disable-subpixel-antialiasing.patch

# HG changeset patch
# User Robert O'Callahan <robert@ocallahan.org>
# Date 1294019288 -46800
# Node ID 8857392e37aea7475ed6d8ee4b45023e1233bcec
# Parent  c53f60831c43cca397dfed8adf8d350aeec7d3ca
Bug 363861. Part 2: Introduce cairo_surface_get/set_subpixel_antialiasing. r=jrmuizel,sr=vlad,a=blocking

diff --git a/gfx/cairo/cairo/src/cairo-quartz-surface.c b/gfx/cairo/cairo/src/cairo-quartz-surface.c
--- a/gfx/cairo/cairo/src/cairo-quartz-surface.c
+++ b/gfx/cairo/cairo/src/cairo-quartz-surface.c
@@ -2473,16 +2473,17 @@ _cairo_quartz_surface_show_glyphs (void 
     cairo_int_status_t rv = CAIRO_STATUS_SUCCESS;
     cairo_quartz_drawing_state_t state;
     float xprev, yprev;
     int i;
     CGFontRef cgfref = NULL;
 
     cairo_bool_t isClipping = FALSE;
     cairo_bool_t didForceFontSmoothing = FALSE;
+    cairo_antialias_t effective_antialiasing;
 
     if (IS_EMPTY(surface))
 	return CAIRO_STATUS_SUCCESS;
 
     if (num_glyphs <= 0)
 	return CAIRO_STATUS_SUCCESS;
 
     if (cairo_scaled_font_get_type (scaled_font) != CAIRO_FONT_TYPE_QUARTZ)
@@ -2514,16 +2515,22 @@ _cairo_quartz_surface_show_glyphs (void 
 	goto BAIL;
     }
 
     /* this doesn't addref */
     cgfref = _cairo_quartz_scaled_font_get_cg_font_ref (scaled_font);
     CGContextSetFont (state.context, cgfref);
     CGContextSetFontSize (state.context, 1.0);
 
+    effective_antialiasing = scaled_font->options.antialias;
+    if (effective_antialiasing == CAIRO_ANTIALIAS_SUBPIXEL &&
+        !surface->base.permit_subpixel_antialiasing) {
+        effective_antialiasing = CAIRO_ANTIALIAS_GRAY;
+    }
+
     switch (scaled_font->options.antialias) {
 	case CAIRO_ANTIALIAS_SUBPIXEL:
 	    CGContextSetShouldAntialias (state.context, TRUE);
 	    CGContextSetShouldSmoothFonts (state.context, TRUE);
 	    if (CGContextSetAllowsFontSmoothingPtr &&
 		!CGContextGetAllowsFontSmoothingPtr (state.context))
 	    {
 		didForceFontSmoothing = TRUE;
diff --git a/gfx/cairo/cairo/src/cairo-surface-private.h b/gfx/cairo/cairo/src/cairo-surface-private.h
--- a/gfx/cairo/cairo/src/cairo-surface-private.h
+++ b/gfx/cairo/cairo/src/cairo-surface-private.h
@@ -58,16 +58,17 @@ struct _cairo_surface {
 
     cairo_reference_count_t ref_count;
     cairo_status_t status;
     unsigned int unique_id;
 
     unsigned finished : 1;
     unsigned is_clear : 1;
     unsigned has_font_options : 1;
+    unsigned permit_subpixel_antialiasing : 1;
 
     cairo_user_data_array_t user_data;
     cairo_user_data_array_t mime_data;
 
     cairo_matrix_t device_transform;
     cairo_matrix_t device_transform_inverse;
 
