Bug 1833733 - Properly detect page sequence background from FindEffectiveBackgroundColor. r=dholbert

And specify it since we don't look at gradients.

Differential Revision: https://phabricator.services.mozilla.com/D178476

layout/base/PresShell.cpp

@@ -5288,15 +5288,6 @@ void AddDisplayItemToBottom(nsDisplayListBuilder* aBuilder,
   aList->AppendToTop(&list);
 }
 
-void PresShell::AddPrintPreviewBackgroundItem(nsDisplayListBuilder* aBuilder,
-                                              nsDisplayList* aList,
-                                              nsIFrame* aFrame,
-                                              const nsRect& aBounds) {
-  nsDisplayItem* item = MakeDisplayItem<nsDisplaySolidColor>(
-      aBuilder, aFrame, aBounds, NS_RGB(115, 115, 115));
-  AddDisplayItemToBottom(aBuilder, aList, item);
-}
-
 static bool AddCanvasBackgroundColor(const nsDisplayList* aList,
                                      nsIFrame* aCanvasFrame, nscolor aColor,
                                      bool aCSSBackgroundColor) {
@@ -5451,33 +5442,28 @@ PresShell::CanvasBackground PresShell::ComputeCanvasBackground() const {
   // If we have a frame tree and it has style information that
   // specifies the background color of the canvas, update our local
   // cache of that color.
-  nsIFrame* rootStyleFrame = FrameConstructor()->GetRootElementStyleFrame();
-  if (!rootStyleFrame) {
+  nsIFrame* canvas = GetCanvasFrame();
+  if (!canvas) {
     // If the root element of the document (ie html) has style 'display: none'
     // then the document's background color does not get drawn; return the color
     // we actually draw.
     return {GetDefaultBackgroundColorToDraw(), false};
   }
 
-  const ComputedStyle* bgStyle =
-      nsCSSRendering::FindRootFrameBackground(rootStyleFrame);
-  // XXX We should really be passing the canvasframe, not the root element
-  // style frame but we don't have access to the canvasframe here. It isn't
-  // a problem because only a few frames can return something other than true
-  // and none of them would be a canvas frame or root element style frame.
+  const nsIFrame* bgFrame = nsCSSRendering::FindBackgroundFrame(canvas);
   nscolor color = NS_RGBA(0, 0, 0, 0);
   bool drawBackgroundImage = false;
   bool drawBackgroundColor = false;
-  const nsStyleDisplay* disp = rootStyleFrame->StyleDisplay();
+  const nsStyleDisplay* disp = bgFrame->StyleDisplay();
   StyleAppearance appearance = disp->EffectiveAppearance();
-  if (rootStyleFrame->IsThemed(disp) &&
+  if (bgFrame->IsThemed(disp) &&
       appearance != StyleAppearance::MozWinBorderlessGlass) {
     // Ignore the CSS background-color if -moz-appearance is used and it is
     // not one of the glass values. (Windows 7 Glass has traditionally not
     // overridden background colors, so we preserve that behavior for now.)
   } else {
     color = nsCSSRendering::DetermineBackgroundColor(
-        mPresContext, bgStyle, rootStyleFrame, drawBackgroundImage,
+        mPresContext, bgFrame->Style(), canvas, drawBackgroundImage,
         drawBackgroundColor);
   }
   if (!IsTransparentContainerElement()) {

layout/base/PresShell.h

@@ -905,15 +905,6 @@ class PresShell final : public nsStubDocumentObserver,
   CanvasBackground ComputeCanvasBackground() const;
   void UpdateCanvasBackground();
 
