add Canvas constructor & add canvas:blit

src/graphics/core/Atlas.cpp

@@ -97,7 +97,7 @@ std::unique_ptr<Atlas> AtlasBuilder::build(uint extrusion, bool prepare, uint ma
         uint y = rect.y;
         uint w = rect.width;
         uint h = rect.height;
-        canvas->blit(entry.image.get(), rect.x, rect.y);
+        canvas->blit(*entry.image, rect.x, rect.y);
         for (uint j = 0; j < extrusion; j++) {
             canvas->extrude(x - j, y - j, w + j*2, h + j*2);
         }

src/graphics/core/ImageData.cpp

@@ -81,13 +81,13 @@ void ImageData::flipY() {
     }
 }
 
-void ImageData::blit(const ImageData* image, int x, int y) {
-    if (format == image->format) {
+void ImageData::blit(const ImageData& image, int x, int y) {
+    if (format == image.format) {
         blitMatchingFormat(image, x, y);
         return;
     }
     if (format == ImageFormat::rgba8888 && 
-        image->format == ImageFormat::rgb888) {
+        image.format == ImageFormat::rgb888) {
         blitRGB_on_RGBA(image, x, y);
         return;
     }
@@ -187,10 +187,10 @@ void ImageData::drawLine(int x1, int y1, int x2, int y2, const glm::ivec4& color
     }
 }
 
-void ImageData::blitRGB_on_RGBA(const ImageData* image, int x, int y) {
-    ubyte* source = image->getData();
-    uint srcwidth = image->getWidth();
-    uint srcheight = image->getHeight();
+void ImageData::blitRGB_on_RGBA(const ImageData& image, int x, int y) {
+    ubyte* source = image.getData();
+    uint srcwidth = image.getWidth();
+    uint srcheight = image.getHeight();
 
     for (uint srcy = std::max(0, -y);
          srcy < std::min(srcheight, height - y);
@@ -210,7 +210,7 @@ void ImageData::blitRGB_on_RGBA(const ImageData* image, int x, int y) {
     }
 }
 
-void ImageData::blitMatchingFormat(const ImageData* image, int x, int y) {
+void ImageData::blitMatchingFormat(const ImageData& image, int x, int y) {
     uint comps;
     switch (format) {
         case ImageFormat::rgb888: comps = 3; break;
@@ -218,20 +218,24 @@ void ImageData::blitMatchingFormat(const ImageData* image, int x, int y) {
         default:
             throw std::runtime_error("only unsigned byte formats supported");    
     }
-    ubyte* source = image->getData();
-    uint srcwidth = image->getWidth();
-    uint srcheight = image->getHeight();
+    ubyte* source = image.getData();
+
+    const uint width = this->width;
+    const uint height = this->height;
+    const uint src_width = image.getWidth();
+    const uint src_height = image.getHeight();
+    ubyte* data = this->data.get();
 
     for (uint srcy = std::max(0, -y);
-         srcy < std::min(srcheight, height - y);
+         srcy < std::min(src_height, height - y);
          srcy++) {
         for (uint srcx = std::max(0, -x);
-             srcx < std::min(srcwidth, width - x);
+             srcx < std::min(src_width, width - x);
              srcx++) {
             uint dstx = srcx + x;
             uint dsty = srcy + y;
             uint dstidx = (dsty * width + dstx) * comps;
-            uint srcidx = (srcy * srcwidth + srcx) * comps;
+            uint srcidx = (srcy * src_width + srcx) * comps;
             for (uint c = 0; c < comps; c++) {
                 data[dstidx + c] = source[srcidx + c];
             }

src/graphics/core/ImageData.hpp

@@ -15,6 +15,9 @@ class ImageData {
     uint width;
     uint height;
     std::unique_ptr<ubyte[]> data;
+
+    void blitRGB_on_RGBA(const ImageData& image, int x, int y);
+    void blitMatchingFormat(const ImageData& image, int x, int y);
 public:
     ImageData(ImageFormat format, uint width, uint height);
     ImageData(ImageFormat format, uint width, uint height, std::unique_ptr<ubyte[]> data);
@@ -25,9 +28,7 @@ public:
     void flipY();
 
