diff --git a/src/gfx.cpp b/src/gfx.cpp
index e6765db622..1543ed7ea3 100644
--- a/src/gfx.cpp
+++ b/src/gfx.cpp
@@ -83,9 +83,6 @@ int _gui_scale_cfg;                        ///< GUI scale in config.
 static const byte *_colour_remap_ptr;
 static byte _string_colourremap[3]; ///< Recoloursprite for stringdrawing. The grf loader ensures that #ST_FONT sprites only use colours 0 to 2.
 
-static const uint DIRTY_BLOCK_HEIGHT   = 8;
-static const uint DIRTY_BLOCK_WIDTH    = 64;
-
 extern uint _dirty_block_colour;
 static bool _whole_screen_dirty = false;
 bool _gfx_draw_active = false;
@@ -1687,7 +1684,7 @@ static void DrawDirtyViewport(uint occlusion, int left, int top, int right, int
 		ViewportDrawChk(_dirty_viewport, left, top, right, bottom);
 
 		if (_dirty_viewport_disp_flags & (ND_SHADE_GREY | ND_SHADE_DIMMED)) {
-			GfxFillRect(left, top, right, bottom,
+			GfxFillRect(left, top, right - 1, bottom - 1,
 					(_dirty_viewport_disp_flags & ND_SHADE_DIMMED) ? PALETTE_TO_TRANSPARENT : PALETTE_NEWSPAPER, FILLRECT_RECOLOUR);
 		}
 		VideoDriver::GetInstance()->MakeDirty(left, top, right - left, bottom - top);
diff --git a/src/viewport.cpp b/src/viewport.cpp
index 16d47f6ecc..98ef07e2f5 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -279,8 +279,8 @@ void InitializeWindowViewport(Window *w, int x, int y,
 
 	vp->virtual_left = 0;
 	vp->virtual_top = 0;
-	vp->virtual_width = ScaleByZoom(width, zoom);
-	vp->virtual_height = ScaleByZoom(height, zoom);
+	vp->virtual_width = ScaleByZoom(width, vp->zoom);
+	vp->virtual_height = ScaleByZoom(height, vp->zoom);
 
 	UpdateViewportSizeZoom(vp);
 
diff --git a/src/widget.cpp b/src/widget.cpp
index 33e0c2bd9d..8297f6fb19 100644
--- a/src/widget.cpp
+++ b/src/widget.cpp
@@ -1025,7 +1025,7 @@ NWidgetBase::NWidgetBase(WidgetType tp) : ZeroedMemoryAllocator()
 void NWidgetBase::SetDirty(Window *w)
 {
 	this->base_flags |= WBF_DIRTY;
-	w->flags |= WF_DIRTY;
+	w->flags |= WF_WIDGETS_DIRTY;
 }
 
 /**
@@ -2397,8 +2397,8 @@ void NWidgetViewport::UpdateViewportCoordinates(Window *w)
 	if (vp != nullptr) {
 		vp->left = w->left + this->pos_x;
 		vp->top  = w->top + this->pos_y;
-		vp->width  = this->current_x;
-		vp->height = this->current_y;
+		vp->width  = w->IsShaded() ? 0 : this->current_x;
+		vp->height = w->IsShaded() ? 0 : this->current_y;
 
 		vp->virtual_width  = ScaleByZoom(vp->width, vp->zoom);
 		vp->virtual_height = ScaleByZoom(vp->height, vp->zoom);