UnifiedPDF: Page previews disappear when zoomed enough

https://bugs.webkit.org/show_bug.cgi?id=284458
rdar://141280757

Reviewed by Simon Fraser.

Page overview layer would turn to tiled backing layer when zoomed enough.
Changing to tiled backing would change GraphicsLayer primary layer id.
The presentation controller would disambiguate what to paint as contents
based on which primary layer the updated GraphicsLayer has. Since
the presentation controller would not know the new id, the layer would
stay empty.

Fix by:
Force the background layer to not allow tiling.

To avoid similar bugs in the future, disambiguate the contents based on
the GraphicsLayer, not based on the primary layer id of the
GraphicsLayer. The primary layer is a implementation detail of the
GraphicsLayer, and its behavior cannot be anticipated by the client,
PDFPresentationController. AsyncPDFRenderer has similar problem, but
this cannot be solved as we cannot navigate from tile grid id to
graphics layer.

* Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp:
(WebCore::GraphicsLayerCA::changeLayerTypeTo):
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/AsyncPDFRenderer.h:
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/AsyncPDFRenderer.mm:
(WebKit::AsyncPDFRenderer::releaseMemory):
(WebKit::AsyncPDFRenderer::startTrackingLayer):
(WebKit::AsyncPDFRenderer::stopTrackingLayer):
(WebKit::AsyncPDFRenderer::layerForTileGrid const):
(WebKit::AsyncPDFRenderer::coverageRectDidChange):
(WebKit::AsyncPDFRenderer::renderInfoForTile const):
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDiscretePresentationController.h:
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDiscretePresentationController.mm:
(WebKit::PDFDiscretePresentationController::buildRows):
(WebKit::PDFDiscretePresentationController::customContentsScale const):
(WebKit::PDFDiscretePresentationController::layerNeedsPlatformContext const):
(WebKit::PDFDiscretePresentationController::rowDataForLayer const const):
(WebKit::PDFDiscretePresentationController::rowForLayer const):
(WebKit::PDFDiscretePresentationController::paintContents):
(WebKit::PDFDiscretePresentationController::rowDataForLayerID const const): Deleted.
(WebKit::PDFDiscretePresentationController::rowForLayerID const): Deleted.
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFPresentationController.h:
(WebKit::PDFPresentationController::rowForLayer const):
(WebKit::PDFPresentationController::rowForLayerID const): Deleted.
* Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFPresentationController.mm:
(WebKit::PDFPresentationController::makePageContainerLayer):

Canonical link: https://commits.webkit.org/287788@main

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/AsyncPDFRenderer.h

@@ -155,7 +155,7 @@ class AsyncPDFRenderer final : public WebCore::TiledBackingClient,
 private:
     AsyncPDFRenderer(PDFPresentationController&);
 
-    WebCore::GraphicsLayer* layerForTileGrid(WebCore::TileGridIdentifier) const;
+    RefPtr<WebCore::GraphicsLayer> layerForTileGrid(WebCore::TileGridIdentifier) const;
 
     TileRenderInfo renderInfoForFullTile(const WebCore::TiledBacking&, const TileForGrid& tileInfo, const WebCore::FloatRect& tileRect) const;
     TileRenderInfo renderInfoForTile(const WebCore::TiledBacking&, const TileForGrid& tileInfo, const WebCore::FloatRect& tileRect, const WebCore::FloatRect& renderRect, RefPtr<WebCore::NativeImage>&& background) const;

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/AsyncPDFRenderer.mm

@@ -84,39 +84,38 @@
     if (!presentationController)
         return;
 
-    for (auto& [layerID, layer] : m_layerIDtoLayerMap) {
+    for (Ref layer : m_layerIDtoLayerMap.values()) {
         // Ideally we'd be able to make the ImageBuffer memory volatile which would eliminate the need for this callback: webkit.org/b/274878
         if (auto* tiledBacking = layer->tiledBacking())
-            removePagePreviewsOutsideCoverageRect(tiledBacking->coverageRect(), presentationController->rowForLayerID(layerID));
+            removePagePreviewsOutsideCoverageRect(tiledBacking->coverageRect(), presentationController->rowForLayer(layer.ptr()));
     }
 
