improving actions history

src/canvas_layer.cpp

@@ -0,0 +1,45 @@
+#include "pch.h"
+#include "canvas_layer.h"
+
+void Layer::Snapshot::create(int w, int h)
+{
+    for (int i = 0; i < 6; i++)
+    {
+        image[i] = std::make_unique<uint8_t[]>(w * h * 4);
+        std::fill_n(image[i].get(), w * h * 4, 0);
+    }
+}
+
+void Layer::Snapshot::clear()
+{
+    for (int i = 0; i < 6; i++)
+    {
+        m_dirty_face[i] = false;
+        m_dirty_box[i] = glm::vec4(0);
+        std::fill_n(image[i].get(), width * height * 4, 0);
+    }
+}
+
+void Layer::Snapshot::optimize()
+{
+    for (int i = 0; i < 6; i++)
+    {
+        if (!m_dirty_face[i] || !image[i])
+            continue;
+        auto data = reinterpret_cast<glm::u8vec4*>(image[i].get());
+        glm::ivec2 bbmin(width, height);
+        glm::ivec2 bbmax(0);
+        for (int y = 0; y < height; y++)
+        {
+            for (int x = 0; x < width; x++)
+            {
+                if (data[x + y * width].a > 0)
+                {
+                    bbmin = glm::min(bbmin, { x, y });
+                    bbmax = glm::max(bbmax, { x + 1, y + 1 });
+                }
+            }
+        }
+        //glm::vec2 bbsz = bbmax - bbmin;
+    }
+}