quartz: Improve gradient consistency

By keeping "virtual extents", quartz surfaces now keep track of
the extents where they want the gradients to be consistent.
This works across various API for surface creation and editing:
 - cairo_surface_create_for_rectangle
 - cairo_surface_create_similar + cairo_surface_set_device_offset
 - cairo_push_group/cairo_pop_group

This method does not use clip extents, so it also makes gradient
rasterization independent of clip/path extents.

1 files changed, 45 insertions, 69 deletions

diff --git a/src/cairo-quartz-surface.c b/src/cairo-quartz-surface.c
index d8ae8869..935ab34b 100644
--- a/src/cairo-quartz-surface.c
+++ b/src/cairo-quartz-surface.c
@@ -890,7 +890,7 @@ static CGFunctionRef
 CreateRepeatingLinearGradientFunction (cairo_quartz_surface_t *surface,
 				       const cairo_gradient_pattern_t *gpat,
 				       CGPoint *start, CGPoint *end,
-				       cairo_rectangle_int_t *extents)
+				       const cairo_rectangle_int_t *extents)
 {
     cairo_pattern_t *pat;
     cairo_quartz_float_t input_value_range[2];
@@ -900,9 +900,6 @@ CreateRepeatingLinearGradientFunction (cairo_quartz_surface_t *surface,
     double dy = end->y - start->y;
     double bounds_x1, bounds_x2, bounds_y1, bounds_y2;
 
-    if (!extents) {
-        extents = &surface->extents;
-    }
     bounds_x1 = extents->x;
     bounds_y1 = extents->y;
     bounds_x2 = extents->x + extents->width;
@@ -999,7 +996,7 @@ CreateRepeatingRadialGradientFunction (cairo_quartz_surface_t *surface,
                                        const cairo_gradient_pattern_t *gpat,
                                        CGPoint *start, double *start_radius,
                                        CGPoint *end, double *end_radius,
-                                       cairo_rectangle_int_t *extents)
+                                       const cairo_rectangle_int_t *extents)
 {
     cairo_pattern_t *pat;
     cairo_quartz_float_t input_value_range[2];
@@ -1014,9 +1011,6 @@ CreateRepeatingRadialGradientFunction (cairo_quartz_surface_t *surface,
     double dr, dx, dy;
     double bounds_x1, bounds_x2, bounds_y1, bounds_y2;
 
-    if (!extents) {
-        extents = &surface->extents;
-    }
     bounds_x1 = extents->x;
     bounds_y1 = extents->y;
     bounds_x2 = extents->x + extents->width;
@@ -1345,7 +1339,7 @@ clip region).
 static cairo_quartz_action_t
 _cairo_quartz_setup_linear_source (cairo_quartz_surface_t *surface,
 				   const cairo_linear_pattern_t *lpat,
-				   cairo_rectangle_int_t *extents)
+				   const cairo_rectangle_int_t *extents)
 {
     const cairo_pattern_t *abspat = &lpat->base.base;
     cairo_matrix_t mat;
@@ -1392,7 +1386,7 @@ _cairo_quartz_setup_linear_source (cairo_quartz_surface_t *surface,
 static cairo_quartz_action_t
 _cairo_quartz_setup_radial_source (cairo_quartz_surface_t *surface,
 				   const cairo_radial_pattern_t *rpat,
-				   cairo_rectangle_int_t *extents)
+				   const cairo_rectangle_int_t *extents)
 {
     const cairo_pattern_t *abspat = &rpat->base.base;
     cairo_matrix_t mat;
@@ -1447,7 +1441,7 @@ _cairo_quartz_setup_radial_source (cairo_quartz_surface_t *surface,
 static cairo_quartz_action_t
 _cairo_quartz_setup_source (cairo_quartz_surface_t *surface,
 			    const cairo_pattern_t *source,
-			    cairo_rectangle_int_t *extents)
+			    const cairo_rectangle_int_t *extents)
 {
     assert (!(surface->sourceImage || surface->sourceShading || surface->sourcePattern));
 
@@ -1859,8 +1853,8 @@ _cairo_quartz_surface_create_similar (void *abstract_surface,
 				      int width,
 				      int height)
 {
-    /*cairo_quartz_surface_t *surface = (cairo_quartz_surface_t *) abstract_surface;*/
-
+    cairo_quartz_surface_t *surface, *similar_quartz;
+    cairo_surface_t *similar;
     cairo_format_t format;
 
     if (content == CAIRO_CONTENT_COLOR_ALPHA)
@@ -1878,7 +1872,15 @@ _cairo_quartz_surface_create_similar (void *abstract_surface,
 					       (CAIRO_STATUS_INVALID_SIZE));
     }
 
