From 8c9c394de30ea4903457099cf30ce0d9436188fa Mon Sep 17 00:00:00 2001
From: itsmattkc <itsmattkc@gmail.com>
Date: Tue, 20 Nov 2018 09:37:08 +1100
Subject: [PATCH] revised superimpose effect code

---
 ui/viewerwidget.cpp | 12 ++++++------
 ui/viewerwidget.h   |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/ui/viewerwidget.cpp b/ui/viewerwidget.cpp
index 0b199414a..8a652d5ca 100644
--- a/ui/viewerwidget.cpp
+++ b/ui/viewerwidget.cpp
@@ -216,14 +216,14 @@ void ViewerWidget::drawTitleSafeArea() {
     glEnd();
 }
 
-GLuint ViewerWidget::draw_clip(QOpenGLFramebufferObject* fbo, GLuint texture) {
+GLuint ViewerWidget::draw_clip(QOpenGLFramebufferObject* fbo, GLuint texture, bool clear) {
 	glPushMatrix();
 	glLoadIdentity();
 	glOrtho(0, 1, 0, 1, -1, 1);
 
 	fbo->bind();
 
-	glClear(GL_COLOR_BUFFER_BIT);
+    if (clear) glClear(GL_COLOR_BUFFER_BIT);
 
 	glBindTexture(GL_TEXTURE_2D, texture);
 	glBegin(GL_QUADS);
@@ -254,13 +254,13 @@ void ViewerWidget::process_effect(Clip* c, Effect* e, double timecode, GLTexture
 			e->startEffect();
 			if (e->enable_shader) {
 				e->process_shader(timecode, coords);
+                composite_texture = draw_clip(c->fbo[fbo_switcher], composite_texture, true);
+                fbo_switcher = !fbo_switcher;
 			}
-			composite_texture = draw_clip(c->fbo[fbo_switcher], composite_texture);
 			if (e->enable_superimpose) {
 				GLuint superimpose_texture = e->process_superimpose(timecode);
-				if (superimpose_texture != 0) draw_clip(c->fbo[fbo_switcher], superimpose_texture);
+                if (superimpose_texture != 0) composite_texture = draw_clip(c->fbo[!fbo_switcher], superimpose_texture, false);
 			}
-			fbo_switcher = !fbo_switcher;
 		}
 	}
 }
@@ -424,7 +424,7 @@ GLuint ViewerWidget::compose_sequence(QVector<Clip*>& nests, bool render_audio)
                         c->fbo[fbo_switcher]->release();
 						composite_texture = c->fbo[fbo_switcher]->texture();
 					} else {
-						composite_texture = draw_clip(c->fbo[fbo_switcher], textureID);
+                        composite_texture = draw_clip(c->fbo[fbo_switcher], textureID, true);
 					}
 
 					fbo_switcher = !fbo_switcher;
diff --git a/ui/viewerwidget.h b/ui/viewerwidget.h
index 15d6e41b7..f8faa1eac 100644
--- a/ui/viewerwidget.h
+++ b/ui/viewerwidget.h
@@ -43,7 +43,7 @@ private:
 	bool dragging;
 	void seek_from_click(int x);
 	GLuint compose_sequence(QVector<Clip *> &nests, bool render_audio);
-	GLuint draw_clip(QOpenGLFramebufferObject *clip, GLuint texture);
+    GLuint draw_clip(QOpenGLFramebufferObject *clip, GLuint texture, bool clear);
 	void process_effect(Clip* c, Effect* e, double timecode, GLTextureCoords& coords, GLuint& composite_texture, bool& fbo_switcher);
 private slots:
 	void retry();