Bug 454059 - Add a new PaintForPrinting display list builder mode, and only create a Linkifier when printing. r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D114474

layout/base/nsLayoutUtils.cpp

@@ -3131,6 +3131,10 @@ nsresult nsLayoutUtils::PaintFrame(gfxContext* aRenderingContext,
   TimeStamp startBuildDisplayList = TimeStamp::Now();
 
   const bool buildCaret = !(aFlags & PaintFrameFlags::HideCaret);
+
+  // Note that isForPainting here does not include the PaintForPrinting builder
+  // mode; that's OK because there is no point in using retained display lists
+  // for a print destination.
   const bool isForPainting = (aFlags & PaintFrameFlags::WidgetLayers) &&
                              aBuilderMode == nsDisplayListBuilderMode::Painting;
 

layout/generic/nsPageSequenceFrame.cpp

@@ -673,7 +673,7 @@ nsresult nsPageSequenceFrame::PrintNextSheet() {
   nsRegion drawingRegion(drawingRect);
   nsLayoutUtils::PaintFrame(gCtx, currentSheetFrame, drawingRegion,
                             NS_RGBA(0, 0, 0, 0),
-                            nsDisplayListBuilderMode::Painting,
+                            nsDisplayListBuilderMode::PaintForPrinting,
                             nsLayoutUtils::PaintFrameFlags::SyncDecodeImages);
   return rv;
 }

layout/painting/nsDisplayList.h

@@ -341,6 +341,7 @@ struct ActiveScrolledRoot {
 
 enum class nsDisplayListBuilderMode : uint8_t {
   Painting,
+  PaintForPrinting,
   EventDelivery,
   FrameVisibility,
   TransformComputation,
@@ -463,10 +464,20 @@ class nsDisplayListBuilder {
   }
 
   /**
-   * @return true if the display list is being built for painting.
+   * @return true if the display list is being built for painting. This
+   * includes both painting to a window or other buffer and painting to
+   * a print/pdf destination.
    */
   bool IsForPainting() const {
-    return mMode == nsDisplayListBuilderMode::Painting;
+    return mMode == nsDisplayListBuilderMode::Painting ||
+           mMode == nsDisplayListBuilderMode::PaintForPrinting;
+  }
+
+  /**
+   * @return true if the display list is being built specifically for printing.
+   */
+  bool IsForPrinting() const {
+    return mMode == nsDisplayListBuilderMode::PaintForPrinting;
   }
 
   /**