Fix getBackgroundDrawList() and getForegroundDrawList(). Add methods to create draw list objects with constant pointer

Author: SpaiR

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

@@ -11,7 +11,7 @@
  * BINDING NOTICE: Since it's impossible to do a 1:1 mapping with JNI, current class provides "getCmdList*()" methods.
  * Those are used to get the data needed to do a rendering.
  */
-public final class ImDrawData implements ImDestroyable {
+public final class ImDrawData implements ImGuiDestroyableStruct {
     public static final int SIZEOF_IM_DRAW_IDX = 2;
     public static final int SIZEOF_IM_DRAW_VERT = (4 + 1) * 4;
 

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

@@ -11,18 +11,15 @@
  * but you are totally free to apply whatever transformation matrix to want to the data (if you apply such transformation you'll want to apply it to ClipRect as well)
  * Important: Primitives are always added to the list and not culled (culling is done at higher-level by ImGui:: functions), if you use this API a lot consider coarse culling your drawn objects.
  */
-public final class ImDrawList implements ImDestroyable {
-    final long ptr;
+public final class ImDrawList {
+    // BINDING NOTICE:
+    // For proper usage in getWindowDrawList(), getBackgroundDrawList(), getForegroundDrawList() we should be able to change object pointer.
+    long ptr;
 
     ImDrawList(final long ptr) {
         this.ptr = ptr;
     }
 
-    @Override
-    public void destroy() {
-        nDestroy(ptr);
-    }
-
     /*JNI
         #include <stdint.h>
         #include <imgui.h>
@@ -38,10 +35,6 @@ public void destroy() {
         imDrawListPtrID = env->GetFieldID(jImDrawListClass, "ptr", "J");
     */
 
-    private native void nDestroy(long ptr); /*
-        delete (ImDrawList*)ptr;
-    */
-
     /**
      * Flags, you may poke into these to adjust anti-aliasing settings per-primitive.
      */

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

@@ -4,7 +4,7 @@
  * Font runtime data and rendering
  * ImFontAtlas automatically loads a default embedded font for you when you call GetTexDataAsAlpha8() or GetTexDataAsRGBA32().
  */
-public final class ImFont implements ImDestroyable {
+public final class ImFont implements ImGuiDestroyableStruct {
     final long ptr;
 
     private ImFontGlyph fallbackGlyph = null;

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

@@ -22,7 +22,7 @@
  * - Even though many functions are suffixed with "TTF", OTF data is supported just as well.
  * - This is an old API and it is currently awkward for those and and various other reasons! We will address them in the future!
  */
-public final class ImFontAtlas implements ImDestroyable {
+public final class ImFontAtlas implements ImGuiDestroyableStruct {
     final long ptr;
 
     /**

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

@@ -1,6 +1,6 @@
 package imgui;
 
-public final class ImFontConfig implements ImDestroyable {
+public final class ImFontConfig implements ImGuiDestroyableStruct {
     final long ptr;
 
     private short[] glyphRanges;

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

@@ -4,7 +4,7 @@
  * Hold rendering data for one glyph.
  * (Note: some language parsers may fail to convert the 31+1 bitfield members, in this case maybe drop store a single u32 or we can rework this)
  */
-public final class ImFontGlyph implements ImDestroyable {
+public final class ImFontGlyph implements ImGuiDestroyableStruct {
     final long ptr;
 
     /**

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

@@ -17,13 +17,13 @@ public final class ImGui {
     private static final String LIB_TMP_DIR_PREFIX = "imgui-java-bin_" + System.getProperty("user.name", "user");
 
     private static final ImGuiIO IMGUI_IO;
+    private static final ImDrawList WINDOW_DRAW_LIST;
+    private static final ImDrawList BACKGROUND_DRAW_LIST;
+    private static final ImDrawList FOREGROUND_DRAW_LIST;
 
     private static ImDrawData drawData;
     private static ImFont font;
     private static ImGuiStyle style;
-    private static ImDrawList windowDrawList;
-    private static ImDrawList backgroundDrawList;
-    private static ImDrawList foregroundDrawList;
 
     static {
         final String libPath = System.getProperty(LIB_PATH_PROP);
@@ -41,6 +41,9 @@ public final class ImGui {
         }
 
         IMGUI_IO = new ImGuiIO();
+        WINDOW_DRAW_LIST = new ImDrawList(0);
+        BACKGROUND_DRAW_LIST = new ImDrawList(0);
+        FOREGROUND_DRAW_LIST = new ImDrawList(0);
 
         nInitJni();
         ImDrawList.nInit();
@@ -467,12 +470,22 @@ public static boolean begin(String title, ImBool pOpen, int imGuiWindowFlags) {
 
