss]

I just came across two new messages :

%WM_EXITSIZEMOVE

and

%WM_ENTERSIZEMOVE

Has anyone used these ?


Dominic, I thought about %WM_CAPTURECHANGED and did some testing
with it. That message gets sent "after" the drag when sizing, but both
before and after the drag when moving a control (2 times).

Another consideration is making sure what I do works on all platforms
95/98/NT 3.x/2000

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[This message has been edited by Chris Boss (edited November 30, 2000).]

[Chris Boss]

Semen;

I like the Timer idea, but I "have to poll the statis of the mouse
button" rather than use WM_SIZE. If the end user has the
"show window contents while dragging" flag selected, then the
control will get "multiple" WM_SIZE messages and not just one.

Do you know how to "poll" to see if the mouse button is up ?


Dominic;

The %WM_CAPTURECHANGED message is a good idea, but there
is a problem with that too. When the mouse button is pressed down,
if the mouse doesn't move and the button comes up, then only 1 %WM_CAPTURECHANGED
message is generated. IF the control is dragged, then two %WM_CAPTURECHANGED
messages are generated. I don't want to "mess up" a proper drag.




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[Chris Boss]

repeated message


[This message has been edited by Chris Boss (edited November 30, 2000).]

[Dominic Mitchell]

Chris,
You should not have any problems using WM_CAPTURECHANGED. The following
is a basic outline of my implementation for dragging, resizing or creating
a new control in a visual designer. This is bullet proof.
Hints:
1. do not let the control capture the mouse
2. do not use the WM_MOVE or WM_SIZE messages for dragging or resizing
a control. Use them for the form.

    
WM_LBUTTONDOWN
  SetFocus hWnd
  SetCapture hWnd
  ' Get the current position of the mouse
  x = LoIntVPB(lParam)
  y = HiIntVPB(lParam)
  ' Set flag indicating type of operation
  lAction = selecting, dragging, resizing etc.
  .
  .
  Code to initialize marquee etc.
  .
  .
  FUNCTION = %FALSE
  EXIT FUNCTION
    
WM_MOUSEMOVE
  lKeyState = (%MK_LBUTTON	AND wParam)
  ' If something is being selected, dragged, drawn or resized
  IF (ISTRUE lAction) AND (ISTRUE lKeyState) THEN
    ' If we have capture
    IF hWnd = GetCapture() THEN
      .
      .
      Code to move and/or resize marquee etc.
      .
      .
      FUNCTION = %FALSE
      EXIT FUNCTION
      
WM_LBUTTONUP
  ReleaseCapture
  .
  .
  Code to reset action flag etc.
  .
  .
  FUNCTION = %FALSE
  EXIT FUNCTION
    
WM_CAPTURECHANGED
  .
  .
  Code to erase marquee, draw new control, move control to new location,
  resize control, reset action flag etc.
  .
  .
  FUNCTION = %FALSE
  EXIT FUNCTION

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Dominic Mitchell

[Chris Boss]

Dominic;

I am "modifying" the WM_NCHITTEST values for controls so the
control now receives the WM_NCLBUTTONDOWN message which
initiates dragging or sizing of a control (not a Dialog).

The control that is getting this message is a custom control
which displays "drag Handles" over another control.

The custom control displays drag handles "outside" the borders
of the other control, but when the WM_NCLBUTTONDOWN message occurs
, the custom control changes its shape, just before the dragging
or sizing begins. Once the dragging is done, the custom control
must change its shape back to its original form. I have no problem
if the control is moved or dragged. The problem is when the mouse
button is simply clicked on the control, without dragging or
sizing. My control gets the WM_NCLBUTTON message, changes it shape,
passes the message to DefWindowProc, Windows captures the mouse,
no drag or size occurs, the mouse button goes up canceling the drag
mode (Windows is in control), but my custom control doesn't get
a WM_NCLBUTTONUP message, so I can't tell the mouse button is
up and my control doesn't know its time to change its shape
back to its original shape.

The custom control is a "Drag Handle" control which attaches itself
to another control and impliments dragging and sizing. The other
controls handle is sent to my custom control (as a buddy) and the
Drag Handle control moves the buddy control to whereever the
custom control moves to.

The custom control displays drag handles "outside" of the buddy control
but when the dragging starts, the handles display "inside" the
buddy control. I have everything working, but it can't handle
when the custom control is just clicked and not moved/sized.



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[Dominic Mitchell]

Chris,
So that's how you implemented the drag operation, a variation of the
transparent(WS_EX_TRANSPARENT) window method. Without some code snippets
to see what you are doing I am shooting in the dark but here goes.
Maybe you can try intercepting WM_SETCURSOR.
You said Windows captured the mouse. How did it do that?
If the mouse is captured you will not get a WM_NCLBUTTONUP.

The technique of overlaying a window above controls to draw handles has
problems and limitations. In a simple application like the MS dialog
editor then its ok. However, if you intend to allow the user to select
and/or drag more than one control at a time or use nested controls you
will run into serious problems.

A program like VisualBasic does the following for drag handles-
1. When a single control is selected - 8 windows
2. When more than one control is selected - paint 8 rectangles
using the client device context of the control the handles are over.


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Dominic Mitchell

[Chris Boss]

I solved my problem !

First, I use the %WM_EXITSIZEMOVE message to determine when
the drag (move) or size operation is done.

The big problem was when the user lets the mouse button up without
dragging or sizing the control.

It was basically impossible to track the mouse button event, since
Windows is processing the drag/size operation and it eats up the
message.

The solution ?

SetWindowsHookEx API function !

Using this function, I can create a "hook" into the windows
message processing. I can preprocess all the mouse messages
even though windows takes control. Using this technique, I can
track the mouse button up message and then I post the mouse
button up message to my controls window procedure and then
in my window procedure, I remove the hook procedure when the
mouse button goes up.


The beauty of a mouse hook procedure, is that it tracks the mouse
events even when another window has Captured the mouse.

The hook is only in effect between when the mouse button goes down
and when it comes up.

It works perfectly !

Thanks for all the suggestions. They kept me searching for a
solution, rather than give up.




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