[API] Add a mechanism for Dear ImGui assertion callbacks (#100)

* Syncing wip to github

* Assertion callback works

* Restore example that does not crash

* Add comment in build script. Merge with upstream.

* Fix assert always triggering

* Resolve jvm env at runtime to prevent looking up bad stack address

* Fixed EXCEPTION_ACCESS_VIOLATION within native code after callback was complete.

* Fix linting errors

* Change ImGui to Dear ImGui

Co-authored-by: SpaiR <klimbetoo@gmail.com>

* Move jvm native layer to its own header/source

Co-authored-by: SpaiR <klimbetoo@gmail.com>

buildSrc/src/main/groovy/tool/generator/GenerateLibs.groovy

@@ -4,6 +4,7 @@ import com.badlogic.gdx.jnigen.*
 import groovy.transform.CompileStatic
 import org.gradle.api.DefaultTask
 import org.gradle.api.file.CopySpec
+import org.gradle.api.file.DuplicatesStrategy
 import org.gradle.api.tasks.Internal
 import org.gradle.api.tasks.TaskAction
 
@@ -53,6 +54,13 @@ class GenerateLibs extends DefaultTask {
             }
             spec.from(project.rootProject.file('imgui-binding/src/main/native'))
             spec.into(jniDir)
+            spec.duplicatesStrategy = DuplicatesStrategy.INCLUDE //Allows for duplicate imconfig.h, we ensure the correct one is copied below
+        }
+
+        //Ensure we overwrite imconfig.h with our own
+        project.copy { CopySpec spec ->
+            spec.from(project.rootProject.file('imgui-binding/src/main/native/imconfig.h'))
+            spec.into(jniDir)
         }
 
         //Copy dirent for ImGuiFileDialog

imgui-binding/src/main/java/imgui/ImGui.java

@@ -1,5 +1,6 @@
 package imgui;
 
+import imgui.assertion.ImAssertCallback;
 import imgui.flag.ImGuiCond;
 import imgui.flag.ImGuiDragDropFlags;
 import imgui.flag.ImGuiInputTextFlags;
@@ -76,6 +77,14 @@ public class ImGui {
         ImFontAtlas.nInit();
         ImGuiPlatformIO.init();
         nInitInputTextData();
+        setAssertCallback(new ImAssertCallback() {
+            @Override
+            public void imAssertCallback(String assertion, int line, String file) {
+                System.err.println("Dear ImGui Assertion Failed: " + assertion);
+                System.err.println("Assertion Located At: " + file + ":" + line);
+                Thread.dumpStack();
+            }
+        });
     }
 
     private static String resolveFullLibName() {
@@ -131,7 +140,9 @@ public class ImGui {
      */
 
     private static native void nInitJni(); /*
+        Jni::InitJvm(env);
         Jni::InitCommon(env);
+        Jni::InitAssertion(env);
         Jni::InitCallbacks(env);
         Jni::InitBindingStruct(env);
     */
@@ -190,6 +201,17 @@ public class ImGui {
         ImGui::SetCurrentContext((ImGuiContext*) ptr);
     */
 
+    /**
+     * Set a custom assertion callback for ImGui assertions.
+     * Take note: Any custom assertion callback SHOULD NOT throw any exception.
+     * After any callback the application will be terminated, any attempt to bypass this behavior
+     * will result in a EXCEPTION_ACCESS_VIOLATION from within the native layer.
+     * @param callback The custom ImGui assertion callback
+     */
+    public static native void setAssertCallback(ImAssertCallback callback); /*
+        Jni::SetAssertionCallback(callback);
+    */
+
     // Main
 
