[PDF Ink Signatures] Account for device scale in Ink zoom

PdfInkModule relies upon a client query to know the scale factor to
apply when transforming points.  This has included the zoom factor
within the PDF viewer plugin, but has been missing any extra screen
scaling for OS-level display scaling.  HiRes on some macOS devices or
Windows devices with display scale settings set to something other than
100% could cause a significant shift in stroke placement.

Update the PdfViewWebPlugin::PdfInkModuleClientImpl to incorporate the
device scale when providing zoom for Ink strokes.

Bug: 378623808
Change-Id: Ic4bc2b89eaa0de99d38345249552986e9aeb17f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6017318
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Alan Screen <awscreen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1382514}

pdf/pdf_view_web_plugin.cc

@@ -293,7 +293,9 @@ class PdfViewWebPlugin::PdfInkModuleClientImpl : public PdfInkModuleClient {
     return plugin_->available_area_.OffsetFromOrigin();
   }
 
-  float GetZoom() const override { return plugin_->zoom_; }
+  float GetZoom() const override {
+    return plugin_->zoom_ * plugin_->client_->DeviceScaleFactor();
+  }
 
   void Invalidate(const gfx::Rect& rect) override {
     return plugin_->Invalidate(rect);

pdf/pdf_view_web_plugin_unittest.cc

@@ -230,6 +230,7 @@ class FakePdfViewWebPluginClient : public PdfViewWebPlugin::Client {
       return associated_loader;
     });
     ON_CALL(*this, GetIsolate).WillByDefault(Return(GetBlinkIsolate()));
+    ON_CALL(*this, DeviceScaleFactor).WillByDefault(Return(1.0f));
     ON_CALL(*this, GetEmbedderOriginString)
         .WillByDefault(
             Return("chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/"));
@@ -2716,6 +2717,36 @@ TEST_F(PdfViewWebPluginInkTest, UpdateCursor) {
   EXPECT_EQ(ui::mojom::CursorType::kPointer, cursor.type());
 }
 
+TEST_F(PdfViewWebPluginInkTest, GetZoom) {
+  // Demonstrate that default zoom is identity.
+  EXPECT_EQ(1.0f, plugin_->ink_module_client_for_testing()->GetZoom());
+
+  // Verify that changing the plugin zoom shows effect.
+  EXPECT_CALL(*engine_ptr_, ZoomUpdated(2.0f));
+  plugin_->OnMessage(ParseMessage(R"({
+    "type": "viewport",
+    "userInitiated": false,
+    "zoom": 2,
+    "layoutOptions": {
+      "direction": 0,
+      "defaultPageOrientation": 0,
+      "twoUpViewEnabled": false,
+    },
+    "xOffset": 0,
+    "yOffset": 0,
+    "pinchPhase": 0,
+  })"));
+  EXPECT_EQ(2.0f, plugin_->ink_module_client_for_testing()->GetZoom());
+
+  // Verify that changing the platform device scale shows effect.
+  ON_CALL(*client_ptr_, DeviceScaleFactor).WillByDefault(Return(1.25f));
+  EXPECT_CALL(*engine_ptr_, ZoomUpdated(2.5f));
+  constexpr gfx::Rect kWindowRect(12, 24, 36, 48);
+  plugin_->UpdateGeometry(kWindowRect, kWindowRect, kWindowRect,
+                          /*is_visible=*/true);
+  EXPECT_EQ(2.5f, plugin_->ink_module_client_for_testing()->GetZoom());
+}
+
 TEST_F(PdfViewWebPluginInkTest, UpdateThumbnail) {
   SetUpWithTrivialInkStrokes();