C# how to loop while mouse button is held down

Question

Can you point me in the right direction? I'm trying to get a loop to trigger while the form button is depressed.

//pseudocode
While (button1 is pressed)
value1 += 1

And then of course stop looping when the button is released

Marika

pmichaels.net/2015/01/01/… – Saltzman

Answer 1

To avoid using threads you can add a Timer component on your form/control and simply enable it on mouse down and disable it on mouse up. Then put the code you would normally put inside the loop in the Timer_Tick event. If you want to use System.Timers.Timer you can use the Timer.Elapsed event instead.

Example (using System.Timers.Timer):

using Timer = System.Timers.Timer;
using System.Timers;
using System.Windows.Forms;//WinForms example
private static Timer loopTimer;
private Button formButton;
public YourForm()
{ 
    //loop timer
    loopTimer = new Timer();
    loopTimer.Interval = 500;/interval in milliseconds
    loopTimer.Enabled = false;
    loopTimer.Elapsed += loopTimerEvent;
    loopTimer.AutoReset = true;
    //form button
    formButton.MouseDown += mouseDownEvent;
    formButton.MouseUp += mouseUpEvent;
}
private static void loopTimerEvent(Object source, ElapsedEventArgs e)
{
    //this does whatever you want to happen while clicking on the button
}
private static void mouseDownEvent(object sender, MouseEventArgs e)
{
    loopTimer.Enabled = true;
}
private static void mouseUpEvent(object sender, MouseEventArgs e)
{
    loopTimer.Enabled = false;
}

Ritualize

Good answer: Provides an alternative to my thread-based solution. +1. – Canst

There is a good chance you want to check that (e.Button == MouseButtons.Left), otherwise you end up doing the loop on LeftClick, or RightClick, or MiddleClick, or any other mouse button. Typically buttons should only respond to Left-Click. – Putout

problem with Timer is that it is not accurate and it is known. Try to set timer to known millisecond interval, then count number of ticks and compare it with stopwatch elapsed_milliseconds/interval. You will see noticeable difference in values you get. But if OP don't want a high precision it is a good solution. – Coaction

Answer 2

You could use a thread to do the counting, and stop the thread when the mouse is released. The following has worked nicely for me:

var b = new Button { Text = "Press me" };

int counter = 0;
Thread countThread = null;
bool stop = false;

b.MouseDown += (s, e) =>
{
    stop = false;
    counter = 0;
    countThread = new Thread(() =>
    {
        while (!stop)
        {
            counter++;
            Thread.Sleep(100);
        }
    });
    countThread.Start();
};

b.MouseUp += (s, e) =>
{
    stop = true;
    countThread.Join();
    MessageBox.Show(counter.ToString());
};

Of course, if you want the event handlers to be methods rather than lambdas, you will have to turn all the variables into fields.

Canst

Answer 3

    private void button1_MouseDown(object sender, MouseEventArgs e)
    {
        timer1.Enabled = true;
        timer1.Start();

    }

    private void button1_MouseUp(object sender, MouseEventArgs e)
    {
        timer1.Stop();
    }



    private void timer1_Tick(object sender, EventArgs e)
    {
        numericUpDown1.Value++;

    }

Orose

Answer 4

A recent article from Fabulous Adventures in Coding provides this narrative, which might help answer your question:

A surprising number of people have magical beliefs about how exactly applications respond to user inputs in Windows. I assure you that it is not magic. The way that interactive user interfaces are built in Windows is quite straightforward. When something happens, say, a mouse click on a button, the operating system makes a note of it. At some point, a process asks the operating system "did anything interesting happen recently?" and the operating system says "why yes, someone clicked this thing." The process then does whatever action is appropriate for that. What happens is up to the process; it can choose to ignore the click, handle it in its own special way, or tell the operating system "go ahead and do whatever the default is for that kind of event." All this is typically driven by some of the simplest code you'll ever see:

while(GetMessage(&msg, NULL, 0, 0) > 0) 
{ 
  TranslateMessage(&msg); 
  DispatchMessage(&msg); 
}

That's it. Somewhere in the heart of every process that has a UI thread is a loop that looks remarkably like this one. One call gets the next message. That message might be at too low a level for you; for example, it might say that a key with a particular keyboard code number was pressed. You might want that translated into "the numlock key was pressed". TranslateMessage does that. There might be some more specific procedure that deals with this message. DispatchMessage passes the message along to the appropriate procedure.

