Add cairo-get-matrix and cairo-set-matrix bindings

Message

Needed for text rendering at non-1x canvas scales, where the CTM must be inspected and modified to keep HarfBuzz shaping in sync with Cairo glyph rendering.

Changed

 src/cairo.sgl | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

Diff

src/cairo.sglmodified

@@ -186,6 +186,8 @@

186

cairo-scale

187

cairo-rotate

188

cairo-identity-matrix

+189

cairo-get-matrix

+190

cairo-set-matrix

191

192

;; Patterns

193

cairo-pattern-create-rgb

@@ -654,6 +656,14 @@

656

(c-function cairo-lib "cairo_identity_matrix"

657

(list ffi/pointer) ffi/void))

658

+659

(define %get-matrix

+660

(c-function cairo-lib "cairo_get_matrix"

+661

(list ffi/pointer ffi/pointer) ffi/void))

+662

+663

(define %set-matrix

+664

(c-function cairo-lib "cairo_set_matrix"

+665

(list ffi/pointer ffi/pointer) ffi/void))

+666

667

;; Patterns

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(define %pattern-create-rgb

669

(c-function cairo-lib "cairo_pattern_create_rgb"

@@ -1147,6 +1157,36 @@

1157

(: pointer? -> void?)

1158

(%identity-matrix cr))

1159

+1160

;;; Get the current transformation matrix.

+1161

;;; Returns a dict with xx: yx: xy: yy: x0: y0: fields.

+1162

(define (cairo-get-matrix cr)

+1163

(: pointer? -> dict?)

+1164

(let* ((matrix-size (c-struct-size cairo-matrix-layout))

+1165

(buf (c-alloc matrix-size)))

+1166

(%get-matrix cr buf)

+1167

(let ((result (dict xx: (c-struct-ref buf cairo-matrix-layout xx:)

+1168

yx: (c-struct-ref buf cairo-matrix-layout yx:)

+1169

xy: (c-struct-ref buf cairo-matrix-layout xy:)

+1170

yy: (c-struct-ref buf cairo-matrix-layout yy:)

+1171

x0: (c-struct-ref buf cairo-matrix-layout x0:)

+1172

y0: (c-struct-ref buf cairo-matrix-layout y0:))))

+1173

(c-free buf)

+1174

result)))

+1175

+1176

;;; Set the transformation matrix from a dict with xx: yx: xy: yy: x0: y0:.

+1177

(define (cairo-set-matrix cr matrix)

+1178

(: pointer? dict? -> void?)

+1179

(let* ((matrix-size (c-struct-size cairo-matrix-layout))

+1180

(buf (c-alloc matrix-size)))

+1181

(c-struct-set! buf cairo-matrix-layout xx: (dict-ref matrix xx:))

+1182

(c-struct-set! buf cairo-matrix-layout yx: (dict-ref matrix yx:))

+1183

(c-struct-set! buf cairo-matrix-layout xy: (dict-ref matrix xy:))

+1184

(c-struct-set! buf cairo-matrix-layout yy: (dict-ref matrix yy:))

+1185

(c-struct-set! buf cairo-matrix-layout x0: (dict-ref matrix x0:))

+1186

(c-struct-set! buf cairo-matrix-layout y0: (dict-ref matrix y0:))

+1187

(%set-matrix cr buf)

+1188

(c-free buf)))

+1189

1190

;; ============================================================

1191

;; Public API — Patterns

1192

;; ============================================================