-  /**
-   * Add a solid color item to the bottom of aList with frame aFrame and
-   * bounds aBounds representing the dark grey background behind the page of a
-   * print preview presentation.
-   */
-  void AddPrintPreviewBackgroundItem(nsDisplayListBuilder* aBuilder,
-                                     nsDisplayList* aList, nsIFrame* aFrame,
-                                     const nsRect& aBounds);
-
   /**
    * Computes the backstop color for the view: transparent if in a transparent
    * widget, otherwise the PresContext default background color. This color is

layout/base/nsLayoutUtils.cpp

@@ -2849,36 +2849,23 @@ void nsLayoutUtils::AddExtraBackgroundItems(nsDisplayListBuilder* aBuilder,
                                             const nsRect& aCanvasArea,
                                             const nsRegion& aVisibleRegion,
                                             nscolor aBackstop) {
-  LayoutFrameType frameType = aFrame->Type();
-  nsPresContext* presContext = aFrame->PresContext();
-  PresShell* presShell = presContext->PresShell();
-
-  // For the viewport frame in print preview/page layout we want to paint
-  // the grey background behind the page, not the canvas color.
-  if (frameType == LayoutFrameType::Viewport &&
-      nsLayoutUtils::NeedsPrintPreviewBackground(presContext)) {
-    nsRect bounds =
-        nsRect(aBuilder->ToReferenceFrame(aFrame), aFrame->GetSize());
-    nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(
-        aBuilder, aFrame, bounds, bounds);
-    presShell->AddPrintPreviewBackgroundItem(aBuilder, aList, aFrame, bounds);
-  } else if (frameType != LayoutFrameType::Page) {
+  if (aFrame->IsPageFrame()) {
     // For printing, this function is first called on an nsPageFrame, which
     // creates a display list with a PageContent item. The PageContent item's
-    // paint function calls this function on the nsPageFrame's child which is
-    // an nsPageContentFrame. We only want to add the canvas background color
-    // item once, for the nsPageContentFrame.
-
-    // Add the canvas background color to the bottom of the list. This
-    // happens after we've built the list so that AddCanvasBackgroundColorItem
-    // can monkey with the contents if necessary.
-    nsRect canvasArea = aVisibleRegion.GetBounds();
-    canvasArea.IntersectRect(aCanvasArea, canvasArea);
-    nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(
-        aBuilder, aFrame, canvasArea, canvasArea);
-    presShell->AddCanvasBackgroundColorItem(aBuilder, aList, aFrame, canvasArea,
-                                            aBackstop);
+    // paint function calls this function on the nsPageFrame's child which is an
+    // nsPageContentFrame. We only want to add the canvas background color item
+    // once, for the nsPageContentFrame.
+    return;
   }
+  // Add the canvas background color to the bottom of the list. This
+  // happens after we've built the list so that AddCanvasBackgroundColorItem
+  // can monkey with the contents if necessary.
+  nsRect canvasArea = aVisibleRegion.GetBounds();
+  canvasArea.IntersectRect(aCanvasArea, canvasArea);
+  nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(
+      aBuilder, aFrame, canvasArea, canvasArea);
+  aFrame->PresShell()->AddCanvasBackgroundColorItem(aBuilder, aList, aFrame,
+                                                    canvasArea, aBackstop);
 }
 
 // #define PRINT_HITTESTINFO_STATS
@@ -8557,12 +8544,6 @@ bool nsLayoutUtils::IsNonWrapperBlock(nsIFrame* aFrame) {
   return aFrame->IsBlockFrameOrSubclass() && !aFrame->IsBlockWrapper();
 }
 
-bool nsLayoutUtils::NeedsPrintPreviewBackground(nsPresContext* aPresContext) {
-  return aPresContext->IsRootPaginatedDocument() &&
-         (aPresContext->Type() == nsPresContext::eContext_PrintPreview ||
-          aPresContext->Type() == nsPresContext::eContext_PageLayout);
-}
-
 AutoMaybeDisableFontInflation::AutoMaybeDisableFontInflation(nsIFrame* aFrame) {
   // FIXME: Now that inflation calculations are based on the flow
   // root's NCA's (nearest common ancestor of its inflatable

layout/generic/nsSubDocumentFrame.cpp

@@ -485,21 +485,13 @@ void nsSubDocumentFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
         bounds = bounds.ScaleToOtherAppUnitsRoundOut(parentAPD, subdocAPD);
       }
 