     /**

imgui-binding/src/main/java/imgui/assertion/ImAssertCallback.java

@@ -0,0 +1,45 @@
+
+package imgui.assertion;
+
+/**
+ * Callback for native IM_ASSERT calls.
+ */
+public abstract class ImAssertCallback {
+    /**
+     * Called from native code to bring the callback into java side.
+     * Will force the application to terminate with exit code 1 after forwarding the callback, this is required, otherwise
+     * if execution is returned to the native layer, a EXCEPTION_ACCESS_VIOLATION will be thrown.
+     * If the callback throws an exception, it will be caught and printed along with a warning to prevent execution
+     * from returning to the native layer.
+     *
+     * @param assertion The assertion string
+     * @param line      The line number of the assertion in the source file
+     * @param file      The source file where the assertion occurred
+     */
+    public void imAssert(final String assertion, final int line, final String file) {
+        try {
+            imAssertCallback(assertion, line, file);
+        } catch (Exception ex) {
+            System.err.println("WARNING: Exception thrown in Dear ImGui Assertion Callback!");
+            System.err.println("Dear ImGui Assertion Failed: " + assertion);
+            System.err.println("Assertion Located At: " + file + ":" + line);
+            ex.printStackTrace();
+        }
+        System.exit(1);
+    }
+
+    /**
+     * The assertion callback from ImGui.
+     * Do not throw an exception within this callback, to prevent
+     * execution from returned to the native layer and cause a EXCEPTION_ACCESS_VIOLATION,
+     * the callback will catch any exceptions and print a warning.
+     * <p>
+     * There is no way to catch the assertion and continue execution.
+     * You may however call <code>System.exit(code)</code> with your own exit code.
+     *
+     * @param assertion The assertion string
+     * @param line      The line number of the assertion in the source file
+     * @param file      The source file where the assertion occurred
+     */
+    public abstract void imAssertCallback(String assertion, int line, String file);
+}

imgui-binding/src/main/native/_binding.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "jni_jvm.h"
 #include "jni_common.h"
 #include "jni_callbacks.h"
 #include "jni_binding_struct.h"
+#include "jni_assertion.h"

imgui-binding/src/main/native/_imnodes.h

@@ -1,5 +1,4 @@
 #pragma once
 
-#include "_base.h"
+#include "_common.h"
 #include <imnodes.h>
-#include "_binding.h"

imgui-binding/src/main/native/_implot.h

@@ -1,6 +1,5 @@
 #pragma once
 
-#include "_base.h"
-#include "_binding.h"
+#include "_common.h"
 #include <imgui_internal.h>
 #include "implot.h"

imgui-binding/src/main/native/_nodeeditor.h

@@ -1,9 +1,5 @@
 #pragma once
 
-#include <stdint.h>
-#include <imgui.h>
+#include "_common.h"
 #include <imgui_node_editor.h>
 #include <imgui_node_editor_internal.h>
-#include "jni_common.h"
-#include "jni_callbacks.h"
-#include "jni_binding_struct.h"

imgui-binding/src/main/native/_texteditor.h

@@ -8,6 +8,5 @@
 #include <unordered_map>
 #include <map>
 #include <regex>
-#include "_base.h"
-#include "_binding.h"
+#include "_common.h"
 #include "TextEditor.h"

