diff --git a/engine/canvas.cpp b/engine/canvas.cpp
index 8db8041..ff626ff 100644
--- a/engine/canvas.cpp
+++ b/engine/canvas.cpp
@@ -144,17 +144,18 @@ void ui::Canvas::snap_history(const std::vector<int>& planes)
     auto action = new ActionStroke;
     for (auto i : planes)
     {
-        if (!m_dirty_face[i])
+        if (!m_layers[m_current_layer_idx].m_dirty_face[i])
             continue; // no stroke on this face, skip it
 
         m_layers[m_current_layer_idx].m_rtt[i].bindFramebuffer();
 
         // save image before commit
-        glm::vec2 box_sz = m_dirty_box[i].zw() - m_dirty_box[i].xy();
+        glm::vec2 box_or = m_layers[m_current_layer_idx].m_dirty_box[i].xy();
+        glm::vec2 box_sz = m_layers[m_current_layer_idx].m_dirty_box[i].zw() - m_layers[m_current_layer_idx].m_dirty_box[i].xy();
         action->m_image[i] = std::make_unique<uint8_t[]>(box_sz.x * box_sz.y * 4);
-        glReadPixels(m_dirty_box[i].x, m_dirty_box[i].y, box_sz.x, box_sz.y, GL_RGBA, GL_UNSIGNED_BYTE, action->m_image[i].get());
+        glReadPixels(box_or.x, box_or.y, box_sz.x, box_sz.y, GL_RGBA, GL_UNSIGNED_BYTE, action->m_image[i].get());
 
-        action->m_box[i] = m_dirty_box[i];
+        action->m_box[i] = m_layers[m_current_layer_idx].m_dirty_box[i];
         action->m_old_box[i] = m_layers[m_current_layer_idx].m_dirty_box[i];
         action->m_old_dirty[i] = m_layers[m_current_layer_idx].m_dirty_face[i];