-      // If we are in print preview/page layout we want to paint the grey
-      // background behind the page, not the canvas color. The canvas color gets
-      // painted on the page itself.
-      if (nsLayoutUtils::NeedsPrintPreviewBackground(presContext)) {
-        presShell->AddPrintPreviewBackgroundItem(aBuilder, &childItems, frame,
-                                                 bounds);
-      } else {
-        // Add the canvas background color to the bottom of the list. This
-        // happens after we've built the list so that
-        // AddCanvasBackgroundColorItem can monkey with the contents if
-        // necessary.
-        presShell->AddCanvasBackgroundColorItem(
-            aBuilder, &childItems, frame, bounds, NS_RGBA(0, 0, 0, 0),
-            AddCanvasBackgroundColorFlags::ForceDraw);
-      }
+      // Add the canvas background color to the bottom of the list. This
+      // happens after we've built the list so that
+      // AddCanvasBackgroundColorItem can monkey with the contents if
+      // necessary.
+      presShell->AddCanvasBackgroundColorItem(
+          aBuilder, &childItems, frame, bounds, NS_RGBA(0, 0, 0, 0),
+          AddCanvasBackgroundColorFlags::ForceDraw);
     }
   }
 

layout/painting/nsCSSRendering.cpp

@@ -30,10 +30,12 @@
 #include "skia/include/core/SkTextBlob.h"
 
 #include "BorderConsts.h"
+#include "nsCanvasFrame.h"
 #include "nsStyleConsts.h"
 #include "nsPresContext.h"
 #include "nsIFrame.h"
 #include "nsIFrameInlines.h"
+#include "nsPageSequenceFrame.h"
 #include "nsPoint.h"
 #include "nsRect.h"
 #include "nsFrameManager.h"
@@ -1127,13 +1129,32 @@ void nsImageRenderer::ComputeObjectAnchorPoint(const Position& aPos,
                            aImageSize.height, &aTopLeft->y, &aAnchorPoint->y);
 }
 
+// In print / print preview we have multiple canvas frames (one for each page,
+// and one for the document as a whole). For the topmost one, we really want the
+// page sequence page background, not the root or body's background.
+static nsIFrame* GetPageSequenceForCanvas(const nsIFrame* aCanvasFrame) {
+  MOZ_ASSERT(aCanvasFrame->IsCanvasFrame(), "not a canvas frame");
+  nsPresContext* pc = aCanvasFrame->PresContext();
+  if (!pc->IsPrintingOrPrintPreview()) {
+    return nullptr;
+  }
+  auto* ps = pc->PresShell()->GetPageSequenceFrame();
+  if (!ps) {
+    return nullptr;
+  }
+  if (ps->GetParent() != aCanvasFrame) {
+    return nullptr;
+  }
+  return ps;
+}
+
 auto nsCSSRendering::FindEffectiveBackgroundColor(nsIFrame* aFrame,
                                                   bool aStopAtThemed,
                                                   bool aPreferBodyToCanvas)
     -> EffectiveBackgroundColor {
   MOZ_ASSERT(aFrame);
-
-  auto BgColorIfNotTransparent = [](nsIFrame* aFrame) -> Maybe<nscolor> {
+  nsPresContext* pc = aFrame->PresContext();
+  auto BgColorIfNotTransparent = [&](nsIFrame* aFrame) -> Maybe<nscolor> {
     nscolor c =
         aFrame->GetVisitedDependentColor(&nsStyleBackground::mBackgroundColor);
     if (NS_GET_A(c) == 255) {
@@ -1143,7 +1164,7 @@ auto nsCSSRendering::FindEffectiveBackgroundColor(nsIFrame* aFrame,
       // TODO(emilio): We should maybe just blend with ancestor bg colors and
       // such, but this is probably good enough for now, matches pre-existing
       // behavior.
-      const nscolor defaultBg = aFrame->PresContext()->DefaultBackgroundColor();
+      const nscolor defaultBg = pc->DefaultBackgroundColor();
       MOZ_ASSERT(NS_GET_A(defaultBg) == 255, "PreferenceSheet guarantees this");
       return Some(NS_ComposeColors(defaultBg, c));
     }
@@ -1161,8 +1182,8 @@ auto nsCSSRendering::FindEffectiveBackgroundColor(nsIFrame* aFrame,
     }
 
