Detecting a mouse click about imgui

[voidware]

Not sure what an XY problem is, but this is what I'm doing:

I have a picture that you can zoom and pan whilst holding the mouse down. I want to "click" on the picture to reset the zoom and pan.

How do it detect "click" on the picture to reset zoom without it being also interpreted as a pan?

If i call IsMouseClicked it returns true when the mouse goes down but before it is known if this is a pan.

If i call IsMouseReleased it returns true after a pan when it is not a "click" and consequently pans wind up accidentally resetting the zoom.

It seems there is no proper "click" detection in imgui. I wrote a workaround, but i keep thinking i have missed something obvious.

Thanks for your help.

[voidware]

This seems to work;

struct MouseMonitor
{
    bool   _down = false;
    bool   _canClick = false;

    // test this for a click
    bool   _click = false;
    
    void update()
    {
        bool down = ImGui::IsMouseDown(0);

        _click = false;

        if (down)
        {
            
            if (!_down)
            {
                _down = true;
                _canClick = true;
            }
            else if (_canClick)
            {
                auto& io = ImGui::GetIO();
                float d = io.MouseDownDuration[0];
                if (d >= 0.3f) _canClick = false;
                if (ImGui::IsMouseDragging(0)) _canClick = false;
            }
        }
        else
        {
            if (_canClick) _click = true;
            _canClick = false;
            _down = false;
        }
    }
};

I'll run with this until something better.

[ocornut]

This seems like a XY Problem question.
Please first clarify what you are trying to achieve and trying to solve.

[ocornut]

IsMouseXXX functions are direct access to current mouse data and don't relate to more stateful elements, such as which item was clicked, etc. So your logic is fine (I would personally tend to write it in a more compact way, but that's not the point).

I believe one niggle is that IsMouseDragging() correctly returns false at the time of mouse button release, but actually the underlying data is still valid at the time of mouse release.
If you bypass IsMouseDragging() to access this data you get everything you need:

if (ImGui::IsMouseReleased(0))
{
    IMGUI_DEBUG_LOG("duration=%.3f, dragging = %d\n", io.MouseDownDurationPrev[0], io.MouseDragMaxDistanceSqr[0] >= io.MouseDragThreshold * io.MouseDragThreshold);
}

So by your definition of a click (where there is a time limit) you could write:

_click = ImGui::IsMouseReleased(0) && io.MouseDownDurationPrev[0] < 3.0f && io.MouseDragMaxDistanceSqr[0] < io.MouseDragThreshold * io.MouseDragThreshold;

or using imgui_internal.h you can use IsMouseDragPastThreshold():

_click = ImGui::IsMouseReleased(0) && io.MouseDownDurationPrev[0] < 0.3f && ImGui::IsMouseDragPastThreshold(0) == false;

But similar to your posted code that doesn't take into account the location where you initially pressed the button.

---

Higher level concepts include ButtonBehavior(), typically called through InvisibleButton(), which sets ActiveId.

InvisibleButton(...);
_click = IsItemDeactivated() && g.LastActiveIdTimer < 0.3f && g.ActiveIdSource == ImGuiInputSource_Mouse && IsMouseDragPastThreshold(0) == false;

^ This you don't need to track state.

But you can properly emulate the same by tracking state like you did (setting a can_click on IsMouseClicked(), testing it on IsMouseReleased()).

[ocornut]

But you can properly emulate the same by tracking state like you did (setting a can_click on IsMouseClicked(), testing it on IsMouseReleased()).

It's probably more reasonable to do this IMHO:

InvisibleButton();
if (IsItemClicked())
   can_click = true;
if (io.MouseDownDuration[0] >= 0.3f || IsMouseDragPastThreshold(0))
   can_click = false;
if (can_click && IsMouseReleased(0))
   click = true;

But it requires storing "can_click".
The reason being that if you have panning and other features you are likely to want to maintain state anyhow.