Fix for bug #837066: Bucket Tool regressions with Cairo renderer.

(bzr r11949)

1 files changed, 27 insertions, 8 deletions

diff --git a/src/flood-context.cpp b/src/flood-context.cpp
index a6c7fa0dc..3c656527e 100644
--- a/src/flood-context.cpp
+++ b/src/flood-context.cpp
@@ -205,6 +205,10 @@ static void sp_flood_context_setup(SPEventContext *ec)
     }
 }
 
+// Changes from 0.48 -> 0.49 (Cairo)
+// 0.49: Ignores alpha in background
+// 0.48: RGBA, 0.49 ARGB
+// 0.49: premultiplied alpha
 inline static guint32 compose_onto(guint32 px, guint32 bg)
 {
     guint ap = 0, rp = 0, gp = 0, bp = 0;
@@ -212,10 +216,12 @@ inline static guint32 compose_onto(guint32 px, guint32 bg)
     ExtractARGB32(px, ap, rp, gp, bp);
     ExtractRGB32(bg, rb, gb, bb);
 
-    guint ao = 255*255 - (255-ap)*(255-bp);  ao = (ao + 127) / 255;
-    guint ro = (255-ap)*rb + rp;             ro = (ro + 127) / 255;
-    guint go = (255-ap)*gb + gp;             go = (go + 127) / 255;
-    guint bo = (255-ap)*bb + bp;             bo = (bo + 127) / 255;
+    // guint ao = 255*255 - (255-ap)*(255-bp);  ao = (ao + 127) / 255;
+    // guint ao = (255-ap)*ab + 255*ap;             ao = (ao + 127) / 255;
+    guint ao = 255; // Cairo version doesn't allow background to have alpha != 1.
+    guint ro = (255-ap)*rb + 255*rp;             ro = (ro + 127) / 255;
+    guint go = (255-ap)*gb + 255*gp;             go = (go + 127) / 255;
+    guint bo = (255-ap)*bb + 255*bp;             bo = (bo + 127) / 255;
 
     guint pxout = AssembleARGB32(ao, ro, go, bo);
     return pxout;
@@ -314,10 +320,12 @@ static bool compare_pixels(guint32 check, guint32 orig, guint32 merged_orig_pixe
             return abs(static_cast<int>(ac ? unpremul_alpha(bc, ac) : 0) - (ao ? unpremul_alpha(bo, ao) : 0)) <= threshold;
         case FLOOD_CHANNELS_RGB:
             guint32 amc, rmc, bmc, gmc;
-            amc = 255*255 - (255-ac)*(255-ad); amc = (amc + 127) / 255;
-            rmc = (255-ac)*rd + rc; rmc = (rmc + 127) / 255;
-            gmc = (255-ac)*gd + gc; gmc = (gmc + 127) / 255;
-            bmc = (255-ac)*bd + bc; bmc = (bmc + 127) / 255;
+            //amc = 255*255 - (255-ac)*(255-ad); amc = (amc + 127) / 255;
+            //amc = (255-ac)*ad + 255*ac; amc = (amc + 127) / 255;
+            amc = 255; // Why are we looking at desktop? Cairo version ignores destop alpha
+            rmc = (255-ac)*rd + 255*rc; rmc = (rmc + 127) / 255;
+            gmc = (255-ac)*gd + 255*gc; gmc = (gmc + 127) / 255;
+            bmc = (255-ac)*bd + 255*bc; bmc = (bmc + 127) / 255;
 
             diff += abs(static_cast<int>(amc ? unpremul_alpha(rmc, amc) : 0) - (amop ? unpremul_alpha(rmop, amop) : 0));
             diff += abs(static_cast<int>(amc ? unpremul_alpha(gmc, amc) : 0) - (amop ? unpremul_alpha(gmop, amop) : 0));
@@ -826,6 +834,7 @@ static void sp_flood_do_flood_fill(SPEventContext *event_context, GdkEvent *even
     guchar *px = g_new(guchar, stride * height);
     guint32 bgcolor, dtc;
 
+    // Draw image into data block px
     { // this block limits the lifetime of Drawing and DrawingContext
         /* Create DrawingItems and set transform */
         unsigned dkey = SPItem::display_key_new(1);
@@ -854,6 +863,8 @@ static void sp_flood_do_flood_fill(SPEventContext *event_context, GdkEvent *even
 
         drawing.render(ct, final_bbox);
 
+        //cairo_surface_write_to_png( s, "cairo.png" );
+
         cairo_surface_flush(s);
         cairo_surface_destroy(s);
         
@@ -861,6 +872,14 @@ static void sp_flood_do_flood_fill(SPEventContext *event_context, GdkEvent *even
         document->getRoot()->invoke_hide(dkey);
     }
 
+    // {
+    //     // Dump data to png
+    //     cairo_surface_t *s = cairo_image_surface_create_for_data(
+    //         px, CAIRO_FORMAT_ARGB32, width, height, stride);
+    //     cairo_surface_write_to_png( s, "cairo2.png" );
+    //     std::cout << "  Wrote cairo2.png" << std::endl;
+    // }
+
     guchar *trace_px = g_new(guchar, width * height);
     memset(trace_px, 0x00, width * height);