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https://gitlab.freedesktop.org/cairo/cairo.git
synced 2026-05-08 14:58:06 +02:00
[gl] Render glyphs to an intermediate mask as opposed to falling back.
There are many common scenarios, mostly involving overlapping glyphs, for which to guarantee correct rendering we have to composite the glyphs via an explicit mask. That is instead of just blending the glyphs on to the destination, we have to add the glyphs to a mask, and then composite that mask+source with the destination.
This commit is contained in:
Chris Wilson
parent
cd259489e2
commit
b1227dea29
1 changed files with 194 additions and 112 deletions
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@ -323,124 +323,32 @@ _cairo_gl_emit_glyph_rectangle (cairo_gl_context_t *ctx,
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setup->num_prims++;
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}
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cairo_int_status_t
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_cairo_gl_surface_show_glyphs (void *abstract_dst,
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cairo_operator_t op,
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const cairo_pattern_t *source,
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cairo_glyph_t *glyphs,
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int num_glyphs,
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cairo_scaled_font_t *scaled_font,
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cairo_clip_t *clip,
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int *remaining_glyphs)
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static cairo_status_t
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_render_glyphs (cairo_gl_surface_t *dst,
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int dst_x, int dst_y,
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cairo_operator_t op,
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const cairo_pattern_t *source,
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cairo_glyph_t *glyphs,
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int num_glyphs,
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const cairo_rectangle_int_t *glyph_extents,
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cairo_scaled_font_t *scaled_font,
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cairo_region_t *clip_region,
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int *remaining_glyphs)
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{
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cairo_gl_surface_t *dst = abstract_dst;
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cairo_gl_context_t *ctx;
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cairo_rectangle_int_t extents;
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cairo_format_t last_format = (cairo_format_t) -1;
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cairo_gl_glyph_cache_t *cache = NULL;
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cairo_status_t status;
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int i = 0;
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cairo_region_t *clip_region = NULL;
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cairo_solid_pattern_t solid_pattern;
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cairo_gl_context_t *ctx;
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cairo_gl_glyphs_setup_t setup;
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cairo_gl_composite_setup_t composite_setup;
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cairo_bool_t overlap;
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cairo_status_t status;
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int i = 0;
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GLuint vbo = 0;
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if (! GLEW_ARB_vertex_buffer_object)
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return UNSUPPORTED ("requires ARB_vertex_buffer_object");
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if (! _cairo_gl_operator_is_supported (op))
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return UNSUPPORTED ("unsupported operator");
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/* Just let unbounded operators go through the fallback code
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* instead of trying to do the fixups here */
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if (! _cairo_operator_bounded_by_mask (op))
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return UNSUPPORTED ("unhandled unbound operator");
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/* For CLEAR, cairo's rendering equation (quoting Owen's description in:
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* http://lists.cairographics.org/archives/cairo/2005-August/004992.html)
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* is:
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* mask IN clip ? src OP dest : dest
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* or more simply:
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* mask IN CLIP ? 0 : dest
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*
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* where the ternary operator A ? B : C is (A * B) + ((1 - A) * C).
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*
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* The model we use in _cairo_gl_set_operator() is Render's:
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* src IN mask IN clip OP dest
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* which would boil down to:
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* 0 (bounded by the extents of the drawing).
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*
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* However, we can do a Render operation using an opaque source
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* and DEST_OUT to produce:
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* 1 IN mask IN clip DEST_OUT dest
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* which is
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* mask IN clip ? 0 : dest
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*/
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if (op == CAIRO_OPERATOR_CLEAR) {
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_cairo_pattern_init_solid (&solid_pattern, CAIRO_COLOR_WHITE,
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CAIRO_CONTENT_COLOR);
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source = &solid_pattern.base;
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op = CAIRO_OPERATOR_DEST_OUT;
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}
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/* For SOURCE, cairo's rendering equation is:
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* (mask IN clip) ? src OP dest : dest
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* or more simply:
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* (mask IN clip) ? src : dest.
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*
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* If we just used the Render equation, we would get:
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* (src IN mask IN clip) OP dest
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* or:
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* (src IN mask IN clip) bounded by extents of the drawing.
