Add ImGuiListClipper

Add ImGuiListClipper

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

@@ -0,0 +1,65 @@
+package imgui;
+
+import imgui.callbacks.ImListClipperCallback;
+
+/**
+ * Helper: Manually clip large list of items.
+ * If you are submitting lots of evenly spaced items and you have a random access to the list, you can perform coarse clipping based on visibility to save yourself from processing those items at all.
+ * The clipper calculates the range of visible items and advance the cursor to compensate for the non-visible items we have skipped.
+ * ImGui already clip items based on their bounds but it needs to measure text size to do so. Coarse clipping before submission makes this cost and your own data fetching/submission cost null.
+ * Usage:
+ * <pre>
+ *     ImGuiListClipper clipper(1000);  // we have 1000 elements, evenly spaced.
+ *     while (clipper.Step())
+ *         for (int i = clipper.DisplayStart; i {@code <} clipper.DisplayEnd; i++)
+ *             ImGui::Text("line number %d", i);
+ * </pre>
+ * - Step 0: the clipper let you process the first element, regardless of it being visible or not, so we can measure the element height (step skipped if we passed a known height as second arg to constructor).
+ * - Step 1: the clipper infer height from first element, calculate the actual range of elements to display, and position the cursor before the first element.
+ * - (Step 2: dummy step only required if an explicit items_height was passed to constructor or Begin() and user call Step(). Does nothing and switch to Step 3.)
+ * - Step 3: the clipper validate that we have reached the expected Y position (corresponding to element DisplayEnd), advance the cursor to the end of the list and then returns 'false' to end the loop.
+ * <p>
+ * BINDING NOTICE:
+ * It's impossible to implement the same API like in the original. Method {@link #forEach(int, int, ImListClipperCallback)} could be used instead.
+ * <pre>
+ *     ImGuiListClipper.forEach(1000, new ImListClipperCallback() {
+ *         public void accept(int index) {
+ *             ImGui.text(String.format("line number %d", index));
+ *         }
+ *     });
+ * </pre>
+ */
+public final class ImGuiListClipper {
+    private ImGuiListClipper() {
+    }
+
+    /*JNI
+        #include <imgui.h>
+        #include "jni_callbacks.h"
+     */
+
+    /**
+     * @param itemsCount Use -1 to ignore (you can call Begin later).
+     *                   Use INT_MAX if you don't know how many items you have (in which case the cursor won't be advanced in the final step).
+     * @param callback action to do in iterations
+     */
+    public static void forEach(final int itemsCount, final ImListClipperCallback callback) {
+        forEach(itemsCount, -1, callback);
+    }
+
+    /**
+     * @param itemsCount Use -1 to ignore (you can call Begin later).
+     *                   Use INT_MAX if you don't know how many items you have (in which case the cursor won't be advanced in the final step).
+     * @param itemsHeight Use -1.0f to be calculated automatically on first step.
+     *                    Otherwise pass in the distance between your items, typically GetTextLineHeightWithSpacing() or GetFrameHeightWithSpacing().
+     * @param callback action to do in iterations
+     */
+    public static native void forEach(int itemsCount, int itemsHeight, ImListClipperCallback callback); /*
+        ImGuiListClipper clipper(itemsCount);
+        while (clipper.Step()) {
+            for (int i = clipper.DisplayStart; i < clipper.DisplayEnd; i++) {
+                Jni::CallImListClipperCallback(env, callback, i);
+            }
+        }
+    */
+}

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

@@ -0,0 +1,8 @@
+package imgui.callbacks;
+
+/**
+ * Callback for {@link imgui.ImGuiListClipper} class.
+ */
+public abstract class ImListClipperCallback {
+    public abstract void accept(int index);
+}

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

@@ -1,11 +1,8 @@
 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 class ImStrConsumer {
     public abstract void accept(String str);
 }

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

@@ -1,11 +1,8 @@
 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 class ImStrSupplier {
     public abstract String get();
 }

