Print Preview: Make preview generation event driven to eliminate synchronous messages.

chrome/renderer/print_web_view_helper.h

Index: chrome/renderer/print_web_view_helper.h
===================================================================
--- chrome/renderer/print_web_view_helper.h	(revision 92494)
+++ chrome/renderer/print_web_view_helper.h	(working copy)
@@ -6,6 +6,8 @@
 #define CHROME_RENDERER_PRINT_WEB_VIEW_HELPER_H_
 #pragma once
 
+#include <vector>
+
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "base/time.h"
@@ -108,9 +110,24 @@
   // Initiate print preview.
   void OnInitiatePrintPreview();
 
-  // Generate a print preview using |settings|.
+  // Start the process of generating a print preview using |settings|.
   void OnPrintPreview(const base::DictionaryValue& settings);
+  // Initialize the print preview document.

[kmadhusu, 2011/07/15 01:22:46]

nit: Please add blank line after lines 114, 119, 121.

[Lei Zhang, 2011/07/15 01:48:02]

This is a very subtle way of showing OnPrintPreview() and
CreatePreviewDocument() are related.

+  bool CreatePreviewDocument();
 
+  // Continue generating the print preview.
+  void OnContinuePreview();
+  // Renders a print preview page.

[kmadhusu, 2011/07/15 01:22:46]

Document |page_number|. 

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+  void RenderPreviewPage(int page_number);
+  // Finalize the print preview document.
+  bool FinalizePreviewDocument();
+
+  // Cancel the preview to put it into the 'DONE' state.

[kmadhusu, 2011/07/15 01:22:46]

Define "it".

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+  void OnCancelPreview();
+
+  // Abort the preview to put it into the 'UNINITIALIZED' state.

[kmadhusu, 2011/07/15 01:22:46]

Define "it".

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+  void OnAbortPreview();
+
   // Print / preview the node under the context menu.
   void OnPrintNodeUnderContextMenu();
 
@@ -124,14 +141,12 @@
 
   void Print(WebKit::WebFrame* frame, WebKit::WebNode* node);
 
-  void PrintPreview(WebKit::WebFrame* frame,
-                    WebKit::WebNode* node,
-                    const base::DictionaryValue& settings);
-
   enum PrintingResult {
     OK,
     FAIL_PRINT,
     FAIL_PREVIEW,
+    CANCEL_PREVIEW,
+    ABORT_PREVIEW,
   };
 
   // Notification when printing is done - signal tear-down/free resources.
@@ -187,16 +202,6 @@
   // Render the frame for printing.
   bool RenderPagesForPrint(WebKit::WebFrame* frame, WebKit::WebNode* node);
 
-  // Render the frame for preview.
-  bool RenderPagesForPreview(WebKit::WebFrame* frame, WebKit::WebNode* node);
-
-  // Renders all the pages listed in |params| for preview.
-  // On success, Send PrintHostMsg_PagesReadyForPreview message with a
-  // valid metafile data handle.
-  bool CreatePreviewDocument(const PrintMsg_PrintPages_Params& params,
-                             WebKit::WebFrame* frame,
-                             WebKit::WebNode* node);
-
   // Platform specific helper function for rendering page(s) to |metafile|.
 #if defined(OS_WIN)
   void RenderPage(const PrintMsg_Print_Params& params, float* scale_factor,
@@ -208,11 +213,8 @@
                   WebKit::WebFrame* frame, printing::Metafile* metafile);
 #elif defined(OS_POSIX)
   bool RenderPages(const PrintMsg_PrintPages_Params& params,
-                   WebKit::WebFrame* frame,
-                   WebKit::WebNode* node,
-                   int* page_count,
-                   printing::Metafile* metafile,
-                   bool is_preview);
+                   WebKit::WebFrame* frame, WebKit::WebNode* node,
+                   int* page_count, printing::Metafile* metafile);
 #endif  // defined(OS_WIN)
 
   // Helper methods -----------------------------------------------------------
@@ -233,21 +235,14 @@
       double* margin_bottom_in_points,
       double* margin_left_in_points);
 
-  bool IsModifiable(WebKit::WebFrame* frame, WebKit::WebNode* node);
-
   void UpdatePrintableSizeInPrintParameters(WebKit::WebFrame* frame,
                                             WebKit::WebNode* node,
                                             PrintMsg_Print_Params* params);
 
   bool GetPrintFrame(WebKit::WebFrame** frame);
 
-  // This reports the current time - |start_time| as the time to render
-  // a page and returns the current time.
-  base::TimeTicks ReportPreviewPageRenderTime(base::TimeTicks start_time);
-  void ReportTotalPreviewGenerationTime(int selected_pages_length,
-                                        int total_pages,
-                                        base::TimeDelta render_time,
-                                        base::TimeDelta total_time);
+  // This reports the current time - |start_time| as the time to render a page.
+  void ReportPreviewPageRenderTime(base::TimeTicks start_time);
 