I want to emphasize that this is not magic. It's a while loop. It runs like any other while loop in C that you've ever seen. The loop repeatedly calls three methods, each of which reads or writes a buffer and takes some action before returning. If one of those methods takes a long time to return (typically DispatchMessage is the long-running one of course since it is the one actually doing the work associated with the message) then guess what? The UI doesn't fetch, translate or dispatch notifications from the operating system until such a time as it does return.

Gammadion

Sure. Where’s the answer to the question? – Canst

@Timwi: The answer is: "Your question depends on an inaccurate assumption." Rather than stating it bluntly, I presented an explanation of the underlying mechanism, which I felt would help the clarify the OP's thinking. Since the question explicitly asks "Can you point me in the right direction?" this seemed an appropriate way to do so. You are certainly free to disagree, but I appreciate that you explained your reasoning. – Gammadion

Answer 5

I was inspired by what I read here and decided to write my own button class called a RepeatingButton. On first click it waits for 500ms, then repeats ever 300ms until 2s, then repeats every 100ms (i.e. it uses acceleration).

Here is the code;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

/// <summary>
/// A repeating button class.
/// When the mouse is held down on the button it will first wait for FirstDelay milliseconds,
/// then press the button every LoSpeedWait milliseconds until LoHiChangeTime milliseconds,
/// then press the button every HiSpeedWait milliseconds
/// </summary>
public class RepeatingButton : Button
{
    /// <summary>
    /// Initializes a new instance of the <see cref="RepeatingButton"/> class.
    /// </summary>
    public RepeatingButton()
    {
        internalTimer = new Timer();
        internalTimer.Interval = FirstDelay;
        internalTimer.Tick += new EventHandler(internalTimer_Tick);
        this.MouseDown += new MouseEventHandler(RepeatingButton_MouseDown);
        this.MouseUp += new MouseEventHandler(RepeatingButton_MouseUp);
    }

    /// <summary>
    /// The delay before first repeat in milliseconds
    /// </summary>
    public int FirstDelay = 500;

    /// <summary>
    /// The delay in milliseconds between repeats before LoHiChangeTime
    /// </summary>
    public int LoSpeedWait = 300;

    /// <summary>
    /// The delay in milliseconds between repeats after LoHiChangeTime
    /// </summary>
    public int HiSpeedWait = 100;

    /// <summary>
    /// The changeover time between slow repeats and fast repeats in milliseconds
    /// </summary>
    public int LoHiChangeTime = 2000;

    private void RepeatingButton_MouseDown(object sender, MouseEventArgs e)
    {
        internalTimer.Tag = DateTime.Now;
        internalTimer.Start();
    }

    private void RepeatingButton_MouseUp(object sender, MouseEventArgs e)
    {
        internalTimer.Stop();
        internalTimer.Interval = FirstDelay;
    }

    private void internalTimer_Tick(object sender, EventArgs e)
    {
        this.OnClick(e);
        TimeSpan elapsed = DateTime.Now - ((DateTime)internalTimer.Tag);
        if (elapsed.TotalMilliseconds < LoHiChangeTime)
        {
            internalTimer.Interval = LoSpeedWait;
        }
        else
        {
            internalTimer.Interval = HiSpeedWait;
        }
    }

    private Timer internalTimer;
}

Anywhere you have a button, you can just replace it with a repeating button and it will just have all the new functionality built in.

Enjoy!

Sterren

Monkish

Answer 6

Override the OnMouseDown() method in your form and then if the button you want is pressed, that would equal your loop. Example:

protected override void OnMouseDown(MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        // this is your loop
    }
}

It's not a loop in the traditional sense, but should work for what you need.

Rolland

this actually does not work. if you hold the button down, it only runs once. then it runs again when you release the button. – Marika

Answer 7

You will need to handle the MouseDown() event for your form, using the MouseEventArgs argument to figure out which button was pressed.

