From a9b0abe493d4209660e68d0a1850b413c18fd941 Mon Sep 17 00:00:00 2001
From: Nick Gravelyn <nick@gravelyn.com>
Date: Wed, 20 Jan 2016 06:06:31 -0800
Subject: [PATCH] Automatically updating DisplayFrameBufferScale by reading the
 OpenGL drawable size and comparing with the window size. This fixed dear
 imgui which was rendering only to 1/4 of my window.

---
 examples/sdl_opengl_example/imgui_impl_sdl.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/examples/sdl_opengl_example/imgui_impl_sdl.cpp b/examples/sdl_opengl_example/imgui_impl_sdl.cpp
index 8359fd8a5..e222c806d 100644
--- a/examples/sdl_opengl_example/imgui_impl_sdl.cpp
+++ b/examples/sdl_opengl_example/imgui_impl_sdl.cpp
@@ -240,6 +240,10 @@ void ImGui_ImplSdl_NewFrame(SDL_Window *window)
     SDL_GetWindowSize(window, &w, &h);
     io.DisplaySize = ImVec2((float)w, (float)h);
 
+    int glW, glH;
+    SDL_GL_GetDrawableSize(window, &glW, &glH);
+    io.DisplayFramebufferScale = ImVec2(glW / io.DisplaySize.x, glH / io.DisplaySize.y);
+
     // Setup time step
     Uint32	time = SDL_GetTicks();
     double current_time = time / 1000.0;