     /**
      * Get draw list associated to the current window, to append your own drawing primitives
+     * <p>
+     * BINDING NOTICE: to minimize overhead, method ALWAYS returns the same object, but changes its underlying pointer.
+     * If you need to get an object with constant pointer (which will point to the same window all the time) use {@link #getWindowDrawListNew()}.
      */
     public static ImDrawList getWindowDrawList() {
-        if (windowDrawList == null) {
-            windowDrawList = new ImDrawList(nGetWindowDrawList());
-        }
-        return windowDrawList;
+        WINDOW_DRAW_LIST.ptr = nGetWindowDrawList();
+        return WINDOW_DRAW_LIST;
+    }
+
+    /**
+     * Get draw list associated to the current window, to append your own drawing primitives
+     * <p>
+     * BINDING NOTICE: returns {@link ImDrawList} for current window with constant pointer to it. Prefer to use {@link #getWindowDrawList()}.
+     */
+    public static ImDrawList getWindowDrawListNew() {
+        return new ImDrawList(nGetWindowDrawList());
     }
 
     private static native long nGetWindowDrawList(); /*
@@ -4514,12 +4527,23 @@ public static byte[] acceptDragDropPayload(String type, int imGuiDragDropFlags)
     /**
      * Get background draw list for the viewport associated to the current window.
      * This draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+     * <p>
+     * BINDING NOTICE: to minimize overhead, method ALWAYS returns the same object, but changes its underlying pointer.
+     * If you need to get an object with constant pointer (which will point to the same background all the time) use {@link #getBackgroundDrawListNew()}.
      */
     public static ImDrawList getBackgroundDrawList() {
-        if (backgroundDrawList == null) {
-            backgroundDrawList = new ImDrawList(nGetBackgroundDrawList());
-        }
-        return backgroundDrawList;
+        BACKGROUND_DRAW_LIST.ptr = nGetBackgroundDrawList();
+        return BACKGROUND_DRAW_LIST;
+    }
+
+    /**
+     * Get background draw list for the viewport associated to the current window.
+     * This draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+     * <p>
+     * BINDING NOTICE: returns {@link ImDrawList} for current background with constant pointer to it. Prefer to use {@link #getBackgroundDrawList()}.
+     */
+    public static ImDrawList getBackgroundDrawListNew() {
+        return new ImDrawList(nGetBackgroundDrawList());
     }
 
     private static native long nGetBackgroundDrawList(); /*
@@ -4529,12 +4553,23 @@ public static ImDrawList getBackgroundDrawList() {
     /**
      * Get foreground draw list for the viewport associated to the current window.
      * This draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+     * <p>
+     * BINDING NOTICE: to minimize overhead, method ALWAYS returns the same object, but changes its underlying pointer.
+     * If you need to get an object with constant pointer (which will point to the same foreground all the time) use {@link #getForegroundDrawListNew()}.
      */
     public static ImDrawList getForegroundDrawList() {
-        if (foregroundDrawList == null) {
-            foregroundDrawList = new ImDrawList(nGetForegroundDrawList());
-        }
-        return foregroundDrawList;
+        FOREGROUND_DRAW_LIST.ptr = nGetForegroundDrawList();
+        return FOREGROUND_DRAW_LIST;
+    }
+
+    /**
+     * Get foreground draw list for the viewport associated to the current window.
+     * This draw list will be the first rendering one. Useful to quickly draw shapes/text behind dear imgui contents.
+     * <p>
+     * BINDING NOTICE: returns {@link ImDrawList} for current foreground with constant pointer to it. Prefer to use {@link #getForegroundDrawList()}.
+     */
+    public static ImDrawList getForegroundDrawListNew() {
+        return new ImDrawList(nGetForegroundDrawList());
     }
 
     private static native long nGetForegroundDrawList(); /*

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

@@ -0,0 +1,8 @@
+package imgui;
+
+/**
+ * When implement, class could be manually destroyed (free allocated memory on the JNI side).
+ */
+interface ImGuiDestroyableStruct {
+    void destroy();
+}

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

@@ -5,7 +5,7 @@
  * During the frame, use ImGui::PushStyleVar(ImGuiStyleVar_XXXX)/PopStyleVar() to alter the main style values,
  * and ImGui::PushStyleColor(ImGuiCol_XXX)/PopStyleColor() for colors.
  */
-public final class ImGuiStyle implements ImDestroyable {
+public final class ImGuiStyle implements ImGuiDestroyableStruct {
     final long ptr;
 
     /**