[cairo-spans] New abstract types for scan converting polygons.

A cairo_span_renderer_t implementation can be provided by a surface if
it wants to render paths as horizontal spans of the alpha component of
a mask.  Its job is to composite a source pattern to the destination
surface when given spans of alpha coverage for a row while taking care
of backend specific clipping.

A cairo_scan_converter_t takes edges of a flattened path and generates
spans for a span renderer to render.

1 files changed, 242 insertions, 0 deletions

diff --git a/src/cairo-spans.c b/src/cairo-spans.c
new file mode 100644
index 000000000..9cf351bdb
--- /dev/null
+++ b/src/cairo-spans.c
@@ -0,0 +1,242 @@
+/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright (c) 2008  M Joonas Pihlaja
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following
+ * conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "cairoint.h"
+
+static void
+_cairo_nil_destroy (void *abstract)
+{
+    (void) abstract;
+}
+
+static cairo_status_t
+_cairo_nil_scan_converter_add_edge (void *abstract_converter,
+				    cairo_fixed_t x1,
+				    cairo_fixed_t y1,
+				    cairo_fixed_t x2,
+				    cairo_fixed_t y2)
+{
+    (void) abstract_converter;
+    (void) x1;
+    (void) y1;
+    (void) x2;
+    (void) y2;
+    return _cairo_scan_converter_status (abstract_converter);
+}
+
+static cairo_status_t
+_cairo_nil_scan_converter_generate (void *abstract_converter,
+				    cairo_span_renderer_t *renderer)
+{
+    (void) abstract_converter;
+    (void) renderer;
+    return _cairo_scan_converter_status (abstract_converter);
+}
+
+cairo_status_t
+_cairo_scan_converter_status (void *abstract_converter)
+{
+    cairo_scan_converter_t *converter = abstract_converter;
+    return converter->status;
+}
+
+cairo_status_t
+_cairo_scan_converter_set_error (void *abstract_converter,
+				 cairo_status_t error)
+{
+    cairo_scan_converter_t *converter = abstract_converter;
+    if (error == CAIRO_STATUS_SUCCESS)
+	ASSERT_NOT_REACHED;
+    if (converter->status == CAIRO_STATUS_SUCCESS) {
+	converter->add_edge = _cairo_nil_scan_converter_add_edge;
+	converter->generate = _cairo_nil_scan_converter_generate;
+	converter->status = error;
+    }
+    return converter->status;
+}
+
+static void
+_cairo_nil_scan_converter_init (cairo_scan_converter_t *converter,
+				cairo_status_t status)
+{
+    converter->destroy = _cairo_nil_destroy;
+    converter->status = CAIRO_STATUS_SUCCESS;
+    status = _cairo_scan_converter_set_error (converter, status);
+}
+
+cairo_scan_converter_t *
+_cairo_scan_converter_create_in_error (cairo_status_t status)
+{
+#define RETURN_NIL {\
+	    static cairo_scan_converter_t nil;\
+	    _cairo_nil_scan_converter_init (&nil, status);\
+	    return &nil;\
+	}
+    switch (status) {
+    case CAIRO_STATUS_SUCCESS:
+	ASSERT_NOT_REACHED;
+	break;
+    case CAIRO_STATUS_INVALID_RESTORE: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_POP_GROUP: RETURN_NIL;
+    case CAIRO_STATUS_NO_CURRENT_POINT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_MATRIX: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STATUS: RETURN_NIL;
+    case CAIRO_STATUS_NULL_POINTER: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STRING: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_PATH_DATA: RETURN_NIL;
+    case CAIRO_STATUS_READ_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_WRITE_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_SURFACE_FINISHED: RETURN_NIL;
+    case CAIRO_STATUS_SURFACE_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_PATTERN_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_CONTENT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_FORMAT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_VISUAL: RETURN_NIL;
+    case CAIRO_STATUS_FILE_NOT_FOUND: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_DASH: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_DSC_COMMENT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_INDEX: RETURN_NIL;
+    case CAIRO_STATUS_CLIP_NOT_REPRESENTABLE: RETURN_NIL;
+    case CAIRO_STATUS_TEMP_FILE_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STRIDE: RETURN_NIL;
