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Bug 1692316 - Part 3: Document Duplex Printing Constants r=dholbert,jfkthame

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This patch attempts to add a clear explanation and mapping among the
duplex-printing constants that vary across platforms.

Differential Revision: https://phabricator.services.mozilla.com/D105512
This commit is contained in:
Erik Nordin 2021-02-17 23:57:27 +00:00
parent d718e71945
commit 885851456a
1 changed files with 50 additions and 6 deletions
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56
widget/nsIPrintSettings.idl
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@ -88,15 +88,59 @@ interface nsIPrintSettings : nsISupports
/**
* Duplex printing options.
*
* Note that other libraries refer to equivalent duplex settings
* using different terminology. The equivalent terms are listed
* above each value in a comma-separated list.
* Note that other libraries refer to equivalent duplex settings using
* various sets of terminology. This can be confusing and inconsistent both
* with other libraries, and with the behavior that these terms intend to describe.
*
* kDuplexNone is equivalent to Simplex. Thankfully, both of these terms are
* consistent with the behavior that they describe, which is to have single-sided
* printing per sheet.
*
* kDuplexFlipOnLongEdge is equivalent to the following platform-specific constants:
* CUPS/macOS: NoTumble
* Windows: DMDUP_VERTICAL
* GTK: GTK_PRINT_DUPLEX_HORIZONTAL
*
* kDuplexFlipOnShortEdge is equivalent to the following platform-specific constants:
* CUPS/macOS: Tumble
* Windows: DMDUP_HORIZONTAL
* GTK: GTK_PRINT_DUPLEX_VERTICAL
*
*
* Notice that the GTK and Windows constants have opposite meanings for
* VERTICAL and HORIZONTAL.
*
* To make matters more confusing, these platform-specific terms describe different
* behavior (from the user's perspective) depending on whether the sheet is in
* portrait vs. landscape orientation.
*
* For example, the generic term "tumble" describes behavior where a sheet flips over
* a binding on the top edge (like a calendar). This requires that the back side of
* the sheet is printed upside down with respect to the front side of the sheet,
* so that its content appears upright to the reader when they tumble-flip the
* sheet over the top-edge binding.
*
* However, the CUPS/macOS Tumble setting only inverts the back side of the
* sheet in portrait orientation. When you switch to landscape orientation, the
* Tumble setting behaves like a book-like sheet flip, where the front and back
* sides of the sheet are both printed upright with respect to each other.
*
* This is why it is more consistent and more clear to think of these terms
* with regard to sheets being bound on the long edge or the short edge.
*
* kDuplexFlipOnLongEdge + Portrait = book-like flip (front/back same direction)
* kDuplexFlipOnLongEdge + Landscape = calendar-like flip (front/back inverted)
*
* kDuplexFlipOnShortEdge + Portrait = calendar-like flip (front/back inverted)
* kDuplexFlipOnShortEdge + Landscape = book-like flip (front/back same direction)
*
* The long-edge and short-edge terminology unfortunately breaks down when printing
* with square sheet dimensions. Thankfully this edge case (hah) is quite uncommon,
* since most standard printing paper dimensions are not square. Such a paper size
* would even break the uniformly used portrait and landscape terminology.
*/
// Equivalent to: Simplex
const short kDuplexNone = 0;
// Equivalent to: DMDUP_VERTICAL, NoTumble
const short kDuplexFlipOnLongEdge = 1;
// Equivalent to: DMDUP_HORIZONTAL, Tumble
const short kDuplexFlipOnShortEdge = 2;
/**