Improved Pinch-Zoom for PDF.

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 38 matching lines @@
 const char kChromeExtension[] =
     "chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai";
 
 // Constants used in handling postMessage() messages.
 const char kType[] = "type";
 // Viewport message arguments. (Page -> Plugin).
 const char kJSViewportType[] = "viewport";
 const char kJSXOffset[] = "xOffset";
 const char kJSYOffset[] = "yOffset";
 const char kJSZoom[] = "zoom";
+const char kJSPinchPhase[] = "pinchPhase";
+// kJSPinchX and kJSPinchY represent the center of the pinch gesture.
+const char kJSPinchX[] = "pinchX";
+const char kJSPinchY[] = "pinchY";
+// kJSPinchVector represents the amount of panning caused by the pinch gesture.
+const char kJSPinchVectorX[] = "pinchVectorX";
+const char kJSPinchVectorY[] = "pinchVectorY";
 // Stop scrolling message (Page -> Plugin)
 const char kJSStopScrollingType[] = "stopScrolling";
 // Document dimension arguments (Plugin -> Page).
 const char kJSDocumentDimensionsType[] = "documentDimensions";
 const char kJSDocumentWidth[] = "width";
 const char kJSDocumentHeight[] = "height";
 const char kJSPageDimensions[] = "pageDimensions";
 const char kJSPageX[] = "x";
 const char kJSPageY[] = "y";
 const char kJSPageWidth[] = "width";
@@ skipping 198 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_current_scroll_(0, 0),
+      was_smaller_(false),
       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),
       print_preview_page_count_(0),
       last_progress_sent_(0),
@@ skipping 101 matching lines @@
   if (!dict.Get(kType).is_string()) {
     NOTREACHED();
     return;
   }
 
   std::string type = dict.Get(kType).AsString();
 
   if (type == kJSViewportType &&
       dict.Get(pp::Var(kJSXOffset)).is_number() &&
       dict.Get(pp::Var(kJSYOffset)).is_number() &&
-      dict.Get(pp::Var(kJSZoom)).is_number()) {
+      dict.Get(pp::Var(kJSZoom)).is_number() &&
+      dict.Get(pp::Var(kJSPinchPhase)).is_number()) {
     received_viewport_message_ = true;
     stop_scrolling_ = false;
+    PinchPhase pinch_phase =
+        static_cast<PinchPhase>(dict.Get(pp::Var(kJSPinchPhase)).AsInt());
     double zoom = dict.Get(pp::Var(kJSZoom)).AsDouble();
+    double zoom_delta = zoom / zoom_;
+
     pp::FloatPoint scroll_offset(dict.Get(pp::Var(kJSXOffset)).AsDouble(),
                                  dict.Get(pp::Var(kJSYOffset)).AsDouble());
 
+    if (pinch_phase == PINCH_START) {
+      last_current_scroll_ = scroll_offset;
+      old_zoom_ = zoom;

[Lei Zhang, 2016/10/27 23:04:33]

From just reading the header, I thought this was the previous |zoom_| value, but
this "old zoom" turns out to actually be the zoom value passed in via JS. Isn't
that more like a "new zoom" value? It's a bit confusing.

[Kevin McNee - google account, 2016/10/28 19:19:37]

If I'm following alessandroa's logic correctly, this is only actually relevant
to the was_smaller_ case to track the zoom from the previous call, so I've
updated the name accordingly and removed the unneeded initialization here.

Done.

+      initial_zoom_delta_ = zoom_delta;

[Lei Zhang, 2016/10/27 23:04:33]

It's not clear that this is a ratio and not a difference, when just looking at
the variable decl in the header.

[Kevin McNee - google account, 2016/10/28 19:19:37]

Done.

+      was_smaller_ = false;
+      needs_reraster_ = false;
+      return;
+    }
+
+    if (pinch_phase == PINCH_UPDATE_ZOOM_IN) {
+      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());
+      // Pinch vector is the panning caused due to change in pinch
+      // center between start and end of the gesture.
+      pp::Point pinch_vector =
+          pp::Point(dict.Get(kJSPinchVectorX).AsDouble() * zoom_delta,
+                    dict.Get(kJSPinchVectorY).AsDouble() * zoom_delta);
+      pp::Point scroll_delta(0, 0);

[Lei Zhang, 2016/10/27 23:04:33]

nit: No need to explicitly initialized to (0, 0).