imgui-binding/src/main/native/imconfig.h

@@ -0,0 +1,125 @@
+//-----------------------------------------------------------------------------
+// COMPILE-TIME OPTIONS FOR DEAR IMGUI
+// Runtime options (clipboard callbacks, enabling various features, etc.) can generally be set via the ImGuiIO structure.
+// You can use ImGui::SetAllocatorFunctions() before calling ImGui::CreateContext() to rewire memory allocation functions.
+//-----------------------------------------------------------------------------
+// A) You may edit imconfig.h (and not overwrite it when updating Dear ImGui, or maintain a patch/rebased branch with your modifications to it)
+// B) or '#define IMGUI_USER_CONFIG "my_imgui_config.h"' in your project and then add directives in your own file without touching this template.
+//-----------------------------------------------------------------------------
+// You need to make sure that configuration settings are defined consistently _everywhere_ Dear ImGui is used, which include the imgui*.cpp
+// files but also _any_ of your code that uses Dear ImGui. This is because some compile-time options have an affect on data structures.
+// Defining those options in imconfig.h will ensure every compilation unit gets to see the same data structure layouts.
+// Call IMGUI_CHECKVERSION() from your .cpp files to verify that the data structures your files are using are matching the ones imgui.cpp is using.
+//-----------------------------------------------------------------------------
+
+#pragma once
+#include "jni_assertion.h"
+
+//---- Define assertion handler. Defaults to calling assert().
+// If your macro uses multiple statements, make sure is enclosed in a 'do { .. } while (0)' block so it can be used as a single statement.
+//#define IM_ASSERT(_EXPR)  MyAssert(_EXPR)
+//#define IM_ASSERT(_EXPR)  ((void)(_EXPR))     // Disable asserts
+#define IM_ASSERT(_EXPR)  do { if (!(_EXPR)) { if (Jni::ImAssertionSet()) { Jni::ImAssertToCallback(#_EXPR, __LINE__, __FILE__); } else { assert(_EXPR); } } } while (0)
+
+//---- Define attributes of all API symbols declarations, e.g. for DLL under Windows
+// Using Dear ImGui via a shared library is not recommended, because of function call overhead and because we don't guarantee backward nor forward ABI compatibility.
+// DLL users: heaps and globals are not shared across DLL boundaries! You will need to call SetCurrentContext() + SetAllocatorFunctions()
+// for each static/DLL boundary you are calling from. Read "Context and Memory Allocators" section of imgui.cpp for more details.
+//#define IMGUI_API __declspec( dllexport )
+//#define IMGUI_API __declspec( dllimport )
+
+//---- Don't define obsolete functions/enums/behaviors. Consider enabling from time to time after updating to avoid using soon-to-be obsolete function/names.
+//#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+
+//---- Disable all of Dear ImGui or don't implement standard windows.
+// It is very strongly recommended to NOT disable the demo windows during development. Please read comments in imgui_demo.cpp.
+//#define IMGUI_DISABLE                                     // Disable everything: all headers and source files will be empty.
+//#define IMGUI_DISABLE_DEMO_WINDOWS                        // Disable demo windows: ShowDemoWindow()/ShowStyleEditor() will be empty. Not recommended.
+//#define IMGUI_DISABLE_METRICS_WINDOW                      // Disable metrics/debugger and other debug tools: ShowMetricsWindow() and ShowStackToolWindow() will be empty.
+
+//---- Don't implement some functions to reduce linkage requirements.
+//#define IMGUI_DISABLE_WIN32_DEFAULT_CLIPBOARD_FUNCTIONS   // [Win32] Don't implement default clipboard handler. Won't use and link with OpenClipboard/GetClipboardData/CloseClipboard etc. (user32.lib/.a, kernel32.lib/.a)
+//#define IMGUI_ENABLE_WIN32_DEFAULT_IME_FUNCTIONS          // [Win32] [Default with Visual Studio] Implement default IME handler (require imm32.lib/.a, auto-link for Visual Studio, -limm32 on command-line for MinGW)
+//#define IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCTIONS         // [Win32] [Default with non-Visual Studio compilers] Don't implement default IME handler (won't require imm32.lib/.a)
+//#define IMGUI_DISABLE_WIN32_FUNCTIONS                     // [Win32] Won't use and link with any Win32 function (clipboard, ime).
+//#define IMGUI_ENABLE_OSX_DEFAULT_CLIPBOARD_FUNCTIONS      // [OSX] Implement default OSX clipboard handler (need to link with '-framework ApplicationServices', this is why this is not the default).
+//#define IMGUI_DISABLE_DEFAULT_FORMAT_FUNCTIONS            // Don't implement ImFormatString/ImFormatStringV so you can implement them yourself (e.g. if you don't want to link with vsnprintf)
+//#define IMGUI_DISABLE_DEFAULT_MATH_FUNCTIONS              // Don't implement ImFabs/ImSqrt/ImPow/ImFmod/ImCos/ImSin/ImAcos/ImAtan2 so you can implement them yourself.
