Fix named destination "FitR" zooming in at the wrong region issue.

In the PDF viewer, the viewport uses goToPageAndXY() to navigate inside
the document, which takes in-screen coordinates as x and y input. The
parameters we get from FPDFDest_GetVieware() are directly from the named
destination, which uses the in-page coordinates.

However, these in-page coordinates are sent to the viewport for
navigation without getting transformed into in-screen coordinates, which
results in PDF viewer zooming in at the wrong region of the page for
FitR type named destination.

Since coordinate transformation is missing for all view fit types, this
CL adds a helper ParamsTransformPageToScreen() to handle the
transformation according to the view's fit type. (See Table 151 about
Destination syntax from PDF 32000-1:2008.)

Bug: 1136733
Change-Id: I811844260f2ea9b1a5244a178174691e85f2f96d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628492Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Hui Yingst <nigi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843710}

pdf/pdf_engine.h

@@ -108,7 +108,10 @@ class PDFEngine {
     unsigned long num_params;
 
     // Parameters for the view. Their meaning depends on the |view| and their
-    // number is defined by |num_params| but is at most |kMaxViewParams|.
+    // number is defined by |num_params| but is at most |kMaxViewParams|. Note:
+    // If a parameter stands for the x/y coordinates, it should be transformed
+    // into the corresponding in-screen coordinates before it's sent to the
+    // viewport.
     float params[kMaxViewParams];
   };
 

pdf/pdfium/pdfium_engine.cc

@@ -380,6 +380,71 @@ base::string16 GetAttachmentName(FPDF_ATTACHMENT attachment) {
       /*check_expected_size=*/true);
 }
 
+void SetXYZParamsInScreenCoords(PDFiumPage* page, float* params) {
+  gfx::PointF page_coords(params[0], params[1]);
+  gfx::PointF screen_coords = page->TransformPageToScreenXY(page_coords);
+  params[0] = screen_coords.x();
+  params[1] = screen_coords.y();
+}
+
+void SetFitRParamsInScreenCoords(PDFiumPage* page, float* params) {
+  gfx::PointF point_1 =
+      page->TransformPageToScreenXY(gfx::PointF(params[0], params[1]));
+  gfx::PointF point_2 =
+      page->TransformPageToScreenXY(gfx::PointF(params[2], params[3]));
+  params[0] = point_1.x();
+  params[1] = point_1.y();
+  params[2] = point_2.x();
+  params[3] = point_2.y();
+}
+
+void SetFitVParamsInScreenCoords(PDFiumPage* page, float* params) {
+  // FitV/FitBV only has 1 parameter for x coordinate.
+  gfx::PointF screen_coords =
+      page->TransformPageToScreenXY(gfx::PointF(params[0], 0));
+  params[0] = screen_coords.x();
+}
+
+void SetFitHParamsInScreenCoords(PDFiumPage* page, float* params) {
+  // FitH/FitBH only has 1 parameter for y coordinate.
+  gfx::PointF screen_coords =
+      page->TransformPageToScreenXY(gfx::PointF(0, params[0]));
+  params[0] = screen_coords.y();
+}
+
+// A helper function that transforms the in-page coordinates in `params` to
+// in-screen coordinates depending on the view's fit type. `params` is both an
+// input and a output parameter.
+void ParamsTransformPageToScreen(unsigned long view_fit_type,
+                                 PDFiumPage* page,
+                                 float* params) {
+  switch (view_fit_type) {
+    case PDFDEST_VIEW_XYZ:
+      SetXYZParamsInScreenCoords(page, params);
+      break;
+    case PDFDEST_VIEW_FIT:
+    case PDFDEST_VIEW_FITB:
+      // No parameters for coordinates to be transformed.
+      break;
+    case PDFDEST_VIEW_FITBH:
+    case PDFDEST_VIEW_FITH:
+      SetFitHParamsInScreenCoords(page, params);
+      break;
+    case PDFDEST_VIEW_FITBV:
+    case PDFDEST_VIEW_FITV:
+      SetFitVParamsInScreenCoords(page, params);
+      break;
+    case PDFDEST_VIEW_FITR:
+      SetFitRParamsInScreenCoords(page, params);
+      break;
+    case PDFDEST_VIEW_UNKNOWN_MODE:
+      break;
+    default:
+      NOTREACHED();
+      break;
+  }
+}
+
 }  // namespace
 
 void InitializeSDK(bool enable_v8) {
@@ -2437,6 +2502,13 @@ base::Optional<PDFEngine::NamedDestination> PDFiumEngine::GetNamedDestination(
   result.page = page;
   unsigned long view_int =
       FPDFDest_GetView(dest, &result.num_params, result.params);
+
+  // FPDFDest_GetView() gets the in-page coordinates directly from the PDF
+  // document. The in-page coordinates need to be transformed into in-screen
+  // coordinates before getting sent to the viewport.
+  PDFiumPage* page_ptr = pages_[page].get();
+  ParamsTransformPageToScreen(view_int, page_ptr, result.params);
+
   result.view = ConvertViewIntToViewString(view_int);
   return result;
 }