[gimp/gimp-2-10] Issue #4354 - When using color to fade dynamics and gradient with transparency ...

[Ell <ell src gnome org>]

commit 4d5ea7fd95bbd7d57b090ca009555b8a876a4e18
Author: Ell <ell_se yahoo com>
Date:   Thu Jan 9 22:26:35 2020 +0200

    Issue #4354 - When using color to fade dynamics and gradient with transparency ...
    
    ... brush does not have transparency
    
    In the PAINT_MASK_TO_COMP_MASK paintcore-loops algorithm, used when
    painting incrementally, multiply the paint mask values by the paint
    opacity.  Previously, the paint opacity was ignored, breaking
    various dynamics affecting the opacity.
    
    (cherry picked from commit 9fe33702fb051922072831b23b432040ac2225ec)

 app/paint/gimppaintcore-loops.cc | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/app/paint/gimppaintcore-loops.cc b/app/paint/gimppaintcore-loops.cc
index 2180c547be..0702fcd712 100644
--- a/app/paint/gimppaintcore-loops.cc
+++ b/app/paint/gimppaintcore-loops.cc
@@ -1723,7 +1723,8 @@ struct PaintMaskToCompMask : Base
         for (x = 0; x < rect->width; x++)
           {
             comp_mask_pixel[0] = value_to_float (mask_pixel[0]) *
-                                 state->mask_pixel[0];
+                                 state->mask_pixel[0]           *
+                                 params->paint_opacity;
 
             comp_mask_pixel   += 1;
             mask_pixel        += 1;
@@ -1734,7 +1735,8 @@ struct PaintMaskToCompMask : Base
       {
         for (x = 0; x < rect->width; x++)
           {
-            comp_mask_pixel[0] = value_to_float (mask_pixel[0]);
+            comp_mask_pixel[0] = value_to_float (mask_pixel[0]) *
+                                 params->paint_opacity;
 
             comp_mask_pixel += 1;
             mask_pixel      += 1;
@@ -1841,7 +1843,10 @@ struct DispatchPaintMaskToCompMask
           {
             using NewAlgorithm = typename decltype (algorithm)::type;
 
-            Dispatch<NewAlgorithm> () (visitor, params, algorithms, algorithm);
+            if (params->paint_opacity == GIMP_OPACITY_OPAQUE)
+              Dispatch<NewAlgorithm> () (visitor, params, algorithms, algorithm);
+            else
+              DispatchIndirect       () (visitor, params, algorithms, algorithm);
           },
           params, algorithms, algorithm,
           dispatch_paint_mask,