diff --git a/build/Aegisub/Aegisub.vcxproj b/build/Aegisub/Aegisub.vcxproj
index 76209cdae..c0e935cef 100644
--- a/build/Aegisub/Aegisub.vcxproj
+++ b/build/Aegisub/Aegisub.vcxproj
@@ -156,6 +156,7 @@
     <ClInclude Include="$(SrcDir)factory_manager.h" />
     <ClInclude Include="$(SrcDir)ffmpegsource_common.h" />
     <ClInclude Include="$(SrcDir)fft.h" />
+    <ClInclude Include="$(SrcDir)flyweight_hash.h" />
     <ClInclude Include="$(SrcDir)font_file_lister.h" />
     <ClInclude Include="$(SrcDir)frame_main.h" />
     <ClInclude Include="$(SrcDir)gl_text.h" />
diff --git a/build/Aegisub/Aegisub.vcxproj.filters b/build/Aegisub/Aegisub.vcxproj.filters
index ca09046ad..458dc1fe4 100644
--- a/build/Aegisub/Aegisub.vcxproj.filters
+++ b/build/Aegisub/Aegisub.vcxproj.filters
@@ -549,6 +549,9 @@
     <ClInclude Include="$(SrcDir)dialogs.h">
       <Filter>Features</Filter>
     </ClInclude>
+    <ClInclude Include="$(SrcDir)flyweight_hash.h">
+      <Filter>Utilities</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="$(SrcDir)ass_dialogue.cpp">
@@ -1040,9 +1043,6 @@
     <ClCompile Include="$(SrcDir)ass_parser.cpp">
       <Filter>ASS</Filter>
     </ClCompile>
-    <ClCompile Include="$(SrcDir)audio_provider_lock.cpp">
-      <Filter>Audio\Providers</Filter>
-    </ClCompile>
     <ClCompile Include="$(SrcDir)command\keyframe.cpp">
       <Filter>Commands</Filter>
     </ClCompile>
@@ -1093,4 +1093,4 @@
     <ResourceCompile Include="$(SrcDir)res\res.rc" />
     <ResourceCompile Include="$(SrcDir)res\strings.rc" />
   </ItemGroup>
-</Project>
+</Project>
\ No newline at end of file
diff --git a/src/base_grid.cpp b/src/base_grid.cpp
index 1d3801c96..25f9f6197 100644
--- a/src/base_grid.cpp
+++ b/src/base_grid.cpp
@@ -45,6 +45,7 @@
 #include "subs_controller.h"
 #include "video_controller.h"
 
+#include <libaegisub/make_unique.h>
 #include <libaegisub/util.h>
 
 #include <algorithm>
@@ -598,15 +599,17 @@ void BaseGrid::SetColumnWidths() {
 	text_refresh_rects.clear();
 	int x = 0;
 
-	WidthHelper helper{dc, std::unordered_map<boost::flyweight<std::string>, int>{}};
-	helper.widths.reserve(prev_unique_string_widths);
+	if (!width_helper)
+		width_helper = agi::make_unique<WidthHelper>();
+	width_helper->SetDC(&dc);
+
 	for (auto const& column : columns) {
-		column->UpdateWidth(context, helper);
+		column->UpdateWidth(context, *width_helper);
 		if (column->Width() && column->RefreshOnTextChange())
 			text_refresh_rects.emplace_back(x, 0, column->Width(), h);
 		x += column->Width();
 	}
-	prev_unique_string_widths = helper.widths.size();
+	width_helper->Age();
 }
 
 AssDialogue *BaseGrid::GetDialogue(int n) const {
diff --git a/src/base_grid.h b/src/base_grid.h
index 86ca3071d..366189588 100644
--- a/src/base_grid.h
+++ b/src/base_grid.h
@@ -30,6 +30,7 @@
 #include <libaegisub/signal.h>
 
 #include <memory>
+#include <string>
 #include <vector>
 #include <wx/window.h>
 
@@ -39,6 +40,7 @@ namespace agi {
 }
 class AssDialogue;
 class GridColumn;
+class WidthHelper;
 
 class BaseGrid final : public wxWindow {
 	std::vector<agi::signal::Connection> connections;
@@ -57,7 +59,7 @@ class BaseGrid final : public wxWindow {
 
 	int active_row = -1;
 
-	size_t prev_unique_string_widths = 0;
+	std::unique_ptr<WidthHelper> width_helper;
 
 	/// Rows which are visible on the current video frame
 	std::vector<int> visible_rows;
diff --git a/src/flyweight_hash.h b/src/flyweight_hash.h
new file mode 100644
index 000000000..3eb3afff2
--- /dev/null
+++ b/src/flyweight_hash.h
@@ -0,0 +1,28 @@
+// Copyright (c) 2015, Thomas Goyne <plorkyeran@aegisub.org>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+// Aegisub Project http://www.aegisub.org/
+
+#pragma once
+
+#include <boost/flyweight.hpp>
+
+namespace std {
+	template <typename T>
+	struct hash<boost::flyweight<T>> {
+		size_t operator()(boost::flyweight<T> const& ss) const {
+			return hash<const void*>()(&ss.get());
+		}
+	};
+}
diff --git a/src/grid_column.cpp b/src/grid_column.cpp
index 757966b93..289ea79b3 100644
--- a/src/grid_column.cpp
+++ b/src/grid_column.cpp
@@ -27,39 +27,52 @@
 
