From e3dc861932eab0c2a1533e6ee72f6944aaed4035 Mon Sep 17 00:00:00 2001
From: Christian Speckner <christian.speckner@mayflower.de>
Date: Tue, 10 Dec 2019 18:07:40 +0100
Subject: [PATCH] Clear intermediate texture before blitting.

---
 .vscode/settings.json                | 3 ++-
 src/common/sdl_blitter/HqBlitter.cxx | 5 +++++
 src/common/sdl_blitter/HqBlitter.hxx | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/.vscode/settings.json b/.vscode/settings.json
index f355019cf..fb31d406b 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -23,6 +23,7 @@
         "tuple": "cpp",
         "utility": "cpp",
         "*.tcc": "cpp",
-        "functional": "cpp"
+        "functional": "cpp",
+        "iomanip": "cpp"
     }
 }
diff --git a/src/common/sdl_blitter/HqBlitter.cxx b/src/common/sdl_blitter/HqBlitter.cxx
index a47cd003b..ae1baea06 100644
--- a/src/common/sdl_blitter/HqBlitter.cxx
+++ b/src/common/sdl_blitter/HqBlitter.cxx
@@ -106,6 +106,8 @@ void HqBlitter::blitToIntermediate()
     SDL_Rect r = mySrcRect;
     r.x = r.y = 0;
 
+    SDL_UpdateTexture(myIntermediateTexture, nullptr, myBlankBuffer.get(), 4 * myIntermediateRect.w);
+
     SDL_SetRenderTarget(myFB.renderer(), myIntermediateTexture);
     SDL_RenderCopy(myFB.renderer(), mySrcTexture, &r, &myIntermediateRect);
 
@@ -138,6 +140,9 @@ void HqBlitter::recreateTexturesIfNecessary()
   mySrcTexture = SDL_CreateTexture(myFB.renderer(), myFB.pixelFormat().format,
     texAccess, mySrcRect.w, mySrcRect.h);
 
+  myBlankBuffer = make_unique<uInt32[]>(4 * myIntermediateRect.w * myIntermediateRect.h);
+  memset(myBlankBuffer.get(), 0, 4 * myIntermediateRect.w * myIntermediateRect.h);
+
   SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, myAttributes.smoothing ? "1" : "0");
 
   myIntermediateTexture = SDL_CreateTexture(myFB.renderer(), myFB.pixelFormat().format,
diff --git a/src/common/sdl_blitter/HqBlitter.hxx b/src/common/sdl_blitter/HqBlitter.hxx
index 745f869b1..8c60de00e 100644
--- a/src/common/sdl_blitter/HqBlitter.hxx
+++ b/src/common/sdl_blitter/HqBlitter.hxx
@@ -54,6 +54,7 @@ class HqBlitter : public Blitter {
     bool myRecreateTextures;
 
     SDL_Surface* myStaticData;
+    unique_ptr<uInt32[]> myBlankBuffer;
 
     FrameBufferSDL2& myFB;