-    return cairo_quartz_surface_create (format, width, height);
+    similar = cairo_quartz_surface_create (format, width, height);
+    if (unlikely (similar->status))
+	return similar;
+
+    surface = (cairo_quartz_surface_t *) abstract_surface;
+    similar_quartz = (cairo_quartz_surface_t *) similar;
+    similar_quartz->virtual_extents = surface->virtual_extents;
+
+    return similar;
 }
 
 static cairo_status_t
@@ -1984,6 +1986,7 @@ _cairo_quartz_surface_paint_cg (cairo_quartz_surface_t *surface,
 {
     cairo_int_status_t rv = CAIRO_STATUS_SUCCESS;
     cairo_quartz_action_t action;
+    cairo_rectangle_int_t extents;
 
     ND ((stderr, "%p _cairo_quartz_surface_paint op %d source->type %d\n", surface, op, source->type));
 
@@ -1998,7 +2001,11 @@ _cairo_quartz_surface_paint_cg (cairo_quartz_surface_t *surface,
     if (unlikely (rv))
 	return rv;
 
-    action = _cairo_quartz_setup_source (surface, source, NULL);
+    extents = surface->virtual_extents;
+    extents.x -= surface->base.device_transform.x0;
+    extents.y -= surface->base.device_transform.y0;
+    _cairo_rectangle_union (&extents, &surface->extents);
+    action = _cairo_quartz_setup_source (surface, source, &extents);
 
     if (action == DO_SOLID || action == DO_PATTERN) {
 	CGContextFillRect (surface->cgContext, CGRectMake (surface->extents.x,
@@ -2024,25 +2031,6 @@ _cairo_quartz_surface_paint_cg (cairo_quartz_surface_t *surface,
     return rv;
 }
 
-static cairo_bool_t
-_cairo_quartz_source_needs_extents (const cairo_pattern_t *source)
-{
-    /* For repeating gradients we need to manually extend the gradient and
-       repeat stops, since Quartz doesn't support repeating gradients natively.
-       We need to minimze the number of repeated stops, and since rasterization
-       depends on the number of repetitions we use (even if some of the
-       repetitions go beyond the extents of the object or outside the clip
-       region), it's important to use the same number of repetitions when
-       rendering an object no matter what the clip region is. So the
-       computation of the repetition count cannot depended on the clip region,
-       and should only depend on the object extents, so we need to compute
-       the object extents for repeating gradients. */
-    return (source->type == CAIRO_PATTERN_TYPE_LINEAR ||
-            source->type == CAIRO_PATTERN_TYPE_RADIAL) &&
-           (source->extend == CAIRO_EXTEND_REPEAT ||
-            source->extend == CAIRO_EXTEND_REFLECT);
-}
-
 static cairo_int_status_t
 _cairo_quartz_surface_paint (void *abstract_surface,
 			     cairo_operator_t op,
@@ -2083,6 +2071,7 @@ _cairo_quartz_surface_fill_cg (cairo_quartz_surface_t *surface,
     cairo_int_status_t rv = CAIRO_STATUS_SUCCESS;
     cairo_quartz_action_t action;
     CGPathRef path_for_unbounded = NULL;
+    cairo_rectangle_int_t extents;
 
     ND ((stderr, "%p _cairo_quartz_surface_fill op %d source->type %d\n", surface, op, source->type));
 
@@ -2101,17 +2090,11 @@ _cairo_quartz_surface_fill_cg (cairo_quartz_surface_t *surface,
 
     CGContextSetShouldAntialias (surface->cgContext, (antialias != CAIRO_ANTIALIAS_NONE));
 
-    if (_cairo_quartz_source_needs_extents (source))
-    {
-        /* We don't need precise extents since these are only used to
-           compute the number of gradient reptitions needed to cover the
-           object. */
-        cairo_rectangle_int_t path_extents;
-        _cairo_path_fixed_approximate_fill_extents (path, &path_extents);
-        action = _cairo_quartz_setup_source (surface, source, &path_extents);
-    } else {
-        action = _cairo_quartz_setup_source (surface, source, NULL);
-    }
+    extents = surface->virtual_extents;
+    extents.x -= surface->base.device_transform.x0;
+    extents.y -= surface->base.device_transform.y0;
+    _cairo_rectangle_union (&extents, &surface->extents);
+    action = _cairo_quartz_setup_source (surface, source, &extents);
 
