WM_MOUSEWHEEL message and the Touchpad : SOLVED thanks to Randor - C / C++ / MFC Discussion Boards

Re: getchar / putchar - how does it really works ?

Richard MacCutchan16-Jun-19 5:48

Richard MacCutchan

16-Jun-19 5:48

I know that, I was merely pointing out its behaviour on Windows as opposed to Linux.

Re: getchar / putchar - how does it really works ?

Stefan_Lang16-Jun-19 21:29

Stefan_Lang

16-Jun-19 21:29

Richard MacCutchan wrote:
the system does not present them until after the enter key was pressed.

Not quite true, or at least not complete: if there is something in the input buffer already, getchar will immediately return with the next char it finds in that buffer. It will only wait if the input buffer is empty. AFAIK this is not dependend on the OS.

GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)

Re: getchar / putchar - how does it really works ?

Richard MacCutchan16-Jun-19 21:48

Richard MacCutchan

16-Jun-19 21:48

Well that is exactly what happened in my tests, none of the characters were retrieved until the enter key was pressed.

Re: getchar / putchar - how does it really works ?

leon de boer17-Jun-19 2:43

leon de boer

17-Jun-19 2:43

No it doesn't always it depends on the canonical mode of your input, this was covered above.
The C standard doesn't cover how the underlying system is operating and it cant present what it doesn't yet have.

Richard simply has an OS that is in canonical mode.

In vino veritas

Re: getchar / putchar - how does it really works ?

Stefan_Lang18-Jun-19 5:13

Stefan_Lang

18-Jun-19 5:13

Well it always worked as I described for me. But I admit I haven't heard of the canonical mode before, so I'm going to trust you on this.

Change Icon

JM225113-Jun-19 18:12

JM2251

13-Jun-19 18:12

Hi,
There are icon for Maximize and Restore Down on Wondow Title.
Can I change Maximize icon to Restore down on button click?

Re: Change Icon

Richard MacCutchan13-Jun-19 21:32

Richard MacCutchan

13-Jun-19 21:32

Yes, but you need to do all the drawing of the frame and title bar. Take a look at WM_NCPAINT message - Windows applications | Microsoft Docs[^].

WM_MOUSEWHEEL message and the Touchpad : SOLVED thanks to Randor

Richard MacCutchan13-Jun-19 4:28

Richard MacCutchan

13-Jun-19 4:28

I am processing the WM_MOUSEWHEEL messages in a C++ application,

C++

void CView::OnMouseWheel(
    HWND    hWnd,
    int	    xPos,
    int	    yPos,
    int	    zDelta,
    UINT    fwKeys
)
{
    zDelta /= WHEEL_DELTA;	// calculate the number of lines to move
    if (zDelta != 0)
    {
        // line up or down once per delta
        OnVScroll(hWnd, NULL, zDelta > 0 ? SB_LINEUP : SB_LINEDOWN, 3);
    }
}
</blockquote>

but when I use the touchpad nothing happens. Following the advice in the MSDN documentation I divide the zDelta value by 120 (WHEEL_DELTA) to calculate the (approximate) number of lines to scroll. The debugger shows that the resulting value is always zero. If I use my mouse and turn the wheel it scrolls correctly. The weird part is that using other applications (VS, Word, Chrome etc.) the touchpad works correctly. So I conclude that the code should somehow get some other information that identifies the touchpad, and adjusts the delta accordingly. Anyone else seen similar problems?

[edit]
Thanks to David D's sugestion I modified the code to accumulate deltas that are less than the value of WHEEL_DELTA, thus:

C++

static int myDelta = 0;
if (abs(zDelta) < WHEEL_DELTA)
{
    myDelta += zDelta;
    zDelta = myDelta;
}
zDelta /= WHEEL_DELTA;	// this value works better than WHEEL_DELTA;
if (zDelta != 0)
{
    myDelta = myDelta % WHEEL_DELTA;  // save the remainder for further movements
    // line up or down once per delta
    OnVScroll(hWnd, NULL, zDelta > 0 ? SB_LINEUP : SB_LINEDOWN, 3);
}

which works a treat.

Note that I use the value 3 for the number of lines to scroll. In a proper commercial application the code should use the value of the system parameter: SPI_GETWHEELSCROLLLINES.
[/edit]

modified 14-Jun-19 9:09am.

Re: WM_MOUSEWHEEL message and the Touchpad

Gerry Schmitz13-Jun-19 9:26

Gerry Schmitz

13-Jun-19 9:26

I found the mouse wheel events specific to the "mouse wheel".

When using only touch (tablet swipe) I got the scrolling, but the "wheel event" that I used to detect "at bottom or top" no longer fires and I need to find something else. I think it now has to tie into a "view changing" and / or "view changed" event and / or manipulation started / ended.

(And I think a touchpad is treated as a "pointer" in Windows 10).