     void drawLine(int x1, int y1, int x2, int y2, const glm::ivec4& color);
-    void blitRGB_on_RGBA(const ImageData* image, int x, int y);
-    void blitMatchingFormat(const ImageData* image, int x, int y);
-    void blit(const ImageData* image, int x, int y);
+    void blit(const ImageData& image, int x, int y);
     void extrude(int x, int y, int w, int h);
     void fixAlphaColor();
 

src/logic/scripting/lua/lua_custom_types.hpp

@@ -114,10 +114,14 @@ namespace lua {
             return *mData;
         }
 
+        [[nodiscard]] bool hasTexture() const {
+            return mTexture != nullptr;
+        }
+
         static int createMetatable(lua::State*);
         inline static std::string TYPENAME = "Canvas";
     private:
-        std::shared_ptr<Texture> mTexture;
+        std::shared_ptr<Texture> mTexture; // nullable
         std::shared_ptr<ImageData> mData;
     };
     static_assert(!std::is_abstract<LuaCanvas>());

src/logic/scripting/lua/usertypes/lua_type_canvas.cpp

@@ -79,12 +79,18 @@ static int l_set(State* L) {
     return 0;
 }
 
-static int l_clear(State* L) {
-    auto canvas = touserdata<LuaCanvas>(L, 1);
-    if (canvas == nullptr) {
-        throw std::runtime_error("used canvas.clear instead of canvas:clear");
+static LuaCanvas& require_canvas(State* L, int idx) {
+    if (const auto canvas = touserdata<LuaCanvas>(L, idx)) {
+        return *canvas;
     }
-    auto& image = canvas->data();
+    throw std::runtime_error(
+        "canvas expected as argument #" + std::to_string(idx)
+    );
+}
+
+static int l_clear(State* L) {
+    auto& canvas = require_canvas(L, 1);
+    auto& image = canvas.data();
     ubyte* data = image.getData();
     RGBA rgba {};
     if (gettop(L) == 1) {
@@ -117,9 +123,20 @@ static int l_line(State* L) {
     return 0;
 }
 
+static int l_blit(State* L) {
+    auto& dst = require_canvas(L, 1);
+    auto& src = require_canvas(L, 2);
+    int dst_x = tointeger(L, 3);
+    int dst_y = tointeger(L, 4);
+    dst.data().blit(src.data(), dst_x, dst_y);
+    return 0;
+}
+
 static int l_update(State* L) {
     if (auto canvas = touserdata<LuaCanvas>(L, 1)) {
-        canvas->texture().reload(canvas->data());
+        if (canvas->hasTexture()) {
+            canvas->texture().reload(canvas->data());
+        }
     }
     return 0;
 }
@@ -128,8 +145,10 @@ static std::unordered_map<std::string, lua_CFunction> methods {
     {"at", lua::wrap<l_at>},
     {"set", lua::wrap<l_set>},
     {"line", lua::wrap<l_line>},
+    {"blit", lua::wrap<l_blit>},
     {"clear", lua::wrap<l_clear>},
-    {"update", lua::wrap<l_update>}};
+    {"update", lua::wrap<l_update>},
+};
 
 static int l_meta_index(State* L) {
     auto texture = touserdata<LuaCanvas>(L, 1);
@@ -171,11 +190,28 @@ static int l_meta_newindex(State* L) {
     return 0;
 }
 
+static int l_meta_meta_call(lua::State* L) {
+    auto size = glm::ivec2(tovec2(L, 2));
+    if (size.x <= 0 || size.y <= 0) {
+        throw std::runtime_error("size must be positive");
+    }
+    return newuserdata<LuaCanvas>(
+        L,
+        nullptr,
+        std::make_shared<ImageData>(ImageFormat::rgba8888, size.x, size.y)
+    );
+}
+
 int LuaCanvas::createMetatable(State* L) {
     createtable(L, 0, 3);
     pushcfunction(L, lua::wrap<l_meta_index>);
     setfield(L, "__index");
     pushcfunction(L, lua::wrap<l_meta_newindex>);
     setfield(L, "__newindex");
+
+    createtable(L, 0, 1);
+    pushcfunction(L, lua::wrap<l_meta_meta_call>);
+    setfield(L, "__call");
+    setmetatable(L);
     return 1;
 }