[Example] Add example of Drag & Drop

example/src/main/java/ExampleDragAndDrop.java

@@ -0,0 +1,128 @@
+import imgui.ImGui;
+import imgui.flag.ImGuiDragDropFlags;
+import imgui.flag.ImGuiInputTextFlags;
+import imgui.flag.ImGuiWindowFlags;
+import imgui.type.ImBoolean;
+import imgui.type.ImInt;
+import imgui.type.ImString;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class ExampleDragAndDrop {
+    private static final String PAYLOAD_TYPE = "PAYLOAD";
+
+    private static final StringPayload STRING_PAYLOAD = new StringPayload();
+    private static final IntegerPayload INTEGER_PAYLOAD = new IntegerPayload();
+
+    private static final AtomicInteger CLASS_SPECIFIC_PAYLOAD = new AtomicInteger(23);
+
+    private static String data = "No Data...";
+
+    public static void show(final ImBoolean showDragNDropWindow) {
+        if (ImGui.begin("Drag'N'Drop Demo", showDragNDropWindow, ImGuiWindowFlags.AlwaysAutoResize)) {
+            ImGui.text("Drag from here:");
+
+            ImGui.inputText("String payload", STRING_PAYLOAD.input, ImGuiInputTextFlags.CallbackResize);
+            setupPayload(STRING_PAYLOAD);
+
+            ImGui.inputInt("Integer payload", INTEGER_PAYLOAD.input);
+            setupPayload(INTEGER_PAYLOAD);
+
+            ImGui.button("Class specific payload");
+            setupClassSpecificPayload();
+
+            ImGui.separator();
+
+            ImGui.text("Drop here any:");
+            ImGui.button(data, 100, 50);
+            setupTarget();
+
+            ImGui.separator();
+
+            ImGui.text("Drop here string payload only");
+            ImGui.button(data, 100, 50);
+            setupStringPayloadTarget();
+
+            ImGui.separator();
+
+            ImGui.text("Drop here class specific payload only");
+            ImGui.button(data, 100, 50);
+            setupClassSpecificPayloadTarget();
+        }
+        ImGui.end();
+    }
+
+    private static void setupPayload(final Payload<?> payload) {
+        if (ImGui.beginDragDropSource(ImGuiDragDropFlags.SourceAllowNullID)) {
+            ImGui.setDragDropPayload(PAYLOAD_TYPE, payload);
+            ImGui.text("Dragging: " + payload.getData());
+            ImGui.endDragDropSource();
+        }
+    }
+
+    private static void setupClassSpecificPayload() {
+        if (ImGui.beginDragDropSource()) {
+            ImGui.setDragDropPayload(CLASS_SPECIFIC_PAYLOAD);
+            ImGui.text("Dragging class specific payload");
+            ImGui.endDragDropSource();
+        }
+    }
+
+    private static void setupTarget() {
+        if (ImGui.beginDragDropTarget()) {
+            Payload<?> payload = ImGui.acceptDragDropPayload(PAYLOAD_TYPE);
+            if (payload != null) {
+                data = String.valueOf(payload.getData());
+            }
+            ImGui.endDragDropTarget();
+        }
+    }
+
+    /**
+     * Type safe example. ImGui will show that it can accept payload, but payload itself will be null.
+     */
+    private static void setupStringPayloadTarget() {
+        if (ImGui.beginDragDropTarget()) {
+            StringPayload payload = ImGui.acceptDragDropPayload(PAYLOAD_TYPE, StringPayload.class);
+            if (payload != null) {
+                data = payload.getData();
+            }
+            ImGui.endDragDropTarget();
+        }
+    }
+
+    /**
+     * Class specific example. We can bind our payload to a specific class, so it will be 100% type safe.
+     */
+    private static void setupClassSpecificPayloadTarget() {
+        if (ImGui.beginDragDropTarget()) {
+            AtomicInteger payload = ImGui.acceptDragDropPayload(AtomicInteger.class);
+            if (payload != null) {
+                data = String.valueOf(payload.get());
+            }
+            ImGui.endDragDropTarget();
+        }
+    }
+
+    private interface Payload<T> {
+        T getData();
+    }
+
+    private static final class StringPayload implements Payload<String> {
+        ImString input = new ImString("You can drag inputs as well");
+
+        @Override
+        public String getData() {
+            return input.get();
+        }
+    }
+
+    private static final class IntegerPayload implements Payload<Integer> {
+        ImInt input = new ImInt();
+
+        @Override
+        public Integer getData() {
+            return input.get();
+        }
+    }
+}

example/src/main/java/Extra.java

@@ -6,6 +6,7 @@ public class Extra {
     private static final ImBoolean SHOW_DEMO_WINDOW = new ImBoolean(false);
     private static final ImBoolean SHOW_IMNODES_DEMO_WINDOW = new ImBoolean(false);
     private static final ImBoolean SHOW_IMGUI_NODE_EDITOR_DEMO_WINDOW = new ImBoolean(false);
+    private static final ImBoolean SHOW_DRAG_N_DROP_WINDOW = new ImBoolean(false);
 
     private static final Graph GRAPH = new Graph();
 
@@ -14,6 +15,7 @@ public class Extra {
         ImGui.checkbox("Show Demo Window", SHOW_DEMO_WINDOW);
         ImGui.checkbox("Show ImNodes Demo Window", SHOW_IMNODES_DEMO_WINDOW);
         ImGui.checkbox("Show imgui-node-editor Demo Window", SHOW_IMGUI_NODE_EDITOR_DEMO_WINDOW);
+        ImGui.checkbox("Show Drag'N'Drop Demo Window", SHOW_DRAG_N_DROP_WINDOW);
 
         if (SHOW_DEMO_WINDOW.get()) {
             ImGui.showDemoWindow(SHOW_DEMO_WINDOW);
@@ -26,5 +28,9 @@ public class Extra {
         if (SHOW_IMGUI_NODE_EDITOR_DEMO_WINDOW.get()) {
             ExampleImGuiNodeEditor.show(SHOW_IMGUI_NODE_EDITOR_DEMO_WINDOW, GRAPH);
         }
+
+        if (SHOW_DRAG_N_DROP_WINDOW.get()) {
+            ExampleDragAndDrop.show(SHOW_DRAG_N_DROP_WINDOW);
+        }
     }
 }