+//#define IMGUI_DISABLE_FILE_FUNCTIONS                      // Don't implement ImFileOpen/ImFileClose/ImFileRead/ImFileWrite and ImFileHandle at all (replace them with dummies)
+//#define IMGUI_DISABLE_DEFAULT_FILE_FUNCTIONS              // Don't implement ImFileOpen/ImFileClose/ImFileRead/ImFileWrite and ImFileHandle so you can implement them yourself if you don't want to link with fopen/fclose/fread/fwrite. This will also disable the LogToTTY() function.
+//#define IMGUI_DISABLE_DEFAULT_ALLOCATORS                  // Don't implement default allocators calling malloc()/free() to avoid linking with them. You will need to call ImGui::SetAllocatorFunctions().
+//#define IMGUI_DISABLE_SSE                                 // Disable use of SSE intrinsics even if available
+
+//---- Include imgui_user.h at the end of imgui.h as a convenience
+//#define IMGUI_INCLUDE_IMGUI_USER_H
+
+//---- Pack colors to BGRA8 instead of RGBA8 (to avoid converting from one to another)
+//#define IMGUI_USE_BGRA_PACKED_COLOR
+
+//---- Use 32-bit for ImWchar (default is 16-bit) to support unicode planes 1-16. (e.g. point beyond 0xFFFF like emoticons, dingbats, symbols, shapes, ancient languages, etc...)
+//#define IMGUI_USE_WCHAR32
+
+//---- Avoid multiple STB libraries implementations, or redefine path/filenames to prioritize another version
+// By default the embedded implementations are declared static and not available outside of Dear ImGui sources files.
+//#define IMGUI_STB_TRUETYPE_FILENAME   "my_folder/stb_truetype.h"
+//#define IMGUI_STB_RECT_PACK_FILENAME  "my_folder/stb_rect_pack.h"
+//#define IMGUI_DISABLE_STB_TRUETYPE_IMPLEMENTATION
+//#define IMGUI_DISABLE_STB_RECT_PACK_IMPLEMENTATION
+
+//---- Use stb_printf's faster implementation of vsnprintf instead of the one from libc (unless IMGUI_DISABLE_DEFAULT_FORMAT_FUNCTIONS is defined)
+// Requires 'stb_sprintf.h' to be available in the include path. Compatibility checks of arguments and formats done by clang and GCC will be disabled in order to support the extra formats provided by STB sprintf.
+// #define IMGUI_USE_STB_SPRINTF
+
+//---- Use FreeType to build and rasterize the font atlas (instead of stb_truetype which is embedded by default in Dear ImGui)
+// Requires FreeType headers to be available in the include path. Requires program to be compiled with 'misc/freetype/imgui_freetype.cpp' (in this repository) + the FreeType library (not provided).
+// On Windows you may use vcpkg with 'vcpkg install freetype --triplet=x64-windows' + 'vcpkg integrate install'.
+//#define IMGUI_ENABLE_FREETYPE
+
+//---- Use stb_truetype to build and rasterize the font atlas (default)
+// The only purpose of this define is if you want force compilation of the stb_truetype backend ALONG with the FreeType backend.
+//#define IMGUI_ENABLE_STB_TRUETYPE
+
+//---- Define constructor and implicit cast operators to convert back<>forth between your math types and ImVec2/ImVec4.
+// This will be inlined as part of ImVec2 and ImVec4 class declarations.
+/*
+#define IM_VEC2_CLASS_EXTRA                                                 \
+        ImVec2(const MyVec2& f) { x = f.x; y = f.y; }                       \
+        operator MyVec2() const { return MyVec2(x,y); }
+
+#define IM_VEC4_CLASS_EXTRA                                                 \
+        ImVec4(const MyVec4& f) { x = f.x; y = f.y; z = f.z; w = f.w; }     \
+        operator MyVec4() const { return MyVec4(x,y,z,w); }
+*/
+
+//---- Use 32-bit vertex indices (default is 16-bit) is one way to allow large meshes with more than 64K vertices.
+// Your renderer backend will need to support it (most example renderer backends support both 16/32-bit indices).
+// Another way to allow large meshes while keeping 16-bit indices is to handle ImDrawCmd::VtxOffset in your renderer.
+// Read about ImGuiBackendFlags_RendererHasVtxOffset for details.
+//#define ImDrawIdx unsigned int
+
+//---- Override ImDrawCallback signature (will need to modify renderer backends accordingly)
+//struct ImDrawList;
+//struct ImDrawCmd;
+//typedef void (*MyImDrawCallback)(const ImDrawList* draw_list, const ImDrawCmd* cmd, void* my_renderer_user_data);
+//#define ImDrawCallback MyImDrawCallback
+
+//---- Debug Tools: Macro to break in Debugger
+// (use 'Metrics->Tools->Item Picker' to pick widgets with the mouse and break into them for easy debugging.)
+//#define IM_DEBUG_BREAK  IM_ASSERT(0)
+//#define IM_DEBUG_BREAK  __debugbreak()
+
+//---- Debug Tools: Have the Item Picker break in the ItemAdd() function instead of ItemHoverable(),
+// (which comes earlier in the code, will catch a few extra items, allow picking items other than Hovered one.)
+// This adds a small runtime cost which is why it is not enabled by default.
+//#define IMGUI_DEBUG_TOOL_ITEM_PICKER_EX
+
+//---- Debug Tools: Enable slower asserts
+//#define IMGUI_DEBUG_PARANOID
+
+//---- Tip: You can add extra functions within the ImGui:: namespace, here or in your own headers files.
+/*
+namespace ImGui
+{
+    void MyFunction(const char* name, const MyMatrix44& v);
+}
+*/

