Add a scroll offset to PDF documents to account for the top material design toolbar.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 
 #include "base/i18n/icu_encoding_detection.h"
 #include "base/i18n/icu_string_conversions.h"
@@ skipping 1053 matching lines @@
     // Convert the current page's rectangle to screen rectangle.  We do this
     // instead of the reverse (converting the dirty rectangle from screen to
     // page coordinates) because then we'd have to convert back to screen
     // coordinates, and the rounding errors sometime leave pixels dirty or even
     // move the text up or down a pixel when zoomed.
     pp::Rect page_rect_in_screen = GetPageScreenRect(index);
     pp::Rect dirty_in_screen = page_rect_in_screen.Intersect(leftover);
     if (dirty_in_screen.IsEmpty())
       continue;
 
+    // Compute the leftover dirty region. The first page may have blank space
+    // above it, in which case we also need to subtract that space from the
+    // dirty region.
+    if (i == 0) {
+      pp::Rect blank_space_in_screen = dirty_in_screen;
+      blank_space_in_screen.set_y(0);
+      blank_space_in_screen.set_height(dirty_in_screen.y());
+      leftover = leftover.Subtract(blank_space_in_screen);
+    }
     leftover = leftover.Subtract(dirty_in_screen);
 
     if (pages_[index]->available()) {
       int progressive = GetProgressiveIndex(index);
       if (progressive != -1) {
         DCHECK_GE(progressive, 0);
         DCHECK_LT(static_cast<size_t>(progressive), progressive_paints_.size());
         if (progressive_paints_[progressive].rect != dirty_in_screen) {
           // The PDFium code can only handle one progressive paint at a time, so
           // queue this up. Previously we used to merge the rects when this
@@ skipping 2959 matching lines @@
     double* height) {
   FPDF_DOCUMENT doc = FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, NULL);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf