PDF pinch zoom: Update layer transform for a zoom out after a zoom in.

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 410 matching lines @@
                                  dict.Get(pp::Var(kJSYOffset)).AsDouble());
 
     if (pinch_phase == PINCH_START) {
       starting_scroll_offset_ = scroll_offset;
       initial_zoom_ratio_ = zoom_ratio;
       last_bitmap_smaller_ = false;
       needs_reraster_ = false;
       return;
     }
 
-    if (pinch_phase == PINCH_UPDATE_ZOOM_IN) {
+    // When zooming in, we set a layer transform to avoid unneeded rerasters.
+    // Also, if we're zooming out and the last time we rerastered was when
+    // we were even further zoomed out (i.e. we pinch zoomed in and are now
+    // pinch zooming back out in the same gesture), we update the layer
+    // transform instead of rerastering.
+    if (pinch_phase == PINCH_UPDATE_ZOOM_IN ||
+        (pinch_phase == PINCH_UPDATE_ZOOM_OUT && zoom_ratio > 1.0)) {
       if (!(dict.Get(pp::Var(kJSPinchX)).is_number() &&
             dict.Get(pp::Var(kJSPinchY)).is_number() &&
             dict.Get(pp::Var(kJSPinchVectorX)).is_number() &&
             dict.Get(pp::Var(kJSPinchVectorY)).is_number())) {
         NOTREACHED();
         return;
       }
 
       pp::Point pinch_center(dict.Get(pp::Var(kJSPinchX)).AsDouble(),
                              dict.Get(pp::Var(kJSPinchY)).AsDouble());
@@ skipping 1186 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