PDF Viewer pinch zoom: Compute the zoom needed for the paint offset.

pdf/out_of_process_instance.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/out_of_process_instance.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>  // for min/max()
@@ skipping 265 matching lines @@
 }  // namespace
 
 OutOfProcessInstance::OutOfProcessInstance(PP_Instance instance)
     : pp::Instance(instance),
       pp::Find_Private(this),
       pp::Printing_Dev(this),
       cursor_(PP_CURSORTYPE_POINTER),
       zoom_(1.0),
       needs_reraster_(true),
       last_bitmap_smaller_(false),
-      last_zoom_when_smaller_(1.0),
       device_scale_(1.0),
       full_(false),
       paint_manager_(this, this, true),
       first_paint_(true),
       document_load_state_(LOAD_STATE_LOADING),
       preview_document_load_state_(LOAD_STATE_COMPLETE),
       uma_(this),
       told_browser_about_unsupported_feature_(false),
       font_substitution_reported_(false),
       print_preview_page_count_(0),
@@ skipping 162 matching lines @@
 
       if (plugin_size_.width() > GetDocumentPixelWidth() * zoom_ratio) {
         // We want to keep the paint in the middle but it must stay in the same
         // position relative to the scroll bars.
         paint_offset = pp::Point(0, (1 - zoom_ratio) * pinch_center.y());
         scroll_delta = pp::Point(0,
             (scroll_offset.y() -
              starting_scroll_offset_.y() * zoom_ratio / initial_zoom_ratio_));
 
         pinch_vector = pp::Point();
-        last_zoom_when_smaller_ = zoom;
         last_bitmap_smaller_ = true;
       } else if (last_bitmap_smaller_) {
           pinch_center = pp::Point((plugin_size_.width() / device_scale_) / 2,
               (plugin_size_.height() / device_scale_) / 2);
+          const double zoom_when_doc_covers_plugin_width =
+              zoom_ * plugin_size_.width() / GetDocumentPixelWidth();
           paint_offset = pp::Point(
-              (1 - zoom / last_zoom_when_smaller_) * pinch_center.x(),
+              (1 - zoom / zoom_when_doc_covers_plugin_width) * pinch_center.x(),
               (1 - zoom_ratio) * pinch_center.y());
           pinch_vector = pp::Point();
           scroll_delta = pp::Point(
               (scroll_offset.x() -
                starting_scroll_offset_.x() * zoom_ratio / initial_zoom_ratio_),
               (scroll_offset.y() -
                starting_scroll_offset_.y() * zoom_ratio / initial_zoom_ratio_));
       }
 
       paint_manager_.SetTransform(zoom_ratio, pinch_center,
@@ skipping 1164 matching lines @@
     const pp::FloatPoint& scroll_offset) {
   float max_x = document_size_.width() * zoom_ - plugin_dip_size_.width();
   float x = std::max(std::min(scroll_offset.x(), max_x), 0.0f);
   float min_y = -top_toolbar_height_;
   float max_y = document_size_.height() * zoom_ - plugin_dip_size_.height();
   float y = std::max(std::min(scroll_offset.y(), max_y), min_y);
   return pp::FloatPoint(x, y);
 }
 
 }  // namespace chrome_pdf