From 1a3af35726889f16fb6b62d395660ec2d1d337dc Mon Sep 17 00:00:00 2001
From: Lei Zhang <[email protected]>
Date: Wed, 20 May 2026 13:22:44 -0700
Subject: [PATCH] [PDF Ink Signatures] Cancel painting when modifying PDFium pages

In PDFiumEngine, when methods like ApplyStroke() and DiscardText()
modify the list of FPDF_PAGEOBJECTs in a page, that may interact badly
with progressive rendering. It can be very complicated to build a
queuing mechanism for these modifications, so avoid doing that and
cancel the progressive paints instead. Do this by calling CancelPaint().

Unlike existing CancelPaint() calls, which presumably can already
somehow trigger page invalidation, these new CancelPaint() calls should
restart progressive paint after the FPDF_PAGEOBJECT modification takes
place. To support this, change CancelPaint() to return the list of rects
that were pending for painting. Then invalidate those rects to let
progressive paint restart.

Bug: 504417768
Change-Id: I678ab56b1127227ccfb88c3f37ca2dc9160869b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7861421
Reviewed-by: Andy Phan <[email protected]>
Commit-Queue: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1633790}
---

diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index bf6a9ed..ddac0bee8 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -3723,12 +3723,15 @@
   MaybeRequestPendingThumbnail(page_index);
 }
 
-void PDFiumEngine::CancelPaints() {
+std::vector<gfx::Rect> PDFiumEngine::CancelPaints() {
+  std::vector<gfx::Rect> canceled_rects;
   for (const auto& paint : progressive_paints_) {
     FPDF_RenderPage_Close(pages_[paint.page_index()]->GetPage());
+    canceled_rects.push_back(paint.rect());
   }
 
   progressive_paints_.clear();
+  return canceled_rects;
 }
 
 void PDFiumEngine::FillPageSides(int progressive_index) {
@@ -5144,6 +5147,8 @@
 }
 
 void PDFiumEngine::DiscardText(InkTextId id) {
+  std::vector<gfx::Rect> canceled_rects = CancelPaints();
+
   auto it = ink_text_data_.find(id);
   CHECK(it != ink_text_data_.end());
 
@@ -5164,6 +5169,10 @@
   if (!PageStillHasEdits(page_index)) {
     edited_pages_unload_preventers_.erase(page_index);
   }
+
+  for (const gfx::Rect& rect : canceled_rects) {
+    client_->Invalidate(rect);
+  }
 }
 
 void PDFiumEngine::DrawText(int page_index,
@@ -5171,6 +5180,8 @@
                             base::span<const InkTextInfo> text_info,
                             double pdf_zoom,
                             const InkTextBoxAttributes& attributes) {
+  std::vector<gfx::Rect> canceled_rects = CancelPaints();
+
   CHECK(PageIndexInBounds(page_index));
   PDFiumPage* pdfium_page = GetPage(page_index);
   CHECK(pdfium_page);
@@ -5258,6 +5269,10 @@
     edited_pages_unload_preventers_.insert(
         {page_index, PDFiumPage::ScopedPageUnloadPreventer(pdfium_page)});
   }
+
+  for (const gfx::Rect& rect : canceled_rects) {
+    client_->Invalidate(rect);
+  }
 }
 
 void PDFiumEngine::UpdateTextActiveAndInvalidate(InkTextId id, bool active) {
@@ -5302,6 +5317,8 @@
 void PDFiumEngine::ApplyStroke(int page_index,
                                InkStrokeId id,
                                const ink::Stroke& stroke) {
+  std::vector<gfx::Rect> canceled_rects = CancelPaints();
+
   // Saving a stroke will have the same page bounds limitations as the original
   // document.
   PDFiumPage* pdfium_page = GetPage(page_index);
@@ -5326,6 +5343,10 @@
     edited_pages_unload_preventers_.insert(
         {page_index, PDFiumPage::ScopedPageUnloadPreventer(pdfium_page)});
   }
+
+  for (const gfx::Rect& rect : canceled_rects) {
+    client_->Invalidate(rect);
+  }
 }
 
 void PDFiumEngine::UpdateStrokeActive(int page_index,
@@ -5342,6 +5363,8 @@
 }
 
 void PDFiumEngine::DiscardStroke(int page_index, InkStrokeId id) {
+  std::vector<gfx::Rect> canceled_rects = CancelPaints();
+
   CHECK(PageIndexInBounds(page_index));
   auto it = ink_stroke_data_.find(id);
   CHECK(it != ink_stroke_data_.end());
@@ -5353,6 +5376,10 @@
   if (!PageStillHasEdits(page_index)) {
     edited_pages_unload_preventers_.erase(page_index);
   }
+
+  for (const gfx::Rect& rect : canceled_rects) {
+    client_->Invalidate(rect);
+  }
 }
 
 PDFLoadedWithV2InkAnnotations PDFiumEngine::ContainsV2InkPath(
diff --git a/pdf/pdfium/pdfium_engine.h b/pdf/pdfium/pdfium_engine.h
index 594dc71..1e9d6cc 100644
--- a/pdf/pdfium/pdfium_engine.h
+++ b/pdf/pdfium/pdfium_engine.h
@@ -938,7 +938,8 @@
   void FinishPaint(size_t progressive_index, SkBitmap& image_data);
 
   // Stops any paints that are in progress.
-  void CancelPaints();
+  // Returns the rectangles, in screen coordinates, that had painting canceled.
+  std::vector<gfx::Rect> CancelPaints();
 
   // Invalidates all pages. Use this when some global parameter, such as page
   // orientation, has changed.