Fix group opacity

(bzr r9508.1.13)

5 files changed, 21 insertions, 25 deletions

diff --git a/src/display/nr-arena-glyphs.cpp b/src/display/nr-arena-glyphs.cpp
index ad3006950..faf10bd38 100644
--- a/src/display/nr-arena-glyphs.cpp
+++ b/src/display/nr-arena-glyphs.cpp
@@ -322,7 +322,6 @@ nr_arena_glyphs_group_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPi
     }
 
     // NOTE: this is very similar to nr-arena-shape.cpp; the only difference is path feeding
-    bool needs_opacity = ((1.0 - ggroup->nrstyle.opacity) >= 0.01);
     bool has_stroke, has_fill;
 
     cairo_save(ct);
@@ -333,10 +332,6 @@ nr_arena_glyphs_group_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPi
     has_stroke = ggroup->nrstyle.prepareStroke(ct, &ggroup->paintbox);
 
     if (has_fill || has_stroke) {
-        if (needs_opacity) {
-            cairo_push_group(ct);
-        }
-
         for (NRArenaItem *child = ggroup->children; child != NULL; child = child->next) {
             NRArenaGlyphs *g = NR_ARENA_GLYPHS(child);
             Geom::PathVector const &pathv = *g->font->PathVector(g->glyph);
@@ -356,11 +351,6 @@ nr_arena_glyphs_group_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPi
             cairo_stroke_preserve(ct);
         }
         cairo_new_path(ct); // clear path
-
-        if (needs_opacity) {
-            cairo_pop_group_to_source(ct);
-            cairo_paint_with_alpha(ct, ggroup->nrstyle.opacity);
-        }
     } // has fill or stroke pattern
     cairo_restore(ct);
 
diff --git a/src/display/nr-arena-item.cpp b/src/display/nr-arena-item.cpp
index 338940fb6..f5731c0e3 100644
--- a/src/display/nr-arena-item.cpp
+++ b/src/display/nr-arena-item.cpp
@@ -571,10 +571,14 @@ nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area
 
     bool needs_intermediate_rendering = false;
     bool &nir = needs_intermediate_rendering;
+    bool needs_opacity = (item->opacity != 255);
 
     // this item needs an intermediate rendering if:
     nir |= (item->mask != NULL); // 1. it has a mask
     nir |= (item->filter != NULL && filter); // 2. it has a filter
+    nir |= needs_opacity; // 3. it is non-opaque
+
+    double opacity = static_cast<double>(item->opacity) / 255.0;
 
     if (needs_intermediate_rendering) {
         cairo_surface_t *intermediate = cairo_surface_create_similar(
@@ -590,6 +594,7 @@ nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area
     CairoSave clipsave(this_ct); // RAII for save / restore
     CairoGroup maskgroup(this_ct); // RAII for push_group / pop_group
     CairoGroup drawgroup(this_ct);
+    CairoGroup maskopacitygroup(this_ct);
 
     if (item->clip && !(item->filter && filter)) {
         clipsave.save();
@@ -603,12 +608,20 @@ nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area
 
     if (item->mask) {
         maskgroup.push_with_content(CAIRO_CONTENT_ALPHA);
-
+        // handle opacity of a masked object by composing it with the mask
+        // this uses 1/4 the memory of composing it with full rendering
+        if (needs_opacity) {
+            maskopacitygroup.push();
+        }
         state = NR_ARENA_ITEM_VIRTUAL (item->mask, render) (this_ct, item->mask, this_area, pb, flags);
         if (state & NR_ARENA_ITEM_STATE_INVALID) {
             item->state |= NR_ARENA_ITEM_STATE_INVALID;
             return item->state;
         }
+        if (needs_opacity) {
+            maskopacitygroup.pop_to_source();
+            cct.paint_with_alpha(opacity);
+        }
         mask = maskgroup.popmm();
     }
 
@@ -632,8 +645,14 @@ nr_arena_item_invoke_render (cairo_t *ct, NRArenaItem *item, NRRectL const *area
             cairo_matrix_translate(&m, area->x0 - carea.x0, area->y0 - carea.y0);
             cairo_pattern_set_matrix(cmask, &m);
             cairo_mask(ct, cmask);
+            // opacity of masked objects is handled by premultiplying the mask
         } else {
-            cairo_paint(ct);
+            // opacity of non-masked objects must be rendered explicitly
+            if (needs_opacity) {
+                cairo_paint_with_alpha(ct, opacity);
+            } else {
+                cairo_paint(ct);
+            }
         }
         cairo_set_source_rgba(ct,0,0,0,0);
         cairo_destroy(this_ct);
diff --git a/src/display/nr-arena-shape.cpp b/src/display/nr-arena-shape.cpp
index 3f673c944..b51f3a9cf 100644
--- a/src/display/nr-arena-shape.cpp
+++ b/src/display/nr-arena-shape.cpp
@@ -360,7 +360,6 @@ nr_arena_shape_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPixBlock
         if (ret & NR_ARENA_ITEM_STATE_INVALID) return ret;
 
     } else {
-        bool needs_opacity = ((1.0 - shape->nrstyle.opacity) >= 0.01);
         bool has_stroke, has_fill;
         // we assume the context has no path
         cairo_save(ct);
@@ -374,10 +373,6 @@ nr_arena_shape_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPixBlock
         has_stroke = shape->nrstyle.prepareStroke(ct, &shape->paintbox);
 
         if (has_fill || has_stroke) {
-            if (needs_opacity) {
-                cairo_push_group(ct);
-            }
-
             // TODO: remove segments outside of bbox when no dashes present
             feed_pathvector_to_cairo(ct, shape->curve->get_pathvector());
             if (has_fill) {
@@ -389,11 +384,6 @@ nr_arena_shape_render(cairo_t *ct, NRArenaItem *item, NRRectL *area, NRPixBlock
                 cairo_stroke_preserve(ct);
             }
             cairo_new_path(ct); // clear path
-
-            if (needs_opacity) {
-                cairo_pop_group_to_source(ct);
-                cairo_paint_with_alpha(ct, shape->nrstyle.opacity);
-            }
         } // has fill or stroke pattern
         cairo_restore(ct);
     }
diff --git a/src/display/nr-style.cpp b/src/display/nr-style.cpp
index c15dd78a3..bf2f2d305 100644
--- a/src/display/nr-style.cpp
+++ b/src/display/nr-style.cpp
@@ -137,8 +137,6 @@ void NRStyle::set(SPStyle *style)
         dash = NULL;
     }
 
-    opacity = SP_SCALE24_TO_FLOAT(style->opacity.value);
-
     update();
 }
 
diff --git a/src/display/nr-style.h b/src/display/nr-style.h
index b2116a6c5..e741e46b4 100644
--- a/src/display/nr-style.h
+++ b/src/display/nr-style.h
@@ -55,7 +55,6 @@ struct NRStyle {
     Paint stroke;
     float stroke_width;
     float miter_limit;
-    float opacity;
     unsigned int n_dash;
     double *dash;
     float dash_offset;