 #include <wx/dc.h>
 
+void WidthHelper::Age() {
+	for (auto it = begin(widths), e = end(widths); it != e; ) {
+		if (it->second.age == age)
+			++it;
+		else
+			it = widths.erase(it);
+	}
+	++age;
+}
+
 int WidthHelper::operator()(boost::flyweight<std::string> const& str) {
 	if (str.get().empty()) return 0;
 	auto it = widths.find(str);
-	if (it != end(widths)) return it->second;
+	if (it != end(widths)) {
+		it->second.age = age;
+		return it->second.width;
+	}
 
 #ifdef _WIN32
 	wxMBConvUTF8 conv;
 	size_t len = conv.ToWChar(nullptr, 0, str.get().c_str(), str.get().size());
 	scratch.resize(len);
 	conv.ToWChar(const_cast<wchar_t *>(scratch.wx_str()), len, str.get().c_str(), str.get().size());
-	int width = dc.GetTextExtent(scratch).GetWidth();
+	int width = dc->GetTextExtent(scratch).GetWidth();
 #else
-	int width = dc.GetTextExtent(to_wx(str)).GetWidth();
+	int width = dc->GetTextExtent(to_wx(str)).GetWidth();
 #endif
 
-	widths[str] = width;
+	widths[str] = {width, age};
 	return width;
 }
 
 int WidthHelper::operator()(std::string const& str) {
-	return dc.GetTextExtent(to_wx(str)).GetWidth();
+	return dc->GetTextExtent(to_wx(str)).GetWidth();
 }
 
 int WidthHelper::operator()(wxString const& str) {
-	return dc.GetTextExtent(str).GetWidth();
+	return dc->GetTextExtent(str).GetWidth();
 }
 
 int WidthHelper::operator()(const char *str) {
-	return dc.GetTextExtent(wxString::FromUTF8(str)).GetWidth();
+	return dc->GetTextExtent(wxString::FromUTF8(str)).GetWidth();
 }
 
 int WidthHelper::operator()(const wchar_t *str) {
-	return dc.GetTextExtent(str).GetWidth();
+	return dc->GetTextExtent(str).GetWidth();
 }
 
 void GridColumn::UpdateWidth(const agi::Context *c, WidthHelper &helper) {
diff --git a/src/grid_column.h b/src/grid_column.h
index 54497610b..16b70f2a9 100644
--- a/src/grid_column.h
+++ b/src/grid_column.h
@@ -14,7 +14,8 @@
 //
 // Aegisub Project http://www.aegisub.org/
 
-#include <boost/flyweight.hpp>
+#include "flyweight_hash.h"
+
 #include <memory>
 #include <string>
 #include <vector>
@@ -25,19 +26,21 @@ class wxDC;
 class wxString;
 namespace agi { struct Context; }
 
-namespace std {
-	template <typename T>
-	struct hash<boost::flyweight<T>> {
-		size_t operator()(boost::flyweight<T> const& ss) const {
-			return hash<const void*>()(&ss.get());
-		}
+class WidthHelper {
+	struct Entry {
+		int width;
+		int age;
 	};
-}
-
-struct WidthHelper {
-	wxDC &dc;
-	std::unordered_map<boost::flyweight<std::string>, int> widths;
+	int age = 0;
+	wxDC *dc = nullptr;
+	std::unordered_map<boost::flyweight<std::string>, Entry> widths;
+#ifdef _WIN32
 	wxString scratch;
+#endif
+
+public:
+	void SetDC(wxDC *dc) { this->dc = dc; }
+	void Age();
 
 	int operator()(boost::flyweight<std::string> const& str);
 	int operator()(std::string const& str);
diff --git a/src/subs_edit_box.cpp b/src/subs_edit_box.cpp
index 7ed9111bc..c19b2f9c8 100644
--- a/src/subs_edit_box.cpp
+++ b/src/subs_edit_box.cpp
@@ -40,6 +40,7 @@
 #include "command/command.h"
 #include "compat.h"
 #include "dialog_style_editor.h"
+#include "flyweight_hash.h"
 #include "include/aegisub/context.h"
 #include "include/aegisub/hotkey.h"
 #include "initial_line_state.h"
@@ -69,15 +70,6 @@
 #include <wx/sizer.h>
 #include <wx/spinctrl.h>
 
-namespace std {
-	template <typename T>
-	struct hash<boost::flyweight<T>> {
-		size_t operator()(boost::flyweight<T> const& ss) const {
-			return hash<const void*>()(&ss.get());
-		}
-	};
-}
-
 namespace {
 
 /// Work around wxGTK's fondness for generating events from ChangeValue