Louettalough

Same thing on mine... someone up, someone down... ill make it +1 for you – Rolland

This answer doesn’t answer the question at all. Where’s the loop? – Canst

@Timwi: The loop itself is not important. Once you handle the necessary event correctly, you can add whatever code you want in the event, loop or otherwise. – Louettalough

Timwi posted to the thread. He always leaves a trail of downvotes in his wake. – Piers

@Bernard: Hans is lying. I downvote answers that are wrong, not answers that “compete” with mine. (See Doggett’s answer for example.) Regarding your comment, you can’t just add a loop to the event, because then you can’t listen for the event that is supposed to stop the loop. – Canst

@Timwi: I would rather you initially supplied this explanation when you decided my answer is incorrect. This not only benefits me, but others that believe my answer is correct. – Louettalough

@Bernard: I would rather do that too, and I used to do that, but the community on this website generally discourages this. Just look at @Hans’s reaction. He’s become incredibly bitter at me, for no other reason than the simple fact that I pointed out the errors in his answers, thus revealing that it was me that downvoted. It seems that most people are emotionally unable to cope with the suggestion that their answer has a flaw. – Canst

@Timwi: I actually don't mind finding out that my answers are wrong or perhaps not completely correct. I end up learning something new. One person cannot know everything, even if they think they do. – Louettalough

Answer 8

RepeatButton is perfect for that:

<RepeatButton Delay="1000" Interval="500" HorizontalAlignment="Left" Content="+" Click="IncreaseButton_Click"/>

private void IncreaseButton_Click(object sender, RoutedEventArgs e)
{
    value1++;
}

Tisman

Answer 9

It's been several years since I posted this but someone upvoted it so it popped up in my notifications. Now that I have a lot more experience lol, I thought I'd see if this simple problem is as simple as it sounds, and it was:

public partial class Form1 : Form
{
    private bool _isRunning;

    public Form1()
    {
        InitializeComponent();
        txtValue.Text = @"0";

        btnTest.MouseDown += (sender, args) =>
        {
            _isRunning = true;
            Run();
        };

        btnTest.MouseUp += (sender, args) => _isRunning = false;
    }

    private void Run()
    {
        Task.Run(() =>
        {
            while (_isRunning)
            {
                var currentValue = long.Parse(txtValue.Text);
                currentValue++;
                txtValue.Invoke((MethodInvoker) delegate
                {
                    txtValue.Text = currentValue.ToString();
                });
            }
        });
    }
}

Marika

Answer 10

Based on Steztric's answer, an extension method with a few bug fixes and different options for the rate of increase.

/// <summary>
/// An extension method to add a repeat click feature to a button. Clicking and holding  on a button will cause it
/// to repeatedly fire. This is useful for up-down spinner buttons. Typically the longer the mouse is held, the
/// more quickly the click events are fired. There are different options when it comes to increasing the rate of
/// clicks:
/// 1) Exponential - this is the mode used in the NumericUpDown buttons. The first delay starts off around 650 ms
/// and each successive delay is multiplied by 75% of the current delay.
/// 2) Linear - the delay more slowly reaches the fastest repeat speed. Each successive delay subtracts a fixed
/// amount from the current delay. Decreases in delays occur half a second apart.
/// 3) Two Speed - this delay starts off at a slow speed, and then increases to a faster speed after a specified delay.
/// 4) Three Speed - the repeat speed can increase from slow, to medium, to fastest after a specified delay.
///
/// If repeating is added to a button that already has it, then it will be replaced with the new values.
/// </summary>
public static class RepeatingButtonEx {

    private static Hashtable ht = new Hashtable();
    private class Data {
        private static readonly System.Reflection.MethodInfo methodOnClick = null;
        static Data() {
            methodOnClick = typeof(Button).GetMethod("OnClick", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
        }

        public Button Button = null;
        private Timer Timer = new Timer();
        public double? GradientRate;
        public int? LinearGradient = null;
        public int FirstDelayMillis;
        public int FastestRepeatMillis;
        public int[] SwitchesMillis;
        public int[] SpeedsMillis;

        private DateTime lastEvent = DateTime.MinValue;
        private int millisCount = 0;
        private int currentSpeed = 0;
        private int waitSum = 0;

        public Data(Button button, double? gradientRate, int? linearGradient, int firstDelayMillis, int fastestRepeatMillis, int[] switchesMillis, int[] speedsMillis) {
            Button = button;
            GradientRate = gradientRate;
            LinearGradient = linearGradient;
            FirstDelayMillis = firstDelayMillis;
            FastestRepeatMillis = fastestRepeatMillis;
            SwitchesMillis = switchesMillis;
            SpeedsMillis = speedsMillis;
            Timer.Interval = firstDelayMillis;
            Timer.Tick += Timer_Tick;
            Button.MouseDown += Button_MouseDown;
            Button.MouseUp += Button_MouseUp;
            Button.MouseLeave += Button_MouseLeave;
        }