The Master said, 'Am I indeed possessed of knowledge? I am not knowing. But if a mean person, who appears quite empty-like, ask anything of me, I set it forth from one end to the other, and exhaust it.'
― Confucian Analects

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan13-Jun-19 21:19

Richard MacCutchan

13-Jun-19 21:19

The messages are coming through correctly, but the delta value is always less than 120. That is unless I give a fast swipe from top to bottom of the pad. I have checked the parameters sent with the message and, apart from the delta value, they are the same for the mouse or the touchpad. More debugging required I expect.

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan14-Jun-19 1:04

Richard MacCutchan

14-Jun-19 1:04

The touchpad is just a mouse to the system, but it sends WM_MOUSEWHEEL messages somewhat differently. I have added the solution to my original post.

Re: WM_MOUSEWHEEL message and the Touchpad

Gerry Schmitz15-Jun-19 5:36

Gerry Schmitz

15-Jun-19 5:36

Glad you got it working.

Yes, "delta" is a double, so it has quite a range.

I needed the "Manipulation events" which give scroll direction and distance.

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan15-Jun-19 6:58

Richard MacCutchan

15-Jun-19 6:58

The strange thing was that using both the debugger and Spy++, I could not 'see' the multiple messages coming in. In both cases after a scroll gesture on the touchpad, they both showed just one message and then went back to the application window. So it as if the delta values were just too small.

BTW, thanks for your interest.

Re: WM_MOUSEWHEEL message and the Touchpad

David Crow13-Jun-19 10:45

David Crow

13-Jun-19 10:45

Is your message loop receiving any other messages (e.g., WM_TOUCH) when the touch pad is being interacted with?

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan13-Jun-19 21:20

Richard MacCutchan

13-Jun-19 21:20

Not sure about that, but thanks I will definitely check.

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan14-Jun-19 1:03

Richard MacCutchan

14-Jun-19 1:03

No, it never gets WM_TOUCH. But see my update and solution.

Re: WM_MOUSEWHEEL message and the Touchpad

Randor 14-Jun-19 0:31

Randor

14-Jun-19 0:31

Hi,

Richard MacCutchan wrote:
I divide the zDelta value by 120 (WHEEL_DELTA) to calculate the (approximate) number of lines to scroll.

While it is true that the many of the old mouse drivers sent WHEEL_DELTA in multiples of 120 that is not always the case for high-precision mice and touchpads.

You are probably getting values much smaller than 120. To fix your code you need to keep track of the delta modulo of +/- 120 in a static local or class variable and add/subtract the latest delta from the previous value.

I also observe that you are hard-coding the line count rather than retrieving the user preference via SystemParametersInfo with SPI_GETWHEELSCROLLLINES.

Best Wishes,
-David Delaune

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan14-Jun-19 0:55

Richard MacCutchan

14-Jun-19 0:55

Randor wrote:
you need to keep track of the delta

Thanks David, that works perfectly - simple when you know how. As to the fixed value, this is purely for personal use so I am not too concerned with system settings; although I notice that 3 is the default value.

Re: WM_MOUSEWHEEL message and the Touchpad

Randor 14-Jun-19 2:00

Randor

14-Jun-19 2:00

Richard MacCutchan wrote:
Thanks David, that works perfectly

Looks good, although I do see a minor issue with your latest code.

You are dropping the remainder without the modulo operation. Rather than setting your delta to zero you should keep the remainder after scrolling with:

C++

myDelta = myDelta % WHEEL_DELTA;

Such a precision loss is probably not a big deal for simply scrolling a text window. But let's make our code samples more correct.

Best Wishes,
-David Delaune

Re: WM_MOUSEWHEEL message and the Touchpad

Richard MacCutchan14-Jun-19 3:07

Richard MacCutchan

14-Jun-19 3:07

Thanks again, I will certainly update my code (and the original question).

C++ Callback process is dea

Member 1422104112-Jun-19 23:05

Member 14221041

12-Jun-19 23:05

Hi all!
I want to build a program to manage other processes. The program is responsible for any process that suddenly stops and the program will call back that process. I am wondering how to use CreateEvent() to create a global event variable to manage it. I hope you give me advice and methods to solve that problem.
Thank you!

Re: C++ Callback process is dea

Victor Nijegorodov12-Jun-19 23:18

Victor Nijegorodov

12-Jun-19 23:18

See an example in Kernel object namespaces - Windows applications | Microsoft Docs and Using Event Objects - Windows applications | Microsoft Docs

And I guess the program you are going to develop should be a service.

Re: C++ Callback process is dea

Member 1422104112-Jun-19 23:48

Member 14221041

12-Jun-19 23:48

It is true that the program I will develop should be a service. Do you have experience with this issue please share with me. thank you very much!

Re: C++ Callback process is dea

David Crow13-Jun-19 7:45

David Crow

13-Jun-19 7:45

Here is but one of many examples.

Re: C++ Callback process is dea

Victor Nijegorodov13-Jun-19 10:24

Victor Nijegorodov

13-Jun-19 10:24

Well, it was more than six years back... I used the NSSM - the Non-Sucking Service Manager
The most important thing is you could used the original UI application to use with..., however, in "service" mode you must forbid all UI features.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.