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WebAPI/WebPrintAPI: Difference between revisions
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This is about implementing a new API for printing on the web. It's a "low level" API that allows web developers to have rich control about printing output. | This is about implementing a new API for printing on the web. It's a "low level" API that allows web developers to have rich control about printing output. | ||
== | Defining the PrintSetting API as used in PrintDocument.print(printSetting) is out of the scope of this document. | ||
== Notes == | |||
* Use points as metric for printing (72 points per inch) | * Use points as metric for printing (72 points per inch) | ||
* Open Questions | * Open Questions | ||
** What is (0,0)? The top left corner of the physical page OR of the page taking into account the print margin? | ** What is (0,0)? The top left corner of the physical page OR of the page taking into account the print margin? | ||
** Should there be different color spaces then RGB? How to make them work, as there are no CSS colors defined for CMYK. | ** Should there be different color spaces then RGB? How to make them work, as there are no CSS colors defined for CMYK. | ||
** Should the browser display a progress view while the pages are drawn (this doesn't mean the actual printing output progress)? | |||
** Lot more... TBD | ** Lot more... TBD | ||
=== Possible values for the 'scale' property (see below) === | |||
* 'scale': Scales the drawing while keeping the ration to to fit on the print paper size | |||
* 'fit': Scales the drawing while not taking the ration of the printer paper size in account | |||
* 'center': No scaling, just placing the center of the drawing onto the center of the printer paper. | |||
== Example == | |||
var pDoc = new PrintDocument( | var pDoc = new PrintDocument( | ||
'documentTitle', // Title | 'documentTitle', // Title | ||
'letter', // Paper size | 'letter', // Paper size | ||
'scale', // optional: see notes about "scale" | |||
false // optional: isLandscape? | false // optional: isLandscape? | ||
); | |||
// --- | // --- | ||
// Following | // Following functions MUST be defined by the developer. | ||
// --- | // --- | ||
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// .. | // .. | ||
// The fontCtx is | // The fontCtx is a very limited subset of the normal print ctx, that | ||
// | // is just about doing text measurements. | ||
fontCtx.font = '...'; | fontCtx.font = '...'; | ||
fontCtx.measureText(...); | fontCtx.measureText(...); | ||
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}; | }; | ||
// Actually drawing function. Each page is | // Actually drawing function. Each page is drawn individually. This is | ||
// handy for page preview or if the user picks only a subset of the total | // handy for page preview or if the user picks only a subset of the total | ||
// pages. | // pages. | ||
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// ... | // ... | ||
} | } | ||
// Render the page <pageNumber> to the ctx. | // Render the page <pageNumber> to the ctx. | ||
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setTimeout(function() { | setTimeout(function() { | ||
// Continue drawing... | // Continue drawing... | ||
// This page is done drawing. | // This page is done drawing. | ||
ctx.endPage(); | ctx.endPage(); | ||
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// --- | // --- | ||
// | // Provided API functions | ||
// --- | // --- | ||
pDoc.getPageSize = function() { | pDoc.getPageSize = function() { | ||
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} | } | ||
pDoc.getUnwriteableMargin = function() { | |||
return { | |||
top: <inch>, | |||
bottom: <inch>, | |||
left: <inch>, | |||
right: <inch> | |||
} | |||
} | |||
// Was the printing started but is not finished yet? | |||
pDoc.isPrinting; | pDoc.isPrinting; | ||
// Are all the pages drawn? | |||
pDoc.isFinished; | |||
// Start the printing progress. This opens the print dialog. | // Start the printing progress. This opens the print dialog. | ||
pDoc.print(); | // The passed in `printSetting` is not defined yet and is outside of the scope | ||
// of this proposal/API. | |||
pDoc.print(printSetting); | |||
// Stops the print process. Once all data is created, there is no way to stop | |||
// the printing anymore; that means, as soon as `pDoc.isFinished` is true, | |||
// calling this function has no effect. | |||
pDoc.abort(); | pDoc.abort(); | ||
== Proposed API == | |||
See the example to get an idea. More details coming soon! | |||
== Implementation == | == Implementation == | ||
Some basic investigation in the Gecko codebase. No code written so far. | |||