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*
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* The trick is that for GL blending, we only get our 4 source values
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* into the blender, and since we need all 4 components of source, we
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* can't also get the mask IN clip into the blender. But if we did
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* two passes we could make it work:
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* dest = (mask IN clip) DEST_OUT dest
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* dest = src IN mask IN clip ADD dest
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*
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* But for now, fall back :)
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*/
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if (op == CAIRO_OPERATOR_SOURCE)
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return UNSUPPORTED ("not handling SOURCE operator");
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/* XXX we don't need ownership of the font as we use a global
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* glyph cache -- but we do need scaled_glyph eviction notification. :-(
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*/
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if (! _cairo_gl_surface_owns_font (dst, scaled_font))
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return UNSUPPORTED ("do not control font");
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if (clip != NULL) {
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status = _cairo_clip_get_region (clip, &clip_region);
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/* the empty clip should never be propagated this far */
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assert (status != CAIRO_INT_STATUS_NOTHING_TO_DO);
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if (unlikely (_cairo_status_is_error (status)))
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return status;
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if (status == CAIRO_INT_STATUS_UNSUPPORTED)
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return UNSUPPORTED ("unhandled clipmask");
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}
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status = _cairo_scaled_font_glyph_device_extents (scaled_font,
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glyphs, num_glyphs,
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&extents,
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&overlap);
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if (unlikely (status))
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return status;
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/* If the glyphs overlap, we need to build an intermediate mask rather
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* then compositing directly.
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* For the time being, just fallback.
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*/
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if (overlap)
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return UNSUPPORTED ("overlapping glyphs");
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status = _cairo_gl_operand_init (&composite_setup.src, source, dst,
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extents.x, extents.y,
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extents.x, extents.y,
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extents.width, extents.height);
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glyph_extents->x, glyph_extents->y,
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dst_x, dst_y,
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glyph_extents->width,
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glyph_extents->height);
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if (unlikely (status))
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return status;
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@ -465,9 +373,7 @@ _cairo_gl_surface_show_glyphs (void *abstract_dst,
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glTexEnvi (GL_TEXTURE_ENV, GL_OPERAND1_ALPHA, GL_SRC_ALPHA);
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_cairo_gl_set_destination (dst);
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_cairo_gl_set_operator (dst, op);
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_cairo_gl_set_src_operand (ctx, &composite_setup);
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_cairo_scaled_font_freeze_cache (scaled_font);
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@ -611,9 +517,185 @@ _cairo_gl_surface_show_glyphs (void *abstract_dst,
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_cairo_gl_operand_destroy (&composite_setup.src);
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*remaining_glyphs = num_glyphs - i;
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return CAIRO_STATUS_SUCCESS;
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}
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static cairo_int_status_t
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_cairo_gl_surface_show_glyphs_via_mask (cairo_gl_surface_t *dst,
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cairo_operator_t op,
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const cairo_pattern_t *source,
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cairo_glyph_t *glyphs,
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int num_glyphs,
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const cairo_rectangle_int_t *glyph_extents,
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cairo_scaled_font_t *scaled_font,
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cairo_clip_t *clip,
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int *remaining_glyphs)
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{
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cairo_surface_t *mask;
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cairo_status_t status;
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cairo_solid_pattern_t solid;
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int i;
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mask = cairo_gl_surface_create (dst->ctx,
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CAIRO_CONTENT_ALPHA,
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glyph_extents->width,
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glyph_extents->height);
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if (unlikely (mask->status))
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return mask->status;
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for (i = 0; i < num_glyphs; i++) {
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glyphs[i].x -= glyph_extents->x;
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glyphs[i].y -= glyph_extents->y;
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}
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_cairo_pattern_init_solid (&solid, CAIRO_COLOR_WHITE, CAIRO_CONTENT_ALPHA);
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status = _render_glyphs ((cairo_gl_surface_t *) mask, 0, 0,
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CAIRO_OPERATOR_ADD, &solid.base,
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glyphs, num_glyphs, glyph_extents,
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scaled_font, NULL, remaining_glyphs);
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if (likely (status == CAIRO_STATUS_SUCCESS)) {
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cairo_surface_pattern_t mask_pattern;
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_cairo_pattern_init_for_surface (&mask_pattern, mask);
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cairo_matrix_init_translate (&mask_pattern.base.matrix,
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-glyph_extents->x, -glyph_extents->y);
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status = _cairo_surface_mask (&dst->base, op,
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source, &mask_pattern.base, clip);
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_cairo_pattern_fini (&mask_pattern.base);
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} else {
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for (i = 0; i < num_glyphs; i++) {
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glyphs[i].x += glyph_extents->x;
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glyphs[i].y += glyph_extents->y;
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}
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*remaining_glyphs = num_glyphs;
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}
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cairo_surface_destroy (mask);
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return status;
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}
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cairo_int_status_t