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

@@ -1,23 +1,32 @@
 #include "jni_callbacks.h"
 
+jmethodID jImListClipperCallbackAcceptMID;
+
 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");
+    void InitCallbacks(JNIEnv* env) {
+        jclass jImListClipperCallback = env->FindClass("imgui/callbacks/ImListClipperCallback");
+        jImListClipperCallbackAcceptMID = env->GetMethodID(jImListClipperCallback, "accept", "(I)V");
 
-    jclass jImStrSupplier = env->FindClass("imgui/callbacks/ImStrSupplier");
-    jImStrSupplierGetMID = env->GetMethodID(jImStrSupplier, "get", "()Ljava/lang/String;");
-}
+        jclass jImStrConsumer = env->FindClass("imgui/callbacks/ImStrConsumer");
+        jImStrConsumerAcceptMID = env->GetMethodID(jImStrConsumer, "accept", "(Ljava/lang/String;)V");
 
-void CallImStrConsumer(JNIEnv* env, jobject consumer, const char* str) {
-    env->CallVoidMethod(consumer, jImStrConsumerAcceptMID, env->NewStringUTF(str));
-}
+        jclass jImStrSupplier = env->FindClass("imgui/callbacks/ImStrSupplier");
+        jImStrSupplierGetMID = env->GetMethodID(jImStrSupplier, "get", "()Ljava/lang/String;");
+    }
 
-jstring CallImStrSupplier(JNIEnv* env, jobject supplier) {
-    return (jstring)env->CallObjectMethod(supplier, jImStrSupplierGetMID);
-}
+    void CallImListClipperCallback(JNIEnv* env, jobject consumer, int index) {
+        env->CallVoidMethod(consumer, jImListClipperCallbackAcceptMID, index);
+    }
+
+    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

@@ -5,10 +5,13 @@
 
 namespace Jni
 {
-void InitCallbacks(JNIEnv* env);
+    void InitCallbacks(JNIEnv* env);
 
-void CallImStrConsumer(JNIEnv* env, jobject consumer, const char* str);
-jstring CallImStrSupplier(JNIEnv* env, jobject supplier);
+    void CallImListClipperCallback(JNIEnv* env, jobject consumer, int index);
+
+    void CallImStrConsumer(JNIEnv* env, jobject consumer, const char* str);
+
+    jstring CallImStrSupplier(JNIEnv* env, jobject supplier);
 }
 
 #endif

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

@@ -12,58 +12,58 @@ static JavaVM* jvm;
 
 namespace Jni
 {
-void InitCommon(JNIEnv* env) {
-    env->GetJavaVM(&jvm);
+    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");
+        jclass jImVec2Class = env->FindClass("imgui/ImVec2");
+        imVec2XID = env->GetFieldID(jImVec2Class, "x", "F");
+        imVec2YID = env->GetFieldID(jImVec2Class, "y", "F");
 
-    jclass jImVec4Class = env->FindClass("imgui/ImVec4");
-    imVec4XID = env->GetFieldID(jImVec4Class, "x", "F");
-    imVec4YID = env->GetFieldID(jImVec4Class, "y", "F");
-    imVec4ZID = env->GetFieldID(jImVec4Class, "z", "F");
-    imVec4WID = env->GetFieldID(jImVec4Class, "w", "F");
-}
+        jclass jImVec4Class = env->FindClass("imgui/ImVec4");
+        imVec4XID = env->GetFieldID(jImVec4Class, "x", "F");
+        imVec4YID = env->GetFieldID(jImVec4Class, "y", "F");
+        imVec4ZID = env->GetFieldID(jImVec4Class, "z", "F");
+        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;
-}
+    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);
-}
+    void ImVec2Cpy(JNIEnv* env, ImVec2* src, jobject dst) {
+        env->SetFloatField(dst, imVec2XID, src->x);
+        env->SetFloatField(dst, imVec2YID, src->y);
+    }
 
