draw many paths with same paint

[jingc...@gmail.com]

    I want to draw many paths  with same paint.  when drawing each path  i use "canvas.drawPath(path, paint) " .   Does the skia have the function i use to draw many paths  with same paint one time rather than mang times.

[Shawn Riordan]

You could combine all the paths into one mega-path.

[Cary Clark]

Note that combining paths with SkPath::addPath()  into one path won't always draw the same.

- if the paint has any transparency (e.g., a transfer mode, or antialiasing) drawing the paths all at once won't generate the same result.

- if the paths have multiple contours, combining them to respect winding is non-trivial

- if the paths have different fill types, again combining them is not necessarily straightforward.

The latter two conditions can be worked around by using SkOpBuilder if the paths are drawn with paint fill style.

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[Brian Osman]

Also, in some cases it may be faster to draw each path separately vs. drawing them all at once. At least with the GPU backend, it's likely that you encounter a situation where the individual paths draw using a faster/simpler algorithm (in particular, if they're known to be convex), but the combined path would be arbitrarily complex and has to use a more complex algorithm.

On Mon, Nov 27, 2017 at 8:39 AM 'Cary Clark' via skia-discuss <skia-d...@googlegroups.com> wrote:

Note that combining paths with SkPath::addPath()  into one path won't always draw the same.

- if the paint has any transparency (e.g., a transfer mode, or antialiasing) drawing the paths all at once won't generate the same result.

- if the paths have multiple contours, combining them to respect winding is non-trivial

- if the paths have different fill types, again combining them is not necessarily straightforward.

The latter two conditions can be worked around by using SkOpBuilder if the paths are drawn with paint fill style.

On Mon, Nov 27, 2017 at 8:23 AM, Shawn Riordan <craste...@gmail.com> wrote:

You could combine all the paths into one mega-path.

On Monday, November 27, 2017 at 1:59:14 AM UTC-7, jingc...@gmail.com wrote:

    I want to draw many paths  with same paint.  when drawing each path  i use "canvas.drawPath(path, paint) " .   Does the skia have the function i use to draw many paths  with same paint one time rather than mang times.

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[Shawn Riordan]

What does Skia's text rendering code do?  All the glyphs end up paths at some point, correct?  

[Cary Clark]

Not necessarily. Text and path back-ends overlap, but text has other requirements, like color emoji, and other capabilities, like LCD rendering. On the GPU, text can take advantage of distance fields as an alternative. Text also is better behaved than paths, so the text back-end doesn't have to deal with arbitrary cubic curves, for instance.

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[Jim Van Verth]

On the GPU, text is generally small enough and reused enough that glyphs can be stored in a texture atlas, and a run of text can be rendered with a single draw. If the glyph data is a path, we rasterize the path before uploading it. We do the same for small concave paths.