Export sk_canvas_save_layer_rec to expose SkCanvas::SaveLayerRec functionality

[ahmed605]

Description of Change

Export sk_canvas_save_layer_rec to expose SkCanvas::SaveLayerRec functionality

SkiaSharp Issue

Related to mono/SkiaSharp#2773

API Changes

Added:

SK_C_API int sk_canvas_save_layer_rec(sk_canvas_t* ccanvas, const sk_canvas_savelayerrec_t* crec);

typedef enum {
    NONE_SK_CANVAS_SAVELAYERREC_FLAGS                     = 0,
    PRESERVE_LCD_TEXT_SK_CANVAS_SAVELAYERREC_FLAGS        = 1 << 1,
    INITIALIZE_WITH_PREVIOUS_SK_CANVAS_SAVELAYERREC_FLAGS = 1 << 2,
    F16_COLOR_TYPE_SK_CANVAS_SAVELAYERREC_FLAGS           = 1 << 4,
} sk_canvas_savelayerrec_flags_t;

typedef struct {
    sk_rect_t* fBounds;
    sk_paint_t* fPaint;
    sk_imagefilter_t* fBackdrop;
    sk_canvas_savelayerrec_flags_t fFlags;
} sk_canvas_savelayerrec_t;

Behavioral Changes

None.

Required SkiaSharp PR

Requires mono/SkiaSharp#2962

PR Checklist

• Rebased on top of skiasharp at time of PR
• Changes adhere to coding standard
• Updated documentation

[mattleibow]

Can the enum also live in the C world and then the generator can find it and do the work. This also helps because you also need to update the src/c/sk_enums.cpp to do static checking. Enums go into include/c/sk_types.h

Many times, the C++ api inserts a new enum or changes the order and thus we have to catch this.

[ahmed605]

The C++ API doesn't actually use an enum but a uint32_t typedef, that's why I did it this way

[mattleibow]

I see what you mean, but I still think we can make the C API more sensible and also get the benefit of static value checking as I know the enum values do change between releases. For example, they have re-ordered/inserted values in the SkColorType enum several times already breaking the whole system because .NET does not work the same way as headers.

[mattleibow]

Also, since the enum is part of the SkCanvas type, to avoid conflicts when they inevatably add a different save layer rec, the name should be sk_canvas_savelayerrec_flags_t.

I see in later versions of skia there are some other options available in the rec, such as filters and colorspace: https://github.com/google/skia/blob/main/include/core/SkCanvas.h#L684

So I think to avoid future confusion, the filter arg name should maybe be backdrop.