with following code:
XGrabPointer(d, root, False, ButtonPressMask
, GrabModeAsync, GrabModeAsync, None,
None, CurrentTime);
I just specify with button press event, but when running other applications can't get any other mouse event such as mouse move.
Is it what this function designed to be? or with something I made wrong understanding. like parameter owner_events, I can't understand well.
If owner_events is False, all generated pointer events are reported with respect to grab_window and are reported only if selected by event_mask. If owner_events is True and if a generated pointer event would normally be reported to this client, it is reported as usual. Otherwise, the event is reported with respect to the grab_window and is reported only if selected by event_mask. For either value of owner_events, unreported events are discarded.
with explaination of owner_event, it looks like I need to register two event type: ButtonPressMask|PointerMotionMask and owner_events True? but that doesn't work either.
The key is in the last sentence of the description you posted:
For either value of owner_events, unreported events are discarded.
I.e. it doesn't matter if owner_events is True or False, events that are not handled are discarded. The subtelty of owner_events is to which window the events are delivered: if owner_events == False all pointer events matching the mask are sent to the grabbing window, even if the event is in other windows that belong to you application (Client in X parlance); coordinates are relative to the grabbing window too. If owner_events == True events are reported to any window of your application, but not to other applications.
XGrabPointer really grabs all pointer events, and this is very strong. It is normally only used for transient (temporary) windows like popups, expanding dropdown windows, etc. The reason is to keep track of clicks outside of the window so you can close the transient. I've used in a color selector popup: when the users clicks on the "choose color" button a popup appears, I do a XGrabPointer (..False..), so I get all click events. If a user clicks outside of my popup window I close the window as if the user did not make a selection. Without XGrabPointer I would not know this happened and the popup would remain open until the user clicked in it. The XGrabPointer is immediately removed when the popup closes.
Related
I have a ClistCtrl (wraps Windows list view for non-MFC users) on a dialog. I set functionality that when the list loses focus, any selected items are unselected.
I also have a "remove items" button, whose on-click handler will delete any selected items in the list.
The idea is you select items in the list, and then either click the button to remove these items, or click somewhere else and the selection is cancelled.
But, when you click the delete button, the list loses focus first and therefore nothing happens! Is there a way around this?
You can receive message about lost focus with WM_KILLFOCUS, its wParam will give you a handle to window which got focus:
wParam
A handle to the window that receives the keyboard focus. This
parameter can be NULL.
You should be able to use Spy++ to see WM_KILLFOCUS on you list window, and read its wParam - and later find also with spy++ which window is it.
As said in other posts, you can use WM_KILLFOCUS for that.
But I think it's a very bad idea to clear the selection on losing focus.
Just imagine: the user selects a whole bunch of items using multiselect (using shift, ctrl, scrollbar..), and then, one of the following happens:
The phone rings, urgent call - the user needs to check a mail: selection: gone!
An annoying message box pops up taking focus (yes, it does happen): selection -> gone.
Your users might hate you for this, so don't do it :) (not even if there are only 3 items in the listcontrol).
The usual way is to gray the selection on losing focus. You could add a 'clear selection' button, but even that isn't needed. Just clicking on one item will clear the selection (except for that one item of course).
Bottom line: don't clear the selection on losing focus, ever.
Update:
If the selection is not visible on losing focus, the LVS_SHOWSELALWAYS flag is what you need:
LVS_SHOWSELALWAYS
The selection, if any, is always shown, even if the control does not
have the focus.
My Table control uses windowless checkboxes (because there can be an arbitrary number of checkboxes here). Right now, I use TrackMouseEvent(TME_LEAVE) and manually checking if the mouse is in the checkbox rect during a WM_LBUTTONUP. I have TODOs marked in my code for the edge cases that this causes, such as a missing WM_LBUTTONUP when the mouse has left the client area.
Now I notice today's The Old New Thing says buttons use mouse captures. This got me thinking, and after looking into it, mouse captures would fit what I need more appropriately; if my assumptions are correct it would handle the various edge cases I mentioned above and be more correct in general.
In particular, the assumptions I make are: I should abandon any capture-related operations on a WM_CAPTURECHANGED even if every other condition is met. I will get a WM_CAPTURECHANGED after a ReleaseCapture(). After a SetCapture(), I will always end with either a WM_LBUTTONUP or a WM_CAPTURECHANGED, whichever comes first.
I've read both MSDN and a few articles I've found by Googling "setcapture correct use"; I just want to make sure I've got the right idea and will be implementing this correctly. Do I?
on WM_LBUTTONDOWN
if the button is in a checkbox
SetCapture()
mark that we're in checkbox clicking mode
on WM_MOUSEMOVE
if we are in checkbox clicking mode
draw the checkbox in the pressed state
on WM_LBUTTONUP
if we are in checkbox clicking mode
leave checkbox clicking mode
THEN call ReleaseCapture(), so we can ignore its WM_CAPTURECHANGED
if the mouse was released in the same checkbox
toggle it
on WM_CAPTURECHANGED
if we are in checkbox clicking mode
abandon checkbox clicking mode and leave the checkbox untoggled, even if the mouse is hovering over the checkbox
Do I have the right idea here? And in particular, is my order of operations for WM_LBUTTONDOWN correct? Thanks.
What you have said is basically right, although a real checkbox tracks WM_MOUSEMOVE while in "clicking mode" and displays the checkbox in its original state if the mouse moves off of it. So to emulate that you should have:
on WM_MOUSEMOVE
if we are in checkbox clicking mode
if mouse is over the checkbox
draw the checkbox in the pressed (toggled) state
else
draw the checkbox in the original state
I have a semi-transparent form (using AlphaBlend) that acts as an overlay. For the user to still be able to interact with the window below I have set WS_EX_NOACTIVATE on my form so all right and left clicks go through to the other window.
