Don't use bmpRT. Use mRT directly for DirectWrite.

dont-use-bmpRT.patch

diff --git a/src/gui.c b/src/gui.c
--- a/src/gui.c
+++ b/src/gui.c
@@ -2419,6 +2419,7 @@ gui_outstr_nowrap(
     if (flags & GUI_MON_TRS_CURSOR)
 	draw_flags |= DRAW_TRANSP;
 
+    gui_mch_draw_string_start();
     /*
      * Draw the text.
      */
@@ -2558,6 +2559,7 @@ gui_outstr_nowrap(
 # endif
     }
 #endif /* !FEAT_GUI_GTK */
+    gui_mch_draw_string_end();
 
     if (!(flags & (GUI_MON_IS_CURSOR | GUI_MON_TRS_CURSOR)))
 	gui.col = col + len;
diff --git a/src/gui_dwrite.cpp b/src/gui_dwrite.cpp
--- a/src/gui_dwrite.cpp
+++ b/src/gui_dwrite.cpp
@@ -232,14 +232,19 @@ class GdiTextRenderer FINAL : public IDW
 {
 public:
     GdiTextRenderer(
-	    IDWriteBitmapRenderTarget* bitmapRenderTarget,
-	    IDWriteRenderingParams* renderingParams) :
+	    //IDWriteBitmapRenderTarget* bitmapRenderTarget,
+	    ID2D1RenderTarget* renderTarget,
+	    IDWriteRenderingParams* renderingParams,
+	    ID2D1Brush* brush) :
 	cRefCount_(0),
-	pRenderTarget_(bitmapRenderTarget),
-	pRenderingParams_(renderingParams)
+	//pRenderTarget_(bitmapRenderTarget),
+	pRenderTarget_(renderTarget),
+	pRenderingParams_(renderingParams),
+	pBrush_(brush)
     {
 	pRenderTarget_->AddRef();
 	pRenderingParams_->AddRef();
+	pBrush_->AddRef();
 	AddRef();
     }
 
@@ -248,6 +253,7 @@ public:
     {
 	SafeRelease(&pRenderTarget_);
 	SafeRelease(&pRenderingParams_);
+	SafeRelease(&pBrush_);
     }
 
     IFACEMETHOD(IsPixelSnappingDisabled)(
@@ -263,7 +269,9 @@ public:
 	__out DWRITE_MATRIX* transform)
     {
 	// forward the render target's transform
-	pRenderTarget_->GetCurrentTransform(transform);
+	//pRenderTarget_->GetCurrentTransform(transform);
+	pRenderTarget_->GetTransform(
+		reinterpret_cast<D2D1_MATRIX_3X2_F*>(transform));
 	return S_OK;
     }
 
@@ -271,7 +279,10 @@ public:
 	__maybenull void* clientDrawingContext,
 	__out FLOAT* pixelsPerDip)
     {
-	*pixelsPerDip = pRenderTarget_->GetPixelsPerDip();
+	//*pixelsPerDip = pRenderTarget_->GetPixelsPerDip();
+	float x, yUnused;
+	pRenderTarget_->GetDpi(&x, &yUnused);
+	*pixelsPerDip = x / 96;
 	return S_OK;
     }
 
@@ -294,14 +305,21 @@ public:
 	// Pass on the drawing call to the render target to do the real work.
 	RECT dirtyRect = {0};
 
-	hr = pRenderTarget_->DrawGlyphRun(
-		baselineOriginX + context->offsetX,
-		baselineOriginY,
-		measuringMode,
+	//hr = pRenderTarget_->DrawGlyphRun(
+	//	baselineOriginX + context->offsetX,
+	//	baselineOriginY,
+	//	measuringMode,
+	//	&adjustedGlyphRun,
+	//	pRenderingParams_,
+	//	context->color,
+	//	&dirtyRect);
+	D2D1_POINT_2F baselineOrigin = {baselineOriginX + context->offsetX,
+		baselineOriginY};
+	pRenderTarget_->DrawGlyphRun(
+		baselineOrigin,
 		&adjustedGlyphRun,
-		pRenderingParams_,
-		context->color,
-		&dirtyRect);
+		pBrush_,
+		DWRITE_MEASURING_MODE_NATURAL);
 
 	context->offsetX += adjustedGlyphRun.getDelta();
 
