Viewporter implementaion (#585)

Implementation of the `wp_viewporter` core protocol and some bugfixes

src/helpers/SubsurfaceTree.cpp

@@ -139,6 +139,9 @@ void Events::listener_newSubsurfaceNode(void* owner, void* data) {
 
     PNEWSUBSURFACE->pWindowOwner = pNode->pWindowOwner;
 
+    if (PSUBSURFACE->mapped)
+        listener_mapSubsurface(PNEWSUBSURFACE, nullptr);
+
     wlr_subsurface* existingWlrSubsurface;
     wl_list_for_each(existingWlrSubsurface, &PSUBSURFACE->surface->current.subsurfaces_below, current.link) {
         listener_newSubsurfaceNode(pNode, existingWlrSubsurface);

src/helpers/Vector2D.hpp

@@ -35,6 +35,10 @@ class Vector2D {
         return a.x != x || a.y != y;
     }
 
+    Vector2D operator*(const Vector2D& a) const {
+        return Vector2D(this->x * a.x, this->y * a.y);
+    }
+
     Vector2D clamp(const Vector2D& min, const Vector2D& max = Vector2D());
 
     Vector2D floor();

src/helpers/WLClasses.hpp

@@ -73,6 +73,9 @@ struct SRenderData {
 
     // only for windows, not popups
     bool squishOversized = true;
+
+    // for calculating UV
+    CWindow* pWindow = nullptr;
 };
 
 struct SExtensionFindingData {