     /* The actual resolution of the device, in dots per inch. */
diff --git a/gfx/cairo/cairo/src/cairo-surface.c b/gfx/cairo/cairo/src/cairo-surface.c
--- a/gfx/cairo/cairo/src/cairo-surface.c
+++ b/gfx/cairo/cairo/src/cairo-surface.c
@@ -49,17 +49,18 @@ const cairo_surface_t name = {					\
     NULL,				/* backend */		\
     CAIRO_SURFACE_TYPE_IMAGE,		/* type */		\
     CAIRO_CONTENT_COLOR,		/* content */		\
     CAIRO_REFERENCE_COUNT_INVALID,	/* ref_count */		\
     status,				/* status */		\
     0,					/* unique id */		\
     FALSE,				/* finished */		\
     TRUE,				/* is_clear */		\
-    FALSE,				/* has_font_options */	\
+    FALSE,                             /* has_font_options */	\
+    FALSE,                             /* permit_subpixel_antialiasing */ \
     { 0, 0, 0, NULL, },			/* user_data */		\
     { 0, 0, 0, NULL, },			/* mime_data */         \
     { 1.0, 0.0, 0.0, 1.0, 0.0, 0.0 },   /* device_transform */	\
     { 1.0, 0.0,	0.0, 1.0, 0.0, 0.0 },	/* device_transform_inverse */	\
     0.0,				/* x_resolution */	\
     0.0,				/* y_resolution */	\
     0.0,				/* x_fallback_resolution */	\
     0.0,				/* y_fallback_resolution */	\
@@ -342,46 +343,48 @@ _cairo_surface_init (cairo_surface_t			*
     surface->content = content;
     surface->type = backend->type;
 
     CAIRO_REFERENCE_COUNT_INIT (&surface->ref_count, 1);
     surface->status = CAIRO_STATUS_SUCCESS;
     surface->unique_id = _cairo_surface_allocate_unique_id ();
     surface->finished = FALSE;
     surface->is_clear = FALSE;
+    surface->has_font_options = FALSE;
+    surface->permit_subpixel_antialiasing = TRUE;
 
     _cairo_user_data_array_init (&surface->user_data);
     _cairo_user_data_array_init (&surface->mime_data);
 
     cairo_matrix_init_identity (&surface->device_transform);
     cairo_matrix_init_identity (&surface->device_transform_inverse);
 
     surface->x_resolution = CAIRO_SURFACE_RESOLUTION_DEFAULT;
     surface->y_resolution = CAIRO_SURFACE_RESOLUTION_DEFAULT;
 
     surface->x_fallback_resolution = CAIRO_SURFACE_FALLBACK_RESOLUTION_DEFAULT;
     surface->y_fallback_resolution = CAIRO_SURFACE_FALLBACK_RESOLUTION_DEFAULT;
 
     _cairo_array_init (&surface->snapshots, sizeof (cairo_surface_t *));
     surface->snapshot_of = NULL;
-
-    surface->has_font_options = FALSE;
 }
 
 static void
 _cairo_surface_copy_similar_properties (cairo_surface_t *surface,
 					cairo_surface_t *other)
 {
     if (other->has_font_options || other->backend != surface->backend) {
 	cairo_font_options_t options;
 
 	cairo_surface_get_font_options (other, &options);
 	_cairo_surface_set_font_options (surface, &options);
     }
 
+    surface->permit_subpixel_antialiasing = other->permit_subpixel_antialiasing;
+
     cairo_surface_set_fallback_resolution (surface,
 					   other->x_fallback_resolution,
 					   other->y_fallback_resolution);
 }
 
 cairo_surface_t *
 _cairo_surface_create_similar_scratch (cairo_surface_t *other,
 				       cairo_content_t	content,
@@ -2482,16 +2485,67 @@ cairo_surface_has_show_text_glyphs (cair
 
     if (surface->backend->has_show_text_glyphs)
 	return surface->backend->has_show_text_glyphs (surface);
     else
 	return surface->backend->show_text_glyphs != NULL;
 }
 slim_hidden_def (cairo_surface_has_show_text_glyphs);
 