   // Script Initiated Printing ------------------------------------------------
 
@@ -267,20 +262,12 @@
 
   void RequestPrintPreview();
 
-  // Called every time print preview renders a page. Notify the browser of the
-  // event and check if print preview should be cancelled. Returns false if
-  // print preview has been cancelled. |page_number| is 0-based, or negative to
-  // indicate its a cancel check only.
-  bool PreviewPageRendered(int page_number);
+  // Notify the browser a print preview page has been rendered.
+  // |page_number| is 0-based.
+  void PreviewPageRendered(int page_number);
 
   WebKit::WebView* print_web_view_;
 
-  // The frame to print for script initiated print preview.
-  WebKit::WebFrame* script_initiated_preview_frame_;
-
-  // The node under the context menu to print preview.
-  scoped_ptr<WebKit::WebNode> context_menu_preview_node_;
-
   scoped_ptr<PrintMsg_PrintPages_Params> print_pages_params_;
   bool is_preview_;
 
@@ -292,9 +279,92 @@
   // the failure came from the browser in the first place.
   bool notify_browser_of_print_failure_;
 
-  int preview_page_count_;
   scoped_ptr<PrintMsg_PrintPages_Params> old_print_pages_params_;
 
+  class PrintPreviewContext {

[kmadhusu, 2011/07/15 01:22:46]

Document this class.

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+   public:
+    PrintPreviewContext();

[kmadhusu, 2011/07/15 01:22:46]

destructor??

[Lei Zhang, 2011/07/15 01:48:02]

Got nothing to destroy.

+
+    // Initializes the print preview context. Need to be called to set
+    // the |web_frame| / |web_node| to generate the print preview for.
+    void InitWithFrame(WebKit::WebFrame* web_frame);
+    void InitWithNode(const WebKit::WebNode& web_node);
+
+    // Does bookkeeping at the beginning of print preview.
+    void OnPrintPreview();
+
+    // Create the print preview document.
+    bool CreatePreviewDocument(const PrintMsg_Print_Params& params,
+                               const std::vector<int>& pages);

[kmadhusu, 2011/07/15 01:22:46]

document |pages|.

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+
+    // Called after a page gets rendered. |page_time| is how long the
+    // rendering took.
+    void RenderedPreviewPage(const base::TimeDelta& page_time);
+
+    // Finalizes the print preview document.
+    void FinalizePreviewDocument();
+
+    // Cleanup after print preview finishes.
+    void Finished();
+
+    // Abort the print preview.
+    void Abort();
+
+    // Cancel the print preview.
+    void Cancel();
+
+    // Helper functions
+    bool GetNextPage(int* page_number);

[kmadhusu, 2011/07/15 01:22:46]

How about GetNextPageNumber? Rather than returning a bool value, Can you return
the actual page number?

int page_number = print_preview_context_.GetNextPageNumber();

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+    bool IsInitialized() const;
+    bool IsBusy() const;
+    bool IsModifiable() const;
+
+    // Getters
+    WebKit::WebFrame* frame() const;
+    WebKit::WebNode* node() const;
+    int page_count() const;
+    printing::Metafile* metafile() const;
+    const PrintMsg_Print_Params& print_params() const;
+    const gfx::Size& GetPrintCanvasSize() const;
+
+   private:
+    enum State {
+      UNINITIALIZED,  // Not ready to print.
+      INITIALIZED,    // Ready to print.
+      PRINTING,       // Printing.

[kmadhusu, 2011/07/15 01:22:46]

Since we are not actually printing, can you change PRINTING => RENDERING ?

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+      DONE            // Finished printing.
+    };
+
+    void Reset();

[kmadhusu, 2011/07/15 01:22:46]

Document the purpose of this function.

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+
+    // Specifies what to print.

[kmadhusu, 2011/07/15 01:22:46]

In PrintPreviewContext class:
s/print/print preview/g 

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+    WebKit::WebFrame* frame_;
+    scoped_ptr<WebKit::WebNode> node_;
+
+    scoped_ptr<PrepareFrameAndViewForPrint> prep_frame_view_;
+    scoped_ptr<printing::Metafile> metafile_;
+    scoped_ptr<PrintMsg_Print_Params> print_params_;
+
+    // Total page count in the renderer.
+    int page_count_;

[kmadhusu, 2011/07/15 01:22:46]

To make it clear:
page_count_ => total_page_count_

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+
+    // Number of pages to print.
+    int actual_page_count_;
+
+    // The current page to print.
+    int current_page_;

[kmadhusu, 2011/07/15 01:22:46]

current_page => current_page_number ?

[Lei Zhang, 2011/07/15 01:48:02]

Done.

+
+    // Array to keep track of which pages have been printed.
+    std::vector<bool> rendered_pages_;
+
+    base::TimeDelta document_render_time_;
+    base::TimeTicks begin_time_;
+
+    State state_;
+  };
+
+  PrintPreviewContext print_preview_context_;
+
   DISALLOW_COPY_AND_ASSIGN(PrintWebViewHelper);
 };