From 83f5680b39a1b77b24bdbce414354625be558bcf Mon Sep 17 00:00:00 2001 From: Michael Orlitzky Date: Sat, 5 Aug 2023 11:07:49 -0400 Subject: [PATCH] README: add one. --- README | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 README diff --git a/README b/README new file mode 100644 index 0000000..7df72d2 --- /dev/null +++ b/README @@ -0,0 +1,90 @@ +== Overview == + +This package builds a GDK Pixbuf Loader for the SVG format that uses +libsvgtiny: + + https://www.netsurf-browser.org/projects/libsvgtiny/ + +Why? I'm glad you asked! + +GTK (https://www.gtk.org/) is a toolkit that powers many modern +desktop environments and applications. GTK uses an abstraction called +a GdkPixbuf for all of its images. When GTK wants to display an icon, +it first loads that icon into a GdkPixbuf before displaying the result +on the screen. GTK itself knows how to import many common formats like +PNG and JPEG into a GdkPixbuf and can handle those formats +out-of-the-box. The programs that handle the importing of the various +formats are called "pixbuf loaders." + +Problem: GTK doesn't know the size of your screen, but it needs to +display icons and images at an appropriate size. How big is that? Good +question: nobody knows. For that reason, GTK makes heavy use of +Scalable Vector Graphics (SVGs). It's much wiser to store one SVG and +scale it to the desired size -- once you know what that is -- than it +would be to store multiple copies of a non-scalable image at each of +the sizes you might need. But, as you may have guessed, GTK itself +doesn't know how to import an SVG into a GdkPixbuf. It doesn't come +with the corresponding pixbuf loader. + +The blessed solution to this problem is to use librsvg: + + https://wiki.gnome.org/Projects/LibRsvg + +That package builds a pixbuf loader that can be plugged into GTK, +allowing it to import SVG files into a GdkPixbuf, and everything is +great. Until January 3rd, 2017. On that day, librsvg-2.41.0 became the +only dependency of GTK that requires Rust, which in turn requires +LLVM. The rest of GTK (and its dependencies) are written in C or +C++. This has several downsides: + + * Rust is big and slow to compile + * LLVM is big and slow to compile + * Rust is far less portable than C; it doesn't run on as many CPUs + * The Rust ecosystem ironically burdens you with easily-avoidable + security vulnerabilities [0]. + +It's not feasible to keep the old librsvg around forever, because that +will *also* result in security vulnerabilities. Which brings us to... + +== Why == + +Because if you have a problem with any of the bullet points above, +then you need to replace librsvg if you want to keep using GTK. And, + + * libsvgtiny is written in portable C + * libsvgtiny is actively maintained + * libsvgtiny is already packaged on a few distributions as part of the + netsurf browser + +== Caveats == + +This is a REPLACEMENT for librsvg, and cannot be used alongside it +(the filenames and mimetypes clash). + +The main downside is that libsvgtiny isn't as robust as librsvg. It +renders some things wrong, or a bit uglier than its counterpart. These +are in theory all fixable upstream however, and you will help the +netsurf browser by doing so. Regardless, it more or less works. + +== Components == + +This package builds three things: + + 1. The pixbuf loader, libpixbufloader-svg.so. It's a shared library + that should be installed in your GDK_PIXBUF_MODULEDIR. Afterwards, + you have to run "gdk-pixbuf-query-loaders --update-cache" to tell + GTK about it. + + 2. A GTK thumbnailer entry, libsvgtiny.thumbnailer, that tells GTK + how to create thumbnails of SVG images. (Spoiler: we just run + gdk-pixbuf-thumbnailer.) + + 3. A test program, svg2png, that converts an SVG to a PNG. It does + this by loading an SVG into a pixbuf, and then saving that pixbuf + as a PNG. **It uses the pixbuf loaders from the live filesystem** + so you have to install libpixbufloader-svg.so and update the + loader cache before svg2png will use it. + +== References == + + [0] https://blogs.gentoo.org/mgorny/2021/02/19/the-modern-packagers-security-nightmare/ -- 2.44.2