-void ImVec2Cpy(JNIEnv* env, ImVec2 src, jobject dst) {
-    env->SetFloatField(dst, imVec2XID, src.x);
-    env->SetFloatField(dst, imVec2YID, src.y);
-}
+    void ImVec2Cpy(JNIEnv* env, ImVec2 src, jobject dst) {
+        env->SetFloatField(dst, imVec2XID, src.x);
+        env->SetFloatField(dst, imVec2YID, src.y);
+    }
 
-void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2* dst) {
-    dst->x = env->GetFloatField(src, imVec2XID);
-    dst->y = env->GetFloatField(src, imVec2YID);
-}
+    void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2* dst) {
+        dst->x = env->GetFloatField(src, imVec2XID);
+        dst->y = env->GetFloatField(src, imVec2YID);
+    }
 
-void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2 dst) {
-    dst.x = env->GetFloatField(src, imVec2XID);
-    dst.y = env->GetFloatField(src, imVec2YID);
-}
+    void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2 dst) {
+        dst.x = env->GetFloatField(src, imVec2XID);
+        dst.y = env->GetFloatField(src, imVec2YID);
+    }
 
-void ImVec4Cpy(JNIEnv* env, ImVec4* src, jobject dst) {
-    env->SetFloatField(dst, imVec4XID, src->x);
-    env->SetFloatField(dst, imVec4YID, src->y);
-    env->SetFloatField(dst, imVec4ZID, src->z);
-    env->SetFloatField(dst, imVec4WID, src->w);
-}
+    void ImVec4Cpy(JNIEnv* env, ImVec4* src, jobject dst) {
+        env->SetFloatField(dst, imVec4XID, src->x);
+        env->SetFloatField(dst, imVec4YID, src->y);
+        env->SetFloatField(dst, imVec4ZID, src->z);
+        env->SetFloatField(dst, imVec4WID, src->w);
+    }
 
-void ImVec4Cpy(JNIEnv* env, ImVec4 src, jobject dst) {
-    env->SetFloatField(dst, imVec4XID, src.x);
-    env->SetFloatField(dst, imVec4YID, src.y);
-    env->SetFloatField(dst, imVec4ZID, src.z);
-    env->SetFloatField(dst, imVec4WID, src.w);
-}
+    void ImVec4Cpy(JNIEnv* env, ImVec4 src, jobject dst) {
+        env->SetFloatField(dst, imVec4XID, src.x);
+        env->SetFloatField(dst, imVec4YID, src.y);
+        env->SetFloatField(dst, imVec4ZID, src.z);
+        env->SetFloatField(dst, imVec4WID, src.w);
+    }
 }

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

@@ -6,18 +6,18 @@
 
 namespace Jni
 {
-void InitCommon(JNIEnv* env);
+    void InitCommon(JNIEnv* env);
 
-JNIEnv* GetEnv();
+    JNIEnv* GetEnv();
 
-void ImVec2Cpy(JNIEnv* env, ImVec2* src, jobject dst);
-void ImVec2Cpy(JNIEnv* env, ImVec2 src, jobject dst);
+    void ImVec2Cpy(JNIEnv* env, ImVec2* src, jobject dst);
+    void ImVec2Cpy(JNIEnv* env, ImVec2 src, jobject dst);
 
-void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2* dst);
-void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2 dst);
+    void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2* dst);
+    void ImVec2Cpy(JNIEnv* env, jobject src, ImVec2 dst);
 
-void ImVec4Cpy(JNIEnv* env, ImVec4* src, jobject dst);
-void ImVec4Cpy(JNIEnv* env, ImVec4 src, jobject dst);
+    void ImVec4Cpy(JNIEnv* env, ImVec4* src, jobject dst);
+    void ImVec4Cpy(JNIEnv* env, ImVec4 src, jobject dst);
 }
 
 #endif