     _cairo_quartz_cairo_path_to_quartz_context (path, surface->cgContext);
 
@@ -2216,6 +2199,7 @@ _cairo_quartz_surface_stroke_cg (cairo_quartz_surface_t *surface,
     cairo_quartz_action_t action;
     CGAffineTransform origCTM, strokeTransform;
     CGPathRef path_for_unbounded = NULL;
+    cairo_rectangle_int_t extents;
 
     ND ((stderr, "%p _cairo_quartz_surface_stroke op %d source->type %d\n", surface, op, source->type));
 
@@ -2266,15 +2250,11 @@ _cairo_quartz_surface_stroke_cg (cairo_quartz_surface_t *surface,
 
     CGContextSaveGState (surface->cgContext);
 
-
-    if (_cairo_quartz_source_needs_extents (source))
-    {
-        cairo_rectangle_int_t path_extents;
-        _cairo_path_fixed_approximate_stroke_extents (path, style, ctm, &path_extents);
-        action = _cairo_quartz_setup_source (surface, source, &path_extents);
-    } else {
-        action = _cairo_quartz_setup_source (surface, source, NULL);
-    }
+    extents = surface->virtual_extents;
+    extents.x -= surface->base.device_transform.x0;
+    extents.y -= surface->base.device_transform.y0;
+    _cairo_rectangle_union (&extents, &surface->extents);
+    action = _cairo_quartz_setup_source (surface, source, &extents);
 
     _cairo_quartz_cairo_path_to_quartz_context (path, surface->cgContext);
 
@@ -2386,7 +2366,7 @@ _cairo_quartz_surface_show_glyphs_cg (cairo_quartz_surface_t *surface,
     CGGlyph *cg_glyphs = &glyphs_static[0];
     CGSize *cg_advances = &cg_advances_static[0];
 
-    cairo_rectangle_int_t glyph_extents;
+    cairo_rectangle_int_t extents;
     cairo_int_status_t rv = CAIRO_STATUS_SUCCESS;
     cairo_quartz_action_t action;
     cairo_quartz_float_t xprev, yprev;
@@ -2415,14 +2395,11 @@ _cairo_quartz_surface_show_glyphs_cg (cairo_quartz_surface_t *surface,
 
     CGContextSaveGState (surface->cgContext);
 
-    if (_cairo_quartz_source_needs_extents (source) &&
-	!_cairo_scaled_font_glyph_device_extents (scaled_font, glyphs, num_glyphs,
-						  &glyph_extents, NULL))
-    {
-        action = _cairo_quartz_setup_source (surface, source, &glyph_extents);
-    } else {
-        action = _cairo_quartz_setup_source (surface, source, NULL);
-    }
+    extents = surface->virtual_extents;
+    extents.x -= surface->base.device_transform.x0;
+    extents.y -= surface->base.device_transform.y0;
+    _cairo_rectangle_union (&extents, &surface->extents);
+    action = _cairo_quartz_setup_source (surface, source, &extents);
 
     if (action == DO_SOLID || action == DO_PATTERN) {
 	CGContextSetTextDrawingMode (surface->cgContext, kCGTextFill);
@@ -2662,17 +2639,15 @@ _cairo_quartz_surface_mask_with_generic (cairo_quartz_surface_t *surface,
 					 const cairo_pattern_t *mask,
 					 cairo_clip_t *clip)
 {
-    int width = surface->extents.width;
-    int height = surface->extents.height;
-
     cairo_surface_t *gradient_surf;
     cairo_surface_pattern_t surface_pattern;
     cairo_int_status_t status;
 
     /* Render the gradient to a surface */
-    gradient_surf = cairo_quartz_surface_create (CAIRO_FORMAT_A8,
-						 width,
-						 height);
+    gradient_surf = _cairo_quartz_surface_create_similar (surface,
+							  CAIRO_CONTENT_ALPHA,
+							  surface->extents.width,
+							  surface->extents.height);
     status = gradient_surf->status;
     if (unlikely (status))
 	goto BAIL;
@@ -2875,6 +2850,7 @@ _cairo_quartz_surface_create_internal (CGContextRef cgContext,
     surface->extents.x = surface->extents.y = 0;
     surface->extents.width = width;
     surface->extents.height = height;
+    surface->virtual_extents = surface->extents;
 
     if (IS_EMPTY (surface)) {
 	surface->cgContext = NULL;