Add basic support of Java<->Native callbacks

Implement them for ImGuiIO::GetClipboardTextFn and ImGuiIO::SetClipboardTextFn

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

@@ -18,7 +18,7 @@ public final class ImGui {
 
     static {
         System.loadLibrary(System.getProperty(LIB_NAME_PROP, LIB_NAME_DEFAULT));
-        initJniCommon();
+        initJni();
         ImDrawList.nInit();
         ImDrawData.nInit();
         nInitInputTextData();
@@ -31,10 +31,12 @@ public final class ImGui {
         #include <stdint.h>
         #include <imgui.h>
         #include "jni_common.h"
+        #include "jni_callbacks.h"
      */
 
-    private static native void initJniCommon(); /*
+    private static native void initJni(); /*
         Jni::InitCommon(env);
+        Jni::InitCallbacks(env);
     */
 
     // Context creation and access

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

@@ -1,5 +1,8 @@
 package imgui;
 
+import imgui.callbacks.ImStrConsumer;
+import imgui.callbacks.ImStrSupplier;
+
 /**
  * Communicate most settings and inputs/outputs to Dear ImGui using this structure.
  * Access via ImGui::GetIO(). Read 'Programmer guide' section in .cpp file for general usage.
@@ -11,6 +14,7 @@ public final class ImGuiIO {
     /*JNI
         #include <imgui.h>
         #include "jni_common.h"
+        #include "jni_callbacks.h"
      */
 
     //------------------------------------------------------------------
@@ -253,7 +257,41 @@ public final class ImGuiIO {
         ImGui::GetIO().BackendRendererName = obj_backendRendererName == NULL ? NULL : (char*)env->GetStringUTFChars(obj_backendRendererName, JNI_FALSE);
     */
 
-    // TODO clipboard callback
+    // Optional: Access OS clipboard
+    // (default to use native Win32 clipboard on Windows, otherwise uses a private clipboard. Override to access OS clipboard on other architectures)
+
+    /*JNI
+        jobject _setClipboardTextCallback = nullptr;
+        jobject _getClipboardTextCallback = nullptr;
+
+        void setClipboardTextStub(void* userData, const char* text) {
+            Jni::CallImStrConsumer(Jni::GetEnv(), _setClipboardTextCallback, text);
+        }
+
+        const char* getClipboardTextStub(void* user_data) {
+            JNIEnv* env = Jni::GetEnv();
+            jstring jstr = Jni::CallImStrSupplier(env, _getClipboardTextCallback);
+            return env->GetStringUTFChars(jstr, 0);
+        }
+     */
+
+    public native void setSetClipboardTextFn(ImStrConsumer setClipboardTextCallback); /*
+        if (_setClipboardTextCallback != nullptr) {
+            env->DeleteGlobalRef(_setClipboardTextCallback);
+        }
+
+        _setClipboardTextCallback = env->NewGlobalRef(setClipboardTextCallback);
+        ImGui::GetIO().SetClipboardTextFn = setClipboardTextStub;
+    */
+
+    public native void setGetClipboardTextFn(ImStrSupplier getClipboardTextCallback); /*
+        if (_getClipboardTextCallback != nullptr) {
+            env->DeleteGlobalRef(_getClipboardTextCallback);
+        }
+
+        _getClipboardTextCallback = env->NewGlobalRef(getClipboardTextCallback);
+        ImGui::GetIO().GetClipboardTextFn = getClipboardTextStub;
+    */
 
     //------------------------------------------------------------------
     // Input - Fill before calling NewFrame()

imgui-binding/src/main/java/imgui/callbacks/ImStrConsumer.java

@@ -0,0 +1,11 @@
+package imgui.callbacks;
+
+import java.util.function.Consumer;
+
+/**
+ * Callback to supply Java string form native code.
+ */
+public abstract class ImStrConsumer implements Consumer<String> {
+    @Override
+    public abstract void accept(String str);
+}

imgui-binding/src/main/java/imgui/callbacks/ImStrSupplier.java

@@ -0,0 +1,11 @@
+package imgui.callbacks;
+
+import java.util.function.Supplier;
+
+/**
+ * Callback to get Java string from native code.
+ */
+public abstract class ImStrSupplier implements Supplier<String> {
+    @Override
+    public abstract String get();
+}

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

@@ -0,0 +1,23 @@
+#include "jni_callbacks.h"
+
+jmethodID jImStrConsumerAcceptMID;
+jmethodID jImStrSupplierGetMID;
+
+namespace Jni
+{
+void InitCallbacks(JNIEnv* env) {
+    jclass jImStrConsumer = env->FindClass("imgui/callbacks/ImStrConsumer");
+    jImStrConsumerAcceptMID = env->GetMethodID(jImStrConsumer, "accept", "(Ljava/lang/String;)V");
+
+    jclass jImStrSupplier = env->FindClass("imgui/callbacks/ImStrSupplier");
+    jImStrSupplierGetMID = env->GetMethodID(jImStrSupplier, "get", "()Ljava/lang/String;");
+}
+
+void CallImStrConsumer(JNIEnv* env, jobject consumer, const char* str) {
+    env->CallVoidMethod(consumer, jImStrConsumerAcceptMID, env->NewStringUTF(str));
+}
+
+jstring CallImStrSupplier(JNIEnv* env, jobject supplier) {
+    return (jstring)env->CallObjectMethod(supplier, jImStrSupplierGetMID);
+}
+}

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

@@ -0,0 +1,14 @@
+#include <jni.h>
+
+#ifndef JNI_CALLBACK_H
+#define JNI_CALLBACK_H
+
+namespace Jni
+{
+void InitCallbacks(JNIEnv* env);
+
+void CallImStrConsumer(JNIEnv* env, jobject consumer, const char* str);
+jstring CallImStrSupplier(JNIEnv* env, jobject supplier);
+}
+
+#endif

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

@@ -8,9 +8,13 @@ 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");
@@ -22,6 +26,13 @@ void InitCommon(JNIEnv* env) {
     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

@@ -8,6 +8,8 @@ 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-lwjgl3/src/test/java/ImGuiGlfwExample.java

@@ -2,6 +2,8 @@ import imgui.ImBool;
 import imgui.ImGui;
 import imgui.ImGuiIO;
 import imgui.ImString;
+import imgui.callbacks.ImStrConsumer;
+import imgui.callbacks.ImStrSupplier;
 import imgui.enums.ImGuiBackendFlags;
 import imgui.enums.ImGuiColorEditFlags;
 import imgui.enums.ImGuiCond;
@@ -214,6 +216,20 @@ public final class ImGuiGlfwExample {
             io.setMouseWheel(io.getMouseWheel() + (float) yOffset);
         });
 
+        io.setSetClipboardTextFn(new ImStrConsumer() {
+            @Override
+            public void accept(final String s) {
+                glfwSetClipboardString(window, s);
+            }
+        });
+
+        io.setGetClipboardTextFn(new ImStrSupplier() {
+            @Override
+            public String get() {
+                return glfwGetClipboardString(window);
+            }
+        });
+
         // Initialize renderer itself
         imGuiGl3.init();
     }