Font bug when using multiple instances #591

Cthutu · 2016-04-15T19:39:38Z

This is briefly mentioned in #586 but when I switch state via the ImGui::SetInternalState() API, the fonts that is the not most recently created instance get corrupted. There is a work around. I run this code before the draw loops (OpenGL renderer):

unsigned char* pixels;
int width, height;
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);

And immediately I bind the texture:

glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)drawCmd.TextureId);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, (GLint)GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, (GLint)GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, (GLint)GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

I am essentially reloading the OpenGL textures. Is this because ImGui::SetInternalState() is moving the font texure around in memory and the OpenGL texture is referencing old memory? I haven't analysed the behaviour between switching internal states yet, but I thought I'd let you be aware of it.

The text was updated successfully, but these errors were encountered:

ocornut · 2016-04-17T08:23:06Z

SetInternalState() is only assigning to a pointer so isn't affecting anything font related.
Now, I believe you that may be a bug but I would need more detailed information and ideally a repro. What may be obvious/trivial in your context may not be obvious everywhere.

How are you creating the second state? Are you reassigning the font atlas pointer?

itamago · 2016-04-17T10:45:50Z

I had the same issue few time ago while using 2 different ImGui contexts with their own fonts. After reading the source code I understood that you need to have separate texture atlases too.
So, create an additional atlas for each additional context, and when you SetInternalState you must swap the atlases too. It works perfectly well.

ocornut · 2016-04-17T11:08:28Z

This isn't as intended, you should be able to share the same atlas for two instances.

Cthutu · 2016-04-17T11:27:29Z

I do create an additional atlas for each context. In fact, I have a
different OpenGL context per ImGui context. I will look at the code on
Monday and show you how I manage the ImGui contexts.

On Sun, 17 Apr 2016 at 07:08 omar notifications@github.com wrote:

This isn't as intended, you should be able to share the same atlas for two
instances.

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#591 (comment)

ocornut · 2016-04-17T12:50:40Z

Thanks!

Similarly, you should be able to reuse the same atlas if they are going to be the same (tho obviously you need to upload texture to your two opengl context and find a way to pass textureid that works for both).

This looks fishy so I'll need to give it a closer look.

ocornut · 2016-04-17T18:11:55Z

This worked for me:

    // Setup ImGui binding
    void* state1 = ImGui::GetInternalState();
    ImGui_ImplGlfw_Init(window, true);

    void* state2 = (void*)new char[ImGui::GetInternalStateSize()];
    ImGui::SetInternalState(state2, true);
    ImGui_ImplGlfw_Init(window, true);

    [...] Main Loop

        ImGui::SetInternalState(state2);

        ImGui_ImplGlfw_NewFrame();

        ImGui::Begin("HELLO");
        ImGui::Text("Hello");
        ImGui::End();

        ImGui::SetInternalState(state1);

        ImGui_ImplGlfw_NewFrame();
        [...] 

        ImGui::SetInternalState(state1);
        ImGui::Render();

        ImGui::SetInternalState(state2);
        ImGui::Render();

BUT I had to fix code in ImGui_ImplGlfw_NewFrame(), added the else statement else:

    ImGuiIO& io = ImGui::GetIO();
    if (!g_FontTexture)
        ImGui_ImplGlfw_CreateDeviceObjects();
    else
        io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;

Maybe the sample code should be more aware of multiple contexts? Are you using this code as is, or something that made more sense for your own use of multiple contexts?

Also the InternalState function names/API sucks (will be renamed).

Cthutu · 2016-04-17T21:22:41Z

I will compare what you have to what I have on Monday and will report in!

On Sun, 17 Apr 2016 at 14:11 omar notifications@github.com wrote:

This worked for me:

// Setup ImGui binding
void* state1 = ImGui::GetInternalState();
ImGui_ImplGlfw_Init(window, true);

void* state2 = (void*)new char[ImGui::GetInternalStateSize()];
ImGui::SetInternalState(state2, true);
ImGui_ImplGlfw_Init(window, true);

[...] Main Loop

    ImGui::SetInternalState(state2);

    ImGui_ImplGlfw_NewFrame();

    ImGui::Begin("HELLO");
    ImGui::Text("Hello");
    ImGui::End();

    ImGui::SetInternalState(state1);

    ImGui_ImplGlfw_NewFrame();
    [...]

