Fonts at runtime after initial initiation?

[nnoc]

Hi!
Hope format is correct and I'll go straight to the matter / deleted most of the format for things I don't have. I've been looking at related issues but I didn't see anyone trying this.

Version: // dear imgui, v1.67 WIP
Branch: master

My Question:
Is it even possible to use io.Fonts->AddFontFromFileTTF(filePath.c_str(), fontSize); at runtime after the initial initiation of ImGui?
It does load the font but doesn't build the atlas somehow: when I try to use the loaded font, it throws an error at,
IM_ASSERT(font && font->IsLoaded());
in ImGui::SetCurrentFont(ImFont* font) when trying to use ImGui::PushFont(ImFont* font)

Thank you for your time.

[ocornut]

Hello,

You need to rebuild the atlas if you add new fonts. Atlas needs to be rebuilt before NewFrame().

[nnoc]

I can't rebuild Atlas in runtime?
Say in a scenario where an user decides to load a custom font.
I can't really do this, can I?

[ocornut]

Yes you can.. just call Fonts->Build() et Fonts->GetTexDataAsXXX() and reupload the texture..

[zejal]

Hello, I am trying to implement similar feature but does not seem to work. I call Fonts->AddFontFromFileTTF() + Fonts->Build() before NewFrame() but everything in main window disappears (modifying code in example_win32_directx11 main.cpp file).

    // Main loop
    MSG msg;
    ZeroMemory(&msg, sizeof(msg));
    while (msg.message != WM_QUIT)
    {
          if (PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE)) {…};
          if (load_font_file)  {  // set to true if some button has been hit
                 const auto * font = io.Fonts->AddFontFromFileTTF(new_font_file.c_str(), 12.0f);
                 io.Fonts->Build();
                 load_font_file = false;
           }
           // Start the Dear ImGui frame
           ImGui_ImplDX11_NewFrame();
           ImGui_ImplWin32_NewFrame();
           ImGui::NewFrame();
          ....
      ....

Is there any missing function call? You mention "reupload the texture", but I have no idea on how to do this.
Thanks in advance.

EDIT: Adding call to ImGui_ImplDX11_InvalidateDeviceObjects(); after io.Fonts->Build(); seems to solve the problem.

[ocornut]

Adding call to ImGui_ImplDX11_InvalidateDeviceObjects(); after io.Fonts->Build(); seems to solve the problem.

Good to hear!

[GordonEldest]

Is there any missing function call? You mention "reupload the texture", but I have no idea on how to do this.
Thanks in advance.

EDIT: Adding call to ImGui_ImplDX11_InvalidateDeviceObjects(); after io.Fonts->Build(); seems to solve the problem.

ImGui_ImplDX11_InvalidateDeviceObjects() may be overkill
Reason:
This will trigger a call to ImGui_ImplDX11_CreateDeviceObjects() which do the heavy lifting to create every shaders etc ...

While ok once in a while, For those who want more optimal use of CPU, AND feel ready to modify the imgui_impl_dx11.cpp (not a big deal) hereafter a suggestion:

For good reason (at least to ease avoiding resources leak) the ImGui_ImplDX11_CreateFontsTexture(); is a static procedure in imgui_impl_dx11.cpp
Circumvent that by creating hereafter code in global void ImGui_ImplDX11_ReCreateFontsTexture()
(tail it in imgui_impl_dx11.cpp, tail is safer and easier to track)
which will in charge of Releasing any previous resources (did seems doing the work for me) and just reload the texture.

void ImGui_ImplDX11_ReCreateFontsTexture(){
    if (g_pFontSampler) { g_pFontSampler->Release(); g_pFontSampler = NULL; }
    if (g_pFontTextureView) { g_pFontTextureView->Release(); g_pFontTextureView = NULL; ImGui::GetIO().Fonts->SetTexID(NULL);}
    ImGui_ImplDX11_CreateFontsTexture();
}

Usage:
in main loop, locate ImGui_ImplDX11_NewFrame() and put below code BEFORE it, like:

extern void ImGui_ImplDX11_ReCreateFontsTexture();
blabla code
...

		if (g_bAtlasNeedUpdate) {
			io.Fonts->Build();
			ImGui_ImplDX11_ReCreateFontsTexture();
		}
		ImGui_ImplDX11_NewFrame();
		ImGui_ImplWin32_NewFrame();
		ImGui::NewFrame();

[ocornut]

#3761 will provide a more generic solution to this.

