Tips & FAQ
Capture a .skp file on a web page in Chromium
Use the script experimental/tools/web_to_skp , or do the following:
- Launch Chrome or Chromium with
--no-sandbox --enable-gpu-benchmarking - Open the JS console (Ctrl+Shift+J (Windows / Linux) or Cmd+Opt+J (MacOS))
- Execute:
chrome.gpuBenchmarking.printToSkPicture('/tmp')This returns “undefined” on success.
Open the resulting file in the Skia Debugger,
rasterize it with dm, or use Skia’s viewer to view it:
out/Release/dm --src skp --skps /tmp/layer_0.skp -w /tmp \
--config 8888 gpu pdf --verbose
ls -l /tmp/*/skp/layer_0.skp.*
out/Release/viewer --skps /tmp --slide layer_0.skp
Capture a .mskp file on a web page in Chromium
Multipage Skia Picture files capture the commands sent to produce PDFs and printed documents.
Use the script experimental/tools/web_to_mskp , or do the following:
- Launch Chrome or Chromium with
--no-sandbox --enable-gpu-benchmarking - Open the JS console (Ctrl+Shift+J (Windows / Linux) or Cmd+Opt+J (MacOS))
- Execute:
chrome.gpuBenchmarking.printPagesToSkPictures('/tmp/filename.mskp')This returns “undefined” on success.
Open the resulting file in the Skia Debugger or
process it with dm.
experimental/tools/mskp_parser.py /tmp/filename.mskp /tmp/filename.mskp.skp
ls -l /tmp/filename.mskp.skp
# open filename.mskp.skp in the debugger.
out/Release/dm --src mskp --mskps /tmp/filename.mskp -w /tmp \
--config pdf --verbose
ls -l /tmp/pdf/mskp/filename.mskp.pdf
How to add hardware acceleration in Skia
There are two ways Skia takes advantage of specific hardware.
-
Custom bottleneck routines
There are sets of bottleneck routines inside the blits of Skia that can be replace on a platform in order to take advantage of specific CPU features. One such example is the NEON SIMD instructions on ARM v7 devices. See src/opts/
Does Skia support Font hinting?
Skia has a built-in font cache, but it does not know how to actually render font
files like TrueType into its cache. For that it relies on the platform to supply
an instance of SkScalerContext. This is Skia’s abstract interface for
communicating with a font scaler engine. In src/ports you can see support files
for FreeType, macOS, and Windows GDI font engines. Other font engines can easily
be supported in a like manner.
Does Skia shape text (kerning)?
Shaping is the process that translates a span of Unicode text into a span of positioned glyphs with the appropriate typefaces.
Skia does not shape text. Skia provides interfaces to draw glyphs, but does not implement a text shaper. Skia’s client’s often use HarfBuzz to generate the glyphs and their positions, including kerning.
Here is an example of how to use Skia and HarfBuzz together.
In the example, a SkTypeface and a hb_face_t are created using the same
mmap()ed .ttf font file. The HarfBuzz face is used to shape unicode text
into a sequence of glyphs and positions, and the SkTypeface can then be used
to draw those glyphs.