+    case CAIRO_STATUS_FONT_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_USER_FONT_IMMUTABLE: RETURN_NIL;
+    case CAIRO_STATUS_USER_FONT_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_NEGATIVE_COUNT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_CLUSTERS: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_SLANT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_WEIGHT: RETURN_NIL;
+    case CAIRO_STATUS_NO_MEMORY: RETURN_NIL;
+    default:
+	break;
+    }
+    status = CAIRO_STATUS_NO_MEMORY;
+    RETURN_NIL;
+#undef RETURN_NIL
+}
+
+static cairo_status_t
+_cairo_nil_span_renderer_render_row (
+    void				*abstract_renderer,
+    int					 y,
+    const cairo_half_open_span_t	*coverages,
+    unsigned				 num_coverages)
+{
+    (void) y;
+    (void) coverages;
+    (void) num_coverages;
+    return _cairo_span_renderer_status (abstract_renderer);
+}
+
+static cairo_status_t
+_cairo_nil_span_renderer_finish (void *abstract_renderer)
+{
+    return _cairo_span_renderer_status (abstract_renderer);
+}
+
+cairo_status_t
+_cairo_span_renderer_status (void *abstract_renderer)
+{
+    cairo_span_renderer_t *renderer = abstract_renderer;
+    return renderer->status;
+}
+
+cairo_status_t
+_cairo_span_renderer_set_error (
+    void *abstract_renderer,
+    cairo_status_t error)
+{
+    cairo_span_renderer_t *renderer = abstract_renderer;
+    if (error == CAIRO_STATUS_SUCCESS) {
+	ASSERT_NOT_REACHED;
+    }
+    if (renderer->status == CAIRO_STATUS_SUCCESS) {
+	renderer->render_row = _cairo_nil_span_renderer_render_row;
+	renderer->finish = _cairo_nil_span_renderer_finish;
+	renderer->status = error;
+    }
+    return renderer->status;
+}
+
+static void
+_cairo_nil_span_renderer_init (cairo_span_renderer_t *renderer,
+			       cairo_status_t status)
+{
+    renderer->destroy = _cairo_nil_destroy;
+    renderer->status = CAIRO_STATUS_SUCCESS;
+    status = _cairo_span_renderer_set_error (renderer, status);
+}
+
+cairo_span_renderer_t *
+_cairo_span_renderer_create_in_error (cairo_status_t status)
+{
+#define RETURN_NIL {\
+	    static cairo_span_renderer_t nil;\
+	    _cairo_nil_span_renderer_init (&nil, status);\
+	    return &nil;\
+	}
+    switch (status) {
+    case CAIRO_STATUS_SUCCESS:
+	ASSERT_NOT_REACHED;
+	break;
+    case CAIRO_STATUS_INVALID_RESTORE: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_POP_GROUP: RETURN_NIL;
+    case CAIRO_STATUS_NO_CURRENT_POINT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_MATRIX: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STATUS: RETURN_NIL;
+    case CAIRO_STATUS_NULL_POINTER: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STRING: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_PATH_DATA: RETURN_NIL;
+    case CAIRO_STATUS_READ_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_WRITE_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_SURFACE_FINISHED: RETURN_NIL;
+    case CAIRO_STATUS_SURFACE_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_PATTERN_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_CONTENT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_FORMAT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_VISUAL: RETURN_NIL;
+    case CAIRO_STATUS_FILE_NOT_FOUND: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_DASH: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_DSC_COMMENT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_INDEX: RETURN_NIL;
+    case CAIRO_STATUS_CLIP_NOT_REPRESENTABLE: RETURN_NIL;
+    case CAIRO_STATUS_TEMP_FILE_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_STRIDE: RETURN_NIL;
+    case CAIRO_STATUS_FONT_TYPE_MISMATCH: RETURN_NIL;
+    case CAIRO_STATUS_USER_FONT_IMMUTABLE: RETURN_NIL;
+    case CAIRO_STATUS_USER_FONT_ERROR: RETURN_NIL;
+    case CAIRO_STATUS_NEGATIVE_COUNT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_CLUSTERS: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_SLANT: RETURN_NIL;
+    case CAIRO_STATUS_INVALID_WEIGHT: RETURN_NIL;
+    case CAIRO_STATUS_NO_MEMORY: RETURN_NIL;
+    default:
+	break;
+    }
+    status = CAIRO_STATUS_NO_MEMORY;
+    RETURN_NIL;
+#undef RETURN_NIL
+}