+/**
+ * cairo_surface_set_subpixel_antialiasing:
+ * @surface: a #cairo_surface_t
+ *
+ * Sets whether the surface permits subpixel antialiasing. By default,
+ * surfaces permit subpixel antialiasing.
+ *
+ * Enabling subpixel antialiasing for CONTENT_COLOR_ALPHA surfaces generally
+ * requires that the pixels in the areas under a subpixel antialiasing
+ * operation already be opaque.
+ *
+ * Since: 1.12
+ **/
+void
+cairo_surface_set_subpixel_antialiasing (cairo_surface_t *surface,
+                                         cairo_subpixel_antialiasing_t enabled)
+{
+    if (surface->status)
+        return;
+
+    if (surface->finished) {
+        _cairo_surface_set_error (surface, CAIRO_STATUS_SURFACE_FINISHED);
+        return;
+    }
+
+    surface->permit_subpixel_antialiasing =
+        enabled == CAIRO_SUBPIXEL_ANTIALIASING_ENABLED;
+}
+slim_hidden_def (cairo_surface_set_subpixel_antialiasing);
+
+/**
+ * cairo_surface_get_subpixel_antialiasing:
+ * @surface: a #cairo_surface_t
+ *
+ * Gets whether the surface supports subpixel antialiasing. By default,
+ * CAIRO_CONTENT_COLOR surfaces support subpixel antialiasing but other
+ * surfaces do not.
+ *
+ * Since: 1.12
+ **/
+cairo_subpixel_antialiasing_t
+cairo_surface_get_subpixel_antialiasing (cairo_surface_t *surface)
+{
+    if (surface->status)
+        return CAIRO_SUBPIXEL_ANTIALIASING_DISABLED;
+
+    return surface->permit_subpixel_antialiasing ?
+        CAIRO_SUBPIXEL_ANTIALIASING_ENABLED : CAIRO_SUBPIXEL_ANTIALIASING_DISABLED;
+}
+slim_hidden_def (cairo_surface_get_subpixel_antialiasing);
+
 /* Note: the backends may modify the contents of the glyph array as long as
  * they do not return %CAIRO_INT_STATUS_UNSUPPORTED. This makes it possible to
  * avoid copying the array again and again, and edit it in-place.
  * Backends are in fact free to use the array as a generic buffer as they
  * see fit.
  *
  * For show_glyphs backend method, and NOT for show_text_glyphs method,
  * when they do return UNSUPPORTED, they may adjust remaining_glyphs to notify
diff --git a/gfx/cairo/cairo/src/cairo-win32-font.c b/gfx/cairo/cairo/src/cairo-win32-font.c
--- a/gfx/cairo/cairo/src/cairo-win32-font.c
+++ b/gfx/cairo/cairo/src/cairo-win32-font.c
@@ -1380,16 +1380,17 @@ _cairo_win32_scaled_font_show_glyphs (vo
     cairo_win32_surface_t *surface = (cairo_win32_surface_t *)generic_surface;
     cairo_status_t status;
 
     if (width == 0 || height == 0)
 	return CAIRO_STATUS_SUCCESS;
 
     if (_cairo_surface_is_win32 (generic_surface) &&
 	surface->format == CAIRO_FORMAT_RGB24 &&
+	(generic_surface->permit_subpixel_antialiasing || scaled_font->quality != CLEARTYPE_QUALITY) &&
 	op == CAIRO_OPERATOR_OVER &&
 	_cairo_pattern_is_opaque_solid (pattern)) {
 
 	cairo_solid_pattern_t *solid_pattern = (cairo_solid_pattern_t *)pattern;
 
 	/* When compositing OVER on a GDI-understood surface, with a
 	 * solid opaque color, we can just call ExtTextOut directly.
 	 */
@@ -1411,16 +1412,18 @@ _cairo_win32_scaled_font_show_glyphs (vo
 	 * surface by drawing the the glyphs onto a DIB, black-on-white then
 	 * inverting. GDI outputs gamma-corrected images so inverted black-on-white
 	 * is very different from white-on-black. We favor the more common
 	 * case where the final output is dark-on-light.
 	 */
 	cairo_win32_surface_t *tmp_surface;
 	cairo_surface_t *mask_surface;
 	cairo_surface_pattern_t mask;
+	cairo_bool_t use_subpixel_antialiasing =
+	    scaled_font->quality == CLEARTYPE_QUALITY && generic_surface->permit_subpixel_antialiasing;
 	RECT r;
 
 	tmp_surface = (cairo_win32_surface_t *)cairo_win32_surface_create_with_dib (CAIRO_FORMAT_ARGB32, width, height);
 	if (tmp_surface->base.status)
 	    return tmp_surface->base.status;
 
 	r.left = 0;
 	r.top = 0;
@@ -1432,17 +1435,17 @@ _cairo_win32_scaled_font_show_glyphs (vo
 		                          scaled_font, RGB (0, 0, 0),
 					  dest_x, dest_y,
 					  glyphs, num_glyphs);
 	if (status) {
 	    cairo_surface_destroy (&tmp_surface->base);
 	    return status;
 	}
 