@@ -385,8 +403,10 @@ public:
 
 private:
     long cRefCount_;
-    IDWriteBitmapRenderTarget* pRenderTarget_;
+    //IDWriteBitmapRenderTarget* pRenderTarget_;
+    ID2D1RenderTarget* pRenderTarget_;
     IDWriteRenderingParams* pRenderingParams_;
+    ID2D1Brush* pBrush_;
 };
 
 struct DWriteContext {
@@ -422,9 +442,22 @@ struct DWriteContext {
 
     void SetFont(const LOGFONTW &logFont);
 
-    void DrawText(HDC hdc, const WCHAR* text, int len,
+    void DrawText(HWND hwnd, HDC hdc, const WCHAR* text, int len,
 	int x, int y, int w, int h, int cellWidth, COLORREF color);
 
+    void BindDC(HDC hdc, RECT *rect);
+
+    void AssureDrawing(void);
+
+    ID2D1Brush* SolidBrush(COLORREF color);
+
+//    void DrawText1(const WCHAR* text, int len,
+//           int x, int y, int w, int h, COLORREF color);
+
+    void FillRect(RECT *rc, COLORREF color);
+
+    void Flush(void);
+
     float PixelsToDipsX(int x);
 
     float PixelsToDipsY(int y);
@@ -663,11 +696,11 @@ DWriteContext::SetFont(const LOGFONTW &l
 }
 
     void
-DWriteContext::DrawText(HDC hdc, const WCHAR* text, int len,
+DWriteContext::DrawText(HWND hwnd, HDC hdc, const WCHAR* text, int len,
 	int x, int y, int w, int h, int cellWidth, COLORREF color)
 {
     HRESULT hr = S_OK;
-    IDWriteBitmapRenderTarget *bmpRT = NULL;
+    //IDWriteBitmapRenderTarget *bmpRT = NULL;
 
     // Skip when any fonts are not set.
     if (mTextFormat == NULL)
@@ -677,19 +710,51 @@ DWriteContext::DrawText(HDC hdc, const W
     if (cellWidth == 0 || mDpiScaleX == 0.0f || mDpiScaleY == 0.0f)
 	return;
 
-    if (SUCCEEDED(hr))
-	hr = mGdiInterop->CreateBitmapRenderTarget(hdc, w, h, &bmpRT);
+//    if (SUCCEEDED(hr))
+//	hr = mGdiInterop->CreateBitmapRenderTarget(hdc, w, h, &bmpRT);
 
     if (SUCCEEDED(hr))
     {
 	IDWriteTextLayout *textLayout = NULL;
 
-	HDC memdc = bmpRT->GetMemoryDC();
-	BitBlt(memdc, 0, 0, w, h, hdc, x, y, SRCCOPY);
+	mRT->SetDpi(mDpiScaleX * 96.0f, mDpiScaleY * 96.0f);
+
+	//RECT rect = { x, y, x + w, y + h };
+	RECT rect;
+	static RECT rcOld = {0};
+	static HDC hdcOld = NULL;
+	GetClientRect(hwnd, &rect);
+
+	//if (hdc != hdcOld || memcmp(&rect, &rcOld, sizeof(RECT)) != 0)
+	//{
+	//    mRT->BindDC(hdc, &rect);
+	//    hdcOld = hdc;
+	//    rcOld = rect;
+	//}
+
+	//mRT->BeginDraw();
+
+	COLORREF rgb = GetTextColor(hdc);
 
