libmythtv: Fix some lingering issues with visualiser rendering

- in MythPlayerVisualiserUI, don't try and optimise away the visualiser
rendering when we are entirely obscured - we still need to drain the
buffers
- in the visualisers, if obscured, don't actually render

mythtv/libs/libmythtv/mythplayervisualiserui.cpp

@@ -26,15 +26,19 @@ void MythPlayerVisualiserUI::UIScreenRectChanged(const QRect& Rect)
 
 void MythPlayerVisualiserUI::PrepareVisualiser()
 {
-    if (!(m_visual && m_painter) || (m_embedding && m_embedRect.isEmpty()))
+    // Note - we must call the visualiser to drain its buffers even if it is not
+    // to be displayed (otherwise it fails). So do not check for output rect
+    // size (embedding) etc
+    if (!m_visual)
         return;
     if (m_visual->NeedsPrepare())
         m_visual->Prepare(m_embedding ? m_embedRect : m_uiScreenRect);
 }
 
 void MythPlayerVisualiserUI::RenderVisualiser()
 {
-    if (!(m_visual && m_painter) || (m_embedding && m_embedRect.isEmpty()))
+    // As for PrepareVisualiser - always call the visualiser if it is present
+    if (!m_visual)
         return;
     m_visual->Draw(m_embedding ? m_embedRect : m_uiScreenRect, m_painter, nullptr);
 }

mythtv/libs/libmythtv/visualisations/opengl/mythvisualmonoscopeopengl.cpp

@@ -61,19 +61,28 @@ void MythVisualMonoScopeOpenGL::Draw(const QRect& Area, MythPainter* /*Painter*/
     vbo.second[1] = 1.0;
     vbo.second[2] = 1.0;
 
+    bool updated = false;
     vbo.first->bind();
     if (m_bufferMaps)
     {
         void* buffer = vbo.first->map(QOpenGLBuffer::WriteOnly);
-        UpdateVertices(static_cast<float*>(buffer));
+        updated = UpdateVertices(static_cast<float*>(buffer));
         vbo.first->unmap();
     }
     else
     {
-        UpdateVertices(m_vertices.data());
+        updated = UpdateVertices(m_vertices.data());
         vbo.first->write(0, m_vertices.data(), static_cast<int>(m_vertices.size() * sizeof(GLfloat)));
     }
 
+    if (!updated)
+    {
+        // this is generally when the visualiser is embedding and hidden. We must
+        // still drain the buffers but don't actually draw
+        render->doneCurrent();
+        return;
+    }
+
     // Common calls
     render->glEnableVertexAttribArray(0);
     QPointF center { m_area.left() + static_cast<qreal>(m_area.width()) / 2,

mythtv/libs/libmythtv/visualisations/videovisualmonoscope.cpp

@@ -28,16 +28,16 @@ void VideoVisualMonoScope::InitCommon(const QRect& Area)
     m_lineWidth = qMax(1.0F, m_area.height() * 0.004F);
 }
 
-void VideoVisualMonoScope::UpdateVertices(float* Buffer)
+bool VideoVisualMonoScope::UpdateVertices(float* Buffer)
 {
     if (!Buffer)
-        return;
+        return false;
 
     QMutexLocker locker(mutex());
     auto * node = GetNode();
 
     if (m_area.isEmpty() || !node)
-        return;
+        return false;
 
     float y = (static_cast<float>(m_area.height()) / 2.0F) + m_area.top();
     float x = m_area.left();
@@ -65,6 +65,7 @@ void VideoVisualMonoScope::UpdateVertices(float* Buffer)
         Buffer[i * 2 + 1] = y + static_cast<float>(value);
         x += xstep;
     }
+    return true;
 }
 
 void VideoVisualMonoScope::UpdateTime()

mythtv/libs/libmythtv/visualisations/videovisualmonoscope.h

@@ -17,7 +17,7 @@ class VideoVisualMonoScope : public VideoVisual
   protected:
     Q_DISABLE_COPY(VideoVisualMonoScope)
     void                  InitCommon      (const QRect& Area);
-    void                  UpdateVertices  (float* Buffer);
+    bool                  UpdateVertices  (float* Buffer);
     void                  UpdateTime      ();
 
     int64_t               m_lastTime      { 0     };

mythtv/libs/libmythtv/visualisations/vulkan/mythvisualmonoscopevulkan.cpp

@@ -229,7 +229,8 @@ void MythVisualMonoScopeVulkan::Prepare(const QRect &Area)
     vertex.second[1] = 1.0;
     vertex.second[2] = 1.0;
     auto * buffer = vertex.first->GetMappedMemory();
-    UpdateVertices(static_cast<float*>(buffer));
+    if (!UpdateVertices(static_cast<float*>(buffer)))
+        return;
     vertex.first->Update(nullptr);
 }
 
@@ -238,6 +239,9 @@ void MythVisualMonoScopeVulkan::Draw(const QRect& Area, MythPainter* /*Painter*/
     if (!InitialiseVulkan(Area))
         return;
 
+    if (Area.isEmpty())
+        return;
+
     // Retrieve current command buffer
     auto *currentcmdbuf = m_vulkanWindow->currentCommandBuffer();