First attempt at fixing the 'straight' blend method. It now applies to the whole...

[synfig.git] / synfig-core / trunk / src / synfig / layer_pastecanvas.cpp

diff --git a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
index d19f066..d343530 100644 (file)
--- a/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
+++ b/synfig-core/trunk/src/synfig/layer_pastecanvas.cpp
@@ -202,7 +202,8 @@ Layer_PasteCanvas::set_sub_canvas(etl::handle<synfig::Canvas> x)
                );
        */
        if(canvas)
-               bounds=(canvas->get_context().get_full_bounding_rect()-canvas->rend_desc().get_focus())*exp(zoom)+origin+canvas->rend_desc().get_focus();
+               bounds = ((canvas->get_context().get_full_bounding_rect() - canvas->rend_desc().get_focus()) * exp(zoom) +
+                                 origin + canvas->rend_desc().get_focus());
 
        if(canvas && muck_with_time_)
                add_child(canvas.get());
@@ -332,6 +333,7 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
 
        Color::BlendMethod blend_method(get_blend_method());
        const Rect full_bounding_rect(canvas->get_context().get_full_bounding_rect());
+       bool blend_using_straight = false; // use 'straight' just for the central blit
 
        if(context->empty())
        {
@@ -347,10 +349,14 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
                 * effect if the affected area of the lower layer is
                 * transparent;  however, if we're not clipping the blit to
                 * just the bounding rectangle, the affected area is the whole
-                * tile, so we can't use this optimisation
+                * tile, so we can't use this optimisation.  if we are
+                * clipping, then we can use 'straight' to blit the clipped
+                * rectangle, but we shouldn't set blend_method to 'straight',
+                * or the surrounding areas will be blanked, which we don't
+                * want.
                 */
 #ifdef SYNFIG_CLIP_PASTECANVAS
-               if (blend_method==Color::BLEND_COMPOSITE) blend_method=Color::BLEND_STRAIGHT;
+               if (blend_method==Color::BLEND_COMPOSITE) blend_using_straight = true;
 #endif // SYNFIG_CLIP_PASTECANVAS
        }
 
@@ -368,6 +374,9 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
        const int w( ceil_to_int((max[0] - desc.get_tl()[0]) / desc.get_pw()) - x);
        const int h( ceil_to_int((max[1] - desc.get_tl()[1]) / desc.get_ph()) - y);
 
+       const int tw = desc.get_w();
+       const int th = desc.get_h();
+
        desc.set_subwindow(x,y,w,h);
 
        // \todo this used to also have "area.area()<=0.000001 || " - is it useful?
@@ -377,6 +386,50 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
                if(cb && !cb->amount_complete(10000,10000)) return false;
                return true;
        }
+
+       // SYNFIG_CLIP_PASTECANVAS is defined, so we are only touching the
+       // pixels within the affected rectangle.  If the blend method is
+       // 'straight', then we need to blend transparent pixels with the
+       // clipped areas of this tile, because with the 'straight' blend
+       // method, even transparent pixels have an effect on the layers below
+       if (blend_method == Color::BLEND_STRAIGHT)
+       {
+               Surface clearsurface;
+
+               Surface::alpha_pen apen(surface->begin());
+               apen.set_alpha(get_amount());
+               apen.set_blend_method(Color::BLEND_STRAIGHT);
+
+               /* This represents the area we're pasting into the tile,
+                * within the tile as a whole.  Areas (A), (B), (C) and (D)
+                * need blending with the underlying context if they're not
+                * zero-sized:
+                *
+                *               0         x             x+w      tw
+                *       0       +------------------------+
+                *               |                                                |
+                *               |                      (A)                       |
+                *               |                                                |
+                *       y       | - - +----------+ - - - |
+                *               |         |              |               |
+                *               | (C) |  w by h  |      (D)  |
+                *               |         |              |               |
+                *       y+h | - - +----------+ - - - |
+                *               |                                                |
+                *               |                      (B)                       |
+                *               |                                                |
+                *       tw      +------------------------+
+                */
+
+               if (y > 0)                              // draw the full-width strip above the rectangle (A)
+               { apen.move_to(0,0);   clearsurface.set_wh(tw,y);        clearsurface.clear(); clearsurface.blit_to(apen); }
+               if (y+h < th)                   // draw the full-width strip below the rectangle (B)
+               { apen.move_to(0,y+h); clearsurface.set_wh(tw,th-(y+h)); clearsurface.clear(); clearsurface.blit_to(apen); }
+               if (x > 0)                              // draw the box directly left of the rectangle (C)
+               { apen.move_to(0,y);   clearsurface.set_wh(x,h);         clearsurface.clear(); clearsurface.blit_to(apen); }
+               if (x+w < tw)                   // draw the box directly right of the rectangle (D)
+               { apen.move_to(x+w,y); clearsurface.set_wh(tw-(x+w),h);  clearsurface.clear(); clearsurface.blit_to(apen); }
+       }
 #endif // SYNFIG_CLIP_PASTECANVAS
 
        // render the canvas to be pasted onto pastesurface
@@ -391,7 +444,7 @@ Layer_PasteCanvas::accelerated_render(Context context,Surface *surface,int quali
 #endif // SYNFIG_CLIP_PASTECANVAS
 
        apen.set_alpha(get_amount());
-       apen.set_blend_method(blend_method);
+       apen.set_blend_method(blend_using_straight ? Color::BLEND_STRAIGHT : blend_method);
        pastesurface.blit_to(apen);
 
        if(cb && !cb->amount_complete(10000,10000)) return false;