Crash destroying imgui context in dynamic fonts branch

[Aarkham]

Version/Branch of Dear ImGui:

Version 1.92.0 WIP, Branch: dynamic_fonts

Back-ends:

Custom

Compiler, OS:

Windows 10 Visual Studio

Full config/build information:

Dear ImGui 1.92.0 WIP (19195)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201703
define: _WIN32
define: _WIN64
define: _MSC_VER=1944
define: _MSVC_LANG=201703
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: Entity ComputerPane
io.BackendRendererName: Entity ComputerPane Drawer
io.ConfigFlags: 0x00000000
io.ConfigViewportsNoDecoration
io.ConfigNavCaptureKeyboard
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00000010
 RendererHasTextures
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000006, TexSize: 2048,2048
io.Fonts->FontLoaderName: "stb_truetype"
io.DisplaySize: 2560.00,1715.07
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Details:

Crash destroying imgui context

In my game I have a debug imgui and also some computers running imgui as UI. So, I have a debug context and may have several ingame contexts, they are not multi threaded. I attach a video showing three ingame imguis and later show the debug UI (in it you can see there are 14 ingame UIs).

The debug UI does not implement the ImGuiBackendFlags_RendererHasTextures but the ingame UIs do.

The debug UI does not have any issue that I'm aware of.

This is the code that creates the ingame UIs:

bool ComputerPane::Create(int aId
                      , const math::Vector2f& aO,const math::Vector2f& aP1,const math::Vector2f& aP2
                      , float32_t aZPos
                      , float32_t aDisplayWidth
                      , float32_t aFontSize,bool aDrawMouse
                      , const std::string& aColourMode
                      , std::unique_ptr<ComputerPaneAction>&& aComputerPaneAction
                      , const ActionParms_t& aParms)
{
  AC_ASSERT_MSG(aDisplayWidth>0.0f,"aDisplayWidth must be greater than 0.");
  AC_ASSERT_MSG(aFontSize>0.0f,    "aFontSize must be greater than 0.");

  AC_ASSERT_MSG(!m_ImGuiTexture,"ComputerPane texture already created.");
  AC_ASSERT_MSG(!m_ImGuiContext,"ComputerPane context already created.");

  m_Id=aId;
  m_DisplayWidth=aDisplayWidth;
  SetPosition(aO,aP1,aP2,math::Vector2f(0.0f,0.0f));

  m_ZPos=aZPos;
  m_Active=true;
  m_Enabled=true;

  m_DrawMouseCursor=aDrawMouse;

//  m_Position.SetCenter(m_Center.m_X,m_Center.m_Y);

  m_ComputerPaneAction=std::move(aComputerPaneAction);
  AC_ASSERT_MSG(m_ComputerPaneAction,"Can not get aComputerPaneAction.");

  m_Parms.Assign(aParms);

  graphics::Device* dev=ac::GetApp().GetGraphicsDevice();
  AC_ASSERT_MSG(dev,"Can not get graphics::Device.");

  ImGuiContext* prev_context=ImGui::GetCurrentContext();
  ImGui::SetCurrentContext(nullptr);
  m_ImGuiContext=ImGui::CreateContext();
  AC_ASSERT_MSG(m_ImGuiContext,"Error creating m_ImGuiContextd.");

  ImGui::SetCurrentContext(m_ImGuiContext);
  ImGuiIO& imgui_io=ImGui::GetIO();
  imgui_io.DisplaySize.x=aDisplayWidth;
  imgui_io.DisplaySize.y=aDisplayWidth*static_cast<float>(m_Position.GetHeight())/static_cast<float>(m_Position.GetWidth());
  imgui_io.IniFilename=nullptr;
  imgui_io.BackendPlatformName="Entity ComputerPane";
  imgui_io.BackendRendererName="Entity ComputerPane Drawer";
#if defined IMGUI_HAS_TEXTURES
  imgui_io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures;
#endif
  imgui_io.MouseDrawCursor=false;



  const graphics::FontManager* font_manager=dev->GetTextRenderer().GetFontManager();


