imgui IM_ASSERT(g.FrameScopeActive) failure

[astroesteban]

Compiler: Visual Studio Community 2019 (MSVC 16)
Operating System: Windows 10 64-bit

My Issue/Question:

When running my application in x64-Debug I get:
Assertion failed: g.FrameScopeActive, file C:\vcpkg\buildtrees\imgui\src\v1.73-a85d24b4b8\imgui.cpp, line 5400
only when I add ImGui::Begin and ImGui::End calls to my source file.

I am attempting to start a new C++ project using vcpkg, CMake, and Visual Studio on windows. I installed the following packages through vcpkg:

• imgui-sfml:x64-windows v2.1
• imgui:x64-windows v1.73-1
• sfml:x64-windows v2.5.1-4

In my CMakeLists.txt I include the following:

...
find_package(SFML CONFIG COMPONENTS REQUIRED windows graphics system)
find_package(imgui CONFIG REQUIRED)
find_package(ImGui-SFML CONFIG REQUIRED)
...
add_executable(main app/main.cpp)
target_link_libraries(main
                                PRIVATE imgui::imgui
                                              ImGui-SFML::ImGui-SFML
                                             sfml-system
                                             sfml-window
                                             sfml-graphics)

My main.cpp file consists of the following:

#include <imgui.h>
#include <imgui-SFML.h>

#include <SFML/Graphics/RenderWindow.hpp>
#include <SFML/System/Clock.hpp>
#include <SFML/Window/Event.hpp>

int main()
{
	// Setup ImGui context
	ImGui::CreateContext();
	sf::RenderWindow window(sf::VideoMode(640, 480), "Test GUI");
	ImGui::SFML::Init(window);

	sf::Clock deltaClock;

	while (window.isOpen()) {
		sf::Event event{};
		while (window.pollEvent(event)) {
			ImGui::SFML::ProcessEvent(event);

			if (event.type == sf::Event::Closed) { window.close(); }
		}

		ImGui::SFML::Update(window, deltaClock.restart());

		ImGui::Begin("Test Begin");
                ImGui::Button("Test Button");
		ImGui::End();

		window.clear();
		ImGui::SFML::Render(window);
		window.display();
	} //end while

	ImGui::SFML::Shutdown();
}

When running my application in Visual Studio using the x64-Debug configuration I immediately get the following assertion failure for IM_ASSERT(g.FrameScopeActive). This only happens when I add the lines

ImGui::Begin("Test Begin");
ImGui::Button("Test Button");
ImGui::End();

Without them I get a running black window (first image below).

I have been unable to find a solution to this problem. I am unsure if this is an issue with ImGui-SFML or ImGui itself. Any help with this would be greatly appreciated. Thank you!

Screenshots/Video

[eliasdaler]

Did you try to run minimal example from README.md? Does it work?

This line looks suspicious - you don't need to do it:

ImGui::CreateContext();

Also please check with debugger that ImGui::NewFrame really gets called. Maybe vcpkg package is not correct and patches something out...

[reworks-org]

Running the example also triggers this for me:
IM_ASSERT(g.WithinFrameScope); // Forgot to call ImGui::NewFrame()

[astroesteban]

I ran the minimal example from the README and still get the same result. I don't think ImGui::NewFrame() is actually being called.

[eliasdaler]

Can you please debug why it doesn't get called? At the moment I'm not able to reproduce this on my machine.

See the call to ImGui::NewFrame here: https:/eliasdaler/imgui-sfml/blob/master/imgui-SFML.cpp#L455

You need to make sure that this ImGui::SFML::Update gets called before any ImGui::Begin calls

[chenzdshao]

I encountered the same issue!

[eliasdaler]

@chenzdshao can you please debug it a bit as I've described in my previous comment?

[chenzdshao]

@eliasdaler When I build and link ImGui-SFML.lib with vcpkg or cmake, here comes the error. When I compile and link imgui-SFML.cpp manually, the error disappears!

[eliasdaler]

This means there are some problems with imgui-sfml's vcpkg package, and so the issue should probably be created in vcpkg repo...

[astroesteban]

I encounter the same thing as @chenzdshao. I will open a new issue in the vcpkg repo.

[JackBoosY]

After debugging, I found that there are multiple variable GImGui, the first variable is initialized, and the second variable is used subsequently.
I don't know why .I can reproduce it in Visual Studio 2019, but not in Visual Studio 2017.

Anyone can help me?

[eliasdaler]

Might be something to do with linking and having multiple copies of one static object.
Can you try to link imgui-sfml statically?

[JackBoosY]

@esduran Why is GimGui not set as a static variable to avoid this situation?

[eliasdaler]

This is not something that I can control - it's an ImGui thing... Both static and dynamic linking work fine for me if I compile sources myself. vcpkg does something wrong, I can't tell what...

[astroesteban]

The issue is also opened in vcpkg.
I'll go ahead and compile the sources myself as well.

[Eric-Ackles]

The vcpkg port of imgui enforces to build it as a static library. Its portfile.cmake has a vcpkg_check_linkage(ONLY_STATIC_LIBRARY) command.

But imgui-sfml is built as dll by vcpkg (default triplet). Then your executable and the dll will be linked to the static library twice.

https://stackoverflow.com/questions/31209693/static-library-linked-two-times

[eliasdaler]

Then maybe ImGui-SFML should only be build as static lib as well?

[eliasdaler]

Looks like it's been fixed in vcpkg package.