    ImGui::SetInternalState(state1);
    ImGui::Render();

    ImGui::SetInternalState(state2);
    ImGui::Render();

Apart from the fact that the function names/API sucks (will be fixed!).

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#591 (comment)

Cthutu · 2016-04-17T21:25:07Z

Immediately I notice that you're only using one OpenGL context, but if that
would affect anything, I couldn't tell you.

On Sun, 17 Apr 2016 at 17:22 Matt Davies mattie.davies@gmail.com wrote:

I will compare what you have to what I have on Monday and will report in!

On Sun, 17 Apr 2016 at 14:11 omar notifications@github.com wrote:
This worked for me:
// Setup ImGui binding
void* state1 = ImGui::GetInternalState();
ImGui_ImplGlfw_Init(window, true);

void* state2 = (void*)new char[ImGui::GetInternalStateSize()];
ImGui::SetInternalState(state2, true);
ImGui_ImplGlfw_Init(window, true);

[...] Main Loop

    ImGui::SetInternalState(state2);

    ImGui_ImplGlfw_NewFrame();

    ImGui::Begin("HELLO");
    ImGui::Text("Hello");
    ImGui::End();

    ImGui::SetInternalState(state1);

    ImGui_ImplGlfw_NewFrame();
    [...]

    ImGui::SetInternalState(state1);
    ImGui::Render();

    ImGui::SetInternalState(state2);
    ImGui::Render();
Apart from the fact that the function names/API sucks (will be fixed!).

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#591 (comment)

ocornut · 2016-05-08T15:01:47Z

@Cthutu Any news on that?

I still have to admit that contexts are confusing because a) imgui_impl_xxx files aren't very context aware. b) Font Atlas being shared by default makes things confusing.

Would definitively need to clarify the situation with font atlas.

    // Setup ImGui binding
    ImGuiContext* ctx1 = ImGui::GetCurrentContext();
    ImGui_ImplGlfw_Init(window, true);

    ImGuiContext* ctx2 = ImGui::CreateContext();
    ImGui::SetCurrentContext(ctx2);
    ImGui_ImplGlfw_Init(window, true);

...

        ImGui::SetCurrentContext(ctx1);
        ImGui_ImplGlfw_NewFrame();
        ImGui::Text("Hello");

        ImGui::SetCurrentContext(ctx2);
        ImGui_ImplGlfw_NewFrame();

...

        ImGui::SetCurrentContext(ctx1);
        ImGui::Render();

        ImGui::SetCurrentContext(ctx2);
        ImGui::Render();

…inter thread-safety (#586, #591)

Cthutu · 2016-05-08T16:22:47Z

I haven't been able to check this out yet. I'm currently busy at ToJam but
when I get to work I will figure it out. But first I have to port my code
to use your tree nodes :) Sorry I can't be more timely on this but things
are a bit crazy at the moment. Expect a reply towards the end of the week.

On Sun, 8 May 2016 at 11:01 omar notifications@github.com wrote:

@Cthutu https://github.com/Cthutu Any news on that?

I still have to admit that contexts are confusing because a)
imgui_impl_xxx files aren't very context aware. b) Font Atlas being shared
by default makes things confusing.

Would definitively need to clarify the situation with font atlas.
// Setup ImGui binding
ImGuiContext* ctx1 = ImGui::GetCurrentContext();
ImGui_ImplGlfw_Init(window, true);

ImGuiContext* ctx2 = ImGui::CreateContext();
ImGui::SetCurrentContext(ctx2);
ImGui_ImplGlfw_Init(window, true);
...
    ImGui::SetCurrentContext(ctx1);
    ImGui_ImplGlfw_NewFrame();
    ImGui::Text("Hello");

    ImGui::SetCurrentContext(ctx2);
    ImGui_ImplGlfw_NewFrame();
...
    ImGui::SetCurrentContext(ctx1);
    ImGui::Render();

    ImGui::SetCurrentContext(ctx2);
    ImGui::Render();
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#591 (comment)

Cthutu · 2016-05-13T13:21:41Z

FYI, things have been delayed to Monday so I will look at updating my imgui
repo on Tuesday.