#if defined IMGUI_HAS_TEXTURES

  m_FontManager=font_manager;
  m_FontSize=/*trunc*/(kTestFontSize * aFontSize);

  m_CustomLoader=new ImFontLoader;
  AC_ASSERT_MSG(m_CustomLoader, "new m_CustomLoader failed.");
  m_CustomLoader->Name="ImGuiSDF";
  m_CustomLoader->FontSrcInit=FontSrcInit;
  m_CustomLoader->FontSrcContainsGlyph=FontSrcContainsGlyph;
  m_CustomLoader->FontBakedLoadGlyph=FontBakedLoadGlyph;

  imgui_io.Fonts->Flags|=ImFontAtlasFlags_NoBakedLines;
  imgui_io.Fonts->Flags|=ImFontAtlasFlags_NoMouseCursors;


  ImFontConfig empty_font;
  strcpy(empty_font.Name, "cpane");
  empty_font.FontLoader=m_CustomLoader;
  empty_font.SizePixels=m_FontSize;
  imgui_io.Fonts->TexMinWidth=kTextureWidth;
  imgui_io.Fonts->TexMinHeight=kTextureHeight;
  empty_font.FontData=this;

  //m_ImGuiContext->FontAtlasOwnedByContext=false;

  m_ImFont=imgui_io.Fonts->AddFont(&empty_font);

  imgui_io.Fonts->TexUvWhitePixel=ImVec2(0.0f,0.0f);
  SetBgColour(m_ImFont,IM_COL32(139,108,0,255));
  ReserveWhiteSpace(imgui_io.Fonts,*font_manager);
  Preload(m_ImFont, m_FontSize,(const ImWchar*)"\xe1\xe9\xed\xf3\xfa\xb4"
                                        "abcdefghijklmnopqrstuvwxyz"
                                        "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
                                        ",;.:#@!?<>[](){}/&%$_=-+*'~|\\"
                                        L"\x0080\x0081\x0082\x0083\x0084\x0085\x0086\x0087\x0088\x0089\x00A6\x00A7\x007f"
                                        L"\x00a1\x00bf"
                                        L"\x00d1\x00f1"
                                        L"\x008a" // Bug
                                        "©®"
                                        "\""
                                        L"¡¿"
                                        L"\x20ac" // Euro
                                        L"\x2026" // Horizontal ellipsis
                                        L"\xfffd" // Unknown char
                                        L"\xf245" // Mouse Cursor
                                        L"\xf118" // Smile
                                        L"\xf14d" // Share Square
                                        L"\xf1f8" // Trash
                                        L"\xf01c" // Inbox
                                        L"\xf0e0" // Envelop
                                        L"\xf55a" // BackSpace
                                        L"\xf1bb" // Tree
                                        L"\xf0f3" // Bell
                                        L"\xf30a" // Long arrow left
                                        L"\xf30b" // Long arrow right
                                        L"\xf7c0" // Satellite dish
                                        L"\xf085" // Cogs
                                        L"\xf04d" // Stop
                                        L"\xf071" // Exclamation triangle
                                        L"\xf059" // Question circle
                                        L"\xf084" // Key
                                        L"\xf5d2" // Atom
                                        L"\xf5df" // Reversi icon
                                        L"\xf044" // Edit
                                        L"\xf439" // Chess
                                        L"\xf43c" // Chess board
                                        L"\xf024" // Flag
                                        L"\xf017" // Clock
                                        L"\xf3ed" // Shield
                                        L"\xf003" // Envelope o
                                        L"\xf2b7" // Envelope o open
                                        L"\xf014" // Trash o
                                        L"\xf11d" // Flag o
                                        L"\xf011" // Power Off
                                        L"\xf28c" // Pause circle o
                                        L"\xf29c" // Question circle o
                                        L"\xf0e2" // Undo
                                        L"\xf01e" // Repeat
                                        L"\xf5df" // Car battery
                           );
  m_ImFont->Flags|=ImFontFlags_LockBakedSizes;
  m_ImFont->Scale=1.0f;
  imgui_io.Fonts->TexUvWhitePixel.x=0.0f;
  imgui_io.Fonts->TexUvWhitePixel.y=0.0f;

#else


  unsigned char* pixels;
  int width, height;