imgui-binding/src/main/native/jni_assertion.cpp

@@ -0,0 +1,37 @@
+#include "jni_assertion.h"
+
+jmethodID jImAssertCallbackMID = NULL;
+jobject jImAssertCallbackInstance = NULL;
+
+namespace Jni
+{    
+    void InitAssertion(JNIEnv* env) {      
+        jclass jImAssertCallback = env->FindClass("imgui/assertion/ImAssertCallback");
+        jImAssertCallbackMID = env->GetMethodID(jImAssertCallback, "imAssert", "(Ljava/lang/String;ILjava/lang/String;)V");
+    }
+    
+    void SetAssertionCallback(jobject func) {
+        JNIEnv* env = Jni::GetEnv();
+        if (jImAssertCallbackInstance != NULL) {
+            env->DeleteGlobalRef(jImAssertCallbackInstance);
+        }
+        if (func != NULL) {
+            jImAssertCallbackInstance = env->NewGlobalRef(func);
+        } else {
+            jImAssertCallbackInstance = NULL;   
+        }
+    }
+        
+    void ImAssertToCallback(const char* assertion, int line, const char* file) {
+        JNIEnv* env = Jni::GetEnv();
+        assert(jImAssertCallbackMID != NULL);
+        assert(assertion != NULL);
+        if (jImAssertCallbackInstance != NULL) {
+            env->CallVoidMethod(jImAssertCallbackInstance, jImAssertCallbackMID, env->NewStringUTF(assertion), line, env->NewStringUTF(file));
+        }
+    }
+    
+    bool ImAssertionSet() {
+        return jImAssertCallbackInstance != NULL;
+    }
+}

imgui-binding/src/main/native/jni_assertion.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "jni_jvm.h"
+#include <assert.h>
+
+namespace Jni
+{
+    void InitAssertion(JNIEnv* env);
+    
+    void SetAssertionCallback(jobject func);
+    
+    void ImAssertToCallback(const char* assertion, int line, const char* file);
+    
+    bool ImAssertionSet();
+}

imgui-binding/src/main/native/jni_common.cpp

@@ -8,13 +8,9 @@ jfieldID imVec4YID;
 jfieldID imVec4ZID;
 jfieldID imVec4WID;
 
-static JavaVM* jvm;
-
 namespace Jni
 {
     void InitCommon(JNIEnv* env) {
-        env->GetJavaVM(&jvm);
-
         jclass jImVec2Class = env->FindClass("imgui/ImVec2");
         imVec2XID = env->GetFieldID(jImVec2Class, "x", "F");
         imVec2YID = env->GetFieldID(jImVec2Class, "y", "F");
@@ -26,13 +22,6 @@ namespace Jni
         imVec4WID = env->GetFieldID(jImVec4Class, "w", "F");
     }
 
-    JNIEnv* GetEnv() {
-        JNIEnv* env;
-        jint res = jvm->GetEnv((void**)(&env), JNI_VERSION_1_8);
-        assert(res == JNI_OK);
-        return env;
-    }
-
     void ImVec2Cpy(JNIEnv* env, ImVec2* src, jobject dst) {
         env->SetFloatField(dst, imVec2XID, src->x);
         env->SetFloatField(dst, imVec2YID, src->y);

imgui-binding/src/main/native/jni_common.h

@@ -7,8 +7,6 @@ namespace Jni
 {
     void InitCommon(JNIEnv* env);
 
-    JNIEnv* GetEnv();
-
     void ImVec2Cpy(JNIEnv* env, ImVec2* src, jobject dst);
     void ImVec2Cpy(JNIEnv* env, ImVec2 src, jobject dst);
 

imgui-binding/src/main/native/jni_jvm.cpp

@@ -0,0 +1,17 @@
+#include "jni_jvm.h"
+
+static JavaVM* jvm;
+
+namespace Jni
+{
+    void InitJvm(JNIEnv* env) {
+        env->GetJavaVM(&jvm);
+    }
+
+    JNIEnv* GetEnv() {
+        JNIEnv* env;
+        jint res = jvm->GetEnv((void**)(&env), JNI_VERSION_1_8);
+        assert(res == JNI_OK);
+        return env;
+    }
+}

imgui-binding/src/main/native/jni_jvm.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <jni.h>
+#include <assert.h>
+
+namespace Jni
+{
+    void InitJvm(JNIEnv* env);
+
+    JNIEnv* GetEnv();
+}