-	if (scaled_font->quality == CLEARTYPE_QUALITY) {
+	if (use_subpixel_antialiasing) {
 	    /* For ClearType, we need a 4-channel mask. If we are compositing on
 	     * a surface with alpha, we need to compute the alpha channel of
 	     * the mask (we just copy the green channel). But for a destination
 	     * surface without alpha the alpha channel of the mask is ignored
 	     */
 
 	    if (surface->format != CAIRO_FORMAT_RGB24)
 		_compute_argb32_mask_alpha (tmp_surface);
@@ -1460,17 +1463,17 @@ _cairo_win32_scaled_font_show_glyphs (vo
 
 	/* For op == OVER, no-cleartype, a possible optimization here is to
 	 * draw onto an intermediate ARGB32 surface and alpha-blend that with the
 	 * destination
 	 */
 	_cairo_pattern_init_for_surface (&mask, mask_surface);
 	cairo_surface_destroy (mask_surface);
 
-	if (scaled_font->quality == CLEARTYPE_QUALITY)
+	if (use_subpixel_antialiasing)
 	    mask.base.has_component_alpha = TRUE;
 
 	status = _cairo_surface_composite (op, pattern,
 					   &mask.base,
 					   &surface->base,
 					   source_x, source_y,
 					   0, 0,
 					   dest_x, dest_y,
diff --git a/gfx/cairo/cairo/src/cairo-xlib-surface.c b/gfx/cairo/cairo/src/cairo-xlib-surface.c
--- a/gfx/cairo/cairo/src/cairo-xlib-surface.c
+++ b/gfx/cairo/cairo/src/cairo-xlib-surface.c
@@ -3570,16 +3570,17 @@ typedef struct _cairo_xlib_font_glyphset
     GlyphSet		glyphset;
     cairo_format_t	format;
     XRenderPictFormat	*xrender_format;
     cairo_xlib_font_glyphset_free_glyphs_t *pending_free_glyphs;
 } cairo_xlib_font_glyphset_info_t;
 
 typedef struct _cairo_xlib_surface_font_private {
     cairo_scaled_font_t		    *scaled_font;
+    cairo_scaled_font_t         *grayscale_font;
     cairo_xlib_hook_t                close_display_hook;
     cairo_xlib_display_t	    *display;
     cairo_xlib_font_glyphset_info_t  glyphset_info[NUM_GLYPHSETS];
 } cairo_xlib_surface_font_private_t;
 
 /* callback from CloseDisplay */
 static void
 _cairo_xlib_surface_remove_scaled_font (cairo_xlib_display_t	*display,
@@ -3599,16 +3600,20 @@ _cairo_xlib_surface_remove_scaled_font (
 
     _cairo_scaled_font_reset_cache (scaled_font);
     CAIRO_MUTEX_UNLOCK (scaled_font->mutex);
 
     if (font_private != NULL) {
 	Display *dpy;
 	int i;
 
+    if (font_private->grayscale_font) {
+        cairo_scaled_font_destroy (font_private->grayscale_font);
+    }
+
 	dpy = _cairo_xlib_display_get_dpy (display);
 	for (i = 0; i < NUM_GLYPHSETS; i++) {
 	    cairo_xlib_font_glyphset_info_t *glyphset_info;
 
 	    glyphset_info = &font_private->glyphset_info[i];
 	    if (glyphset_info->glyphset)
 		XRenderFreeGlyphSet (dpy, glyphset_info->glyphset);
 
