Refactor win printing workflow to support print preview.

chrome/renderer/print_web_view_helper_win.cc

Index: chrome/renderer/print_web_view_helper_win.cc
diff --git a/chrome/renderer/print_web_view_helper_win.cc b/chrome/renderer/print_web_view_helper_win.cc
index 94b622ff96eaa848ecfb147e0514ea92e5ef3e72..2780267920412c348aea4a4698e7aa7a1befe61a 100644
--- a/chrome/renderer/print_web_view_helper_win.cc
+++ b/chrome/renderer/print_web_view_helper_win.cc
@@ -63,6 +63,22 @@ int CALLBACK EnhMetaFileProc(HDC dc,
   return 1;  // Continue enumeration
 }
 
+gfx::Size PrintWebViewHelper::GetUpdatedPageSizeForRendering(
+    const ViewMsg_Print_Params& params, WebFrame* frame, int page_number) {

[Lei Zhang, 2011/01/26 08:06:52]

Have you considered putting this code in RenderPage()? Its return value isn't
used anywhere else. Just pass params.params to RenderPage() instead of page_size
and params.params.supports_alpha_blend.

[kmadhusu, 2011/01/26 18:08:29]

Moved this code to RenderPage().

+  double content_width_in_points;
+  double content_height_in_points;
+  GetPageSizeAndMarginsInPoints(frame, page_number, params,
+      &content_width_in_points, &content_height_in_points, NULL, NULL, NULL,
+      NULL);
+
+  // Since WebKit extends the page width depending on the magical scale factor
+  // we make sure the canvas covers the worst case scenario (x2.0 currently).
+  // PrintContext will then set the correct clipping region.
+  return gfx::Size(
+      static_cast<int>(content_width_in_points * params.max_shrink),
+      static_cast<int>(content_height_in_points * params.max_shrink));
+}
+
 void PrintWebViewHelper::PrintPage(const ViewMsg_PrintPage_Params& params,
                                    const gfx::Size& canvas_size,
                                    WebFrame* frame) {
@@ -75,22 +91,12 @@ void PrintWebViewHelper::PrintPage(const ViewMsg_PrintPage_Params& params,
 
   int page_number = params.page_number;
 
-  double content_width_in_points;
-  double content_height_in_points;
-  GetPageSizeAndMarginsInPoints(frame, page_number, params.params,
-      &content_width_in_points, &content_height_in_points, NULL, NULL, NULL,
-      NULL);
-
   // Calculate the dpi adjustment.
   float scale_factor = static_cast<float>(params.params.desired_dpi /
                                           params.params.dpi);
 
-  // Since WebKit extends the page width depending on the magical |scale_factor|
-  // we make sure the canvas covers the worst case scenario (x2.0 currently).
-  // PrintContext will then set the correct clipping region.
-  gfx::Size page_size(
-      static_cast<int>(content_width_in_points * params.params.max_shrink),
-      static_cast<int>(content_height_in_points * params.params.max_shrink));
+  gfx::Size page_size = GetUpdatedPageSizeForRendering(params.params, frame,
+                                                       page_number);
 
   // Render page for printing.
   RenderPage(page_size, &scale_factor, page_number, frame, &metafile,
@@ -129,6 +135,79 @@ void PrintWebViewHelper::PrintPage(const ViewMsg_PrintPage_Params& params,
   }
 }
 
+void PrintWebViewHelper::CreatePreviewDocument(
+    const ViewMsg_PrintPages_Params& params, WebFrame* frame,
+    ViewHostMsg_DidPreviewDocument_Params* print_params) {
+  int page_count = 0;
+  ViewMsg_Print_Params printParams = params.params;

[Lei Zhang, 2011/01/26 08:06:52]

You still use params.params in several places below.

[Lei Zhang, 2011/01/26 08:06:52]

Having both |print_params| and |printParams| is confusing. Can you give them
better names? Same goes for print_web_view_helper_mac.mm. Maybe do this in a
separate CL.

