fixed bug that caused flickering textures

The ViewerGLWidget would receive raw GLuint textures while most of Olive uses
an OpenGLTexture C++ wrapper. Unfortunately this would lead to the C++ wrapper
getting destroyed since its instance wasn't kept in the ViewerGLWidget. This
meant by the time the ViewerGLWidget would re-draw, the texture would have
already been destroyed leading to some black frames. This is now fixed.

app/widget/viewer/viewer.cpp

@@ -205,11 +205,7 @@ VideoRenderBackend *ViewerWidget::video_renderer() const
 
 void ViewerWidget::SetTexture(OpenGLTexturePtr tex)
 {
-  if (tex == nullptr) {
-    gl_widget_->SetTexture(0);
-  } else {
-    gl_widget_->SetTexture(tex->texture());
-  }
+  gl_widget_->SetTexture(tex);
 }
 
 void ViewerWidget::UpdateTimeInternal(int64_t i)

app/widget/viewer/viewerglwidget.cpp

@@ -96,7 +96,7 @@ void ViewerGLWidget::SetOCIOLook(const QString &look)
   update();
 }
 
-void ViewerGLWidget::SetTexture(GLuint tex)
+void ViewerGLWidget::SetTexture(OpenGLTexturePtr tex)
 {
   // Update the texture
   texture_ = tex;
@@ -124,7 +124,7 @@ void ViewerGLWidget::initializeGL()
 void ViewerGLWidget::paintGL()
 {
   // We only draw if we have a pipeline
-  if (!pipeline_) {
+  if (!pipeline_ || !texture_) {
     return;
   }
 
@@ -135,17 +135,14 @@ void ViewerGLWidget::paintGL()
   f->glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
   f->glClear(GL_COLOR_BUFFER_BIT);
 
-  // Check if we have a texture to draw
-  if (texture_ > 0) {
-    // Bind retrieved texture
-    f->glBindTexture(GL_TEXTURE_2D, texture_);
+  // Bind retrieved texture
+  f->glBindTexture(GL_TEXTURE_2D, texture_->texture());
 
-    // Blit using the pipeline retrieved in initializeGL()
-    OpenGLRenderFunctions::OCIOBlit(pipeline_, ocio_lut_, true, matrix_);
+  // Blit using the pipeline retrieved in initializeGL()
+  OpenGLRenderFunctions::OCIOBlit(pipeline_, ocio_lut_, true, matrix_);
 
-    // Release retrieved texture
-    f->glBindTexture(GL_TEXTURE_2D, 0);
-  }
+  // Release retrieved texture
+  f->glBindTexture(GL_TEXTURE_2D, 0);
 }
 
 void ViewerGLWidget::RefreshColorPipeline()

app/widget/viewer/viewerglwidget.h

@@ -23,8 +23,9 @@
 
 #include <QOpenGLWidget>
 
-#include "render/colormanager.h"
 #include "render/backend/opengl/openglshader.h"
+#include "render/backend/opengl/opengltexture.h"
+#include "render/colormanager.h"
 
 /**
  * @brief The inner display/rendering widget of a Viewer class.
@@ -109,7 +110,7 @@ public slots:
    *
    * @param tex
    */
-  void SetTexture(GLuint tex);
+  void SetTexture(OpenGLTexturePtr tex);
 
   void SetOCIOParameters(const QString& display, const QString& view, const QString& look);
 
@@ -178,7 +179,7 @@ private:
   /**
    * @brief Internal reference to the OpenGL texture to draw. Set in SetTexture() and used in paintGL().
    */
-  GLuint texture_;
+  OpenGLTexturePtr texture_;
 
   /**
    * @brief Internal shader object to use as the pipeline shader