        void Button_MouseDown(object sender, MouseEventArgs e) {
            if (!Button.Enabled)
                return;

            lastEvent = DateTime.UtcNow;
            Timer.Start();
        }

        void Button_MouseUp(object sender, MouseEventArgs e) {
            Reset();
        }

        void Button_MouseLeave(object sender, EventArgs e) {
            Reset();
        }

        private void Reset() {
            Timer.Stop();
            Timer.Interval = FirstDelayMillis;
            millisCount = 0;
            currentSpeed = 0;
            waitSum = 0;
        }

        void Timer_Tick(object sender, EventArgs e) {
            if (!Button.Enabled) {
                Reset();
                return;
            }

            methodOnClick.Invoke(Button, new Object[] { EventArgs.Empty });
            //Button.PerformClick(); // if Button uses SetStyle(Selectable, false); then CanSelect is false, which prevents PerformClick from working.

            if (GradientRate.HasValue || LinearGradient.HasValue) {
                int millis = Timer.Interval;

                if (GradientRate.HasValue)
                    millis = (int) Math.Round(GradientRate.Value * millis);
                else if (LinearGradient.HasValue) {
                    DateTime now = DateTime.UtcNow;
                    var ts = now - lastEvent;
                    int ms = (int) ts.TotalMilliseconds;
                    millisCount += ms;
                    // only increase the rate every 500 milliseconds
                    // otherwise it appears too get to the maximum rate too quickly
                    if (millisCount >= 500) {
                        millis -= LinearGradient.Value;
                        millisCount -= 500;
                        lastEvent = now;
                    }
                }

                if (millis < FastestRepeatMillis)
                    millis = FastestRepeatMillis;

                Timer.Interval = millis;
            }
            else {
                if (currentSpeed < SpeedsMillis.Length) {
                    TimeSpan elapsed = DateTime.UtcNow - lastEvent; 
                    if (elapsed.TotalMilliseconds >= waitSum) {
                        waitSum += SwitchesMillis[currentSpeed];
                        Timer.Interval = SpeedsMillis[currentSpeed];
                        currentSpeed++;
                    }
                }
            }
        }

        public void Dispose() {
            Timer.Stop();
            Timer.Dispose();
            Button.MouseDown -= Button_MouseDown;
            Button.MouseUp -= Button_MouseUp;
            Button.MouseLeave -= Button_MouseLeave;
        }
    }

    ///<summary>The repeating speed becomes exponentially faster. This is the default behavior of the NumericUpDown control.</summary>
    ///<param name="button">The button to add the behavior.<param>
    ///<param name="firstDelayMillis">The delay before first repeat in milliseconds.</param>
    ///<param name="fastestRepeatMillis">The smallest delay allowed. Note: Masharling between the timer and the UI thread has an unavoidable limit of about 10 milliseconds.</param>
    ///<param name="gradientRate">The new interval is the current interval multiplied by the gradient rate.</param>
    public static void AddRepeatingExponential(this Button button, int firstDelayMillis = 500, int fastestRepeatMillis = 15, double gradientRate = 0.75) {
        AddRepeating(button, firstDelayMillis, fastestRepeatMillis, gradientRate, null, null, null);
    }

    ///<summary>The repeating speed becomes linearily faster.</param>
    ///<param name="button">The button to add the behavior.<param>
    ///<param name="firstDelayMillis">The delay before first repeat in milliseconds.</param>
    ///<param name="fastestRepeatMillis">The smallest delay allowed. Note: Masharling between the timer and the UI thread has an unavoidable limit of about 10 milliseconds.</param>
    ///<param name="linearGradient">If specified, the repeats gradually happen more quickly. The new interval is the current interval minus the linear gradient.</param>
    public static void AddRepeatingLinear(this Button button, int firstDelayMillis = 500, int fastestRepeatMillis = 50, int linearGradient = 25) {
        AddRepeating(button, firstDelayMillis, fastestRepeatMillis, null, linearGradient, null, null);
    }

