Cairo surface creation / drawing / write to PNG functions

cairo/cairo.go

@@ -24,6 +24,7 @@ package cairo
 // #include <cairo-gobject.h>
 import "C"
 import (
+	"errors"
 	"reflect"
 	"runtime"
 	"unsafe"
@@ -42,6 +43,9 @@ func init() {
 		{glib.Type(C.cairo_gobject_operator_get_type()), marshalOperator},
 		{glib.Type(C.cairo_gobject_status_get_type()), marshalStatus},
 		{glib.Type(C.cairo_gobject_surface_type_get_type()), marshalSurfaceType},
+		{glib.Type(C.cairo_gobject_format_get_type()), marshalFormat},
+		{glib.Type(C.cairo_gobject_font_slant_get_type()), marshalFontSlant},
+		{glib.Type(C.cairo_gobject_font_weight_get_type()), marshalFontWeight},
 
 		// Boxed
 		{glib.Type(C.cairo_gobject_context_get_type()), marshalContext},
@@ -278,6 +282,51 @@ func marshalSurfaceType(p uintptr) (interface{}, error) {
 	return SurfaceType(c), nil
 }
 
+// Format is a representation of Cairo's cairo_format_t.
+type Format int
+
+const (
+	FORMAT_INVALID   Format = C.CAIRO_FORMAT_INVALID
+	FORMAT_ARGB32    Format = C.CAIRO_FORMAT_ARGB32
+	FORMAT_RGB24     Format = C.CAIRO_FORMAT_RGB24
+	FORMAT_A8        Format = C.CAIRO_FORMAT_A8
+	FORMAT_A1        Format = C.CAIRO_FORMAT_A1
+	FORMAT_RGB16_565 Format = C.CAIRO_FORMAT_RGB16_565
+	FORMAT_RGB30     Format = C.CAIRO_FORMAT_RGB30
+)
+
+func marshalFormat(p uintptr) (interface{}, error) {
+	c := C.g_value_get_enum((*C.GValue)(unsafe.Pointer(p)))
+	return Format(c), nil
+}
+
+// FontSlant is a representation of Cairo's cairo_font_slant_t.
+type FontSlant int
+
+const (
+	FONT_SLANT_NORMAL  FontSlant = C.CAIRO_FONT_SLANT_NORMAL
+	FONT_SLANT_ITALIC  FontSlant = C.CAIRO_FONT_SLANT_ITALIC
+	FONT_SLANT_OBLIQUE FontSlant = C.CAIRO_FONT_SLANT_OBLIQUE
+)
+
+func marshalFontSlant(p uintptr) (interface{}, error) {
+	c := C.g_value_get_enum((*C.GValue)(unsafe.Pointer(p)))
+	return FontSlant(c), nil
+}
+
+// FontWeight is a representation of Cairo's cairo_font_weight_t.
+type FontWeight int
+
+const (
+	FONT_WEIGHT_NORMAL FontWeight = C.CAIRO_FONT_WEIGHT_NORMAL
+	FONT_WEIGHT_BOLD   FontWeight = C.CAIRO_FONT_WEIGHT_BOLD
+)
+
+func marshalFontWeight(p uintptr) (interface{}, error) {
+	c := C.g_value_get_enum((*C.GValue)(unsafe.Pointer(p)))
+	return FontWeight(c), nil
+}
+
 /*
  * cairo_t
  */
@@ -670,6 +719,21 @@ func (v *Context) ShowPage() {
 
 // TODO(jrick) GetUserData (depends on UserDataKey)
 
+// SelectFontFace is a wrapper around cairo_select_font_face().
+func (v *Context) SelectFontFace(name string, slant FontSlant, weight FontWeight) {
+	C.cairo_select_font_face(v.native(), C.CString(name), C.cairo_font_slant_t(slant), C.cairo_font_weight_t(weight))
+}
+
+// SetFontSize is a wrapper around cairo_set_font_size().
+func (v *Context) SetFontSize(size float64) {
+	C.cairo_set_font_size(v.native(), C.double(size))
+}
+
+// ShowText is a wrapper around cairo_show_text().
+func (v *Context) ShowText(text string) {
+	C.cairo_show_text(v.native(), C.CString(text))
+}
+
 /*
  * cairo_surface_t
  */
@@ -715,6 +779,23 @@ func NewSurface(s uintptr, needsRef bool) *Surface {
 	return surface
 }
 
+// ImageSurfaceCreate is a wrapper around cairo_image_surface_create().
+func ImageSurfaceCreate(format Format, width, height int) *Surface {
+	c := C.cairo_image_surface_create(C.cairo_format_t(format), C.int(width), C.int(height))
+	s := wrapSurface(c)
+	runtime.SetFinalizer(s, (*Surface).destroy)
+	return s
+}
+
+// WriteToPNG is a wrapper around cairo_surface_write_to_png().
+func (v *Surface) WriteToPNG(filename string) error {
+	status := C.cairo_surface_write_to_png(v.native(), C.CString(filename))
+	if status != C.CAIRO_STATUS_SUCCESS {
+		return errors.New("error writing to PNG file")
+	}
+	return nil
+}
+
 // CreateSimilar is a wrapper around cairo_surface_create_similar().
 func (v *Surface) CreateSimilar(content Content, width, height int) *Surface {
 	c := C.cairo_surface_create_similar(v.native(),

cairo/examples/paths/paths.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"math"
+	"github.com/conformal/gotk3/cairo"
+)
+
+func main() {
+	surf := cairo.ImageSurfaceCreate(cairo.FORMAT_ARGB32, 256, 256)
+
+	cr := cairo.Create(surf)
+
+	// blank the canvas
+	cr.SetSourceRGB(1, 1, 1)
+	cr.Paint()
+
+	// straight line
+	cr.SetSourceRGB(0.3, 0.2, 0.8)
+	cr.MoveTo(32, 32)
+	cr.LineTo(224, 224)
+	cr.Stroke()
+
+	// curved line, with the inside of the curve filled
+	cr.SetSourceRGB(0.8, 0.2, 0.8)
+	cr.MoveTo(32, 224)
+	cr.CurveTo(64, 64, 192, 192, 224, 32)
+	cr.Fill()
+
+	// square
+	cr.SetSourceRGB(0.75, 0, 0)
+	cr.Rectangle(64, 64, 128, 128)
+	cr.Fill()
+
+	// circle
+	cr.SetSourceRGB(0.3, 0.8, 0.3)
+	cr.Arc(128, 128, 64, 0, math.Pi * 2)
+	cr.Stroke()
+
+	// text
+	cr.SetSourceRGB(0.3, 0.8, 0.8)
+	cr.MoveTo(20, 20)
+	cr.SelectFontFace("sans", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
+	cr.SetFontSize(16)
+	cr.ShowText("Hello World!")
+
+	surf.WriteToPNG("paths.png")
+}