     LOG_WITH_STREAM(PDFAsyncRendering, stream << "AsyncPDFRenderer::releaseMemory - reduced page preview count from " << oldPagePreviewCount << " to " << m_pagePreviews.size());
 }
 
 void AsyncPDFRenderer::startTrackingLayer(GraphicsLayer& layer)
 {
-    Ref layerRef = layer;
-    if (auto* tiledBacking = layerRef->tiledBacking()) {
-        tiledBacking->setClient(this);
-        m_tileGridToLayerIDMap.set(tiledBacking->primaryGridIdentifier(), *layer.primaryLayerID());
-    }
-
-    m_layerIDtoLayerMap.set(*layer.primaryLayerID(), WTFMove(layerRef));
+    auto* tiledBacking = layer.tiledBacking();
+    if (!tiledBacking)
+        return;
+    tiledBacking->setClient(this);
+    m_tileGridToLayerIDMap.set(tiledBacking->primaryGridIdentifier(), *layer.primaryLayerID());
+    m_layerIDtoLayerMap.set(*layer.primaryLayerID(), layer);
 }
 
 void AsyncPDFRenderer::stopTrackingLayer(GraphicsLayer& layer)
 {
-    if (auto* tiledBacking = layer.tiledBacking()) {
-        auto gridIdentifier = tiledBacking->primaryGridIdentifier();
-        m_tileGridToLayerIDMap.remove(gridIdentifier);
-        m_gridRevalidationState.remove(gridIdentifier);
-        tiledBacking->setClient(nullptr);
-    }
-
+    auto* tiledBacking = layer.tiledBacking();
+    if (!tiledBacking)
+        return;
+    auto gridIdentifier = tiledBacking->primaryGridIdentifier();
+    m_tileGridToLayerIDMap.remove(gridIdentifier);
+    m_gridRevalidationState.remove(gridIdentifier);
+    tiledBacking->setClient(nullptr);
     m_layerIDtoLayerMap.remove(*layer.primaryLayerID());
 }
 
-GraphicsLayer* AsyncPDFRenderer::layerForTileGrid(TileGridIdentifier identifier) const
+RefPtr<GraphicsLayer> AsyncPDFRenderer::layerForTileGrid(TileGridIdentifier identifier) const
 {
     auto layerID = m_tileGridToLayerIDMap.getOptional(identifier);
     if (!layerID)
@@ -286,12 +285,9 @@
         return;
 
     std::optional<PDFLayoutRow> layoutRow;
-    RefPtr<GraphicsLayer> layer;
-    auto layerID = m_tileGridToLayerIDMap.getOptional(tiledBacking.primaryGridIdentifier());
-    if (layerID) {
-        layoutRow = presentationController->rowForLayerID(*layerID);
-        layer = m_layerIDtoLayerMap.get(*layerID);
-    }
+    RefPtr<GraphicsLayer> layer = layerForTileGrid(tiledBacking.primaryGridIdentifier());
+    if (layer)
+        layoutRow = presentationController->rowForLayer(layer.get());
 
     auto pageCoverage = presentationController->pageCoverageForContentsRect(coverageRect, layoutRow);
 
@@ -506,9 +502,8 @@
     auto paintingClipRect = convertTileRectToPaintingCoords(tileRect, tilingScaleFactor);
 
     std::optional<PDFLayoutRow> layoutRow;
-    auto layerID = m_tileGridToLayerIDMap.getOptional(tileInfo.gridIdentifier);
-    if (layerID)
-        layoutRow = presentationController->rowForLayerID(*layerID);
+    if (RefPtr layer = layerForTileGrid(tileInfo.gridIdentifier))
+        layoutRow = presentationController->rowForLayer(layer.get());
 
     auto pageCoverage = presentationController->pageCoverageAndScalesForContentsRect(paintingClipRect, layoutRow, tilingScaleFactor);
 

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDiscretePresentationController.h