-	hr = mDWriteFactory->CreateGdiCompatibleTextLayout(
+	ID2D1SolidColorBrush* pBrush = NULL;
+	D2D1_COLOR_F colorBrush = {
+	    GetRValue(rgb) / 255.0f,
+	    GetGValue(rgb) / 255.0f,
+	    GetBValue(rgb) / 255.0f,
+	    1.0f
+	};
+
+	mRT->CreateSolidColorBrush(colorBrush, &pBrush);
+
+//	HDC memdc = bmpRT->GetMemoryDC();
+//	BitBlt(memdc, 0, 0, w, h, hdc, x, y, SRCCOPY);
+
+	//hr = mDWriteFactory->CreateGdiCompatibleTextLayout(
+	//	text, len, mTextFormat, PixelsToDipsX(w),
+	//	PixelsToDipsY(h), mDpiScaleX, NULL, TRUE, &textLayout);
+	hr = mDWriteFactory->CreateTextLayout(
 		text, len, mTextFormat, PixelsToDipsX(w),
-		PixelsToDipsY(h), mDpiScaleX, NULL, TRUE, &textLayout);
+		PixelsToDipsY(h), &textLayout);
 
 	if (SUCCEEDED(hr))
 	{
@@ -700,25 +765,98 @@ DWriteContext::DrawText(HDC hdc, const W
 
 	if (SUCCEEDED(hr))
 	{
-	    GdiTextRenderer *renderer = new GdiTextRenderer(bmpRT,
-		    mRenderingParams);
+	    GdiTextRenderer *renderer = new GdiTextRenderer(/*bmpRT*/mRT,
+		    mRenderingParams, pBrush);
 	    GdiTextRendererContext data = {
 		color,
 		PixelsToDipsX(cellWidth),
 		0.0f
 	    };
-	    textLayout->Draw(&data, renderer, 0, 0);
+	    //textLayout->Draw(&data, renderer, 0, 0);
+	    textLayout->Draw(&data, renderer, PixelsToDipsX(x), PixelsToDipsY(y));
 	    SafeRelease(&renderer);
 	}
 
-	BitBlt(hdc, x, y, w, h, memdc, 0, 0, SRCCOPY);
+	//BitBlt(hdc, x, y, w, h, memdc, 0, 0, SRCCOPY);
+
+	//mRT->EndDraw();
 
 	SafeRelease(&textLayout);
+	SafeRelease(&pBrush);
     }
 
-    SafeRelease(&bmpRT);
+    //SafeRelease(&bmpRT);
+}
+
+    void
+DWriteContext::BindDC(HDC hdc, RECT *rect)
+{
+    Flush();
+    mRT->BindDC(hdc, rect);
+    mRT->SetTransform(D2D1::IdentityMatrix());
+}
+
+    void
+DWriteContext::AssureDrawing(void)
+{
+    if (mDrawing == false)
+    {
+	mRT->BeginDraw();
+	mDrawing = true;
+    }
+}
+
+    ID2D1Brush*
+DWriteContext::SolidBrush(COLORREF color)
+{
+    mBrush->SetColor(D2D1::ColorF(UINT32(GetRValue(color)) << 16 |
+		UINT32(GetGValue(color)) << 8 | UINT32(GetBValue(color))));
+    return mBrush;
 }
 