On Sun, 8 May 2016 at 12:22 Matt Davies mattie.davies@gmail.com wrote:

I haven't been able to check this out yet. I'm currently busy at ToJam
but when I get to work I will figure it out. But first I have to port my
code to use your tree nodes :) Sorry I can't be more timely on this but
things are a bit crazy at the moment. Expect a reply towards the end of
the week.

On Sun, 8 May 2016 at 11:01 omar notifications@github.com wrote:
@Cthutu https://github.com/Cthutu Any news on that?

I still have to admit that contexts are confusing because a)
imgui_impl_xxx files aren't very context aware. b) Font Atlas being shared
by default makes things confusing.

Would definitively need to clarify the situation with font atlas.
// Setup ImGui binding
ImGuiContext* ctx1 = ImGui::GetCurrentContext();
ImGui_ImplGlfw_Init(window, true);

ImGuiContext* ctx2 = ImGui::CreateContext();
ImGui::SetCurrentContext(ctx2);
ImGui_ImplGlfw_Init(window, true);
...
    ImGui::SetCurrentContext(ctx1);
    ImGui_ImplGlfw_NewFrame();
    ImGui::Text("Hello");

    ImGui::SetCurrentContext(ctx2);
    ImGui_ImplGlfw_NewFrame();
...
    ImGui::SetCurrentContext(ctx1);
    ImGui::Render();

    ImGui::SetCurrentContext(ctx2);
    ImGui::Render();
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#591 (comment)

ocornut · 2016-09-23T10:59:08Z

@Cthutu Any news of that? Still looking for a repro :)

ocornut · 2017-08-09T12:31:05Z

Could we get to the bottom of this topic?

AFAIK:

You can share a ImFontAtlas between two ImGuiContext (I might be wrong, maybe there is an issue in which case let me know)
If you have 2 OpenGL contexts sharing texture data is a solvable problem (out of the scope of imgui) but if for some reason it is causing issues you can effectively have 2 ImFontAtlas, or share 1 ImFontAtlas and somehow reinterpret the atlas TextureId to refer to a different OpenGL texture according to your OpenGL context.

ocornut · 2018-02-06T20:54:12Z

@Cthutu The issues discussed here should now be clarified and fixed by the changes discussed in #1565.
Context creation is now explicit, and have a parameter to pass in a font atlas created by the user.
Read #1565 for details.

ocornut added a commit that referenced this issue May 8, 2016

Comments to clarify default shared ImFontAtlas and current context po…

aa11934

…inter thread-safety (#586, #591)

aegagros mentioned this issue Sep 16, 2016

Careful when using ImGuiTextFilter with multiple instances. #833

Closed

ocornut added the font/text label May 1, 2017

ocornut mentioned this issue Jan 18, 2018

Multiple Contexts shutdown leak or not clear #1558

Closed

ocornut added the multi-contexts label Jan 18, 2018

ocornut closed this as completed Feb 6, 2018

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Font bug when using multiple instances #591

Font bug when using multiple instances #591

Cthutu commented Apr 15, 2016

ocornut commented Apr 17, 2016

itamago commented Apr 17, 2016

ocornut commented Apr 17, 2016

Cthutu commented Apr 17, 2016

ocornut commented Apr 17, 2016

ocornut commented Apr 17, 2016 •

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Cthutu commented Apr 17, 2016

Cthutu commented Apr 17, 2016

ocornut commented May 8, 2016

Cthutu commented May 8, 2016

Cthutu commented May 13, 2016

ocornut commented Sep 23, 2016

ocornut commented Aug 9, 2017

ocornut commented Feb 6, 2018

Font bug when using multiple instances #591

Font bug when using multiple instances #591

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Cthutu commented Apr 15, 2016

ocornut commented Apr 17, 2016

itamago commented Apr 17, 2016

ocornut commented Apr 17, 2016

Cthutu commented Apr 17, 2016

ocornut commented Apr 17, 2016

ocornut commented Apr 17, 2016 • edited Loading

Cthutu commented Apr 17, 2016

Cthutu commented Apr 17, 2016

ocornut commented May 8, 2016

Cthutu commented May 8, 2016

Cthutu commented May 13, 2016

ocornut commented Sep 23, 2016

ocornut commented Aug 9, 2017

ocornut commented Feb 6, 2018

ocornut commented Apr 17, 2016 •

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