     if (frame->IsCanvasFrame()) {
-      if (aPreferBodyToCanvas) {
-        if (auto* body = frame->PresContext()->Document()->GetBodyElement()) {
+      if (aPreferBodyToCanvas && !GetPageSequenceForCanvas(frame)) {
+        if (auto* body = pc->Document()->GetBodyElement()) {
           if (nsIFrame* f = body->GetPrimaryFrame()) {
             if (auto bg = BgColorIfNotTransparent(f)) {
               return {*bg};
@@ -1178,7 +1199,7 @@ auto nsCSSRendering::FindEffectiveBackgroundColor(nsIFrame* aFrame,
     }
   }
 
-  return {aFrame->PresContext()->DefaultBackgroundColor()};
+  return {pc->DefaultBackgroundColor()};
 }
 
 nsIFrame* nsCSSRendering::FindBackgroundStyleFrame(nsIFrame* aForFrame) {
@@ -1251,6 +1272,20 @@ ComputedStyle* nsCSSRendering::FindRootFrameBackground(nsIFrame* aForFrame) {
   return FindBackgroundStyleFrame(aForFrame)->Style();
 }
 
+static nsIFrame* FindCanvasBackgroundFrame(const nsIFrame* aForFrame,
+                                           nsIFrame* aRootElementFrame) {
+  MOZ_ASSERT(aForFrame->IsCanvasFrame(), "not a canvas frame");
+  if (auto* ps = GetPageSequenceForCanvas(aForFrame)) {
+    return ps;
+  }
+  if (aRootElementFrame) {
+    return nsCSSRendering::FindBackgroundStyleFrame(aRootElementFrame);
+  }
+  // This should always give transparent, so we'll fill it in with the default
+  // color if needed.  This seems to happen a bit while a page is being loaded.
+  return const_cast<nsIFrame*>(aForFrame);
+}
+
 // Helper for FindBackgroundFrame. Returns true if aForFrame has a meaningful
 // background that it should draw (i.e. that it hasn't propagated to another
 // frame).  See documentation for FindBackground.

layout/painting/nsCSSRendering.h

@@ -296,36 +296,6 @@ struct nsCSSRendering {
    */
   static mozilla::ComputedStyle* FindRootFrameBackground(nsIFrame* aForFrame);
 
-  /**
-   * Returns background style information for the canvas.
-   *
-   * @param aForFrame
-   *   the frame used to represent the canvas, in the CSS sense (i.e.
-   *   aForFrame->IsCanvasFrame() must be true)
-   * @param aRootElementFrame
-   *   the frame representing the root element of the document
-   * @param aBackground
-   *   contains background style information for the canvas on return
-   */
-
-  static nsIFrame* FindCanvasBackgroundFrame(const nsIFrame* aForFrame,
-                                             nsIFrame* aRootElementFrame) {
-    MOZ_ASSERT(aForFrame->IsCanvasFrame(), "not a canvas frame");
-    if (aRootElementFrame) {
-      return FindBackgroundStyleFrame(aRootElementFrame);
-    }
-
-    // This should always give transparent, so we'll fill it in with the
-    // default color if needed.  This seems to happen a bit while a page is
-    // being loaded.
-    return const_cast<nsIFrame*>(aForFrame);
-  }
-
-  static mozilla::ComputedStyle* FindCanvasBackground(
-      nsIFrame* aForFrame, nsIFrame* aRootElementFrame) {
-    return FindCanvasBackgroundFrame(aForFrame, aRootElementFrame)->Style();
-  }
-
   /**
    * Find a non-transparent background color on an ancestor, for various
    * contrast checks. Note that this only accounts for background-color and

layout/style/res/ua.css

@@ -301,7 +301,7 @@
   /* Collection of pages in print/print preview. Visual styles may only appear
    * in print preview. */
   display: block;
-  background: linear-gradient(#606060, #8a8a8a) fixed;
+  background: #606060 linear-gradient(#606060, #8a8a8a) fixed;
   print-color-adjust: exact;
   /* We always fill the available space in both directions */
   height: 100%;