@@ -3629,16 +3634,17 @@ _cairo_xlib_surface_font_init (Display		
     cairo_status_t status;
     int i;
 
     font_private = malloc (sizeof (cairo_xlib_surface_font_private_t));
     if (unlikely (font_private == NULL))
 	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 
     font_private->scaled_font = scaled_font;
+    font_private->grayscale_font = NULL;
     status = _cairo_xlib_display_get (dpy, &font_private->display);
     if (unlikely (status)) {
 	free (font_private);
 	return status;
     }
 
     /* initialize and hook into the CloseDisplay callback */
     font_private->close_display_hook.func =
@@ -3671,16 +3677,20 @@ _cairo_xlib_surface_scaled_font_fini (ca
 {
     cairo_xlib_surface_font_private_t *font_private;
 
     font_private = scaled_font->surface_private;
     if (font_private != NULL) {
 	cairo_xlib_display_t *display;
 	int i;
 
+	if (font_private->grayscale_font) {
+        cairo_scaled_font_destroy (font_private->grayscale_font);
+	}
+
 	display = font_private->display;
 	_cairo_xlib_remove_close_display_hook (display,
 					       &font_private->close_display_hook);
 
 	for (i = 0; i < NUM_GLYPHSETS; i++) {
 	    cairo_xlib_font_glyphset_info_t *glyphset_info;
 
 	    glyphset_info = &font_private->glyphset_info[i];
@@ -4417,16 +4427,62 @@ _cairo_xlib_surface_owns_font (cairo_xli
 	(font_private != NULL && font_private->display != dst->display))
     {
 	return FALSE;
     }
 
     return TRUE;
 }
 
+/* Gets a grayscale version of scaled_font. The grayscale version is cached
+ * in our surface_private data.
+ */
+static cairo_scaled_font_t *
+_cairo_xlib_get_grayscale_font (cairo_xlib_surface_t *dst,
+                                cairo_scaled_font_t *scaled_font)
+{
+    cairo_xlib_surface_font_private_t *font_private = scaled_font->surface_private;
+    cairo_bool_t needs_font;
+
+    if (font_private == NULL) {
+        cairo_status_t status = _cairo_xlib_surface_font_init (dst->dpy, scaled_font);
+        if (unlikely (status))
+            return _cairo_scaled_font_create_in_error (status);
+        font_private = scaled_font->surface_private;
+    }
+
+    CAIRO_MUTEX_LOCK (scaled_font->mutex);
+    needs_font = !font_private->grayscale_font;
+    CAIRO_MUTEX_UNLOCK (scaled_font->mutex);
+
+    if (needs_font) {
+        cairo_font_options_t options;
+        cairo_scaled_font_t *new_font;
+
+        options = scaled_font->options;
+        options.antialias = CAIRO_ANTIALIAS_GRAY;
+        new_font = cairo_scaled_font_create (scaled_font->font_face,
+                                             &scaled_font->font_matrix,
+                                             &scaled_font->ctm, &options);
+
+        CAIRO_MUTEX_LOCK (scaled_font->mutex);
+        if (!font_private->grayscale_font) {
+            font_private->grayscale_font = new_font;
+            new_font = NULL;
+        }
+        CAIRO_MUTEX_UNLOCK (scaled_font->mutex);
+
+        if (new_font) {
+            cairo_scaled_font_destroy (new_font);
+        }
+    }
+
+    return font_private->grayscale_font;
+}
+
 static cairo_int_status_t
 _cairo_xlib_surface_show_glyphs (void                *abstract_dst,
 				 cairo_operator_t     op,
 				 const cairo_pattern_t *src_pattern,
 				 cairo_glyph_t       *glyphs,
 				 int		      num_glyphs,
 				 cairo_scaled_font_t *scaled_font,
 				 cairo_clip_t	     *clip,
@@ -4475,16 +4531,21 @@ _cairo_xlib_surface_show_glyphs (void   
 
     operation = _categorize_composite_operation (dst, op, src_pattern, TRUE);
     if (operation == DO_UNSUPPORTED)
 	return UNSUPPORTED ("unsupported op");
 
     if (! _cairo_xlib_surface_owns_font (dst, scaled_font))
 	return UNSUPPORTED ("unowned font");
 
