documented and completed viewer GL widget

app/widget/viewer/viewerglwidget.cpp

@@ -8,28 +8,44 @@
 #include "render/gl/shadergenerators.h"
 
 ViewerGLWidget::ViewerGLWidget(QWidget *parent) :
-  QOpenGLWidget(parent)
+  QOpenGLWidget(parent),
+  texture_(0)
 {
 }
 
+void ViewerGLWidget::SetTexture(GLuint tex)
+{
+  // Update the texture
+  texture_ = tex;
+
+  // Paint the texture
+  update();
+}
+
+void ViewerGLWidget::initializeGL()
+{
+  // Re-retrieve pipeline pertaining to this context
+  pipeline_ = olive::gl::GetDefaultPipeline();
+}
+
 void ViewerGLWidget::paintGL()
 {
-  /*
+  // Get functions attached to this context (they will already be initialized)
   QOpenGLFunctions* f = context()->functions();
 
-  f->glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+  // Clear background to empty
+  f->glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
   f->glClear(GL_COLOR_BUFFER_BIT);
 
-  QOpenGLTexture* tex = new QOpenGLTexture(img);
+  // Check if we have a texture to draw
+  if (texture_ > 0) {
+    // Bind retrieved texture
+    f->glBindTexture(GL_TEXTURE_2D, texture_);
 
-  ShaderPtr pipeline = olive::gl::GetDefaultPipeline();
+    // Blit using the pipeline retrieved in initializeGL()
+    olive::gl::Blit(pipeline_, true);
 
-  tex->bind();
+    // Release retrieved texture
-
+    f->glBindTexture(GL_TEXTURE_2D, 0);
-  olive::gl::Blit(pipeline, true);
+  }
-
-  tex->release();
-
-  delete tex;
-  */
 }

app/widget/viewer/viewerglwidget.h

@@ -1,18 +1,91 @@
+/***
+
+  Olive - Non-Linear Video Editor
+  Copyright (C) 2019 Olive Team
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+***/
+
 #ifndef VIEWERGLWIDGET_H
 #define VIEWERGLWIDGET_H
 
 #include <QOpenGLWidget>
 
+#include "render/gl/shaderptr.h"
+
+/**
+ * @brief The ViewerGLWidget class
+ *
+ * The inner display/rendering widget of a Viewer class. Actual rendering/composition occurs elsewhere offscreen and
+ * multithreaded, so its main purpose is receiving an OpenGL texture to display it.
+ *
+ * The main entry point is SetTexture() which will receive an OpenGL texture ID, store it, and then call update() to
+ * draw it on screen. The drawing function is in paintGL() (called during the update() process by Qt) and is fairly
+ * simple OpenGL drawing code standardized around OpenGL ES 3.2 Core.
+ *
+ * If the texture has been modified and you're 100% sure this widget is using the same texture object, it's possible
+ * to call update() directly to trigger a repaint, however this is not recommended. If you are not 100% sure it'll be
+ * the same texture object, use SetTexture() since it will nearly always be faster to just set it than to check *and*
+ * set it.
+ */
 class ViewerGLWidget : public QOpenGLWidget
 {
 public:
+  /**
+   * @brief ViewerGLWidget Constructor
+   *
+   * @param parent
+   *
+   * QWidget parent.
+   */
   ViewerGLWidget(QWidget* parent);
 
+  /**
+   * @brief Set the texture to draw and draw it
+   *
+   * Use this function
+   *
+   * @param tex
+   */
   void SetTexture(GLuint tex);
 protected:
+  /**
+   * @brief Initialize function to set up the OpenGL context upon its construction
+   *
+   * Currently primarily used to regenerate the pipeline shader used for drawing.
+   */
+  virtual void initializeGL() override;
+
+  /**
+   * @brief Paint function to display the texture (received in SetTexture()) on screen.
+   *
+   * Simple OpenGL drawing function for painting the texture on screen. Standardized around OpenGL ES 3.2 Core.
+   */
   virtual void paintGL() override;
 private:
+  /**
+   * @brief Internal reference to the OpenGL texture to draw. Set in SetTexture() and used in paintGL().
+   */
   GLuint texture_;
+
+  /**
+   * @brief Internal shader object to use as the pipeline shader
+   *
+   * Retrieved every initializeGL() in order to stay up to date when new contexts are generated.
+   */
+  ShaderPtr pipeline_;
 };
 
 #endif // VIEWERGLWIDGET_H