Fix GLFW issue with texPreviousFrame not working after a lot of windo…

…w resizing

README.md

@@ -167,6 +167,7 @@ As you can see you're gonna need [CMAKE](https://cmake.org/) for this, but don't
 
 ### Windows
 Use at least [Visual C++ 2010](https://support.microsoft.com/ru-ru/help/2977003/the-latest-supported-visual-c-downloads). For the DX9/DX11 builds, obviously you'll be needing a [DirectX SDK](https://www.microsoft.com/en-us/download/details.aspx?id=6812), though a lot of it is already in the Windows 8.1 SDK as well.
+You will need to install NDI SDK and install Visual Studio with components ATL and MFC
 Then:
 mkdir build && cd build
 cmake -DCMAKE_BUILD_TYPE=Release ../

src/platform_glfw/Renderer.cpp

@@ -735,6 +735,7 @@ namespace Renderer
   };
 
   int textureUnit = 0;
+  int RGBA8_textureUnit = -1;
 
   Texture * CreateRGBA8Texture()
   {
@@ -752,12 +753,19 @@ namespace Renderer
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
+    if (RGBA8_textureUnit < 0)
+    {
+      // Reuse the same textureUnit instead of using a new one each time
+      // this solve the issue with recreating the previous frame buffer each time you resize the screen
+      RGBA8_textureUnit = textureUnit++;
+    }
+
     GLTexture * tex = new GLTexture();
     tex->width = nWidth;
     tex->height = nHeight;
     tex->ID = glTexId;
     tex->type = TEXTURETYPE_2D;
-    tex->unit = textureUnit++;
+    tex->unit = RGBA8_textureUnit;
     return tex;
   }