+    if (!dst->base.permit_subpixel_antialiasing &&
+        scaled_font->options.antialias == CAIRO_ANTIALIAS_SUBPIXEL) {
+        scaled_font = _cairo_xlib_get_grayscale_font (dst, scaled_font);
+    }
+
     X_DEBUG ((dst->dpy, "show_glyphs (dst=%x)", (unsigned int) dst->drawable));
 
     if (clip_region != NULL &&
 	cairo_region_num_rectangles (clip_region) == 1)
     {
 	cairo_rectangle_int_t glyph_extents;
 	const cairo_rectangle_int_t *clip_extents;
 
diff --git a/gfx/cairo/cairo/src/cairo.h b/gfx/cairo/cairo/src/cairo.h
--- a/gfx/cairo/cairo/src/cairo.h
+++ b/gfx/cairo/cairo/src/cairo.h
@@ -2101,16 +2101,35 @@ cairo_public void
 cairo_surface_copy_page (cairo_surface_t *surface);
 
 cairo_public void
 cairo_surface_show_page (cairo_surface_t *surface);
 
 cairo_public cairo_bool_t
 cairo_surface_has_show_text_glyphs (cairo_surface_t *surface);
 
+/**
+ * _cairo_subpixel_antialiasing_t:
+ * @CAIRO_SUBPIXEL_ANTIALIASING_ENABLED: subpixel antialiasing is enabled
+ * for this surface.
+ * @CAIRO_SUBPIXEL_ANTIALIASING_DISABLED: subpixel antialiasing is disabled
+ * for this surface.
+ */
+typedef enum _cairo_subpixel_antialiasing_t {
+    CAIRO_SUBPIXEL_ANTIALIASING_ENABLED,
+    CAIRO_SUBPIXEL_ANTIALIASING_DISABLED
+} cairo_subpixel_antialiasing_t;
+
+cairo_public void
+cairo_surface_set_subpixel_antialiasing (cairo_surface_t *surface,
+                                         cairo_subpixel_antialiasing_t enabled);
+
+cairo_public cairo_subpixel_antialiasing_t
+cairo_surface_get_subpixel_antialiasing (cairo_surface_t *surface);
+
 /* Image-surface functions */
 
 /**
  * cairo_format_t:
  * @CAIRO_FORMAT_ARGB32: each pixel is a 32-bit quantity, with
  *   alpha in the upper 8 bits, then red, then green, then blue.
  *   The 32-bit quantities are stored native-endian. Pre-multiplied
  *   alpha is used. (That is, 50% transparent red is 0x80800000,
diff --git a/gfx/cairo/cairo/src/cairoint.h b/gfx/cairo/cairo/src/cairoint.h
--- a/gfx/cairo/cairo/src/cairoint.h
+++ b/gfx/cairo/cairo/src/cairoint.h
@@ -2750,16 +2750,18 @@ slim_hidden_proto (cairo_surface_destroy
 slim_hidden_proto (cairo_surface_finish);
 slim_hidden_proto (cairo_surface_flush);
 slim_hidden_proto (cairo_surface_get_content);
 slim_hidden_proto (cairo_surface_get_device_offset);
 slim_hidden_proto (cairo_surface_get_font_options);
 slim_hidden_proto (cairo_surface_get_mime_data);
 slim_hidden_proto (cairo_surface_get_type);
 slim_hidden_proto (cairo_surface_has_show_text_glyphs);
+slim_hidden_proto (cairo_surface_set_subpixel_antialiasing);
+slim_hidden_proto (cairo_surface_get_subpixel_antialiasing);
 slim_hidden_proto (cairo_surface_mark_dirty_rectangle);
 slim_hidden_proto_no_warn (cairo_surface_reference);
 slim_hidden_proto (cairo_surface_set_device_offset);
 slim_hidden_proto (cairo_surface_set_fallback_resolution);
 slim_hidden_proto (cairo_surface_set_mime_data);
 slim_hidden_proto (cairo_surface_show_page);
 slim_hidden_proto (cairo_surface_status);
 slim_hidden_proto (cairo_text_cluster_allocate);