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_cairo_gl_surface_show_glyphs (void *abstract_dst,
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cairo_operator_t op,
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const cairo_pattern_t *source,
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cairo_glyph_t *glyphs,
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int num_glyphs,
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cairo_scaled_font_t *scaled_font,
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cairo_clip_t *clip,
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int *remaining_glyphs)
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{
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cairo_gl_surface_t *dst = abstract_dst;
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cairo_rectangle_int_t extents;
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cairo_region_t *clip_region = NULL;
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cairo_solid_pattern_t solid_pattern;
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cairo_bool_t overlap, use_mask = FALSE;
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cairo_status_t status;
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if (! GLEW_ARB_vertex_buffer_object)
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return UNSUPPORTED ("requires ARB_vertex_buffer_object");
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if (! _cairo_gl_operator_is_supported (op))
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return UNSUPPORTED ("unsupported operator");
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/* Just let unbounded operators go through the fallback code
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* instead of trying to do the fixups here */
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if (! _cairo_operator_bounded_by_mask (op))
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use_mask |= TRUE;
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/* For CLEAR, cairo's rendering equation (quoting Owen's description in:
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* http://lists.cairographics.org/archives/cairo/2005-August/004992.html)
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* is:
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* mask IN clip ? src OP dest : dest
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* or more simply:
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* mask IN CLIP ? 0 : dest
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*
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* where the ternary operator A ? B : C is (A * B) + ((1 - A) * C).
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*
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* The model we use in _cairo_gl_set_operator() is Render's:
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* src IN mask IN clip OP dest
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* which would boil down to:
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* 0 (bounded by the extents of the drawing).
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*
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* However, we can do a Render operation using an opaque source
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* and DEST_OUT to produce:
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* 1 IN mask IN clip DEST_OUT dest
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* which is
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* mask IN clip ? 0 : dest
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*/
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if (op == CAIRO_OPERATOR_CLEAR) {
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_cairo_pattern_init_solid (&solid_pattern, CAIRO_COLOR_WHITE,
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CAIRO_CONTENT_COLOR);
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source = &solid_pattern.base;
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op = CAIRO_OPERATOR_DEST_OUT;
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}
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/* For SOURCE, cairo's rendering equation is:
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* (mask IN clip) ? src OP dest : dest
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* or more simply:
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* (mask IN clip) ? src : dest.
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*
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* If we just used the Render equation, we would get:
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* (src IN mask IN clip) OP dest
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* or:
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* (src IN mask IN clip) bounded by extents of the drawing.
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*
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* The trick is that for GL blending, we only get our 4 source values
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* into the blender, and since we need all 4 components of source, we
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* can't also get the mask IN clip into the blender. But if we did
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* two passes we could make it work:
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* dest = (mask IN clip) DEST_OUT dest
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* dest = src IN mask IN clip ADD dest
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*
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* But for now, composite via an intermediate mask.
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*/
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if (op == CAIRO_OPERATOR_SOURCE)
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use_mask |= TRUE;
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/* XXX we don't need ownership of the font as we use a global
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* glyph cache -- but we do need scaled_glyph eviction notification. :-(
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*/
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if (! _cairo_gl_surface_owns_font (dst, scaled_font))
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return UNSUPPORTED ("do not control font");
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/* If the glyphs overlap, we need to build an intermediate mask rather
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* then perform the compositing directly.
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*/
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status = _cairo_scaled_font_glyph_device_extents (scaled_font,
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glyphs, num_glyphs,
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&extents,
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&overlap);
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if (unlikely (status))
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return status;
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use_mask |= overlap;
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if (clip != NULL) {
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status = _cairo_clip_get_region (clip, &clip_region);
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/* the empty clip should never be propagated this far */
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assert (status != CAIRO_INT_STATUS_NOTHING_TO_DO);
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if (unlikely (_cairo_status_is_error (status)))
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return status;
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use_mask |= status == CAIRO_INT_STATUS_UNSUPPORTED;
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}
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if (use_mask) {
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return _cairo_gl_surface_show_glyphs_via_mask (dst, op,
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source,
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glyphs, num_glyphs,
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&extents,
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scaled_font,
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clip,
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remaining_glyphs);
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}
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return _render_glyphs (dst, extents.x, extents.y,
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op, source,
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glyphs, num_glyphs, &extents,
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scaled_font, clip_region, remaining_glyphs);
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}
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void
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_cairo_gl_glyph_cache_fini (cairo_gl_glyph_cache_t *cache)
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{
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