[GordonEldest]

Yes!
Nicer.
Cross platforms (99%)

In DX11 far more elegant use of g_pd3dDeviceContext->UpdateSubresource(g_pFontTexture, 0, &box, pixels, g_FontTextureWidth * 4, 0);
I didn't look other backend implementation.

Suggestion:
Implement a check/reject that Font Texture Map is less than 4Kx32K , DX11 Crash is inelegant on this one.
Better be early, somewhere like in AddFont return NULL.
It may require to call ImFontAtlasBuildWithStbTruetype to know final rendered size,. This is less elegant that doing a batch on next frame but surely somebody will hit Texture map size limit even if look crazy high!
It happen to me during my tests!

At least reject (even if silently in release) the UpdateSubresource if map is too big.
Great work!

[Renardjojo]

Hello, I am trying to implement similar feature but does not seem to work. I call Fonts->AddFontFromFileTTF() + Fonts->Build() >before NewFrame() but everything in main window disappears (modifying code in example_win32_directx11 main.cpp file).

I solving this problem in OpenGL thanks to this code (and without Build function):

            ImGui::GetIO().Fonts->AddFontFromFileTTF(path, pixel_size);
            ImGui_ImplOpenGL3_CreateFontsTexture();

Hope that this can help

[spaderthomas]

I am also running into trouble updating fonts at runtime. To me, this seems sufficient:

// Remove the fonts you had
 ImGui::GetIO().Fonts->Clear();

// Add some new fonts
ImGui::GetIO().Fonts->AddFontFromFileTTF(path, size); 

// The next part uses the GLFW + GL3 implementation as an example -- that's what I'm using.
// It is copied verbatim from ImGui_ImplGlfwGL3_CreateFontsTexture, but removes the code that
// creates the GL devices

// Build texture atlas
ImGuiIO& io = ImGui::GetIO();
unsigned char* pixels;
int width, height;
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);

// Upload texture to OpenGL
glBindTexture(GL_TEXTURE_2D, g_FontTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

However, this is not working. InvalidateDeviceObjects() followed by CreateDeviceObjects() does work. Reading through the source code, it is unclear what we are doing when we invalidate / create device objects that is necessary versus simply rebuilding and reuploading the texture.

I also consulted the PR above (https://github.com/ocornut/imgui/pull/3761/files#), and it appears that the GL3 implementation is doing just what I describe.

Could you help me understand what I am missing? Thank you kindly!

[KulaGGin]

ImGui_ImplDX11_InvalidateDeviceObjects() may be overkill Reason: This will trigger a call to ImGui_ImplDX11_CreateDeviceObjects() which do the heavy lifting to create every shaders etc ...

While ok once in a while, For those who want more optimal use of CPU, AND feel ready to modify the imgui_impl_dx11.cpp (not a big deal) hereafter a suggestion:

For good reason (at least to ease avoiding resources leak) the ImGui_ImplDX11_CreateFontsTexture(); is a static procedure in imgui_impl_dx11.cpp Circumvent that by creating hereafter code in global void ImGui_ImplDX11_ReCreateFontsTexture() (tail it in imgui_impl_dx11.cpp, tail is safer and easier to track) which will in charge of Releasing any previous resources (did seems doing the work for me) and just reload the texture.

void ImGui_ImplDX11_ReCreateFontsTexture(){
    if (g_pFontSampler) { g_pFontSampler->Release(); g_pFontSampler = NULL; }
    if (g_pFontTextureView) { g_pFontTextureView->Release(); g_pFontTextureView = NULL; ImGui::GetIO().Fonts->SetTexID(NULL);}
    ImGui_ImplDX11_CreateFontsTexture();
}

Usage: in main loop, locate ImGui_ImplDX11_NewFrame() and put below code BEFORE it, like:

extern void ImGui_ImplDX11_ReCreateFontsTexture();
blabla code
...

		if (g_bAtlasNeedUpdate) {
			io.Fonts->Build();
			ImGui_ImplDX11_ReCreateFontsTexture();
		}
		ImGui_ImplDX11_NewFrame();
		ImGui_ImplWin32_NewFrame();
		ImGui::NewFrame();

This works. I think this is too low level and requires users to know deep implementation details. I want to change the default font, but it doesn't mean that I know how the whole ImGui and DirectX work. I think we as users shouldn't concern ourselves with such low level implementation details.
What if we could just do:

ImGui::GetIO().FontDefault = ImGui::GetIO().Fonts->AddFontFromFileTTF(fontPath, sizePixels);

To set the default font. And let the framework invalidate objects, build fonts, recreate font textures, etc as they're required?