Add 'scale' setting that allows user to render shader at a fraction of the window resolution

README.md

@@ -32,6 +32,8 @@ The file can have the following contents: (all fields are optional)
   "window":{ // default window size / state, if there's a setup dialog, it will override it
     "width":1920,
     "height":1080,
+    "scale":0.5, //render the shader at 1/2 the size of the window and scale up
+    "linearFilter":true, //use linear filtering when scaling up
     "fullscreen":true,
   },
   "font":{ // all paths in the file are also relative to the binary, but again, can be absolute paths if that's more convenient

src/Renderer.h

@@ -10,6 +10,8 @@ typedef struct
 {
   int nWidth;
   int nHeight;
+  float fScale;
+  bool bLinearFilter;
   RENDERER_WINDOWMODE windowMode;
   bool bVsync;
 } RENDERER_SETTINGS;

src/main.cpp

@@ -82,6 +82,8 @@ int main(int argc, const char *argv[])
   }
 
   RENDERER_SETTINGS settings;
+  settings.fScale = 1.0f;
+  settings.bLinearFilter = false;
   settings.bVsync = false;
 #ifdef _DEBUG
   settings.nWidth = 1280;
@@ -97,9 +99,15 @@ int main(int argc, const char *argv[])
       settings.nWidth = options.get<jsonxx::Object>("window").get<jsonxx::Number>("width");
     if (options.get<jsonxx::Object>("window").has<jsonxx::Number>("height"))
       settings.nHeight = options.get<jsonxx::Object>("window").get<jsonxx::Number>("height");
+    if (options.get<jsonxx::Object>("window").has<jsonxx::Number>("scale"))
+      settings.fScale = options.get<jsonxx::Object>("window").get<jsonxx::Number>("scale");
+    if (options.get<jsonxx::Object>("window").has<jsonxx::Boolean>("linearFilter"))
+      settings.bLinearFilter = options.get<jsonxx::Object>("window").get<jsonxx::Boolean>("linearFilter");
     if (options.get<jsonxx::Object>("window").has<jsonxx::Boolean>("fullscreen"))
       settings.windowMode = options.get<jsonxx::Object>("window").get<jsonxx::Boolean>("fullscreen") ? RENDERER_WINDOWMODE_FULLSCREEN : RENDERER_WINDOWMODE_WINDOWED;
   }
+  if (settings.fScale < 0.0f) settings.fScale = 0.0f;
+  if (settings.fScale > 1.0f) settings.fScale = 1.0f;
   if (!Renderer::OpenSetupDialog( &settings ))
     return -1;
 #endif
@@ -424,7 +432,7 @@ int main(int argc, const char *argv[])
     Renderer::keyEventBufferCount = 0;
 
     Renderer::SetShaderConstant( "fGlobalTime", time );
-    Renderer::SetShaderConstant( "v2Resolution", settings.nWidth, settings.nHeight );
+    Renderer::SetShaderConstant( "v2Resolution", settings.nWidth*settings.fScale, settings.nHeight*settings.fScale );
 
     for (std::map<int,std::string>::iterator it = midiRoutes.begin(); it != midiRoutes.end(); it++)
     {

src/platform_glfw/Renderer.cpp

@@ -165,6 +165,8 @@ namespace Renderer
   bool run = true;
 
   GLuint theShader = 0;
+  GLuint glhShaderFB = 0;
+  GLuint glhShaderTex = 0;
   GLuint glhVertexShader = 0;
   GLuint glhFullscreenQuadVB = 0;
   GLuint glhFullscreenQuadVA = 0;
@@ -174,6 +176,8 @@ namespace Renderer
 
   int nWidth = 0;
   int nHeight = 0;
+  float fScale = 1.0f;
+  bool bLinearFilter = false;
 
   void MatrixOrthoOffCenterLH(float * pout, float l, float r, float b, float t, float zn, float zf)
   {
@@ -226,6 +230,8 @@ namespace Renderer
 
     nWidth = settings->nWidth;
     nHeight = settings->nHeight;
+    fScale = settings->fScale;
+    bLinearFilter = settings->bLinearFilter;
 
     glfwWindowHint(GLFW_RED_BITS, 8);
     glfwWindowHint(GLFW_GREEN_BITS, 8);
@@ -305,6 +311,20 @@ namespace Renderer
     nWidth = settings->nWidth = fbWidth;
     nHeight = settings->nHeight = fbHeight;
     printf("[GLFW] Obtained framebuffer size: %d x %d\n", fbWidth, fbHeight);
+
+    if (fScale != 1.0f) {
+      glGenTextures( 1, &glhShaderTex );
+      glBindTexture( GL_TEXTURE_2D, glhShaderTex );
+      glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
+      glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
+      glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA32F, nWidth*fScale, nHeight*fScale, 0, GL_RGBA, GL_FLOAT, NULL );
+      glBindTexture( GL_TEXTURE_2D, 0 );
+
+      glGenFramebuffers( 1, &glhShaderFB );
+      glBindFramebuffer( GL_FRAMEBUFFER, glhShaderFB );
+      glFramebufferTexture( GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, glhShaderTex, 0 );
+      glBindFramebuffer( GL_FRAMEBUFFER, 0 );
+    }
     
     static float pFullscreenQuadVertices[] =
     {
@@ -596,6 +616,10 @@ namespace Renderer
   {
     glBindVertexArray(glhFullscreenQuadVA);
 
+    if (fScale != 1.0f) {
+      glBindFramebuffer(GL_FRAMEBUFFER, glhShaderFB);
+    }
+
     glUseProgram(theShader);
 
     glBindBuffer( GL_ARRAY_BUFFER, glhFullscreenQuadVB );
@@ -624,6 +648,13 @@ namespace Renderer
       glDisableVertexAttribArray( position );
 
     glUseProgram(0);
+
+    if (fScale != 1.0f) {
+      glBindFramebuffer(GL_FRAMEBUFFER, 0);
+      glBindFramebuffer(GL_READ_FRAMEBUFFER, glhShaderFB);
+      glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
+      glBlitFramebuffer(0, 0, nWidth*fScale, nHeight*fScale, 0, 0, nWidth, nHeight, GL_COLOR_BUFFER_BIT, bLinearFilter ? GL_LINEAR : GL_NEAREST);
+    }
   }
 
   bool ReloadShader( const char * szShaderCode, int nShaderCodeSize, char * szErrorBuffer, int nErrorBufferSize )