Fix brush and pasted image preview on empty cels (fix #3882)

Fix regression introduced in 24846eae10c7340a4e7f103b15494ea8338700a9
using the new RenderPlan structure. We have to include empty/nullptr
cels in the plan to paint the preview image in the selected
layer/frame (the preview image is the one used for the brush preview,
and for the transformation preview when we paste the clipboard content
on the canvas).

src/app/render/shader_renderer.cpp

@@ -231,14 +231,14 @@ void ShaderRenderer::renderPlan(SkCanvas* canvas,
 {
   for (const auto& item : plan.items()) {
     const Cel* cel = item.cel;
-    const Layer* layer = cel->layer();
+    const Layer* layer = item.layer;
 
     switch (layer->type()) {
 
       case doc::ObjectType::LayerImage: {
         auto imgLayer = static_cast<const LayerImage*>(layer);
 
-        if (doc::Cel* cel = imgLayer->cel(frame)) {
+        if (cel) {
           const doc::Image* celImage = nullptr;
           gfx::RectF celBounds;
 
@@ -254,7 +254,7 @@ void ShaderRenderer::renderPlan(SkCanvas* canvas,
           // If not, we use the original cel-image from the images' stock
           else {
             celImage = cel->image();
-            if (cel->layer()->isReference())
+            if (layer->isReference())
               celBounds = cel->boundsF();
             else
               celBounds = cel->bounds();
@@ -276,7 +276,8 @@ void ShaderRenderer::renderPlan(SkCanvas* canvas,
 
       case doc::ObjectType::LayerTilemap: {
         auto tilemapLayer = static_cast<const LayerTilemap*>(layer);
-        doc::Cel* cel = tilemapLayer->cel(frame);
+
+        // TODO selected layer?
         if (!cel)
           break;
 

src/doc/render_plan.cpp

@@ -39,9 +39,7 @@ void RenderPlan::addLayer(const Layer* layer,
 
     case ObjectType::LayerImage:
     case ObjectType::LayerTilemap: {
-      if (Cel* cel = layer->cel(frame)) {
-        m_items.emplace_back(m_order, cel);
-      }
+      m_items.emplace_back(m_order, layer, layer->cel(frame));
       break;
     }
 
@@ -62,7 +60,7 @@ void RenderPlan::processZIndexes() const
   // If all cels has a z-index = 0, we can just use the m_items as it is
   bool noZIndex = true;
   for (int i=0; i<int(m_items.size()); ++i) {
-    const int z = m_items[i].cel->zIndex();
+    const int z = m_items[i].zIndex();
     if (z != 0) {
       noZIndex = false;
       break;
@@ -73,12 +71,12 @@ void RenderPlan::processZIndexes() const
 
   // Order cels using its "order" number in m_items array + cel z-index offset
   for (Item& item : m_items)
-    item.order = item.order + item.cel->zIndex();
+    item.order = item.order + item.zIndex();
   std::sort(m_items.begin(), m_items.end(),
             [](const Item& a, const Item& b){
               return
                 (a.order < b.order) ||
-                (a.order == b.order && (a.cel->zIndex() < b.cel->zIndex()));
+                (a.order == b.order && (a.zIndex() < b.zIndex()));
             });
 }
 

src/doc/render_plan.h

@@ -8,6 +8,7 @@
 #define DOC_RENDER_PLAN_H_INCLUDED
 #pragma once
 
+#include "doc/cel.h"
 #include "doc/cel_list.h"
 #include "doc/frame.h"
 
@@ -21,9 +22,13 @@ namespace doc {
   public:
     struct Item {
       int order;
-      Cel* cel;
-      Item(int order = 0, Cel* cel = nullptr)
-        : order(order), cel(cel) { }
+      const Layer* layer;
+      const Cel* cel;
+      int zIndex() const { return (cel ? cel->zIndex(): 0); }
+      Item(const int order = 0,
+           const Layer* layer = nullptr,
+           const Cel* cel = nullptr)
+        : order(order), layer(layer), cel(cel) { }
     };
     using Items = std::vector<Item>;
 

src/doc/sprite.cpp

@@ -634,7 +634,10 @@ void Sprite::pickCels(const gfx::PointF& pos,
   // bottom-most) so we pick first visible cel in the given position.
   const auto& planItems = plan.items();
   for (auto it=planItems.rbegin(), end=planItems.rend(); it!=end; ++it) {
-    Cel* cel = it->cel;
+    const Cel* cel = it->cel;
+    if (!cel)
+      continue;
+
     const Image* image = cel->image();
     if (!image)
       continue;
@@ -698,7 +701,7 @@ void Sprite::pickCels(const gfx::PointF& pos,
     if (!isOpaque)
       continue;
 
-    cels.push_back(cel);
+    cels.push_back(const_cast<Cel*>(cel));
   }
 }
 

src/render/render.cpp

@@ -1006,7 +1006,7 @@ void Render::renderPlan(
 {
   for (const auto& item : plan.items()) {
     const Cel* cel = item.cel;
-    const Layer* layer = cel->layer();
+    const Layer* layer = item.layer;
 
     ASSERT(layer->isVisible()); // Hidden layers shouldn't be in the plan
 
@@ -1034,8 +1034,7 @@ void Render::renderPlan(
       else {
         // Check if we can draw the extra cel when we render a linked
         // frame.
-        cel = layer->cel(frame);
-        Cel* cel2 = layer->cel(m_extraCel->frame());
+        const Cel* cel2 = layer->cel(m_extraCel->frame());
         if (cel && cel2 &&
             cel->data() == cel2->data()) {
           drawExtra = true;
@@ -1085,7 +1084,7 @@ void Render::renderPlan(
           // If not, we use the original cel-image from the images' stock
           else {
             celImage = cel->image();
-            if (cel->layer()->isReference())
+            if (layer->isReference())
               celBounds = cel->boundsF();
             else
               celBounds = cel->bounds();