Bug 1679706 - Communicate to the front-end whether there are no visible pages at all. r=jfkthame

This will allow them to react however they want to empty page ranges as
a result of another setting change.

Differential Revision: https://phabricator.services.mozilla.com/D98183

dom/base/nsFrameLoader.cpp

@@ -3237,6 +3237,7 @@ already_AddRefed<Promise> nsFrameLoader::PrintPreview(
       info.mSheetCount = aInfo.sheetCount();
       info.mTotalPageCount = aInfo.totalPageCount();
       info.mHasSelection = aInfo.hasSelection();
+      info.mIsEmpty = aInfo.isEmpty();
       promise->MaybeResolve(info);
     } else {
       promise->MaybeRejectWithUnknownError("Print preview failed");

dom/chrome-webidl/FrameLoader.webidl

@@ -248,6 +248,11 @@ dictionary PrintPreviewSuccessInfo {
    */
   unsigned long totalPageCount = 0;
 
+  /**
+   * Whether the preview is empty because of page range selection.
+   */
+  boolean isEmpty = false;
+
   /**
    * Whether the document has a selection that can be printed.
    */

dom/ipc/BrowserChild.cpp

@@ -2324,7 +2324,7 @@ mozilla::ipc::IPCResult BrowserChild::RecvPrintPreview(
   // went wrong.
   auto sendCallbackError = MakeScopeExit([&] {
     if (aCallback) {
-      aCallback(PrintPreviewResultInfo(0, 0, false));  // signal error
+      aCallback(PrintPreviewResultInfo(0, 0, false, false));  // signal error
     }
   });
 

dom/ipc/PBrowser.ipdl

@@ -166,6 +166,7 @@ struct PrintPreviewResultInfo
 {
   uint32_t sheetCount;
   uint32_t totalPageCount;
+  bool isEmpty;
   bool hasSelection;
 };
 

layout/generic/PrintedSheetFrame.cpp

@@ -244,6 +244,7 @@ void PrintedSheetFrame::Reflow(nsPresContext* aPresContext,
   MOZ_ASSERT(numPagesOnThisSheet <= desiredPagesPerSheet,
              "Shouldn't have more than desired number of displayable pages "
              "on this sheet");
+  mNumPages = numPagesOnThisSheet;
 
   // Populate our ReflowOutput outparam -- just use up all the
   // available space, for both our desired size & overflow areas.

layout/generic/PrintedSheetFrame.h

@@ -41,6 +41,8 @@ class PrintedSheetFrame final : public nsContainerFrame {
   nsresult GetFrameName(nsAString& aResult) const override;
 #endif
 
+  uint32_t GetNumPages() const { return mNumPages; }
+
  private:
   // Private construtor & destructor, to avoid accidental (non-FrameArena)
   // instantiation/deletion:
@@ -51,6 +53,8 @@ class PrintedSheetFrame final : public nsContainerFrame {
   // Note: this will be set before reflow, and it's strongly owned by our
   // nsPageSequenceFrame, which outlives us.
   nsSharedPageData* mPD = nullptr;
+  // The number of visible pages in this sheet.
+  uint32_t mNumPages = 0;
 };
 
 }  // namespace mozilla

layout/generic/nsPageSequenceFrame.cpp

@@ -232,6 +232,16 @@ nscoord nsPageSequenceFrame::ComputeCenteringMargin(
   return NSToCoordRound(scaledExtraSpace * 0.5 / scale);
 }
 
+uint32_t nsPageSequenceFrame::GetPagesInFirstSheet() const {
+  nsIFrame* firstSheet = mFrames.FirstChild();
+  if (!firstSheet) {
+    return 0;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(firstSheet->IsPrintedSheetFrame());
+  return static_cast<PrintedSheetFrame*>(firstSheet)->GetNumPages();
+}
+
 /*
  * Note: we largely position/size out our children (page frames) using
  * \*physical\* x/y/width/height values, because the print preview UI is always

layout/generic/nsPageSequenceFrame.h

@@ -133,6 +133,8 @@ class nsPageSequenceFrame final : public nsContainerFrame {
 
   int32_t GetRawNumPages() const { return mPageData->mRawNumPages; }
 
+  uint32_t GetPagesInFirstSheet() const;
+
   nsresult DoPageEnd();
 
   // We must allow Print Preview UI to have a background, no matter what the

layout/printing/nsPrintJob.cpp

@@ -862,7 +862,7 @@ nsresult nsPrintJob::PrintPreview(Document* aSourceDoc,
   if (NS_FAILED(rv)) {
     if (mPrintPreviewCallback) {
       mPrintPreviewCallback(
-          PrintPreviewResultInfo(0, 0, false));  // signal error
+          PrintPreviewResultInfo(0, 0, false, false));  // signal error
       mPrintPreviewCallback = nullptr;
     }
   }
@@ -875,6 +875,17 @@ int32_t nsPrintJob::GetRawNumPages() const {
   return seqFrame ? seqFrame->GetRawNumPages() : 0;
 }
 
+bool nsPrintJob::GetIsEmpty() const {
+  auto [seqFrame, numSheets] = GetSeqFrameAndCountSheets();
+  if (!seqFrame) {
+    return true;
+  }
+  if (numSheets > 1) {
+    return false;
+  }
+  return seqFrame->GetPagesInFirstSheet() > 0;
+}
+
 int32_t nsPrintJob::GetPrintPreviewNumSheets() const {
   auto [seqFrame, numSheets] = GetSeqFrameAndCountSheets();
   Unused << seqFrame;
@@ -1066,7 +1077,8 @@ nsresult nsPrintJob::CleanupOnFailure(nsresult aResult, bool aIsPrinting) {
 //---------------------------------------------------------------------
 void nsPrintJob::FirePrintingErrorEvent(nsresult aPrintError) {
   if (mPrintPreviewCallback) {
-    mPrintPreviewCallback(PrintPreviewResultInfo(0, 0, false));  // signal error
+    mPrintPreviewCallback(
+        PrintPreviewResultInfo(0, 0, false, false));  // signal error
     mPrintPreviewCallback = nullptr;
   }
 
@@ -2589,7 +2601,7 @@ nsresult nsPrintJob::FinishPrintPreview() {
 
   if (mPrintPreviewCallback) {
     mPrintPreviewCallback(PrintPreviewResultInfo(
-        GetPrintPreviewNumSheets(), GetRawNumPages(),
+        GetPrintPreviewNumSheets(), GetRawNumPages(), GetIsEmpty(),
         !mDisallowSelectionPrint && printData->mSelectionRoot));
     mPrintPreviewCallback = nullptr;
   }

layout/printing/nsPrintJob.h

@@ -127,6 +127,8 @@ class nsPrintJob final : public nsIObserver,
   bool HasEverPrinted() const { return mHasEverPrinted; }
   /// If the returned value is not greater than zero, an error occurred.
   int32_t GetRawNumPages() const;
+  // Returns whether the preview is empty due to page range exclusion.
+  bool GetIsEmpty() const;
 
   // Returns the total number of PrintedSheetFrames (i.e. faces of a sheet of
   // paper) for this print job. (This may be less than the raw number of pages,