use contents of first frame to initialize the FBO layer

Author: codeanticode

core/src/processing/opengl/PGL.java

@@ -728,10 +728,6 @@ protected void beginRender() {
     pclearStencil = clearStencil;
     clearStencil = false;
 
-    if (SINGLE_BUFFERED && sketch.frameCount == 1) {
-      restoreFirstFrame();
-    }
-
     if (fboLayerEnabledReq) {
       fboLayerEnabled = true;
       fboLayerEnabledReq = false;
@@ -779,6 +775,8 @@ protected void beginRender() {
                     0, 0, (int)(scale * graphics.width), (int)(scale * graphics.height),
                     0, 0, graphics.width, graphics.height);
       }
+    } else if (SINGLE_BUFFERED && sketch.frameCount == 1) {
+      restoreFirstFrame();
     }
   }
 
@@ -935,6 +933,10 @@ private void createFBOLayer() {
     int depthBits = PApplet.min(REQUESTED_DEPTH_BITS, getDepthBits());
     int stencilBits = PApplet.min(REQUESTED_STENCIL_BITS, getStencilBits());
 
+    backTex = 0;
+    frontTex = 1;
+    boolean savedFirstFrame = SINGLE_BUFFERED && sketch.frameCount == 0 && firstFrame != null;
+
     genTextures(2, glColorTex);
     for (int i = 0; i < 2; i++) {
       bindTexture(TEXTURE_2D, glColorTex.get(i));
@@ -944,13 +946,17 @@ private void createFBOLayer() {
       texParameteri(TEXTURE_2D, TEXTURE_WRAP_T, CLAMP_TO_EDGE);
       texImage2D(TEXTURE_2D, 0, RGBA, fboWidth, fboHeight, 0,
                  RGBA, UNSIGNED_BYTE, null);
-      initTexture(TEXTURE_2D, RGBA, fboWidth, fboHeight, graphics.backgroundColor);
+      if (i == frontTex && savedFirstFrame) {
+        // Copy first frame to front texture (will be drawn as background in next frame)
+        texSubImage2D(TEXTURE_2D, 0, 0, 0, graphics.width, graphics.height,
+                      RGBA, UNSIGNED_BYTE, firstFrame);
+      } else {
+        // Intitialize texture with background color
+        initTexture(TEXTURE_2D, RGBA, fboWidth, fboHeight, graphics.backgroundColor);
+      }
     }
     bindTexture(TEXTURE_2D, 0);
 
-    backTex = 0;
-    frontTex = 1;
-
     genFramebuffers(1, glColorFbo);
     bindFramebufferImpl(FRAMEBUFFER, glColorFbo.get(0));
     framebufferTexture2D(FRAMEBUFFER, COLOR_ATTACHMENT0, TEXTURE_2D,