  ImFontConfig font_config;
  //font_config.RasterizerDensity=(22.0f/120.0f);
  font_config.SizePixels=font_manager->GetCurrentFontSize();
  m_ImFont=imgui_io.Fonts->AddFontDefault(&font_config);


  std::tuple<unsigned char*,int,int> ret=CreateImGuiSDF(imgui_io,m_ImFont
                                                       ,font_manager,font_config.SizePixels
                                                       ,
                                                        L"\xe1\xe9\xed\xf3\xfa\xb4"
                                                        "abcdefghijklmnopqrstuvwxyz"
                                                        "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
                                                        ",;.:#@!?<>[](){}/&%$_=-+*'~|\\"
                                                        "\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\xA6\xA7\x7f"
                                                        "\xa1\xbf"
                                                        "ñÑ"
                                                        L"\x008a" // Bug
                                                        "©®"
                                                        "\""
                                                        L"¡¿"
                                                        L"\x20ac" // Euro
                                                        L"\x2026" // Horizontal ellipsis
                                                        L"\xfffd" // Unknown char
                                                        L"\xf245" // Mouse Cursor
                                                        L"\xf118" // Smile
                                                        L"\xf14d" // Share Square
                                                        L"\xf1f8" // Trash
                                                        L"\xf01c" // Inbox
                                                        L"\xf0e0" // Envelop
                                                        L"\xf55a" // BackSpace
                                                        L"\xf1bb" // Tree
                                                        L"\xf0f3" // Bell
                                                        L"\xf30a" // Long arrow left
                                                        L"\xf30b" // Long arrow right
                                                        L"\xf7c0" // Satellite dish
                                                        L"\xf085" // Cogs
                                                        L"\xf04d" // Stop
                                                        L"\xf071" // Exclamation triangle
                                                        L"\xf059" // Question circle
                                                        L"\xf084" // Key
                                                        L"\xf5d2" // Atom
                                                        L"\xf044" // Edit
                                                        L"\xf439" // Chess
                                                        L"\xf43c" // Chess board
                                                        L"\xf024" // Flag
                                                        L"\xf017" // Clock
                                                        L"\xf3ed" // Shield
                                                        L"\xf003" // Envelope o
                                                        L"\xf2b7" // Envelope o open
                                                        L"\xf014" // Trash o
                                                        L"\xf11d" // Flag o
                                                        L"\xf011" // Power Off
                                                        L"\xf28c" // Pause circle o
                                                        L"\xf29c" // Question circle o
                                                        L"\xf0e2" // Undo
                                                        L"\xf01e" // Repeat
                                                       );
  pixels=std::get<0>(ret);
  width=std::get<1>(ret);
  height=std::get<2>(ret);

  static const float kImGuiDefFontSize=13.0f;
  m_ImFont->Scale=kImGuiDefFontSize /font_manager->GetCurrentFontSize(); // font1->FontSize size of default font.
  m_ImFont->Scale*=aFontSize;

  m_ImGuiTexture=CreateTexture(*dev,width,height);
  if(!m_ImGuiTexture)
    {
      LOG_PRINT_F("Can not create font texture.");
      Destroy();
      return false;
    }
  m_ImGuiTexture->SetData(width, height,pixels);
  imgui_io.Fonts->TexID = m_ImGuiTexture->GetTextureId();
  imgui_io.Fonts->Flags|=ImFontAtlasFlags_NoBakedLines;

  m_ImGuiTexture->SetName("ComputerPane SDF Font");

#endif

  ImGui::GetStyle().ScrollbarSize*=1.2f;
  if(aColourMode=="light")
    {
      ImGui::StyleColorsLight();
    }
  else if(aColourMode=="dark")
    {
      ImGui::StyleColorsDark();
    }
  else if(aColourMode=="classic")
    {
      ImGui::StyleColorsClassic();
    }

  imgui_io.AddMouseSourceEvent(ImGuiMouseSource_TouchScreen);

  if(m_ComputerPaneAction->UsesImPlot())
    {
      m_ImPlotContext=ImPlot::CreateContext();
    }

  if(prev_context)
    {
      ImGui::SetCurrentContext(prev_context);
    }

  m_DisplayWidth =imgui_io.DisplaySize.x;
  m_DisplayHeight=imgui_io.DisplaySize.y;
#if defined IMGUI_HAS_TEXTURES
  m_ImGuiTexture=ComputerPane::m_CommonImGuiTexture.get();
#endif
  return true;
}

Some notes:

• The m_ variables are class members.
• I do not share the atlas but I do share the texture memory. I use SDF fonts and I know in advance all the chars that I'm going to use so I preload them.
• FontManager is the class I use that has the SDF data.
• m_ImFont is a ImFont* that I use in every step to push/pop the font.
• SetBgColour() sets the texture background color. It would be nice that you allowed to customize this when creating the texture data for the atlas.
• ReserveWhiteSpace() Sets some texture memory for drawing the solid parts of the UI. In previous versions of dear imgui I used that the TexUvWhitePixel was 0,0 but now it changes with the atlas. Is possible to set if fixed to 0,0?
• Preload() preloads all the chars I use in the game. It basically calls ImFontBaked::FindGlyph().