[kmadhusu, 2011/01/26 18:08:29]

Renamed |print_params| to |preview_params|.

[kmadhusu, 2011/01/26 18:08:29]

To get the expected page count,  |printParams| values are scaled based on dpi in
UpdatePrintableSizeInPrintParameters() function. That is the reason why I did
not use |printParams| in code below.

+  UpdatePrintableSizeInPrintParameters(frame, NULL, &printParams);
+  PrepareFrameAndViewForPrint prep_frame_view(printParams, frame, NULL,
+                                              frame->view());
+  page_count = prep_frame_view.GetExpectedPageCount();
+  if (!page_count)
+    return;
+
+  // NOTE: This is an enhanced-format metafile(EMF) which has an appearance of
+  // single page metafile. For print preview, we need a metafile with multiple
+  // pages.
+  // TODO(kmadhusu): Use a PDF metafile to support multiple pages. After "Skia
+  // PDF backend" work is completed for windows, make changes to replace this
+  // EMF with PDF metafile.
+  // http://code.google.com/p/chromium/issues/detail?id=62889
+  scoped_ptr<printing::NativeMetafile> metafile(new printing::NativeMetafile);
+  metafile->CreateDc(NULL, NULL);
+  DCHECK(metafile->hdc());
+  skia::PlatformDevice::InitializeDC(metafile->hdc());
+
+  gfx::Size page_size = GetUpdatedPageSizeForRendering(printParams, frame,

[Lei Zhang, 2011/01/26 08:06:52]

The third argument to GetUpdatedPageSizeForRendering() is the page number, not
the total page count. You probably should call in the for loop below.

[kmadhusu, 2011/01/26 18:08:29]

Fixed.

+                                                       page_count);
+  float scale_factor;

[Lei Zhang, 2011/01/26 08:06:52]

declare this in the scope in which it is used.

[kmadhusu, 2011/01/26 18:08:29]

Done.

+
+  // Calculate the dpi adjustment.
+  float shrink = static_cast<float>(params.params.desired_dpi /

[Lei Zhang, 2011/01/26 08:06:52]

but I thought you wanted to get rid of variables named "shrink".

[kmadhusu, 2011/01/26 18:08:29]

Yeah. Since I am using |scale_factor| variable within the loop, its ok to have a
temp variable with name "shrink". 

+                                    params.params.dpi);
+
+  if (params.pages.empty()) {
+    for (int i = 0; i < page_count; ++i) {
+      scale_factor = shrink;
+      RenderPage(page_size, &scale_factor, i, frame, &metafile,
+          params.params.supports_alpha_blend);
+    }
+  } else {
+    for (size_t i = 0; i < params.pages.size(); ++i) {
+      if (params.pages[i] >= page_count)
+        break;
+      scale_factor = shrink;
+      RenderPage(page_size, &scale_factor, static_cast<int>(params.pages[i]),
+          frame, &metafile, params.params.supports_alpha_blend);
+    }
+  }
+
+  // Close the device context to retrieve the compiled metafile.
+  if (!metafile->CloseDc())
+    NOTREACHED();
+
+  // Get the size of the compiled metafile.
+  uint32 buf_size = metafile->GetDataSize();
+  DCHECK_GT(buf_size, 128u);
+
+  print_params->document_cookie = params.params.document_cookie;
+  print_params->data_size = 0;
+  print_params->metafile_data_handle = NULL;
+
+  if (CopyMetafileDataToSharedMem(metafile.get(),
+          &(print_params->metafile_data_handle))) {
+    print_params->data_size = buf_size;
+  }
+  metafile->CloseEmf();
+  if (!Send(new ViewHostMsg_DuplicateSection(
+          routing_id(),
+          print_params->metafile_data_handle,
+          &print_params->metafile_data_handle))) {
+    NOTREACHED() << "Send message failed.";
+  }
+}
+
 void PrintWebViewHelper::RenderPage(
     const gfx::Size& page_size, float* scale_factor, int page_number,
     WebFrame* frame, scoped_ptr<printing::NativeMetafile>* metafile,