+//    void
+//DWriteContext::DrawText1(const WCHAR* text, int len,
+//	int x, int y, int w, int h, COLORREF color)
+//{
+//    AssureDrawing();
+//    mBrush->SetColor(D2D1::ColorF(UINT32(GetRValue(color)) << 16 |
+//		UINT32(GetGValue(color)) << 8 | UINT32(GetBValue(color))));
+//    mRT->DrawText(text, len, mTextFormat,
+//	    D2D1::RectF(
+//		PixelsToDipsX(x),
+//		PixelsToDipsY(y),
+//		PixelsToDipsX(x + w),
+//		PixelsToDipsY(y + h)),
+//	    SolidBrush(color),
+//	    (D2D1_DRAW_TEXT_OPTIONS)D2D1_DRAW_TEXT_OPTIONS_ENABLE_COLOR_FONT);
+//    if (mVersion == 2)
+//	Flush();
+//}
+
+    void
+DWriteContext::FillRect(RECT *rc, COLORREF color)
+{
+//    if (mVersion == 1)
+//	return;
+    AssureDrawing();
+    mRT->FillRectangle(
+	    D2D1::RectF(
+		PixelsToDipsX(rc->left),
+		PixelsToDipsY(rc->top),
+		PixelsToDipsX(rc->right),
+		PixelsToDipsY(rc->bottom)),
+	    SolidBrush(color));
+}
+
+    void
+DWriteContext::Flush(void)
+{
+    if (mDrawing)
+    {
+	mRT->EndDraw();
+	mDrawing = false;
+    }
+}
     float
 DWriteContext::PixelsToDipsX(int x)
 {
@@ -838,11 +976,8 @@ DWriteContext_BeginDraw(DWriteContext *c
     void
 DWriteContext_BindDC(DWriteContext *ctx, HDC hdc, RECT *rect)
 {
-    if (ctx != NULL && ctx->mRT != NULL)
-    {
-	ctx->mRT->BindDC(hdc, rect);
-	ctx->mRT->SetTextAntialiasMode(ctx->mTextAntialiasMode);
-    }
+    if (ctx != NULL)
+	ctx->BindDC(hdc, rect);
 }
 
     void
@@ -857,6 +992,7 @@ DWriteContext_SetFont(DWriteContext *ctx
     void
 DWriteContext_DrawText(
 	DWriteContext *ctx,
+	HWND hwnd,
 	HDC hdc,
 	const WCHAR* text,
 	int len,
@@ -867,8 +1003,8 @@ DWriteContext_DrawText(
 	int cellWidth,
 	COLORREF color)
 {
-    if (ctx != NULL)
-	ctx->DrawText(hdc, text, len, x, y, w, h, cellWidth, color);
+    if (ctx != NULL && ctx->mRT != NULL)
+	ctx->DrawText(hwnd, hdc, text, len, x, y, w, h, cellWidth, color);
 }
 
     void
@@ -882,6 +1018,20 @@ DWriteContext_EndDraw(DWriteContext *ctx
 }
 
     void
+DWriteContext_FillRect(DWriteContext *ctx, RECT *rc, COLORREF color)
+{
+    if (ctx != NULL)
+	ctx->FillRect(rc, color);
+}
+
+    void
+DWriteContext_Flush(DWriteContext *ctx)
+{
+    if (ctx != NULL)
+	ctx->Flush();
+}
+
+    void
 DWriteContext_Close(DWriteContext *ctx)
 {
     delete ctx;
diff --git a/src/gui_dwrite.h b/src/gui_dwrite.h
--- a/src/gui_dwrite.h
+++ b/src/gui_dwrite.h
@@ -59,6 +59,7 @@ void DWriteContext_BindDC(DWriteContext 
 void DWriteContext_SetFont(DWriteContext *ctx, HFONT hFont);
 void DWriteContext_DrawText(
 	DWriteContext *ctx,
+	HWND hwnd,
 	HDC hdc,
 	const WCHAR* text,
 	int len,
@@ -69,6 +70,8 @@ void DWriteContext_DrawText(
 	int cellWidth,
 	COLORREF color);
 void DWriteContext_EndDraw(DWriteContext *ctx);
+void DWriteContext_FillRect(DWriteContext *ctx, RECT *rc, COLORREF color);
+void DWriteContext_Flush(DWriteContext *ctx);
 void DWriteContext_Close(DWriteContext *ctx);
 
 void DWriteContext_SetRenderingParams(
diff --git a/src/gui_w32.c b/src/gui_w32.c
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -2858,10 +2858,10 @@ gui_mch_show_popupmenu_at(vimmenu_T *men
 
 	out_flush();	    /* make sure all output has been processed */
 	(void)BeginPaint(hwnd, &ps);
-#if defined(FEAT_DIRECTX)
-	if (IS_ENABLE_DIRECTX())
-	    DWriteContext_BeginDraw(s_dwc);
-#endif
+//#if defined(FEAT_DIRECTX)
+//	if (IS_ENABLE_DIRECTX())
+//	    DWriteContext_BeginDraw(s_dwc);
+//#endif
 