This is the code I use to destroy the ingame UIs:

void ComputerPane::Destroy()
{
  AC_ASSERT_MSG(m_ImGuiContext,"ComputerPane context already destroyed.");

  ImGuiContext* prev_context=ImGui::GetCurrentContext();
  ImGui::SetCurrentContext(m_ImGuiContext);

  if(m_ComputerPaneAction)
    {
      m_ComputerPaneAction->Clear();
      m_ComputerPaneAction.reset();
    }

  if(m_ImPlotContext)
    {
      ImPlot::SetCurrentContext(nullptr);
      ImPlot::DestroyContext(m_ImPlotContext);
      m_ImPlotContext=nullptr;
    }



#if defined IMGUI_HAS_TEXTURES
  //IM_DELETE(m_ImFont); // m_ImFont, destroyed by imgui
  m_ImFont=nullptr;

  m_FontSize=0;
  m_FontManager=nullptr;
#else

  // m_ImFont, destroyed by imgui
  m_ImFont=nullptr;
#endif

  ImGui::SetCurrentContext(prev_context);
  ImGui::DestroyContext(m_ImGuiContext);



#if defined IMGUI_HAS_TEXTURES

  // m_CustomLoader, destroyed by imgui
  //delete m_CustomLoader;
  m_CustomLoader=nullptr;
#endif

  m_ImGuiContext=nullptr;

  DestroyTexture();
  m_ImGuiTexture=nullptr;


  m_ImGuiDrawData=nullptr;

  m_MousePos.SetZero();
  m_MouseDown=false;
  m_Active=false;
  m_Enabled=false;
}

The game crashes after calling this function while destroying the m_Parms member. But if I comment out this member then it crashes in another place. Also the game does not crash if I compile it with the docking branch.

Let me know if you need more information.

Carlos

Screenshots/Video:

Minimal, Complete and Verifiable Example code:

[ocornut]

Sorry this is way too much code, you are not even providing details about the crash. I cannot magically guess what’s wrong without more details.

[ocornut]

Try to craft a minimal standardalone repro that exhibit the problem.

[GamingMinds-DanielC]

In ComputerPane::Create() you have an early out in case of failure where you forgot to restore the previous context. That's probably not the reason for your crash, but still a bug.

As for the unspecified crash: test in a debug build with assertions enabled. The exact location of the crash (or triggered assertion) is important, maybe even including the call stack and values of relevant variables.

[Aarkham]

@GamingMinds-DanielC Thanks for the help. That code was in the part where ImGuiBackendFlags_RendererHasTextures is false, so it could not be the reason for the crash, but a bug is a bug and now is fixed :)

I've solved the issue. The problem was here:

  ImFontConfig empty_font;
  strcpy(empty_font.Name, "cpane");
  empty_font.FontLoader=m_CustomLoader;
  empty_font.SizePixels=m_FontSize;
  imgui_io.Fonts->TexMinWidth=kTextureWidth;
  imgui_io.Fonts->TexMinHeight=kTextureHeight;
  empty_font.FontData=this;  //  <----------   BUG

In the function void ImFontAtlasFontDestroySourceData() imgui frees the field FontData so my class was being freed and the rest of the destructor was handling corrupted data.

Now I have added:

  empty_font.FontData=this;
  empty_font.FontDataSize=sizeof(ComputerPane);
  empty_font.FontDataOwnedByAtlas=false;

And the game can close Ok.

I'm not sure if this is the proper fix, I was doing this because I need to access the class from the callbacks of ImFontLoader. I tried to use the FontLoaderData member but there is an assert that makes sure that is null. I also tried to inherit from ImFontLoader but it did not work. What is the recommended way to do this?