Display a message when we can't debug a pixel shader and show a history

qrenderdoc/Code/Interface/QRDInterface.h

@@ -1390,6 +1390,11 @@ QWidget.
 )");
   virtual void SetHistory(const rdcarray<PixelModification> &history) = 0;
 
+  DOCUMENT(R"(Indicates that the pixel history was launched as a result of failing to debug a shader,
+so a message will be displayed to explain.
+)");
+  virtual void SetFailedDebug() = 0;
+
 protected:
   IPixelHistoryView() = default;
   ~IPixelHistoryView() = default;

qrenderdoc/Windows/PixelHistoryView.cpp

@@ -666,12 +666,13 @@ PixelHistoryView::PixelHistoryView(ICaptureContext &ctx, ResourceId id, QPoint p
     channelStr = lit("Alpha");
 
   QString text;
-  text = tr("Preview colours displayed in visible range %1 - %2 with %3 visible.\n\n")
-             .arg(Formatter::Format(display.rangeMin))
-             .arg(Formatter::Format(display.rangeMax))
-             .arg(channelStr);
+
+  text += tr("Preview colours displayed in visible range %1 - %2 with %3 visible.<br><br>")
+              .arg(Formatter::Format(display.rangeMin))
+              .arg(Formatter::Format(display.rangeMax))
+              .arg(channelStr);
   text +=
-      tr("Double click to jump to an event.\n"
+      tr("Double click to jump to an event.<br>"
          "Right click to debug an event, or hide failed events.");
 
   ui->label->setText(text);
@@ -717,6 +718,16 @@ PixelHistoryView::~PixelHistoryView()
   delete ui;
 }
 
+void PixelHistoryView::SetFailedDebug()
+{
+  QString text = ui->label->text();
+  text = tr("<b>Pixel shader debug failed</b> - most likely this is caused by no write to the "
+            "pixel at the current event.<br>"
+            "Displaying pixel history to find the event which did write.<br><br>") +
+         text;
+  ui->label->setText(text);
+}
+
 void PixelHistoryView::enableTimelineHighlight()
 {
   if(m_Ctx.HasTimelineBar())

qrenderdoc/Windows/PixelHistoryView.h

@@ -47,6 +47,7 @@ public:
   // IPixelHistoryView
   QWidget *Widget() override { return this; }
   void SetHistory(const rdcarray<PixelModification> &history) override;
+  void SetFailedDebug() override;
 
   // ICaptureViewer
   void OnCaptureLoaded() override;

qrenderdoc/Windows/TextureViewer.cpp

@@ -4145,7 +4145,7 @@ void TextureViewer::on_debugPixelContext_clicked()
   if(!trace)
   {
     if(m_Ctx.APIProps().pixelHistory)
-      on_pixelHistory_clicked();
+      ShowPixelHistory(true);
     else
       RDDialog::critical(this, tr("Debug Error"), tr("Error debugging pixel."));
     return;
@@ -4162,6 +4162,11 @@ void TextureViewer::on_debugPixelContext_clicked()
 }
 
 void TextureViewer::on_pixelHistory_clicked()
+{
+  ShowPixelHistory(false);
+}
+
+void TextureViewer::ShowPixelHistory(bool failedDebug)
 {
   TextureDescription *texptr = GetCurrentTexture();
 
@@ -4181,6 +4186,9 @@ void TextureViewer::on_pixelHistory_clicked()
   uint32_t view = m_TexDisplay.subresource.slice - m_Following.GetFirstArraySlice(m_Ctx);
   IPixelHistoryView *hist = m_Ctx.ViewPixelHistory(texptr->resourceId, x, y, view, m_TexDisplay);
 
+  if(failedDebug)
+    hist->SetFailedDebug();
+
   m_Ctx.AddDockWindow(hist->Widget(), DockReference::TransientPopupArea, this, 0.3f);
 
   // we use this pointer to ensure that the history viewer is still visible (and hasn't been closed)

qrenderdoc/Windows/TextureViewer.h

@@ -256,6 +256,8 @@ private:
 
   void SelectPreview(ResourcePreview *prev);
 
+  void ShowPixelHistory(bool failedDebug);
+
   void SetupTextureTabs();
   void RemoveTextureTabs(int firstIndex);