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imgui_markdown

Markdown for Dear ImGui

A permissively licensed markdown single-header library for Dear ImGui.

Requires C++11 or above

imgui_markdown currently supports the following markdown functionality:

• Wrapped text
• Headers H1, H2, H3
• Indented text, multi levels
• Unordered lists and sub-lists
• Links
• Images

Note - the gif above is heavily compressed due to GitHub limitations. There's a (slightly) better version of it on twitter.

Syntax

Wrapping

Text wraps automatically. To add a new line, use 'Return'.

Headers

# H1
## H2
### H3

Lists

Indents

On a new line, at the start of the line, add two spaces per indent.

Normal text
··Indent level 1
····Indent level 2
······Indent level 3
Normal text

Unordered lists

On a new line, at the start of the line, add two spaces, an asterisks and a space. For nested lists, add two additional spaces in front of the asterisk per list level increment.

Normal text
··*·Unordered List level 1
····*·Unordered List level 2
······*·Unordered List level 3
······*·Unordered List level 3
··*·Unordered List level 1
Normal text

Links

[link description](https://...)

Images

![image alt text](image identifier e.g. filename)

Example use on Windows with links opening in a browser

#include "ImGui.h"                // https://github.com/ocornut/imgui
#include "imgui_markdown.h"       // https://github.com/juliettef/imgui_markdown
#include "IconsFontAwesome5.h"    // https://github.com/juliettef/IconFontCppHeaders

// Following includes for Windows LinkCallback
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include "Shellapi.h"
#include <string>

void LinkCallback( ImGui::MarkdownLinkCallbackData data_ );
inline ImGui::MarkdownImageData ImageCallback( ImGui::MarkdownLinkCallbackData data_ );

static ImFont* H1 = NULL;
static ImFont* H2 = NULL;
static ImFont* H3 = NULL;

static ImGui::MarkdownConfig mdConfig; 


void LinkCallback( ImGui::MarkdownLinkCallbackData data_ )
{
    std::string url( data_.link, data_.linkLength );
    if( !data_.isImage )
    {
        ShellExecuteA( NULL, "open", url.c_str(), NULL, NULL, SW_SHOWNORMAL );
    }
}

inline ImGui::MarkdownImageData ImageCallback( ImGui::MarkdownLinkCallbackData data_ )
{
    // In your application you would load an image based on data_ input. Here we just use the imgui font texture.
    ImTextureID image = ImGui::GetIO().Fonts->TexID;
    // > C++14 can use ImGui::MarkdownImageData imageData{ true, false, image, ImVec2( 40.0f, 20.0f ) };
    ImGui::MarkdownImageData imageData;
    imageData.isValid =         true;
    imageData.useLinkCallback = false;
    imageData.user_texture_id = image;
    imageData.size =            ImVec2( 40.0f, 20.0f );

    // For image resize when available size.x > image width, add
    ImVec2 const contentSize = ImGui::GetContentRegionAvail();
    if( imageData.size.x > contentSize.x )
    {
        float const ratio = imageData.size.y/imageData.size.x;
        imageData.size.x = contentSize.x;
        imageData.size.y = contentSize.x*ratio;
    }

    return imageData;
}

void LoadFonts( float fontSize_ = 12.0f )
{
    ImGuiIO& io = ImGui::GetIO();
    io.Fonts->Clear();
    // Base font
    io.Fonts->AddFontFromFileTTF( "myfont.ttf", fontSize_ );
    // Bold headings H2 and H3
    H2 = io.Fonts->AddFontFromFileTTF( "myfont-bold.ttf", fontSize_ );
    H3 = mdConfig.headingFormats[ 1 ].font;
    // bold heading H1
    float fontSizeH1 = fontSize_ * 1.1f;
    H1 = io.Fonts->AddFontFromFileTTF( "myfont-bold.ttf", fontSizeH1 );
}

void ExampleMarkdownFormatCallback( const ImGui::MarkdownFormatInfo& markdownFormatInfo_, bool start_ )
{
    // Call the default first so any settings can be overwritten by our implementation.
    // Alternatively could be called or not called in a switch statement on a case by case basis.
    // See defaultMarkdownFormatCallback definition for furhter examples of how to use it.
    ImGui::defaultMarkdownFormatCallback( markdownFormatInfo_, start_ );        
       
    switch( markdownFormatInfo_.type )
    {
    // example: change the colour of heading level 2
    case ImGui::MarkdownFormatType::HEADING:
    {
        if( markdownFormatInfo_.level == 2 )
        {
            if( start_ )
            {
                ImGui::PushStyleColor( ImGuiCol_Text, ImGui::GetStyle().Colors[ImGuiCol_TextDisabled] );
            }
            else
            {
                ImGui::PopStyleColor();
            }
        }
        break;
    }
    default:
    {
        break;
    }
    }
}

void Markdown( const std::string& markdown_ )
{
    // You can make your own Markdown function with your prefered string container and markdown config.
    // > C++14 can use ImGui::MarkdownConfig mdConfig{ LinkCallback, NULL, ImageCallback, ICON_FA_LINK, { { H1, true }, { H2, true }, { H3, false } }, NULL };
    mdConfig.linkCallback =         LinkCallback;
    mdConfig.tooltipCallback =      NULL;
    mdConfig.imageCallback =        ImageCallback;
    mdConfig.linkIcon =             ICON_FA_LINK;
    mdConfig.headingFormats[0] =    { H1, true };
    mdConfig.headingFormats[1] =    { H2, true };
    mdConfig.headingFormats[2] =    { H3, false };
    mdConfig.userData =             NULL;
    mdConfig.formatCallback =       ExampleMarkdownFormatCallback;
    ImGui::Markdown( markdown_.c_str(), markdown_.length(), mdConfig );
}

void MarkdownExample()
{
    const std::string markdownText = u8R"(
# H1 Header: Text and Links
You can add [links like this one to enkisoftware](https://www.enkisoftware.com/) and lines will wrap well.
## H2 Header: indented text.
  This text has an indent (two leading spaces).
    This one has two.
### H3 Header: Lists
  * Unordered lists
    * Lists can be indented with two extra spaces.
  * Lists can have [links like this one to Avoyd](https://www.avoyd.com/)
)";
    Markdown( markdownText );
}

Projects using imgui_markdown

Avoyd

Avoyd is an abstract 6 degrees of freedom voxel game.
www.avoyd.com

The game and the voxel editor's help and tutorials use imgui_markdown with Dear ImGui.

bgfx

Cross-platform rendering library.
bkaradzic.github.io/bgfx/overview

Imogen

GPU/CPU Texture Generator
skaven.fr/imogen

Light Tracer

Experimental GPU ray tracer for web

Visual 6502 Remix

Transistor level 6502 Hardware Simulation
hfloooh.github.io/visual6502remix

Using imgui_markdown as help viewer for Visual 6502 Remix with internal and external links:

Credits

Design and implementation - Doug Binks - @dougbinks
Implementation and maintenance - Juliette Foucaut - @juliettef
Image resize example code - Soufiane Khiat
Thanks to Omar Cornut for Dear ImGui

License (zlib)

Copyright (c) 2019 Juliette Foucaut and Doug Binks

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.