Column problem

[durswd]

I found a problem.

This code causes assert in Suspend.

ImGui::Begin("Begin");
ImGui::Columns(2);
ImGui::NextColumn();

ed::SetCurrentEditor(g_Context);
ed::Begin("My Editor", ImVec2(0.0, 0.0f));

// assert!
ed::Suspend();
ed::Resume();

ed::End();
ed::SetCurrentEditor(nullptr);

ImGui::Columns(1);
mGui::End();

But this codes runs with Begin and End child.

ImGui::Begin("Begin");
ImGui::Columns(2);
ImGui::NextColumn();

// add
ImGui::BeginChild("Child");
ed::SetCurrentEditor(g_Context);
ed::Begin("My Editor", ImVec2(0.0, 0.0f));

ed::Suspend();
ed::Resume();

ed::End();
ed::SetCurrentEditor(nullptr);

// add
ImGui::EndChild();

ImGui::Columns(1);
mGui::End();

Is it a bug?

Best regards.

[thedmd]

Hello @durswd,

I'm afraid there is a conflict here in the ImDrawList channel splitter. Columns API now is using it to separate column drawing. Node editor is also using channel splitter to manage node drawing.
Wrapping editor in child window avoid the problem, because child window has its own copy of ImDrawList.

Please use workaround with child window now, I will need to think how to address this problem.

@ocornut Is there a way to split single channel into sub-channels, to make channel splitter recursive? Or is this out of the scope of ImDrawList?

[ocornut]

It should be possible now if you use the ImDrawListSplitter helper directly.
The upcoming table system uses that to split recursively.

(ImDrawList carry its own ImDrawListSplitter for legacy reason, but you can ignore that instance and use yours).

[thedmd]

Thank you for advice. This is almost exactly what I did.

Since my code relay on splitter inside ImDrawList I ended up swapping splitter while editor is drawing to avoid major rewrite.

[thedmd]

@durswd Assert is solved. Editor should work in both cases now. Solution was simpler than I initially thought.

[durswd]

Thank you !

[meshula]

I ran into a similar issue. I thought I might organize my node drawing using Columns, but can't due to the ImDrawList issue. Of course I can implement the node contents a different way, but thought I would leave another test case here for you.

    ed::BeginNode(nodeB_Id);
        ImGui::Text("Node B");
        ImGui::Columns(2);
            ed::BeginPin(nodeB_InputPinId1, ed::PinKind::Input);
                ImGui::Text("-> In1");
            ed::EndPin();
            ed::BeginPin(nodeB_InputPinId2, ed::PinKind::Input);
                ImGui::Text("-> In2");
            ed::EndPin();
        ImGui::NextColumn();
            ed::BeginPin(nodeB_OutputPinId, ed::PinKind::Output);
                ImGui::Text("Out ->");
            ed::EndPin();
        ImGui::Columns();
    ed::EndNode();

The assert occurs here:

void ImDrawListSplitter::Split(ImDrawList* draw_list, int channels_count)
{
    IM_ASSERT(_Current == 0 && _Count <= 1);

[thedmd]

I see the problem. I should be able to make similar fix to enable this use case.

[thedmd]

@meshula I fixed an assert. Now channel splitting can be used between Begin/End for nodes and pins.

However Columns API will not work inside node because it relay on windows size internally and always span to full width, which is incorrect for node. In node you want to minimize size, that's why I used stack layouts. There is a workaround for that issue:

void ImGuiEx_BeginColumn()
{
    ImGui::BeginGroup();
}

void ImGuiEx_NextColumn()
{
    ImGui::EndGroup();
    ImGui::SameLine();
    ImGui::BeginGroup();
}

void ImGuiEx_EndColumn()
{
    ImGui::EndGroup();
}

// and code:
    ed::BeginNode(nodeB_Id);
        ImGui::Text("Node B");
        ImGuiEx_BeginColumn();
            ed::BeginPin(nodeB_InputPinId1, ed::PinKind::Input);
                ImGui::Text("-> In1");
            ed::EndPin();
            ed::BeginPin(nodeB_InputPinId2, ed::PinKind::Input);
                ImGui::Text("-> In2");
            ed::EndPin();
        ImGuiEx_NextColumn();
            ed::BeginPin(nodeB_OutputPinId, ed::PinKind::Output);
                ImGui::Text("Out ->");
            ed::EndPin();
        ImGuiEx_EndColumn();
    ed::EndNode();

Does this works for you?

The way Column API work collide with how canvas work. Maybe it is a way to make work both but that will require sending PR's to patch Column API and as far as I know it is still in the flux, changing and probably evolve even more with tables @ocornut is working on. So until that's done I think above workaround is the next best thing we got.

[meshula]

Yes, that's perfect. Your example is a nice "cookbook" reference :)

[mircolosi]

Hi everybody,
first of all I have to admit that the work behind imgui and imgui-node-editor is impressive and high-quality. So thank you all for that.
I had the same problem of assertion fail while trying to right-click the grid canvas in the Blueprint example.
Is there a fast workaround I can use to solve this problem?

This is the error I get

Blueprints:[...]/imgui-node-editor/ThirdParty/imgui/imgui_draw.cpp:1308: void ImDrawListSplitter::SetCurrentChannel(ImDrawList*, int): Assertion `idx < _Count' failed.
Aborted

[thedmd]

Thanks.
Assert is fixed now.