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Example code for reproducing thedmd/imgui-node-editor#205 
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‎.gitignore

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build/
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cmake-build-*/
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external/*
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.idea/

‎CMakeLists.txt

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cmake_minimum_required(VERSION 3.12)
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project(node_clipping_issue)
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set(CMAKE_CXX_STANDARD 17)
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if (NOT IS_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}/external/imgui)
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message(FATAL_ERROR "Please run ./fetch_external.sh in order to populate external/")
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endif()
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##########################################################
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# Add ImGui & HelloImGui
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##########################################################
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# i. HelloImGui will build ImGui as part of its build (and here, we tell it to use our own version in external/imgui)
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set(HELLOIMGUI_IMGUI_SOURCE_DIR "${CMAKE_CURRENT_LIST_DIR}/external/imgui")
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add_subdirectory(external/hello_imgui)
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# ii. HelloImGui provides a function `hello_imgui_add_app` available in order to easily add applications
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list(APPEND CMAKE_MODULE_PATH ${HELLOIMGUI_CMAKE_PATH})
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include(hello_imgui_add_app)
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##########################################################
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# Add imgui-node-editor
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##########################################################
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set(imgui_node_editor_dir ${CMAKE_CURRENT_LIST_DIR}/external/imgui-node-editor)
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file(GLOB imgui_node_editor_src ${imgui_node_editor_dir}/*.cpp ${imgui_node_editor_dir}/*.h)
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add_library(imgui_node_editor ${imgui_node_editor_src})
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target_include_directories(imgui_node_editor PUBLIC ${imgui_node_editor_dir})
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target_link_libraries(imgui_node_editor PUBLIC imgui)
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##########################################################
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# Build your app
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##########################################################
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hello_imgui_add_app(node_clipping_issue node_clipping_issue.cpp)
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target_link_libraries(node_clipping_issue PRIVATE imgui_node_editor)

‎Readme.md

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# Example code for reproducing https://github.com/thedmd/imgui-node-editor/issues/205
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## Build instructions
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```
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./fetch_external.sh
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mkdir build
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cd build
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cmake ..
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make -j
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```
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## Code explanation
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This code is self-contained in a short file: [node_clipping_issue.cpp](node_clipping_issue.cpp)
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It uses HelloImGui in order to simplify the example creation. HelloImGui is based on a quite recent version of the ImGui docking branch.
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It was not possible to use the ImGui version inside node editor, since it is outdated, and adds stack layout patches to ImGui which are not trivial to rebase.
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## Fixes applied to imgui-node-editor (based on the develop branch)
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#### [remove duplicate ImVec2 operator-](https://github.com/pthom/imgui-node-editor/commit/0da24eb1bbc4355113509ab519d37b1f856660c0)
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(operator- is now provided by imgui)
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#### [ed::CreateItemAction::Begin: if (m_CurrentStage == None) => m_InActive = false](https://github.com/pthom/imgui-node-editor/commit/2ba8ca4f3a36ee086950d98b34422c81e550722c)
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(Undo this commit to see the related issue: execution will fail at startup)
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Workaround another unrelated issue that is triggered by this example.
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#### [Fix #205: workaround clipping issues when link with docked windows](https://github.com/pthom/imgui-node-editor/commit/2265a4bad141a07478292186eb282c85a4bb6991)
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(Undo this commit to see the issue: clipping issues will appear when creating links)
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This is a workaround for
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https://github.com/thedmd/imgui-node-editor/issues/205
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https://github.com/pthom/imgui_bundle/issues/117
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Adding a simple pixel at m_WidgetRect.Max is enough to bypass the issue.
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This is not a real fix, since it merely adds a fake pixel at (xmax, ymax), so that the app knows where the clipping should end. A better solution would be required.

‎fetch_external.sh

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THIS_DIR=$(dirname "$0")
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echo THIS_DIR=$THIS_DIR
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mkdir -p external
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cd $THIS_DIR/external
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git clone -b docking https://github.com/ocornut/imgui.git
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git clone -b master https://github.com/pthom/hello_imgui.git
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# Clone imgui-node-editor
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#git clone -b develop https://github.com/thedmd/imgui-node-editor.git # official version
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git clone -b fix_win_clipping https://github.com/pthom/imgui-node-editor.git # fork with fixes + workaround

‎node_clipping_issue.cpp

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#include "imgui.h"
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#include "imgui_node_editor.h"
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#include "hello_imgui/hello_imgui.h"
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namespace ed = ax::NodeEditor;
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// A simple utility to get reproducible ids at each frame
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struct IdCounter
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{
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int _next_id = 0;
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int id()
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{
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_next_id++;
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return _next_id;
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}
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void reset(){
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_next_id = 0;
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}
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};
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// this is the main Gui function: it draws two nodes and enables to initiate a link
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void gui()
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{
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static IdCounter next_id;
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static IdCounter next_link_id;
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next_id.reset();
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next_link_id.reset();
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ImGui::SetNextWindowSize(ImVec2(0.0f, 0.0f));
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ed::Begin("My Editor");
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ed::BeginNode(next_id.id());
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ImGui::Text("Node 1");
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ed::BeginPin(next_id.id(), ed::PinKind::Output);
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ImGui::Text("Out ->");
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ed::EndPin();
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ed::EndNode();
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ed::BeginNode(next_id.id());
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ImGui::Text("Node 2");
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ed::BeginPin(next_id.id(), ed::PinKind::Input);
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ImGui::Text("-> In");
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ed::EndPin();
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ed::EndNode();
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if (ed::BeginCreate())
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{
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ed::PinId input_pin_id;
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ed::PinId output_pin_id;
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if (ed::QueryNewLink(&input_pin_id, &output_pin_id))
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{
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if (ed::AcceptNewItem())
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ed::Link(next_link_id.id(), input_pin_id, output_pin_id);
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}
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ed::EndCreate();
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}
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ed::End();
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}
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int main(int, char**)
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{
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// Prepare the node editor context
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ed::Config gNodeEditorConfig;
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ed::EditorContext *gNodeEditorContext = ed::CreateEditor(&gNodeEditorConfig);
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ed::SetCurrentEditor(gNodeEditorContext);
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// We use HelloImGui, with a DockSpace (since the issue will occur with dockable windows)
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HelloImGui::RunnerParams runner_params;
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runner_params.imGuiWindowParams.defaultImGuiWindowType = HelloImGui::DefaultImGuiWindowType::ProvideFullScreenDockSpace;
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// runner_params.imGuiWindowParams.enableViewports = true;
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// We create a dockable window in HelloImGui
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HelloImGui::DockableWindow dockableWindow;
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{
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dockableWindow.GuiFunction = gui;
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dockableWindow.label = "graph";
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dockableWindow.dockSpaceName = "MainDockSpace";
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}
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runner_params.dockingParams.dockableWindows = { dockableWindow };
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// Run the app
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HelloImGui::Run(runner_params);
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// Destroy node editor context
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ed::DestroyEditor(gNodeEditorContext);
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return 0;
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}

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