Print Preview: Make generate draft mode work again.

chrome/browser/resources/print_preview/preview_generator.js

Index: chrome/browser/resources/print_preview/preview_generator.js
diff --git a/chrome/browser/resources/print_preview/preview_generator.js b/chrome/browser/resources/print_preview/preview_generator.js
index 8313ed736b67de93ec7b07b9178ec17f896dc4f1..80dce339e8e40b22c0e678771944fa75f70b3bba 100644
--- a/chrome/browser/resources/print_preview/preview_generator.js
+++ b/chrome/browser/resources/print_preview/preview_generator.js
@@ -58,6 +58,15 @@ cr.define('print_preview', function() {
     this.inFlightRequestId_ = -1;
 
     /**
+     * Whether the current in flight request requires generating draft pages for
+     * print preview. This is true only for modifiable documents when the print
+     * settings has changed sufficiently to require re-rendering.
+     * @type {boolean}

[dpapad, 2017/04/22 01:32:49]

Nit: @private {boolean}

[Lei Zhang, 2017/04/28 01:38:08]

Done.

+     * @private
+     */
+    this.generateDraft_ = false;
+
+    /**
      * Media size to generate preview with. {@code null} indicates default size.
      * @type {cp.cdd.MediaSizeTicketItem}
      * @private
@@ -173,7 +182,8 @@ cr.define('print_preview', function() {
           !this.destinationStore_.selectedDestination) {
         return false;
       }
-      if (!this.hasPreviewChanged_()) {
+      var previewChanged = this.hasPreviewChanged_();
+      if (!previewChanged && !this.hasPreviewPageRangeChanged_()) {
         // Changes to these ticket items might not trigger a new preview, but
         // they still need to be recorded.
         this.marginsType_ = this.printTicketStore_.marginsType.getValue();
@@ -195,10 +205,12 @@ cr.define('print_preview', function() {
       this.selectedDestination_ = this.destinationStore_.selectedDestination;
 
       this.inFlightRequestId_++;
+      this.generateDraft_ = this.documentInfo_.isModifiable && previewChanged;
       this.nativeLayer_.startGetPreview(
           this.destinationStore_.selectedDestination,
           this.printTicketStore_,
           this.documentInfo_,
+          this.generateDraft_,
           this.inFlightRequestId_);
       return true;
     },
@@ -273,8 +285,9 @@ cr.define('print_preview', function() {
     },
 
     /**
-     * @return {boolean} Whether the print ticket has changed sufficiently to
-     *     determine whether a new preview request should be issued.
+     * @return {boolean} Whether the print ticket, excluding the page range, has
+     *     changed sufficiently to determine whether a new preview request
+     *     should be issued.
      * @private
      */
     hasPreviewChanged_: function() {
@@ -286,9 +299,6 @@ cr.define('print_preview', function() {
           !ticketStore.color.isValueEqual(this.colorValue_) ||
           !ticketStore.scaling.isValueEqual(this.scalingValue_) ||
           !ticketStore.fitToPage.isValueEqual(this.isFitToPageEnabled_) ||
-          this.pageRanges_ == null ||
-          !areRangesEqual(ticketStore.pageRange.getPageRanges(),
-                          this.pageRanges_) ||
           (!ticketStore.marginsType.isValueEqual(this.marginsType_) &&
               !ticketStore.marginsType.isValueEqual(
                   print_preview.ticket_items.MarginsType.Value.CUSTOM)) ||
@@ -305,6 +315,16 @@ cr.define('print_preview', function() {
     },
 
     /**
+     * @return {boolean} Whether the page range in the print ticket has changed.
+     * @private
+     */
+    hasPreviewPageRangeChanged_: function() {
+      return this.pageRanges_ == null ||
+          !areRangesEqual(this.printTicketStore_.pageRange.getPageRanges(),
+              this.pageRanges_);

[dpapad, 2017/04/22 01:32:49]

Nit (optional): There used to be a so called "box rule" in one of our
styleguides, but can't find it anymore. Meaning that one should be able to draw
a box around a subtree of the code.

!areRangesEqual(
    this.printTicketStore_.pageRange.getPageRanges(),
    this.pageRanges_);

[Lei Zhang, 2017/04/28 01:38:08]

Done.

+    },
+
+    /**
      * Called when the page layout of the document is ready. Always occurs
      * as a result of a preview request.
      * @param {Event} event Contains layout info about the document.
@@ -387,9 +407,10 @@ cr.define('print_preview', function() {
       if (this.inFlightRequestId_ != event.previewResponseId) {
         return; // Ignore old response.
       }
-      // Dispatch a PREVIEW_START event since non-modifiable documents don't
-      // trigger PAGE_READY events.
-      if (!this.documentInfo_.isModifiable) {
+      if (!this.generateDraft_) {
+        // Dispatch a PREVIEW_START event since not generating a draft PDF,
+        // which includes print preview for non-modifiable documents, does not
+        // trigger PAGE_READY events.
         this.dispatchPreviewStartEvent_(event.previewUid, 0);
       }
       cr.dispatchSimpleEvent(this, PreviewGenerator.EventType.DOCUMENT_READY);