However I have a few clickable labels on my form. Clicking those and performing the appropriate action works fine since despite the WS_EX_NOACTIVATE flag the OnClick methods are called, but the click will (obviousely) also propagate to the other window, which I do not want in this case.
So, does anyone know how to "stop" the click being sent through to the window below in case I already handled it in my form ? Basically I would like being able to chose whether the click "belongs to me" and does not get propagated or whether the window below mine receives it.
As Rob explained, WS_EX_NOACTIVATE is not relevant here. Most likely you used WS_EX_TRANSPARENT and that made your window transparent to mouse clicks.
To get finer grained control of mouse click transparency, handle the WM_NCHITTEST message in your top level window. Return HTTRANSPARENT for regions that you want to be "click through". Otherwise return, for example, HTCLIENT.
Wm_ex_NoActivate should be irrelevant here. That just controls whether your window receives the input focus. Indeed, if you start with a scratch program and do nothing but change the extended window style, you'll see that when you click within the bounds of that program's window, the clicks are handled in the usual way, except that the window is never activated; programs behind that window do not receive any click events.
Therefore, to make your label controls eat click events instead of forwarding them to the windows behind them, you need to find out what you did to make them start forwarding those messages and simply stop doing that, whatever that is.
A program has called XGrabKey() to make a hotkey.
The user presses that key combination (while another window is focused).
The program receives control to do something in response to the key combination. Meanwhile, the program has been temporarily focused (because of the effects of XGrabKey (see man XGrabKey, man XGrabKeyboard)).
I want the program to create a synthetic X event (a keypress or mouse click) to the originally focused window. In some cases this means I need to focus that window before sending it the event (Firefox ignores synthetic events when it is not focused), which means I need to know which window it is. How can I find out which window it is?
Wait for the next FocusOut event, verify that the mode is set to NotifyUngrab, get the focus with XGetInputFocus(), and send away your synthetic events.
In MFC a double-mouse click event triggers the following sequence of messages
WM_LBUTTONDOWN
WM_LBUTTONUP
WM_LBUTTONDBCLK
WM_LBUTTONUP
So responding to the WM_LBUTTONDBCLK message allows you to detect a double-click. But if I just want to detect a single-click how to I distinguish it?
But just looking at the WM_LBUTTONUP message isn't enough as it could be a single-click or it could be the first click of a double-click.
How can I successfully identify just a single-click?
(Please allow me to call these events Mouse Up and Mouse Down. My MFC is a little rusty. And there's this stuff called .NET who's been messing up my terminology lately ;-)
Short story: You don't simply want to know about Mouse Click. You need more.
Long story:
Although this is counter-intuitive, it appears that simply wanting a mouse-click is fairly uncommon. Most often, you'll want to perform some processing on Mouse Down and do some further processing on Mouse Up. The trick is that simply tracking Mouse Up messages is not enough: Mouse Down may not have happened in your window. Do you consider it a valid click then? Especially considering that the Mouse Down processing (such as selecting an item) did not occur.
Going further up the reasoning, you should not rely on receiving a Mouse Up after you processed Mouse Down: User may have moved the mouse and released the button somewhere else (think drag'n'drop), in which case, you don't receive the MouseUp event... unless you capture the mouse on MouseDown to make sure you get mouse event up to Mouse Up even if the mouse left your window.
All in all, you end up tracking Mouse Down, capture the mouse and when you receive Mouse Up, just check if you own the capture. If not, the mouse was either double-clicked (no 2nd mouse down) or Mouse Down happened somewhere else hence you most likely don't care about this Mouse Up.
In conclusion: There's no MouseClick message simply because you wouldn't go very far with it: You need to handle more messages and implement more mechanics anyway.
Oh! And if your dealing with an existing control which already handles all this items and selection stuff, such as a listview, chances are it provides with a similar custom notification such as Item Activate or Item Selection Changed.
I just tried this in Delphi, the behavior is the same: even when a double click is happening, a single click event is issued right after the first one of the two.
I solved it using a timer, which works like this:
deactivate timer on WM_LBUTTONDBLCLK (and set bDbl to true)
activate timer on WM_LBUTTONUP if bDbl==false
deactivate on WM_LBUTTONUP if bDbl==true (and reset bDbl)
I set the interval of the timer to the time returned by GetDoubleClickTime.
MSDN says:
The GetDoubleClickTime function
retrieves the current double-click
time for the mouse. A double-click is
a series of two clicks of the mouse
button, the second occurring within a
specified time after the first. The
double-click time is the maximum
number of milliseconds that may occur
between the first and second click of
a double-click.
If the timer happens to fire then you have the real click. In my case the double click interval is 500ms, so any "real click" will be delayed this long.
You could check WM_LBUTTONDOWN has not been called more than once before WM_LBUTTONUP. In practice Windows does this for you, in that if you get a WM_LBUTTONDBCLK you tend not to get a WM_LBUTTONUP.
You can use PreTranslateMessage() to count the messages as they appear. If you've received only the mouse messages corresponding to a single-click, and the system-configured time for double-clicking has expired, you can safely assume it's a single-click.
As far as I know there is no way to know that this is the case as it is happening, which makes sense -- until the time is expired, there's no way to know that a second click is or isn't coming.
that's a little tricky.
I would detect the WM_LBUTTONDOWN & WM_LBUTTONUP combo, store that event somewhere and set a timeout for a second or so. If there isn't a WM_LBUTTONDBCLK during that timeout then you have a single click.
This might imply you need to have another thread running but I think you could accomplish it with one thread.
I think the solution is to start a timer after the first click & then check the elapsed time after at the next immediate click, this will tell you if it is a single click or double click.
You typically look at #MLButtonUp and you would not have single click and double click behavior on the same mouse button.