WantCaptureMouse and popups

[neclepsio]

Version/Branch of Dear ImGui:

Version: 1.81
Branch: master

Back-end/Renderer/Compiler/OS

Back-ends: custom backend written in Go (based on glfw+opengl3 backend)
Compiler: Go + GCC
Operating System: Windows

My Issue/Question:

From my understanding of source code, WantCaptureMouse always returns true when non-modal popups are open. I think this is because a click outside the popup should close the popup. In my application I use center and right mouse button to move the view and I'd like to be able doing so with a popup open, but do not find a way to do so.

I'd like to do something like:

if (!io.WantCaptureMouseIgnoreNonModalPopups && !(io.AnyPopupOpen && button == left)) {
     // handle the event in my application
}

But I don't find a way. Could you help me? Thank you.

[ocornut]

This is an interesting question.

• You can use IsPopupOpen(ImGuiPopupFlags_AnyPopup) for the later.
• But this won't differentiate modals from non-modals.
• And technically you would also need to test for IsWindowHovered(ImGuiHoveredFlags_AnyWindow)

So I think this would mostly work:

#include "imgui_internal.h" // for GetTopMostPopupModal()

if (io.WantCaptureMouse)
{
   if (IsPopupOpen(NULL, ImGuiPopupFlags_AnyPopup))
        if (IsWindowHovered(ImGuiHoveredFlags_AnyWindow) == false && GetTopMostPopupModal() == NULL)
           return true; // pass event to app
   return false; // ignore event
}

PS: Would be good to hear your confirmation as to whether this works perfectly or not!

[ocornut]

Technically speaking we could strive to replace the imgui_internals GetTopMostPopupModal()with aImGuiPopupFlags_AnyModal` flag that would do the same thing in the public API, but I think we would consider it if (1) suggested technique worked and (2) it was useful to more users.

[neclepsio]

Thank you. This is the approach I was taking, but I feel it's not complete. ImGui::UpdateHoveredWindowAndCaptureFlags() takes in account several other causes: may them (now or in future) make it want to caputre the mouse even with the mouse hovering on a popup window? E.g.: I'm dragging a DragFloat, but the mouse is hovering a popup. In my understanding, I think Imgui still should want to capture the mouse, but using this approach I would not let so. Or am I missing something?

[ocornut]

I don't understand your example. If you are dragging a DragFloat but hovering a popup, IsWindowHovered(ImGuiHoveredFlags_AnyWindow) would return true therefore my suggested code would not pass the event to you app.

[neclepsio]

Sorry. Dragging a DragFloat, there is a popup open, but the mouse is not hovering on any window. In my understanding, the mouse should be captured. Using your suggestion, it is not. Am I right?

[ocornut]

Right, should also be testing for GetActiveID() == 0

[neclepsio]

Thank you. This should solve my use case.

But what about drag and drop? What about WantCaptureMouseNextFrame? Since it's getting complicated, shouldn't it be the case to just provide a separate WantCaptureMouse* for this?

[ocornut]

Try testing for g.DragDropActive == false as well.

I'm not sure what you mean or want with "WantCaptureMouseNextFrame".

Since it's getting complicated, shouldn't it be the case to just provide a separate WantCaptureMouse* for this?

Not until you've used the current solution extensively and can confirm it catches all cases.
(I think an active InputText() may still cause problem)

 if (IsPopupOpen(NULL, ImGuiPopupFlags_AnyPopup))
        if (IsWindowHovered(ImGuiHoveredFlags_AnyWindow) == false && GetTopMostPopupModal() == NULL)
            if (GetActiveID() == 0 || g.ActiveIdAllowOverlap == true)
                if (g.DragDropActive == false)

[neclepsio]

WantCaptureMouseNextFrame causes WantCaptureMouse to be true overriding all the rest, and that would be ignored with a popup opened and not hovered. I don't know its implications.

As for catching all use cases, the current value is:

g.IO.WantCaptureMouse = (mouse_avail_to_imgui && (g.HoveredWindow != NULL || mouse_any_down)) || (g.OpenPopupStack.Size > 0);

This should already catch all, excluding unknown bugs.
This is my idea:

g.IO.WantCaptureMouseExcludingPopupClose = (mouse_avail_to_imgui && (g.HoveredWindow != NULL || mouse_any_down)) || (GetTopMostPopupModal() != NULL);
g.IO.WantCaptureMouse = g.IO.WantCaptureMouseExcludingPopupClose || (g.OpenPopupStack.Size > 0);

I couln't find a good name for it.

[ocornut]

io.WantCaptureMouseNextFrame is only set via CaptureMouseFromApp() it's a little difficult to know what to do with it since CaptureMouseFromApp() doesn't let user provide more semantic about the use. Since it's a rarely called function for now I think it would override boths. EDIT Also to be honest those functions are confusingly named and properly need a redesign.

This is my idea:

That's a good point, and it is a good idea to do this this way. Thank you!
I'll try to come up with an official version.

[ocornut]

This is my idea

g.IO.WantCaptureMouseExcludingPopupClose = (mouse_avail_to_imgui && (g.HoveredWindow != NULL || mouse_any_down)) || (GetTopMostPopupModal() != NULL);
g.IO.WantCaptureMouse = g.IO.WantCaptureMouseExcludingPopupClose || (g.OpenPopupStack.Size > 0);

This doesn't seem to work unfortunately: because on the initial click MouseDownOwned[i] gets set based on popups being open:

for (int i = 0; i < IM_ARRAYSIZE(g.IO.MouseDown); i++)
{
    if (g.IO.MouseClicked[i])
        g.IO.MouseDownOwned[i] = (g.HoveredWindow != NULL) || (g.OpenPopupStack.Size > 0);

Which leads to us thinking we owned the initial click:

const bool mouse_avail_to_imgui = (mouse_earliest_button_down == -1) || g.IO.MouseDownOwned[mouse_earliest_button_down];

Which leads to an incorrect report while that button is held.

g.IO.WantCaptureMouseExcludingPopupClose = (mouse_avail_to_imgui && (g.HoveredWindow != NULL || mouse_any_down));

Fixing this requires us tracking a second set of MouseDownOwned and mouse_avail_to_imgui.
I'll see how this can be done neatly.

[ocornut]

Pushed a solution for this: 4aea1c5

Called io.WantCaptureMouseUnlessPopupClose

Added tests for it (thanks @rokups)

[neclepsio]

Thank you very much!