From eec4afa26b4bf00fea34fd39337b5a7bffa58a75 Mon Sep 17 00:00:00 2001 From: Benjamin Otte Date: Mon, 3 Feb 2014 15:56:59 +0100 Subject: [PATCH] css: Fix computation of pixels occupied by blur radius These computations were done randomly in lots of places and more often than not, they were also wrong. This function was copied (with docs) from Firefox: http://lxr.mozilla.org/mozilla-central/source/gfx/2d/Blur.cpp https://bugzilla.gnome.org/show_bug.cgi?id=723159 --- gtk/gtkcairoblur.c | 26 ++++++++++++++++++++++++++ gtk/gtkcairoblurprivate.h | 5 +++-- gtk/gtkcssshadowsvalue.c | 12 +++++++----- gtk/gtkcssshadowvalue.c | 8 ++------ 4 files changed, 38 insertions(+), 13 deletions(-) diff --git a/gtk/gtkcairoblur.c b/gtk/gtkcairoblur.c index 3f944e2429..df989898b2 100644 --- a/gtk/gtkcairoblur.c +++ b/gtk/gtkcairoblur.c @@ -251,3 +251,29 @@ _gtk_cairo_blur_surface (cairo_surface_t* surface, /* Inform cairo we altered the surfaces contents. */ cairo_surface_mark_dirty (surface); } + +/** + * _gtk_cairo_blur_compute_pixels: + * @radius: the radius to compute the pixels for + * + * Computes the number of pixels necessary to extend an image in one + * direction to hold the image with shadow. + * + * This is just the number of pixels added by the blur radius, shadow + * offset and spread are not included. + * + * Much of this, the 3 * sqrt(2 * pi) / 4, is the known value for + * approximating a Gaussian using box blurs. This yields quite a good + * approximation for a Gaussian. Then we multiply this by 1.5 since our + * code wants the radius of the entire triple-box-blur kernel instead of + * the diameter of an individual box blur. For more details, see: + * http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement + * https://bugzilla.mozilla.org/show_bug.cgi?id=590039#c19 + */ +#define GAUSSIAN_SCALE_FACTOR ((3.0 * sqrt(2 * G_PI) / 4) * 1.5) + +int +_gtk_cairo_blur_compute_pixels (double radius) +{ + return floor (radius * GAUSSIAN_SCALE_FACTOR + 0.5); +} diff --git a/gtk/gtkcairoblurprivate.h b/gtk/gtkcairoblurprivate.h index e048bac8cd..d3e2f9ac46 100644 --- a/gtk/gtkcairoblurprivate.h +++ b/gtk/gtkcairoblurprivate.h @@ -29,8 +29,9 @@ G_BEGIN_DECLS -void _gtk_cairo_blur_surface (cairo_surface_t *surface, - double radius); +void _gtk_cairo_blur_surface (cairo_surface_t *surface, + double radius); +int _gtk_cairo_blur_compute_pixels (double radius); G_END_DECLS diff --git a/gtk/gtkcssshadowsvalue.c b/gtk/gtkcssshadowsvalue.c index b688594cc1..eb32471cec 100644 --- a/gtk/gtkcssshadowsvalue.c +++ b/gtk/gtkcssshadowsvalue.c @@ -21,6 +21,7 @@ #include "gtkcssshadowsvalueprivate.h" +#include "gtkcairoblurprivate.h" #include "gtkcssshadowvalueprivate.h" #include @@ -309,7 +310,7 @@ _gtk_css_shadows_value_get_extents (const GtkCssValue *shadows, guint i; GtkBorder b = { 0 }; const GtkCssValue *shadow; - gdouble hoffset, voffset, spread, radius; + gdouble hoffset, voffset, spread, radius, clip_radius; g_return_if_fail (shadows->class == >K_CSS_VALUE_SHADOWS); @@ -323,11 +324,12 @@ _gtk_css_shadows_value_get_extents (const GtkCssValue *shadows, _gtk_css_shadow_value_get_geometry (shadow, &hoffset, &voffset, &radius, &spread); + clip_radius = _gtk_cairo_blur_compute_pixels (radius); - b.top = MAX (0, radius + spread - voffset); - b.right = MAX (0, radius + spread + hoffset); - b.bottom = MAX (0, radius + spread + voffset); - b.left = MAX (0, radius + spread - hoffset); + b.top = MAX (0, clip_radius + spread - voffset); + b.right = MAX (0, clip_radius + spread + hoffset); + b.bottom = MAX (0, clip_radius + spread + voffset); + b.left = MAX (0, clip_radius + spread - hoffset); border->top = MAX (border->top, b.top); border->right = MAX (border->right, b.right); diff --git a/gtk/gtkcssshadowvalue.c b/gtk/gtkcssshadowvalue.c index cdfd852612..6dcd2dd798 100644 --- a/gtk/gtkcssshadowvalue.c +++ b/gtk/gtkcssshadowvalue.c @@ -31,10 +31,6 @@ #include -/* The blur of _gtk_cairo_blur_surface only approximately ends at radius, - so we add an extra pixel to make the clips less dramatic */ -#define CLIP_RADIUS_EXTRA 4 - struct _GtkCssValue { GTK_CSS_VALUE_BASE guint inset :1; @@ -327,7 +323,7 @@ gtk_css_shadow_value_start_drawing (const GtkCssValue *shadow, gdk_cairo_get_clip_rectangle (cr, &clip_rect); - clip_radius = radius + CLIP_RADIUS_EXTRA; + clip_radius = _gtk_cairo_blur_compute_pixels (radius); /* Create a larger surface to center the blur. */ surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, @@ -534,7 +530,7 @@ _gtk_css_shadow_value_paint_box (const GtkCssValue *shadow, spread = _gtk_css_number_value_get (shadow->spread, 0); radius = _gtk_css_number_value_get (shadow->radius, 0); - clip_radius = radius + CLIP_RADIUS_EXTRA; + clip_radius = _gtk_cairo_blur_compute_pixels (radius); x = _gtk_css_number_value_get (shadow->hoffset, 0); y = _gtk_css_number_value_get (shadow->voffset, 0);