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

.gitignore

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

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.12)
+project(node_clipping_issue)
+set(CMAKE_CXX_STANDARD 17)
+
+if (NOT IS_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}/external/imgui)
+    message(FATAL_ERROR "Please run ./fetch_external.sh in order to populate external/")
+endif()
+
+##########################################################
+# Add ImGui & HelloImGui
+##########################################################
+# i. HelloImGui will build ImGui as part of its build (and here, we tell it to use our own version in external/imgui)
+set(HELLOIMGUI_IMGUI_SOURCE_DIR "${CMAKE_CURRENT_LIST_DIR}/external/imgui")
+add_subdirectory(external/hello_imgui)
+# ii. HelloImGui provides a function `hello_imgui_add_app` available in order to easily add applications
+list(APPEND CMAKE_MODULE_PATH ${HELLOIMGUI_CMAKE_PATH})
+include(hello_imgui_add_app)
+
+
+##########################################################
+# Add imgui-node-editor
+##########################################################
+set(imgui_node_editor_dir ${CMAKE_CURRENT_LIST_DIR}/external/imgui-node-editor)
+file(GLOB imgui_node_editor_src ${imgui_node_editor_dir}/*.cpp ${imgui_node_editor_dir}/*.h)
+add_library(imgui_node_editor ${imgui_node_editor_src})
+target_include_directories(imgui_node_editor PUBLIC ${imgui_node_editor_dir})
+target_link_libraries(imgui_node_editor PUBLIC imgui)
+
+##########################################################
+# Build your app
+##########################################################
+hello_imgui_add_app(node_clipping_issue node_clipping_issue.cpp)
+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
+
+## Build instructions
+
+```
+./fetch_external.sh
+mkdir build
+cd build
+cmake ..
+make -j
+```
+
+## Code explanation
+
+This code is self-contained in a short file: [node_clipping_issue.cpp](node_clipping_issue.cpp)
+
+It uses HelloImGui in order to simplify the example creation. HelloImGui is based on a quite recent version of the ImGui docking branch.
+
+It was not possible to use the ImGui version inside node editor, since it is outdated, and adds stack layout patches to ImGui which are not trivial to rebase.
+
+## Fixes applied to imgui-node-editor:
+
+#### [remove duplicate ImVec2 operator-](https://github.com/pthom/imgui-node-editor/commit/0da24eb1bbc4355113509ab519d37b1f856660c0)
+(operator- is now provided by imgui)
+
+#### [ed::CreateItemAction::Begin: if (m_CurrentStage == None) => m_InActive = false](https://github.com/pthom/imgui-node-editor/commit/2ba8ca4f3a36ee086950d98b34422c81e550722c)
+(Undo this commit to see the related issue: execution will fail at startup)
+
+Workaround another unrelated issue that is triggered by this example.
+
+#### [Fix #205: workaround clipping issues when link with docked windows](https://github.com/pthom/imgui-node-editor/commit/2265a4bad141a07478292186eb282c85a4bb6991)
+(Undo this commit to see the issue: clipping issues will appear when creating links)
+
+This is a workaround for
+https://github.com/thedmd/imgui-node-editor/issues/205
+https://github.com/pthom/imgui_bundle/issues/117
+Adding a simple pixel at m_WidgetRect.Max is enough to bypass the issue.
+
+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 "$0")
+echo THIS_DIR=$THIS_DIR
+mkdir -p external
+cd $THIS_DIR/external
+
+git clone -b docking https://github.com/ocornut/imgui.git
+git clone -b master https://github.com/pthom/hello_imgui.git
+
+# Clone imgui-node-editor
+#git clone -b develop https://github.com/thedmd/imgui-node-editor.git        # official version
+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"
+#include "imgui_node_editor.h"
+#include "hello_imgui/hello_imgui.h"
+
+namespace ed = ax::NodeEditor;
+
+// A simple utility to get reproducible ids at each frame
+struct IdCounter
+{
+    int _next_id = 0;
+    int id()
+    {
+        _next_id++;
+        return _next_id;
+    }
+    void reset(){
+        _next_id = 0;
+    }
+};
+
+
+// this is the main Gui function: it draws two nodes and enables to initiate a link
+void gui()
+{
+    static IdCounter next_id;
+    static IdCounter next_link_id;
+    next_id.reset();
+    next_link_id.reset();
+
+    ImGui::SetNextWindowSize(ImVec2(0.0f, 0.0f));
+    ed::Begin("My Editor");
+
+    ed::BeginNode(next_id.id());
+    ImGui::Text("Node 1");
+    ed::BeginPin(next_id.id(), ed::PinKind::Output);
+    ImGui::Text("Out ->");
+    ed::EndPin();
+    ed::EndNode();
+
+    ed::BeginNode(next_id.id());
+    ImGui::Text("Node 2");
+    ed::BeginPin(next_id.id(), ed::PinKind::Input);
+    ImGui::Text("-> In");
+    ed::EndPin();
+    ed::EndNode();
+
+    if (ed::BeginCreate()) 
+    {
+        ed::PinId input_pin_id;
+        ed::PinId output_pin_id;
+        if (ed::QueryNewLink(&input_pin_id, &output_pin_id)) 
+        {
+            if (ed::AcceptNewItem())
+                ed::Link(next_link_id.id(), input_pin_id, output_pin_id);
+        }
+        ed::EndCreate();
+    }
+
+    ed::End();
+}
+
+
+int main(int, char**)
+{
+    // Prepare the node editor context 
+    ed::Config gNodeEditorConfig;
+    ed::EditorContext *gNodeEditorContext = ed::CreateEditor(&gNodeEditorConfig);
+    ed::SetCurrentEditor(gNodeEditorContext);
+
+    // We use HelloImGui, with a DockSpace (since the issue will occur with dockable windows)
+    HelloImGui::RunnerParams runner_params;
+    runner_params.imGuiWindowParams.defaultImGuiWindowType = HelloImGui::DefaultImGuiWindowType::ProvideFullScreenDockSpace;
+    // runner_params.imGuiWindowParams.enableViewports = true;
+
+    // We create a dockable window in HelloImGui
+    HelloImGui::DockableWindow dockableWindow;
+    {
+        dockableWindow.GuiFunction = gui;
+        dockableWindow.label = "graph";
+        dockableWindow.dockSpaceName = "MainDockSpace";
+    }
+    runner_params.dockingParams.dockableWindows = { dockableWindow };
+
+    // Run the app
+    HelloImGui::Run(runner_params);
+
+    // Destroy node editor context
+    ed::DestroyEditor(gNodeEditorContext);
+
+    return 0;
+}