@@ -85,7 +85,7 @@ class PDFDiscretePresentationController final : public PDFPresentationController
     WebCore::GraphicsLayerClient& graphicsLayerClient() override { return *this; }
 
     std::optional<PDFLayoutRow> visibleRow() const override;
-    std::optional<PDFLayoutRow> rowForLayerID(WebCore::PlatformLayerIdentifier) const override;
+    std::optional<PDFLayoutRow> rowForLayer(const WebCore::GraphicsLayer*) const override;
 
     WebCore::FloatSize contentsOffsetForPage(PDFDocumentLayout::PageIndex) const;
 
@@ -216,7 +216,7 @@ class PDFDiscretePresentationController final : public PDFPresentationController
 #endif
     };
 
-    const RowData* rowDataForLayerID(WebCore::PlatformLayerIdentifier) const;
+    const RowData* rowDataForLayer(const WebCore::GraphicsLayer*) const;
     WebCore::FloatPoint positionForRowContainerLayer(const PDFLayoutRow&) const;
     WebCore::FloatSize rowContainerSize(const PDFLayoutRow&) const;
 
@@ -225,7 +225,7 @@ class PDFDiscretePresentationController final : public PDFPresentationController
     RefPtr<WebCore::GraphicsLayer> m_rowsContainerLayer;
     Vector<RowData> m_rows;
 
-    HashMap<WebCore::PlatformLayerIdentifier, unsigned> m_layerIDToRowIndexMap;
+    HashMap<const WebCore::GraphicsLayer*, unsigned> m_layerToRowIndexMap;
     std::optional<PDFDocumentLayout::DisplayMode> m_displayModeAtLastLayerSetup;
 
     unsigned m_visibleRowIndex { 0 };

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFDiscretePresentationController.mm

@@ -1069,7 +1069,7 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
 
         row.leftPageContainerLayer = makePageContainerLayer(leftPageIndex);
         RefPtr pageBackgroundLayer = pageBackgroundLayerForPageContainerLayer(*row.protectedLeftPageContainerLayer());
-        m_layerIDToRowIndexMap.add(*pageBackgroundLayer->primaryLayerID(), rowIndex);
+        m_layerToRowIndexMap.add(pageBackgroundLayer.get(), rowIndex);
 
         if (row.pages.numPages() == 1) {
             ASSERT(!row.rightPageContainerLayer);
@@ -1079,7 +1079,7 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
         auto rightPageIndex = layoutRow.pages[1];
         row.rightPageContainerLayer = makePageContainerLayer(rightPageIndex);
         RefPtr rightPageBackgroundLayer = pageBackgroundLayerForPageContainerLayer(*row.protectedRightPageContainerLayer());
-        m_layerIDToRowIndexMap.add(*rightPageBackgroundLayer->primaryLayerID(), rowIndex);
+        m_layerToRowIndexMap.add(rightPageBackgroundLayer.get(), rowIndex);
     };
 
     auto parentRowLayers = [](RowData& row) {
@@ -1112,15 +1112,15 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
         // This is the call that enables async rendering.
         asyncRenderer()->startTrackingLayer(*rowContentsLayer);
 
-        m_layerIDToRowIndexMap.set(*rowContentsLayer->primaryLayerID(), rowIndex);
+        m_layerToRowIndexMap.set(rowContentsLayer.get(), rowIndex);
 
 #if ENABLE(UNIFIED_PDF_SELECTION_LAYER)
         RefPtr rowSelectionLayer = row.selectionLayer = createGraphicsLayer(makeString("Row selection "_s, rowIndex), GraphicsLayer::Type::TiledBacking);
         rowSelectionLayer->setAnchorPoint({ });
         rowSelectionLayer->setDrawsContent(true);
         rowSelectionLayer->setAcceleratesDrawing(true);
         rowSelectionLayer->setBlendMode(BlendMode::Multiply);
-        m_layerIDToRowIndexMap.set(*rowSelectionLayer->primaryLayerID(), rowIndex);
+        m_layerToRowIndexMap.set(rowSelectionLayer.get(), rowIndex);
 #endif
 
         parentRowLayers(row);
@@ -1446,7 +1446,7 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
 
 std::optional<float> PDFDiscretePresentationController::customContentsScale(const GraphicsLayer* layer) const
 {
-    auto* rowData = rowDataForLayerID(*layer->primaryLayerID());
+    auto* rowData = rowDataForLayer(layer);
     if (!rowData)
         return { };
 
