Increase PDF display timeouts

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 <stddef.h>
 #include <stdint.h>
 
@@ skipping 77 matching lines @@
 // http://www.adobe.com/devnet/acrobat/pdfs/pdf_reference_1-7.pdf
 #define kPDFPermissionPrintLowQualityMask  1 << 2
 #define kPDFPermissionPrintHighQualityMask 1 << 11
 #define kPDFPermissionCopyMask             1 << 4
 #define kPDFPermissionCopyAccessibleMask   1 << 9
 
 #define kLoadingTextVerticalOffset 50
 
 // The maximum amount of time we'll spend doing a paint before we give back
 // control of the thread.
-#define kMaxProgressivePaintTimeMs 50
+#define kMaxProgressivePaintTimeMs 300
 
 // The maximum amount of time we'll spend doing the first paint. This is less
-// than the above to keep things smooth if the user is scrolling quickly. We
-// try painting a little because with accelerated compositing, we get flushes
-// only every 16 ms. If we were to wait until the next flush to paint the rest
-// of the pdf, we would never get to draw the pdf and would only draw the
-// scrollbars. This value is picked to give enough time for gpu related code to
-// do its thing and still fit within the timelimit for 60Hz. For the
-// non-composited case, this doesn't make things worse since we're still
-// painting the scrollbars > 60 Hz.
-#define kMaxInitialProgressivePaintTimeMs 10
+// than the above to keep things smooth if the user is scrolling quickly. This
+// is set to 250 ms to give enough time for most PDFs to render, while avoiding
+// adding too much latency to the display of the final image when the user
+// stops scrolling.
+// Setting a higher value has minimal benefit (scrolling at less than 4 fps will
+// never be a great experience) and there is some cost, since when the user
+// stops scrolling the in-progress painting has to complete or timeout before
+// the final painting can start.
+// The scrollbar will always be responsive since it is managed by a separate
+// process.
+#define kMaxInitialProgressivePaintTimeMs 250
 
 std::vector<uint32_t> GetPageNumbersFromPrintPageNumberRange(
     const PP_PrintPageNumberRange_Dev* page_ranges,
     uint32_t page_range_count) {
   std::vector<uint32_t> page_numbers;
   for (uint32_t index = 0; index < page_range_count; ++index) {
     for (uint32_t page_number = page_ranges[index].first_page_number;
          page_number <= page_ranges[index].last_page_number; ++page_number) {
       page_numbers.push_back(page_number);
     }
@@ skipping 3779 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf