1247422 - Expose printing resolution and scaling via CanvasPrintState

Status: RESOLVED WONTFIX

(Core :: Printing: Output, defect)

Description

[Tobias Schneider [:tobytailor]]

In order to render pages in PDF.js that mach the printers DPI when printing, the CanvasPrintState, passed to mozPrintCallback handlers, should contain a printerPixelRatio property so that drawing commands to the printing context can be scaled appropriately.

Comment 1

[Tobias Schneider [:tobytailor]]

Attachment: Part 1: Expose printingPixelRatio in CanvasPrintState

Part 1: Expose printingPixelRatio in CanvasPrintState

Comment 2

[Tobias Schneider [:tobytailor]]

Comment on attachment 8718087 [details] [diff] [review]
Part 1: Expose printingPixelRatio in CanvasPrintState

Robert, asking you to review this since you also reviewed the original patch that introduced the mozPrintCallback event.

Comment 3

[Tobias Schneider [:tobytailor]]

Attachment: Part 2: Reftests

Added ref test. To make this a reliable test I had to change the print preview scaling to something different than the page scaling in nsDocumentViewer.cpp. This doesn't seem to affect other tests, except of the original mozPrintCallBack reftest, which gets updated by this patch as well.

Comment 4

[Tobias Schneider [:tobytailor]]

Attachment: Part 1 (v2): Expose printingPixelRatio in CanvasPrintState

Update patch to also expose the scaling applied on the canvas for printing

Comment 5

[Markus Stange [:mstange]]

Comment on attachment 8736596 [details] [diff] [review]
Part 1 (v2): Expose printingPixelRatio in CanvasPrintState

Review of attachment 8736596 [details] [diff] [review]:
-----------------------------------------------------------------

This seems fine because it's needed when web content creates its own intermediate surfaces.

::: layout/base/nsDocumentViewer.cpp
@@ +842,4 @@
>                   mPresContext->CSSTwipsToAppUnits(NSToIntFloor(pageHeight))));
>          mPresContext->SetIsRootPaginatedDocument(true);
>          mPresContext->SetPageScale(1.0f);
> +        mPresContext->SetPrintPreviewScale(1.5f);

Does this have an effect on anything other than the new printing reftest you're adding?

Comment 6

[Tobias Schneider [:tobytailor]]

>> Does this have an effect on anything other than the new printing reftest you're adding?

No.

Comment 7

[Markus Stange [:mstange]]

Ok. Please add a comment to that line, explaining why you chose 1.5, what it's used for, and why it doesn't affect anything else, and also add a comment to the reftest pointing to this function so that readers know where the number is coming from.

Comment 8

[Farmer Tseng[:fatseng](inactive)]

I don't see you declare 'scale' in PrePrintNextPage.
Doesn't compiler complain it?

@@ -681,7 +681,7 @@ nsSimplePageSequenceFrame::PrePrintNextPage(nsITimerCallback* aCallback, bool* a
 
         // Start the rendering process.
         nsWeakFrame weakFrame = this;
-        canvas->DispatchPrintCallback(aCallback);
+        canvas->DispatchPrintCallback(aCallback, scale);
         NS_ENSURE_STATE(weakFrame.IsAlive());

Comment 9

[Tobias Schneider [:tobytailor]]

Won't fix since we will focus on other efforts to optimize quality of printing PDF's (see bug 1269760).