@@ -1464,7 +1464,7 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
     // We need a platform context if the plugin can not paint selections into its own layer,
     // since we would then have to vend a platform context that PDFKit can paint into.
     // However, this constraint only applies for the contents layer. No other layer needs to be WP-backed.
-    auto* rowData = rowDataForLayerID(*layer->primaryLayerID());
+    auto* rowData = rowDataForLayer(layer);
     if (!rowData)
         return false;
 
@@ -1503,9 +1503,9 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
     }
 }
 
-auto PDFDiscretePresentationController::rowDataForLayerID(PlatformLayerIdentifier layerID) const -> const RowData*
+auto PDFDiscretePresentationController::rowDataForLayer(const GraphicsLayer* layer) const -> const RowData*
 {
-    auto rowIndex = m_layerIDToRowIndexMap.getOptional(layerID);
+    auto rowIndex = m_layerToRowIndexMap.getOptional(layer);
     if (!rowIndex)
         return nullptr;
 
@@ -1523,9 +1523,9 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
     return m_rows[m_visibleRowIndex].pages;
 }
 
-std::optional<PDFLayoutRow> PDFDiscretePresentationController::rowForLayerID(PlatformLayerIdentifier layerID) const
+std::optional<PDFLayoutRow> PDFDiscretePresentationController::rowForLayer(const GraphicsLayer* layer) const
 {
-    auto* rowData = rowDataForLayerID(layerID);
+    auto* rowData = rowDataForLayer(layer);
     if (rowData)
         return rowData->pages;
 
@@ -1534,7 +1534,7 @@ static float elasticDeltaForTimeDelta(float initialPosition, float initialVeloci
 
 void PDFDiscretePresentationController::paintContents(const GraphicsLayer* layer, GraphicsContext& context, const FloatRect& clipRect, OptionSet<GraphicsLayerPaintBehavior>)
 {
-    auto rowIndex = m_layerIDToRowIndexMap.getOptional(*layer->primaryLayerID());
+    auto rowIndex = m_layerToRowIndexMap.getOptional(layer);
     if (!rowIndex)
         return;
 

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFPresentationController.h

@@ -92,7 +92,7 @@ class PDFPresentationController : public ThreadSafeRefCountedAndCanMakeThreadSaf
     virtual void setNeedsRepaintInDocumentRect(OptionSet<RepaintRequirement>, const WebCore::FloatRect& rectInDocumentCoordinates, std::optional<PDFLayoutRow>) = 0;
 
     virtual std::optional<PDFLayoutRow> visibleRow() const { return { }; }
-    virtual std::optional<PDFLayoutRow> rowForLayerID(WebCore::PlatformLayerIdentifier) const { return { }; }
+    virtual std::optional<PDFLayoutRow> rowForLayer(const WebCore::GraphicsLayer*) const { return { }; }
 
     struct VisiblePDFPosition {
         PDFDocumentLayout::PageIndex pageIndex { 0 };

Source/WebKit/WebProcess/Plugins/PDF/UnifiedPDF/PDFPresentationController.mm

@@ -124,6 +124,7 @@
     pageBackgroundLayer->setDrawsContent(true);
     pageBackgroundLayer->setAcceleratesDrawing(true);
     pageBackgroundLayer->setShouldUpdateRootRelativeScaleFactor(false);
+    pageBackgroundLayer->setAllowsTiling(false);
     pageBackgroundLayer->setNeedsDisplay(); // We only need to paint this layer once when page backgrounds change.
 
     // FIXME: <https://webkit.org/b/276981> Need to add a 1px black border with alpha 0.0586.