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In the early days, we chose to delegate the responsibility of generating
invoice PDFs to the client side. We simply designed the invoice in HTML
and utilized the customer's browser for PDF generation.
We adopted this approach because it was quick and straightforward to
implement. However, it had its drawbacks. Primarily, it did not generate
identical PDFs across all browsers as it heavily depended on the browser
and its version. Secondly, we aimed to send invoices as PDFs via email,
necessitating server-side PDF generation.
Given that we already had an HTML template for the invoice, our initial
thought was to convert HTML to PDF. There are multiple tools available
for this, such as wkhtmltopdf. However, we hesitated to add another
dependency as it could complicate our deployment process.
We decided to use prawnpdf [^1] for server-side PDF generation. Prawn is
a pure Ruby PDF generation library that offers a wide range of features
for PDF generation. It is user-friendly and highly flexible.
Prawn provides excellent manuals for reference [^2] [^3]. You can check
the details and its functionalities.
The design process was straightforward. The most significant challenge
was dealing with encoding. Unfortunately, the default PDF fonts do not
support all UTF-8 characters. If your text includes some special
characters, it triggers the following error:
Your document includes text that's not compatible with the
Windows-1252 character set.
(Prawn::Errors::IncompatibleStringEncoding) If you need full UTF-8
support, use external fonts instead of PDF's built-in fonts.
As the exception suggests, we should use external fonts for full UTF-8
support. I considered several fonts, such as "OpenSans" and
"DejaVuSans", before deciding on the "BeVietnamPro" [^4] font. It's
already in use on our website and might be useful in our console at some
point. Thus, it seemed sensible to use it for PDF generation as well.
It's open-source and licensed under the SIL Open Font License [^5].
I added the "pdf-reader" gem to read the generated PDF file in the
tests, which allows us to verify its content.
[^1]: https://github.com/prawnpdf/prawn
[^2]: https://prawnpdf.org/docs/prawn/2.5.0/manual.pdf
[^3]: https://prawnpdf.org/prawn-table-manual.pdf
[^4]: https://fonts.google.com/specimen/Be+Vietnam+Pro/about
[^5]: https://openfontlicense.org
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Copyright 2021 The Be Vietnam Pro Project Authors (https://github.com/bettergui/BeVietnamPro),
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This Font Software is licensed under the SIL Open Font License, Version 1.1.
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This license is copied below, and is also available with a FAQ at:
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http://scripts.sil.org/OFL
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-----------------------------------------------------------
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SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
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-----------------------------------------------------------
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PREAMBLE
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The goals of the Open Font License (OFL) are to stimulate worldwide
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development of collaborative font projects, to support the font creation
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efforts of academic and linguistic communities, and to provide a free and
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open framework in which fonts may be shared and improved in partnership
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with others.
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The OFL allows the licensed fonts to be used, studied, modified and
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redistributed freely as long as they are not sold by themselves. The
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fonts, including any derivative works, can be bundled, embedded,
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redistributed and/or sold with any software provided that any reserved
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names are not used by derivative works. The fonts and derivatives,
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however, cannot be released under any other type of license. The
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requirement for fonts to remain under this license does not apply
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to any document created using the fonts or their derivatives.
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DEFINITIONS
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"Font Software" refers to the set of files released by the Copyright
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Holder(s) under this license and clearly marked as such. This may
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include source files, build scripts and documentation.
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"Reserved Font Name" refers to any names specified as such after the
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copyright statement(s).
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"Original Version" refers to the collection of Font Software components as
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distributed by the Copyright Holder(s).
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"Modified Version" refers to any derivative made by adding to, deleting,
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or substituting -- in part or in whole -- any of the components of the
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Original Version, by changing formats or by porting the Font Software to a
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new environment.
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"Author" refers to any designer, engineer, programmer, technical
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writer or other person who contributed to the Font Software.
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PERMISSION & CONDITIONS
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of the Font Software, to use, study, copy, merge, embed, modify,
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redistribute, and sell modified and unmodified copies of the Font
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Software, subject to the following conditions:
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1) Neither the Font Software nor any of its individual components,
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in Original or Modified Versions, may be sold by itself.
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2) Original or Modified Versions of the Font Software may be bundled,
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redistributed and/or sold with any software, provided that each copy
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contains the above copyright notice and this license. These can be
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included either as stand-alone text files, human-readable headers or
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in the appropriate machine-readable metadata fields within text or
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binary files as long as those fields can be easily viewed by the user.
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3) No Modified Version of the Font Software may use the Reserved Font
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Name(s) unless explicit written permission is granted by the corresponding
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Copyright Holder. This restriction only applies to the primary font name as
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presented to the users.
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4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
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Software shall not be used to promote, endorse or advertise any
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Modified Version, except to acknowledge the contribution(s) of the
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Copyright Holder(s) and the Author(s) or with their explicit written
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permission.
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5) The Font Software, modified or unmodified, in part or in whole,
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must be distributed entirely under this license, and must not be
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distributed under any other license. The requirement for fonts to
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remain under this license does not apply to any document created
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using the Font Software.
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TERMINATION
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This license becomes null and void if any of the above conditions are
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not met.
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DISCLAIMER
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THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
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OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
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COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
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DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
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OTHER DEALINGS IN THE FONT SOFTWARE.
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