    ///<summary>The repeating speed switches from the slow speed to the fastest speed after the specified amount of milliseconds.</summary>
    ///<param name="button">The button to add the behavior.<param>
    ///<param name="firstDelayMillis">The delay before first repeat in milliseconds.</param>
    ///<param name="fastestRepeatMillis">The smallest delay allowed. Note: Masharling between the timer and the UI thread has an unavoidable limit of about 10 milliseconds.</param>
    ///<param name="slowRepeatMillis">The delay in milliseconds between repeats when in the slow repeat state.</param>
    ///<param name="slowToFastestSwitchMillis">The delay in milliseconds before switching from the slow repeat speed to the fastest repeat speed.</param>
    public static void AddRepeatingTwoSpeed(this Button button, int firstDelayMillis = 500, int fastestRepeatMillis = 100, int slowRepeatMillis = 300, int slowToFastestSwitchMillis = 2000) {
        AddRepeating(button, firstDelayMillis, fastestRepeatMillis, null, null, new[] { slowRepeatMillis, fastestRepeatMillis }, new [] { slowToFastestSwitchMillis, 0 });
    }

    ///<summary>The repeating speed switches from the slow to medium to fastest at speed switch interval specified.</summary>
    ///<param name="button">The button to add the behavior.<param>
    ///<param name="firstDelayMillis">The delay before first repeat in milliseconds.</param>
    ///<param name="fastestRepeatMillis">The smallest delay allowed. Note: Masharling between the timer and the UI thread has an unavoidable limit of about 10 milliseconds.</param>
    ///<param name="slowRepeatMillis">The delay in milliseconds between repeats when in the slow repeat state.</param>
    ///<param name="mediumRepeatMillis">The delay in milliseconds between repeats when in the medium repeat state.</param>
    ///<param name="speedSwitchMillis">The delay in milliseconds before switching from one speed state to the next speed state.</param>
    public static void AddRepeatingThreeSpeed(this Button button, int firstDelayMillis = 500, int fastestRepeatMillis = 75, int slowRepeatMillis = 300, int mediumRepeatMillis = 150, int speedSwitchMillis = 2000) {
        AddRepeating(button, firstDelayMillis, fastestRepeatMillis, null, null, new[] { slowRepeatMillis, mediumRepeatMillis, fastestRepeatMillis }, new [] { speedSwitchMillis, speedSwitchMillis, 0 });
    }

    private static void AddRepeating(this Button button, int firstDelayMillis, int fastestRepeatMillis, double? gradientRate, int? linearGradient, int[] speedsMillis, int[] switchesMillis) {
        Data d = (Data) ht[button];
        if (d != null)
            RemoveRepeating(button);

        d = new Data(button, gradientRate, linearGradient, firstDelayMillis, fastestRepeatMillis, switchesMillis, speedsMillis);
        ht[button] = d;
        button.Disposed += delegate {
            RemoveRepeating(button);
        };
    }

    ///<summary>Removes the repeating behavior from the button.</summary>
    public static void RemoveRepeating(this Button button) {
        Data d = (Data) ht[button];
        if (d == null)
            return;

        ht.Remove(button);
        d.Dispose();
    }
}

Corri

Answer 11

you could use the mouseMove Event and check if the mousebutton is held down like:

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if(e.Button==MouseButtons.Left)
        {
        //your code here
        }
    }

Epigrammatize

that will lead to infinite recursion, e will not change intra-method – Nicolasanicolau

Answer 12

Similar to Timwi's solution above except using async/await for asynchronous IO and lock for synchronization for some state...

using System;
using System.Windows.Forms;
using System.Threading.Tasks;

namespace Foo {
    partial class Form1: Form {
        private static readonly object mousePressLock = new object();
        private bool mousePressed;
        private Task task;

        private async Task MouseAction(Action action) {
            while (true) {
                lock (mousePressLock) {
                    if (mousePressed)
                        action();
                    else
                        break;
                }
                await Task.Delay(100).ConfigureAwait(false);
            }
        }

        private void PnlTranslate_Paint(object sender, PaintEventArgs e) {
        }

        private void Up_MouseUp(object sender, MouseEventArgs e) {
            lock (mousePressLock) { mousePressed = false; }
            task.Wait();
        }

        private void Up_MouseDown(object sender, MouseEventArgs e) {
            lock (mousePressLock) { mousePressed = true; }
            int cnt = 0;
            task = MouseAction(() => {
                Console.WriteLine($"mouse up action {++cnt}");
            });
        }

        public Form1() {
            InitializeComponent();
            mousePressed = false;
            task = null;
        }
    }
}

Also, note the ConfigureAwait(false) call. I ran into deadlock without that b.c. tasks were fighting to be on the same thread. It was so annoying.

Ubana