 #ifdef FEAT_MBYTE
 	/* prevent multi-byte characters from misprinting on an invalid
@@ -2878,19 +2878,19 @@ gui_mch_show_popupmenu_at(vimmenu_T *men
 
 	if (!IsRectEmpty(&ps.rcPaint))
 	{
-#if defined(FEAT_DIRECTX)
-	    if (IS_ENABLE_DIRECTX())
-		DWriteContext_BindDC(s_dwc, s_hdc, &ps.rcPaint);
-#endif
+//#if defined(FEAT_DIRECTX)
+//	    if (IS_ENABLE_DIRECTX())
+//		DWriteContext_BindDC(s_dwc, s_hdc, &ps.rcPaint);
+//#endif
 	    gui_redraw(ps.rcPaint.left, ps.rcPaint.top,
 		    ps.rcPaint.right - ps.rcPaint.left + 1,
 		    ps.rcPaint.bottom - ps.rcPaint.top + 1);
 	}
 
-#if defined(FEAT_DIRECTX)
-	if (IS_ENABLE_DIRECTX())
-	    DWriteContext_EndDraw(s_dwc);
-#endif
+//#if defined(FEAT_DIRECTX)
+//	if (IS_ENABLE_DIRECTX())
+//	    DWriteContext_EndDraw(s_dwc);
+//#endif
 	EndPaint(hwnd, &ps);
     }
 }
@@ -6127,6 +6127,29 @@ RevOut( HDC s_hdc,
 #endif
 
     void
+gui_mch_draw_string_start(void)
+{
+#if defined(FEAT_DIRECTX)
+    if (IS_ENABLE_DIRECTX())
+    {
+	RECT rc;
+	GetClientRect(s_hwnd, &rc);
+	DWriteContext_BindDC(s_dwc, s_hdc, &rc);
+	DWriteContext_BeginDraw(s_dwc);
+    }
+#endif
+}
+
+    void
+gui_mch_draw_string_end(void)
+{
+#if defined(FEAT_DIRECTX)
+    if (IS_ENABLE_DIRECTX())
+	DWriteContext_EndDraw(s_dwc);
+#endif
+}
+
+    void
 gui_mch_draw_string(
     int		row,
     int		col,
@@ -6210,6 +6233,12 @@ gui_mch_draw_string(
 	    hbr = hbr_cache[brush_lru];
 	    brush_lru = !brush_lru;
 	}
+
+#if defined(FEAT_DIRECTX)
+	if (IS_ENABLE_DIRECTX())
+	    DWriteContext_FillRect(s_dwc, &rc, gui.currBgColor);
+#endif
+
 	FillRect(s_hdc, &rc, hbr);
 
 	SetBkMode(s_hdc, TRANSPARENT);
@@ -6352,7 +6381,7 @@ gui_mch_draw_string(
 	if (IS_ENABLE_DIRECTX() && font_is_ttf_or_vector)
 	{
 	    /* Add one to "cells" for italics. */
-	    DWriteContext_DrawText(s_dwc, s_hdc, unicodebuf, wlen,
+	    DWriteContext_DrawText(s_dwc, s_hwnd, s_hdc, unicodebuf, wlen,
 		    TEXT_X(col), TEXT_Y(row), FILL_X(cells + 1), FILL_Y(1),
 		    gui.char_width, gui.currFgColor);
 	}