Help With Overlapped Widgets

[AlexvZyl]

Version/Branch of Dear ImGui:

Version: 1.88
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_glfw.cpp + imgui_impl_opengl3.cpp
Operating System: Windows 10

My Issue/Question:

I am trying to create an overlay for my scene, as seen here. Notice the button in the top left and the child in the bottom right.

I want the button to block events to the scene. Basically, I just need to know if the texture is hovered and then I can respond accordingly. I have tried the following:

// The image.
ImGui::Image(m_textureID, m_contentRegionSize, { 0, 1 }, { 1, 0 });
ImGui::SetItemAllowOverlap();
if (ImGui::IsItemHovered()) m_engine->m_isHovered = true;
else         	            m_engine->m_isHovered = false;

// I have drag and drop items here, if that might have an effect.

// The button.
ImGui::SetCursorPos(ImGui::GetWindowContentRegionMin());
ImGui::Button("Test");
ImGui::SetItemAllowOverlap();

// Render child here.

The child seems to be working correctly, but I suspect this has nothing to do with overlapping and just how children work in Dear ImGui. m_engine->m_isHovered is being set to true, even if the button is being hovered. Am I missing something?

[rokups]

You could try this:

static ImDrawListSplitter splitter;
splitter.Split(ImGui::GetWindowDrawList(), 2);

// Render button first, however, put it to the top layer so it is rendered on top of viewport image.
splitter.SetCurrentChannel(ImGui::GetWindowDrawList(), 1);
if (ImGui::Button("Button"))
    printf("Button pressed\n");  // Interacting with the button will prevent interacting with the image.

// Render viewport image later, but it wont cover previously rendered button.
splitter.SetCurrentChannel(ImGui::GetWindowDrawList(), 0);
ImGui::SetCursorPos(ImGui::GetWindowContentRegionMin());
ImGui::Image(io.Fonts->TexID, ImVec2(200, 200));
if (ImGui::IsItemClicked())
    printf("Viewport pressed\n");

// Debug info: image is hovered when hovering "Button", but hovered state gets reset when "Button" is pressed down.
ImGui::Text("Viewport hovered: %d", ImGui::IsItemHovered());
splitter.Merge(ImGui::GetWindowDrawList());

[AlexvZyl]

I tried what you suggested, but it still does not give me the functionality I am looking for. The texture is still seen as hovered even if the button is on top of it.

However, I did learn about the splitter now, so thanks for that! Pretty cool.

[ocornut]

Hello,

This should now all be fixed by changes outlined here:

#6512 (comment)

• SetNextItemAllowOverlap() works better.
• IsItemHovered() previously was never aware of it. It is now aware of it and it can be opted out with ImGuiHoveredFlags_AllowWhenOverlappedByItem.

Thanks for your patience.