With this we can see the exact preview in real-time of the the left
click paiting (e.g. using real Indexed composition, ink, point shape, etc.)
We are able to preview blur, eraser, or flood fill preview too (anyway
these are not enabled at this moment).
Changes:
* Add render::ExtraType enum to indicate if the extra cel acts like a
patch for the current cel (e.g. cursor), or as an extra layer for
composition (e.g. selection/moving pixels)
* Add ExtraCelType property to app::Document and to render::Render
* Add ToolBox::getPointShapeById()
* As the current cursor preview depends on the current layer, when
we change the current layer we've to update the Preview editor
with the new selected layer (now we listen to
Document:.onAfterLayerChanged())
* Add create_tool_loop_preview() and PreviewToolLoopImpl
Changes:
* Add doc::ImageRef to count references to the same image between Cels
(at this moment we cannot generate linked cels anyway)
* Remove doc:Stock class and doc::Sprite::m_stock member variable
* Remove app::undoers::Add/RemoveImage
* Add doc::SubObjectsIO and app::undoers::ObjectIO to
replace doc::LayerSubObjectsSerializer
Changes:
* Create render library (move util/render.cpp to render/render.cpp)
* Move app::Zoom class to render::Zoom
* Remove doc::Image::merge() member function
* Add gfx::Clip helper class (to clip dst/src rectangles before a blit)
* Move doc::composite_image() to render::composite_image()
* Remove doc::Sprite::render()
* Replace Sprite::getPixel() with render::get_sprite_pixel()
* Remove doc::layer_render() function
* Convert DitheringMethod to a enum class
* Add AppRender to configure a render::Render with the app configuration
* Move checked background preferences as document-specific configuration
* Add doc::Sprite::layer() and palette() member functions
* Add doc::Layer::cel() member function
* Add doc::Palette::entry() member function()
* Add doc::frame_t type
* Move create_palette_from_rgb/convert_pixel_format to render library
* ExportSpriteSheet doesn't need a temporary image now that we can specify
the source rectangle in the render routine