[Kevin McNee - google account, 2016/10/28 19:19:37]

Done.

+      // If the rendered document doesn't fill the display area we will
+      // use paint_offset to anchor the paint vertically into the same place. We

[Lei Zhang, 2016/10/27 23:04:33]

nit: Refer to variables as |varname|.

[Kevin McNee - google account, 2016/10/28 19:19:37]

Done.

+      // use the scroll bars instead of the pinch vector to get the actual
+      // position on screen of the paint.
+      pp::Point paint_offset(0, 0);
+
+      if (plugin_size_.width() > GetDocumentPixelWidth() * zoom_delta) {
+        // 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_delta) * pinch_center.y());
+        scroll_delta = pp::Point(0,
+            (scroll_offset.y() -
+             last_current_scroll_.y() * zoom_delta / initial_zoom_delta_));
+
+        pinch_vector = pp::Point();
+        old_zoom_ = zoom;
+        was_smaller_ = true;
+      } else if (was_smaller_) {
+          pinch_center = pp::Point((plugin_size_.width() / device_scale_) / 2,
+              (plugin_size_.height() / device_scale_) / 2);
+          paint_offset = pp::Point((1 - zoom / old_zoom_) * pinch_center.x(),
+              (1 - zoom_delta) * pinch_center.y());
+          pinch_vector = pp::Point(0, 0);
+          scroll_delta = pp::Point(
+              (scroll_offset.x() -
+               last_current_scroll_.x() * zoom_delta / initial_zoom_delta_),
+              (scroll_offset.y() -
+               last_current_scroll_.y() * zoom_delta / initial_zoom_delta_));
+      }
+
+      paint_manager_.SetTransform(zoom_delta, pinch_center,
+          pinch_vector + paint_offset + scroll_delta);
+      needs_reraster_ = false;
+      return;
+    }
+
+    if (pinch_phase == PINCH_UPDATE_ZOOM_OUT || pinch_phase == PINCH_END) {
+      // We reraster on pinch zoom out in order to solve the invalid regions
+      // that appear after zooming out.
+      // On pinch end the scale is again 1.f and we request a reraster
+      // in the new position.
+      paint_manager_.SetTransform(1.f);
+      was_smaller_ = false;
+      needs_reraster_ = true;
+    }
+
     // Bound the input parameters.
     zoom = std::max(kMinZoom, zoom);
     SetZoom(zoom);
     scroll_offset = BoundScrollOffsetToDocument(scroll_offset);
     engine_->ScrolledToXPosition(scroll_offset.x() * device_scale_);
     engine_->ScrolledToYPosition(scroll_offset.y() * device_scale_);
   } else if (type == kJSGetPasswordCompleteType &&
              dict.Get(pp::Var(kJSPassword)).is_string()) {
     if (password_callback_) {
       pp::CompletionCallbackWithOutput<pp::Var> callback = *password_callback_;
@@ skipping 366 matching lines @@
     DCHECK(plugin_size_.IsEmpty());
     return;
   }
   if (first_paint_) {
     first_paint_ = false;
     pp::Rect rect = pp::Rect(pp::Point(), image_data_.size());
     FillRect(rect, background_color_);
     ready->push_back(PaintManager::ReadyRect(rect, image_data_, true));
   }
 
-  if (!received_viewport_message_)
+  if (!received_viewport_message_ || !needs_reraster_)
     return;
 
   engine_->PrePaint();
 
   for (const auto& paint_rect : paint_rects) {
     // Intersect with plugin area since there could be pending invalidates from
     // when the plugin area was larger.
     pp::Rect rect =
         paint_rect.Intersect(pp::Rect(pp::Point(), plugin_size_));
     if (rect.IsEmpty())
@@ skipping 732 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